Glossary Compiled and revised by Debbie Aliya, Aliya Analytical, W.T. Becker, Consultant (University of Tennessee Retired), and roch Shipley, Packer Engineering Inc COMMUNICATION is often the key issue in practical failure analysis. Communication is required among specific parties who are trying to solve a problem. It is recognized that the exact definition of a particular term may be less important than conveying the concept that solves the problem. However, it is typical in failure analysis and problem solving to consult the literature(including Handbooks such as this one)or other people to find information on similar problems. Without clear communication and consistent terminology, one cannot know if the problems are really similar In failure analysis work, it is often not possible to pin down a particular damage sequence or root cause with complete certainty. However, if the work is performed in a professional manner, there is a good probability of identifying some helpful solutions to at least reduce the likelihood of recurrence. This glossary is intended to help promote clear thinking and useful failure analysis. The process of defining terms is useful to the parties involved in solving a failure analysis problem, in that it increases their own comprehension of the physical facts and also facilitates communication with the other parties who need to understand the results of the Investigation Strict use of proper terminology is critical to clear communication. Several organizations have compiled glossaries of terms used in failure analysis, including ASTM, SAE, and ASM International. In some cases(e. g ASTM), accepted definitions of terms is by consensus approval of a committee. In other instances(e.g, ASM), there is no formal approval procedure nor is there a committee responsible for terminology. As a result, there may be more than one common use of a specific term, and there may be more than one definition of a term The definitions used in the following glossary are not al ways consistent with those for the same terms found in the ASM Materials Engineering Dictionary (J.R. Davis, editor, ASM International, 1992) or in glossaries in other ASM Handbook volumes. The use of a term (e.g, corrosion fatigue) may change with time as understanding evolves. The definitions presented here are those used in this volume and reflect common and modern understanding of these terms as used in the literature and in reports by practicing failure analysts However, as in all communication, if the way in which a particular term is being used is not clear, the speaker or author should be asked for clarificati Several terms used in discussions of failure analysis can be confusing or interpreted variously by different persons. Cases in point include mode, stress cracking, ductile, brittle, and cleavage. An example of the evolution of definitions, as previously noted, is the term quasi-cleavage, which is truly a form of cleavage and a microscale fracture surface appearance of a quenched and tempered steel. The fracture surface is typically dominated by cleavage, but there are typically small patches of microvoid coalescence(MvC) present or thin ribbons of MVC contained in the fracture surface. As the patches of MVC increase, the fracture surface is more accurately described as(microscale) mixed cleavage and MVC. In a matrix dominated by cleavage, there is nothing"quasi"about the cleavage, because the term quasi implies something different than cleavage Sometimes a modifying adjective may considerably improve the clarity of the sentence in which it is used. For example, ductile can refer to both a process/mechanism at the microscale or an appearance at the macroscale The term mode is used in multiple ways: It is defined in ASTM E 1823 in terms of surface displacement of the crack tip created by various loading conditions. It is defined within ASME Failure Methods and Effects Analysis terminology, and there are some eight additional definitions in Webster's Unabridged Dictionary There are still more uses of the term, as in fracture mode, failure mode, and so on. These latter two terms are not in the ASM Materials Engineering Dictionary, nor are they in an ASTM glossary. Consequently, their use has no underlying, commonly accepted definition and should be avoided if possible Other examples of terms that may be misinterpreted include static fatigue and stress cracking. The compilers also discourage the use of terms that have been removed from glossaries created by consensus approval.An example is the term endurance limit. The endurance limit presumably indicates a threshold stress for infinite
Glossary Compiled and revised by Debbie Aliya, Aliya Analytical, W.T. Becker, Consultant (University of Tennessee, Retired), and Roch Shipley, Packer Engineering Inc. COMMUNICATION is often the key issue in practical failure analysis. Communication is required among specific parties who are trying to solve a problem. It is recognized that the exact definition of a particular term may be less important than conveying the concept that solves the problem. However, it is typical in failure analysis and problem solving to consult the literature (including Handbooks such as this one) or other people to find information on similar problems. Without clear communication and consistent terminology, one cannot know if the problems are really similar. In failure analysis work, it is often not possible to pin down a particular damage sequence or root cause with complete certainty. However, if the work is performed in a professional manner, there is a good probability of identifying some helpful solutions to at least reduce the likelihood of recurrence. This glossary is intended to help promote clear thinking and useful failure analysis. The process of defining terms is useful to the parties involved in solving a failure analysis problem, in that it increases their own comprehension of the physical facts and also facilitates communication with the other parties who need to understand the results of the investigation. Strict use of proper terminology is critical to clear communication. Several organizations have compiled glossaries of terms used in failure analysis, including ASTM, SAE, and ASM International. In some cases (e.g., ASTM), accepted definitions of terms is by consensus approval of a committee. In other instances (e.g., ASM), there is no formal approval procedure nor is there a committee responsible for terminology. As a result, there may be more than one common use of a specific term, and there may be more than one definition of a term. The definitions used in the following glossary are not always consistent with those for the same terms found in the ASM Materials Engineering Dictionary (J.R. Davis, editor, ASM International, 1992) or in glossaries in other ASM Handbook volumes. The use of a term (e.g., corrosion fatigue) may change with time as understanding evolves. The definitions presented here are those used in this Volume and reflect common and modern understanding of these terms as used in the literature and in reports by practicing failure analysts. However, as in all communication, if the way in which a particular term is being used is not clear, the speaker or author should be asked for clarification. Several terms used in discussions of failure analysis can be confusing or interpreted variously by different persons. Cases in point include mode, stress cracking, ductile, brittle, and cleavage. An example of the evolution of definitions, as previously noted, is the term quasi-cleavage, which is truly a form of cleavage and a microscale fracture surface appearance of a quenched and tempered steel. The fracture surface is typically dominated by cleavage, but there are typically small patches of microvoid coalescence (MVC) present or thin ribbons of MVC contained in the fracture surface. As the patches of MVC increase, the fracture surface is more accurately described as (microscale) mixed cleavage and MVC. In a matrix dominated by cleavage, there is nothing “quasi” about the cleavage, because the term quasi implies something different than cleavage. Sometimes a modifying adjective may considerably improve the clarity of the sentence in which it is used. For example, ductile can refer to both a process/mechanism at the microscale or an appearance at the macroscale. The term mode is used in multiple ways: It is defined in ASTM E 1823 in terms of surface displacement of the crack tip created by various loading conditions. It is defined within ASME Failure Methods and Effects Analysis terminology, and there are some eight additional definitions in Webster's Unabridged Dictionary. There are still more uses of the term, as in fracture mode, failure mode, and so on. These latter two terms are not in the ASM Materials Engineering Dictionary, nor are they in an ASTM glossary. Consequently, their use has no underlying, commonly accepted definition and should be avoided if possible. Other examples of terms that may be misinterpreted include static fatigue and stress cracking. The compilers also discourage the use of terms that have been removed from glossaries created by consensus approval. An example is the term endurance limit. The endurance limit presumably indicates a threshold stress for infinite
life in cyclic loading. It appears in S-N data for materials that strain age and is therefore associated with a dislocation-interstitial pinning mechanism. If some event occurs to cause depinning(say, an increased stress),a new saturation stress is obtained that is the endurance limit is changed. The term endurance limit is no longer contained in a standard glossary of terms used in fracture and fatigue(ASTM E 1823) There are a group of terms used to describe deviations from ideality and that are in some instances the technical root cause for failure. They include imperfection, discontinuity, defect and root cause. In some instances these terms are used interchangeably by some writers, and in other cases clear distinctions are made. In some instances, specific terms have been defined by legal jurisdictions. The failure analyst should consider the legal implication of his terminology. As noted, the courts have defined the meanings of certain words, and these meanings may not correspond to what the analyst intends. Furthermore, various courts may not be consistent For example, some metallurgists have examined a fracture surface and identified a defect at the fracture origin By this they mean nothing more than a discontinuity and perhaps a minute discontinuity. However, within a legal context, the identification of a defect suggests a defective component, legal liability for the manufacturer, and a possible need for a recall or other corrective action The definition of defect herein is based on deviation from a specification or a component being unfit for its intended purpose. An actual or perceived failure does not automatically mean there is a defect. Even if there is a defect, that condition may or may not relate to the failure. It is believed this framework provides a rational method for deciding if there is, in fact, a defect. However, it does not eliminate all controversy as specifications may or may not be clear, appropriate, and up-to-date. There may also be disagreement regarding the intended purpose of a component. a discussion on this matter from a legal perspective is in two references: (a) Asperger, J.J.,"Legal Definition of a Product Failure: What the Law Requires of the Designer and the Manufacturer, Failure Prevention Through Education, Getting to the root Cause, Conference Proceedings, ASM International, May 2000, and(b)"Product Liability and Design""in this Volume of the ASM Handbook. 475° C embrittlement Embrittlement of ferritic and semiferritic steels containing more than 13% Cr that occurs when they are held or slowly cooled through the 400 to 500C (750 to 930F) temperature range. Embrittlement is presumed to be due to the grain-boundary precipitation of a chromium-rich phase together with the creation of a precipitate-free zone(PFZ) adjacent to the grain boundary. Because the precipitation reates a PFZ, fracture is likely to be intergranula 500 to 700C embrittlement Embrittlement that occurs when high-alloy steels(e.g, hot work steels and high-speed steels)are cooled to form martensite and are subsequently tempered or slowly cooled through the 500 to 700C(930 to 1290F)temperature range. Tempering results in a fine dispersion of carbides. A small increase in hardness is associated with the embrittlement abrasion The process of grinding or wearing away through the use of abrasives; a roughening or scratching of a surface due to abrasive wear abrasive wear The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being abraded. Compare with adhesive wear adhesive wear The removal or displacement of material from a surface by the welding together and subsequent shearing of minute areas of two surfaces that slide across each other under pressure. Compare with brasive wear diabatic Occurring without loss or gain of heat in the system, which may result in a local temperature increase or decrease. Adiabatic conditions differ from isothermal conditions(under which the temperature remains constant) diabatic shear bands Thefileisdownloadedfromwww.bzfxw.com
life in cyclic loading. It appears in S-N data for materials that strain age and is therefore associated with a dislocation-interstitial pinning mechanism. If some event occurs to cause depinning (say, an increased stress), a new saturation stress is obtained; that is, the endurance limit is changed. The term endurance limit is no longer contained in a standard glossary of terms used in fracture and fatigue (ASTM E 1823). There are a group of terms used to describe deviations from ideality and that are in some instances the technical root cause for failure. They include imperfection, discontinuity, defect and root cause. In some instances these terms are used interchangeably by some writers, and in other cases clear distinctions are made. In some instances, specific terms have been defined by legal jurisdictions. The failure analyst should consider the legal implication of his terminology. As noted, the courts have defined the meanings of certain words, and these meanings may not correspond to what the analyst intends. Furthermore, various courts may not be consistent. For example, some metallurgists have examined a fracture surface and identified a defect at the fracture origin. By this they mean nothing more than a discontinuity and perhaps a minute discontinuity. However, within a legal context, the identification of a defect suggests a defective component, legal liability for the manufacturer, and a possible need for a recall or other corrective action. The definition of defect herein is based on deviation from a specification or a component being unfit for its intended purpose. An actual or perceived failure does not automatically mean there is a defect. Even if there is a defect, that condition may or may not relate to the failure. It is believed this framework provides a rational method for deciding if there is, in fact, a defect. However, it does not eliminate all controversy as specifications may or may not be clear, appropriate, and up-to-date. There may also be disagreement regarding the intended purpose of a component. A discussion on this matter from a legal perspective is in two references: (a) Asperger, J.J., “Legal Definition of a Product Failure: What the Law Requires of the Designer and the Manufacturer,” Failure Prevention Through Education, Getting to the Root Cause, Conference Proceedings, ASM International, May 2000, and (b) “Product Liability and Design” in this Volume of the ASM Handbook. 475 °C embrittlement Embrittlement of ferritic and semiferritic steels containing more than 13% Cr that occurs when they are held or slowly cooled through the 400 to 500 °C (750 to 930 °F) temperature range. Embrittlement is presumed to be due to the grain-boundary precipitation of a chromium-rich phase together with the creation of a precipitate-free zone (PFZ) adjacent to the grain boundary. Because the precipitation creates a PFZ, fracture is likely to be intergranular. 500 to 700 °C embrittlement Embrittlement that occurs when high-alloy steels (e.g., hot work steels and high-speed steels) are cooled to form martensite and are subsequently tempered or slowly cooled through the 500 to 700 °C (930 to 1290 °F) temperature range. Tempering results in a fine dispersion of carbides. A small increase in hardness is associated with the embrittlement. A abrasion The process of grinding or wearing away through the use of abrasives; a roughening or scratching of a surface due to abrasive wear. abrasive wear The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being abraded. Compare with adhesive wear. adhesive wear The removal or displacement of material from a surface by the welding together and subsequent shearing of minute areas of two surfaces that slide across each other under pressure. Compare with abrasive wear. adiabatic Occurring without loss or gain of heat in the system, which may result in a local temperature increase or decrease. Adiabatic conditions differ from isothermal conditions (under which the temperature remains constant). adiabatic shear bands The file is downloaded from www.bzfxw.com
Shear bands created under adiabatic conditions that is bands created under conditions of local heating created by high strain-rate deformation alligatoring allia the longitudinal splitting of flat slabs in a plane parallel to the rolled surface r skin See orange peel ambient Something usually used in relation to temperature, as "ambient temperature"surrounding a part or assembly. Often taken to mean comfortable indoor temperature annealing or growth twin a twin formed in a crystal or grain during recrystallization or, rarely, during solidification anode The electrode of an electrolytic cell at which oxidation occurs. Contrast with cathode arrest lines(marks) Lines or thin regions that appear on fracture surfaces. There are two types of arrest lines those created in monotonic loading and those from cyclic loading; the latter give information on the crack front position at a given point in time. Arrest lines in monotonic loading are created when the stored elastic strain energy cannot drive a crack completely across the remaining ligament. At the microscale, monotonic arrest lines are regions of microvoid coalescence. while the remainder of the fracture surface shows cleavage or quasi-cleavage cracking. Arrest lines in cyclic loading are created when the mponent remains in the unloaded condition for a time sufficiently long to crevice corrosion at the crack tip or for a sudden change in loading spectra. See also beach marks and rib mark asperity arial In tribology, a protuberance in the small-scale topographical irregularities of a solid surface Longitudinal, or parallel to the axis or centerline of a part. Usually refers to axial compression or axial tension or orientation of a metallographic or mechanical test coup axial strain The linear strain in a plane parallel to the longitudinal axis. Strain may be axial (tensile or compressive or shear. For constant-volume materials, axial strain in a direction is equal in magnitude to the areal strain on a plane whose normal is in the direction of axial strain. Axial strain is the integral of a change in length divided by a length If the length is considered to be a constant( typically the initial, i.e., gage length, Lo) dl L However. if the instantaneous length is considered See also shear strain B banded structur oo. Segregated structure consisting of alternating, nearly parallel bands of different composition and beach of primary flow in hot working but is often caused by conditions present when the material is cas ection bly microstructure(as in steels with pearlite banding). Banding is typically aligned in the dir
Shear bands created under adiabatic conditions; that is, bands created under conditions of local heating created by high strain-rate deformation. alligatoring The longitudinal splitting of flat slabs in a plane parallel to the rolled surface. alligator skin See orange peel. ambient Something usually used in relation to temperature, as “ambient temperature” surrounding a part or assembly. Often taken to mean “comfortable indoor temperature.” annealing or growth twin A twin formed in a crystal or grain during recrystallization or, rarely, during solidification. anode The electrode of an electrolytic cell at which oxidation occurs. Contrast with cathode. arrest lines (marks) Lines or thin regions that appear on fracture surfaces. There are two types of arrest lines: those created in monotonic loading and those from cyclic loading; the latter give information on the crack front position at a given point in time. Arrest lines in monotonic loading are created when the stored elastic strain energy cannot drive a crack completely across the remaining ligament. At the microscale, monotonic arrest lines are regions of microvoid coalescence, while the remainder of the fracture surface shows cleavage or quasi-cleavage cracking. Arrest lines in cyclic loading are created when the component remains in the unloaded condition for a time sufficiently long to cause crevice corrosion at the crack tip or for a sudden change in loading spectra. See also beach marks and rib mark. asperity In tribology, a protuberance in the small-scale topographical irregularities of a solid surface. axial Longitudinal, or parallel to the axis or centerline of a part. Usually refers to axial compression or axial tension or orientation of a metallographic or mechanical test coupon. axial strain The linear strain in a plane parallel to the longitudinal axis. Strain may be axial (tensile or compressive) or shear. For constant-volume materials, axial strain in a direction is equal in magnitude to the areal strain on a plane whose normal is in the direction of axial strain. Axial strain is the integral of a change in length divided by a length: dL L e = ò If the length is considered to be a constant (typically the initial, i.e., gage length, L0): 1 f o L f o o o L L L dL L L e æ ö - = = ç ÷ è ø ò However, if the instantaneous length is considered: ln f o L f L o dL L L L e æ ö = = ç ÷ è ø ò See also shear strain. B banded structure A segregated structure consisting of alternating, nearly parallel bands of different composition and possibly microstructure (as in steels with pearlite banding). Banding is typically aligned in the direction of primary flow in hot working but is often caused by conditions present when the material is cast. beach marks
Macroscopic(visible) progression marks on a fracture surface that indicate successive positions of the advancing crack front. The classic appearance is of irregular elliptical or semielliptical rings radiating outward from one or more origins. After some growth, the curvature may be lost or reversed as affected by component geometry. Curvature is an indication of the stress field and is also affected by biaxial loading conditions and the shape of the remaining uncracked ligament. Beach marks(also known as clamshell marks, tide marks, or arrest marks) are typically found on service fractures where the part is loaded randomly, intermittently, or with periodic variations in mean stress, alternating stress, or environmental conditions. Not to be confused with striation(a microscale feature) and monotonic crack arrest lines(which are macroscale and form by a different mechanism). Beach marks formed during intermittent loading are formed by crevice corrosion. In steels, this causes the progression mark to have a dark or black appearance bifurcation The separation of materials into two parts. See also crack bifurcation blue brittleness Brittleness exhibited by some steels after being heated to a temperature within the range of approximately 205 to 370C (400 to 700F), particularly if the steel is worked at the elevated temperature. Killed steels are virtually free of this kind of brittleness breaking stress See rupture stress Brinell hardness number hB a number related to the applied load and to the surface area of the permanent impression made by a ball indenter, computed from 2P HB= D(D-√D2-d2 where P is applied load, kgf, D is diameter of ball, mm, and d is mean diameter of the impression, mm Brinell hardness test a test for determining the hardness of a material by forcing a hard steel or carbide ball of specified diameter into the surface of the material under a specified load for a specified time. The result is expressed as the brinell hardness number Brinell Damage to a solid bearing surface characterized by one or more plastically formed indentations brougH about by overload. This term is often applied in the case of rolling-element bearings. See also false Brinelling g brittle Permitting little or no plastic(permanent)deformation prior to fracture. The term is used at both the macroscale and microscale Contrast with ductile brittle crack propagation A sudden propagation of a crack with the absorption of no energy except that stored elastically in the body. Microscopic examination may reveal some plastic deformation that is not noticeable to the unaided eye. Contrast with ductile crack propagation brittle erosion behavior Erosion behavior having characteristic properties(e.g, little or no plastic flow, the formation of cracks) that can be associated with brittle fracture of the exposed surface. The maximum volume removal occurs at an angle near 90, in contrast to approximately 25 for ductile erosion behavior brittle fracture Separation of a solid accompanied by little or no macroscopic and/or microscopic plastic deformation Typically, brittle fracture occurs by rapid crack propagation, with less expenditure of energy than for ductile fracture. The term is used at the macroscale to describe appearance and at the microscale to describe both appearance and mechanisn brittleness The tendency of a material to fracture without first undergoing plastic deformation. Contrast with buckle Thefileisdownloadedfromwww.bzfxw.com
Macroscopic (visible) progression marks on a fracture surface that indicate successive positions of the advancing crack front. The classic appearance is of irregular elliptical or semielliptical rings radiating outward from one or more origins. After some growth, the curvature may be lost or reversed as affected by component geometry. Curvature is an indication of the stress field and is also affected by biaxial loading conditions and the shape of the remaining uncracked ligament. Beach marks (also known as clamshell marks, tide marks, or arrest marks) are typically found on service fractures where the part is loaded randomly, intermittently, or with periodic variations in mean stress, alternating stress, or environmental conditions. Not to be confused with striation (a microscale feature) and monotonic crack arrest lines (which are macroscale and form by a different mechanism). Beach marks formed during intermittent loading are formed by crevice corrosion. In steels, this causes the progression mark to have a dark or black appearance. bifurcation The separation of materials into two parts. See also crack bifurcation. blue brittleness Brittleness exhibited by some steels after being heated to a temperature within the range of approximately 205 to 370 °C (400 to 700 °F), particularly if the steel is worked at the elevated temperature. Killed steels are virtually free of this kind of brittleness. breaking stress See rupture stress. Brinell hardness number, HB A number related to the applied load and to the surface area of the permanent impression made by a ball indenter, computed from: ( ) 2 ² ² P HB p D D D d = - - where P is applied load, kgf; D is diameter of ball, mm; and d is mean diameter of the impression, mm. Brinell hardness test A test for determining the hardness of a material by forcing a hard steel or carbide ball of specified diameter into the surface of the material under a specified load for a specified time. The result is expressed as the Brinell hardness number. Brinelling Damage to a solid bearing surface characterized by one or more plastically formed indentations brought about by overload. This term is often applied in the case of rolling-element bearings. See also false Brinelling. brittle Permitting little or no plastic (permanent) deformation prior to fracture. The term is used at both the macroscale and microscale. Contrast with ductile. brittle crack propagation A sudden propagation of a crack with the absorption of no energy except that stored elastically in the body. Microscopic examination may reveal some plastic deformation that is not noticeable to the unaided eye. Contrast with ductile crack propagation. brittle erosion behavior Erosion behavior having characteristic properties (e.g., little or no plastic flow, the formation of cracks) that can be associated with brittle fracture of the exposed surface. The maximum volume removal occurs at an angle near 90°, in contrast to approximately 25° for ductile erosion behavior. brittle fracture Separation of a solid accompanied by little or no macroscopic and/or microscopic plastic deformation. Typically, brittle fracture occurs by rapid crack propagation, with less expenditure of energy than for ductile fracture. The term is used at the macroscale to describe appearance and at the microscale to describe both appearance and mechanism. brittleness The tendency of a material to fracture without first undergoing plastic deformation. Contrast with ductility. buckle The file is downloaded from www.bzfxw.com
(1)An indented valley in the surface of a sand casting due to expansion of the molding sand. (2)A local waviness in metal bar or sheet, usually transverse to the direction of rolling, caused by inconsistencies in the temperature or thickness of the material being rolled buckling A compression and torsion phenomenon that occurs when, after some critical level of load, a bulge, bend, bow, kink, or other wavy condition is produced in a beam, column, plate, bar, or sheet product The level of stress that causes buckling in a given component is dependent mainly on geometry and elastic modulus, but in some shapes, yield strength also has a strong influence on the resistence to bucklin bulk modulus See bulk modulus of elasticity bulk modulus of elasticity, K The measure of resistance to change in volume; the ratio of hydrostatic stress(om) to the corresponding unit change in volume(An). This elastic constant can be expressed by K △∥V△v∥vβ where K is the bulk modulus of elasticity, om is hydrostatic or mean normal stress, p is hydrostatic pressure, and B is compressibility. Also known as bulk modulus, hydrostatic modulus, and volumetric modulus of elasticity b (1)Permanently damaging a metal or alloy by heating to cause either incipient melting or intergranular oxidation. See also overheating and grain-boundary liquation. (2)In grinding, getting the work hot enough to cause discoloration or to change the microstructure by tempering or hardening carbon flotation Free grap that has separated from the molten iron in a cast iron. This imperfection tends to occur at the upper surfaces of the cope of casting casting shrinkage Voids formed in cast products when insufficient molten metal is fed into the solidifying casting to make up for the volume loss due to cooling. See also liquid shrinkage, shrinkage cavity, solidification shrinkage, and solid shrinkage catastrophic wear Rapidly occurring or accelerating surface damage, deterioration, or change of shape caused by wear to such a degree that the service life of a part is appreciably shortened or its function is destroyed cathode The electrode of an electrolytic cell at which reduction is the principal reaction(Electrons flow toward the cathode in the external circuit )Contrast with anode caustic cracking A form of stress-corrosion cracking most frequently encountered in carbon steels or iron-chromium nickel alloys that are exposed to concentrated hydroxide solutions at temperatures of 200 to 250C (400 to 480F). See also caustic embrittlement caustic embrittlement A form of hydrogen embrittlement sometimes caused by caustic cleaning of steel parts, especially those that have been hardened to relatively high strength levels. See also hydrogen embrittlement cavitation (1)The formation and rapid collapse, within a liquid, of cavities or bubbles that contain vapor or gas or both. Cavitation caused by severe turbulent flow often leads to cavitation damage of adjacent materials which may include loss of material or changes in surface properties. (2) The description of microscale oid formation, primarily in the grain boundaries during high-temperature deformation cavitation erosion See cavitation
(1) An indented valley in the surface of a sand casting due to expansion of the molding sand. (2) A local waviness in metal bar or sheet, usually transverse to the direction of rolling, caused by inconsistencies in the temperature or thickness of the material being rolled. buckling A compression and torsion phenomenon that occurs when, after some critical level of load, a bulge, bend, bow, kink, or other wavy condition is produced in a beam, column, plate, bar, or sheet product. The level of stress that causes buckling in a given component is dependent mainly on geometry and elastic modulus, but in some shapes, yield strength also has a strong influence on the resistence to buckling. bulk modulus See bulk modulus of elasticity. bulk modulus of elasticity, K The measure of resistance to change in volume; the ratio of hydrostatic stress (σm) to the corresponding unit change in volume (ΔV). This elastic constant can be expressed by: 1 / / m p K V V V V s b - === D D where K is the bulk modulus of elasticity, σm is hydrostatic or mean normal stress, p is hydrostatic pressure, and β is compressibility. Also known as bulk modulus, hydrostatic modulus, and volumetric modulus of elasticity. burning (1) Permanently damaging a metal or alloy by heating to cause either incipient melting or intergranular oxidation. See also overheating and grain-boundary liquation. (2) In grinding, getting the work hot enough to cause discoloration or to change the microstructure by tempering or hardening. C carbon flotation Free graphite that has separated from the molten iron in a cast iron. This imperfection tends to occur at the upper surfaces of the cope of castings. casting shrinkage Voids formed in cast products when insufficient molten metal is fed into the solidifying casting to make up for the volume loss due to cooling. See also liquid shrinkage, shrinkage cavity, solidification shrinkage, and solid shrinkage. catastrophic wear Rapidly occurring or accelerating surface damage, deterioration, or change of shape caused by wear to such a degree that the service life of a part is appreciably shortened or its function is destroyed. cathode The electrode of an electrolytic cell at which reduction is the principal reaction. (Electrons flow toward the cathode in the external circuit.) Contrast with anode. caustic cracking A form of stress-corrosion cracking most frequently encountered in carbon steels or iron-chromiumnickel alloys that are exposed to concentrated hydroxide solutions at temperatures of 200 to 250 °C (400 to 480 °F). See also caustic embrittlement. caustic embrittlement A form of hydrogen embrittlement sometimes caused by caustic cleaning of steel parts, especially those that have been hardened to relatively high strength levels. See also hydrogen embrittlement. cavitation (1) The formation and rapid collapse, within a liquid, of cavities or bubbles that contain vapor or gas or both. Cavitation caused by severe turbulent flow often leads to cavitation damage of adjacent materials, which may include loss of material or changes in surface properties. (2) The description of microscale void formation, primarily in the grain boundaries during high-temperature deformation. cavitation erosion See cavitation
centerline shrinkage Porosity due to incomplete fill after partial solidification of a casting(ingots or continuous-cast slabs or billets)or that occurs along the central plane or axis of a cast metal section. See also shrinkage porosity chafing fatigue Fatigue initiated in a surface damaged by rubbing against another body See also frettin Charpy (impact) test Pendulum impact test(e.g, per ASTM E 23)in which a V-notched, keyhole-notched, or U-notched, ctangular specimen, supported at both ends, is struck in the center of its length, behind the notch, by striker mounted at the lower end of a bar that can swing as a pendulum. The energy that is absorbed in fracture is calculated from the height to which the striker would have risen had there been no specimen cherro tneasured specimen responses can include lateral contraction and percent shear fracture od test. Other and the height to which it actually rises after fracture of the specimen. Contrast with A macroscale pattern of nested"V-shaped ridges. The apex of the V's point back to the region of fracture initiation. The"V"pattern is created when the crack propagates faster in the interior of the material than at the surface. Half-V-shaped ridges are created when crack propagation is faster at the surface than in the interior The latter marks are often described as radial marks The term chevron pattern is sometimes used interchangeably with the term herringbone pattern. However, there are differences in appearance. First, a chevron pattern is a macroscale pattern, while a herringbone pattern is a microscale pattern. Secondly, a herringbone pattern, although it is a series of nested V's, is created by the different mechanism of a central spine created by cleavage on a 100, plane and continued intermittent lateral crack expansion of the crack on (1, 1, 2) twinning planes(i.e, see tongue) chill white cast iron or cast aluminum structure that is produced by rapid solidification. Usually intentionally produced to provide desirable wear characteristic chor d modulus he slope of the chord drawn between any two specific points on a stress-strain curve. See also modulus of elasticity. a term commonly used in the polymer field to specify how a single value for the modulus of elasticity is determined from a nonlinear load elongation graph from a tensile test clamshell marks See beach marks cleavage ( 1)Fracture of a crystal by crack propagation across a crystallographic plane of low index. (2)The endency to cleave or split along definite crystallographic planes. (3) Sometimes used to describe brittle fracture at the macro-or microscale in amorphous materials(such as glasses cleavage crack In crystalline material, a transgranular fracture that extends along a cleavage plane, resulting in bright reflecting facets. Contrast with microvoid coalescence (MVC). Sometimes used to describe the macroscale brittle fracture of amorphous materials(such as glasses and glassy polymers) cleavage plane (1)In metals, a characteristic crystallographic plane or set of planes in a crystal on which a cleavage crack occurs easily. (2)In noncrystalline material, the plane on which brittle fracture occurs cold shot 1)A portion of the surface of an ingot or casting showing premature solidification; caused by splashing of molten metal onto a cold mold wall during pouring. (2) A small globule of metal embedded in, but not entirely fused with, a casting cold shut (1)In castings, a discontinuity on or immediately beneath the surface of a casting, caused by the meeting of two streams of liquid metal that failed to merge. a cold shut may have the appearance of a crack or seam with smooth, rounded edges. (2)In wrought products, a fissure or lap on a surface that has been closed without fusion during working, or a folding back of metal onto its own surface during flow in the die cavity columnar structure Thefileisdownloadedfromwww.bzfxw.com
centerline shrinkage Porosity due to incomplete fill after partial solidification of a casting (ingots or continuous-cast slabs or billets) or that occurs along the central plane or axis of a cast metal section. See also shrinkage porosity. chafing fatigue Fatigue initiated in a surface damaged by rubbing against another body. See also fretting. Charpy (impact) test Pendulum impact test (e.g., per ASTM E 23) in which a V-notched, keyhole-notched, or U-notched, rectangular specimen, supported at both ends, is struck in the center of its length, behind the notch, by a striker mounted at the lower end of a bar that can swing as a pendulum. The energy that is absorbed in fracture is calculated from the height to which the striker would have risen had there been no specimen and the height to which it actually rises after fracture of the specimen. Contrast with Izod test. Other measured specimen responses can include lateral contraction and percent shear fracture. chevron pattern A macroscale pattern of nested “V”-shaped ridges. The apex of the V's point back to the region of fracture initiation. The “V” pattern is created when the crack propagates faster in the interior of the material than at the surface. Half-V-shaped ridges are created when crack propagation is faster at the surface than in the interior. The latter marks are often described as radial marks. The term chevron pattern is sometimes used interchangeably with the term herringbone pattern. However, there are differences in appearance. First, a chevron pattern is a macroscale pattern, while a herringbone pattern is a microscale pattern. Secondly, a herringbone pattern, although it is a series of nested V's, is created by the different mechanism of a central spine created by cleavage on a {100} plane and continued intermittent lateral crack expansion of the crack on {1,1,2} twinning planes (i.e., see tongue). chill A white cast iron or cast aluminum structure that is produced by rapid solidification. Usually intentionally produced to provide desirable wear characteristics. chord modulus The slope of the chord drawn between any two specific points on a stress-strain curve. See also modulus of elasticity. A term commonly used in the polymer field to specify how a single value for the modulus of elasticity is determined from a nonlinear load elongation graph from a tensile test. clamshell marks See beach marks. cleavage (1) Fracture of a crystal by crack propagation across a crystallographic plane of low index. (2) The tendency to cleave or split along definite crystallographic planes. (3) Sometimes used to describe brittle fracture at the macro- or microscale in amorphous materials (such as glasses). cleavage crack In crystalline material, a transgranular fracture that extends along a cleavage plane, resulting in bright reflecting facets. Contrast with microvoid coalescence (MVC). Sometimes used to describe the macroscale brittle fracture of amorphous materials (such as glasses and glassy polymers). cleavage plane (1) In metals, a characteristic crystallographic plane or set of planes in a crystal on which a cleavage crack occurs easily. (2) In noncrystalline material, the plane on which brittle fracture occurs. cold shot (1) A portion of the surface of an ingot or casting showing premature solidification; caused by splashing of molten metal onto a cold mold wall during pouring. (2) A small globule of metal embedded in, but not entirely fused with, a casting. cold shut (1) In castings, a discontinuity on or immediately beneath the surface of a casting, caused by the meeting of two streams of liquid metal that failed to merge. A cold shut may have the appearance of a crack or seam with smooth, rounded edges. (2) In wrought products, a fissure or lap on a surface that has been closed without fusion during working, or a folding back of metal onto its own surface during flow in the die cavity. columnar structure The file is downloaded from www.bzfxw.com
A coarse structure of parallel, high-aspect-ratio grains formed by directional growth that is most often observed in castings. Similar structures are sometimes seen in steels subjected to extensive surface decarburization composite material A heterogeneous, solid structural material consisting of two or more distinct components that are mechanically or metallurgically bonded together, such as a wire, filament, or particles of a high melting-point substance embedded in a metal or nonmetal matrix compression Pertaining to forces on a body or part of a body that tend to crush, or compress, the body. There is contraction in the direction of the force and expansion perpendicular to the force compressive strength The maximum compressive stress a material is capable of developing. With a brittle material that fail in compression by fracturing, the compressive strength has a definite value. In the case of ductile, malleable, or semiviscous materials(which do not fail in compression by a shattering fracture), the value obtained for compressive stength is an arbitrary value dependent on the degree of distortion that is e regarded as effective failure of the material compressive stress a stress that causes a body to deform(shorten) in the direction of the applied load. Contrast with tensile contact fatigue Cracking and subsequent pitting of a surface subjected to alternating Hertzian(contact stresses), such as those produced under rolling contact or combined rolling and sliding. The phenomenon of contact fatigue is encountered most often in rolling-element bearings or in gears, where the surface stresses are high due to the concentrated loads and are repeated many times during normal operation. Fracture is at the subsurface location of the maximum hertzian shear stress contact (Hertzian) stress The pressure at a contact between two solid bodies calculated according to Hertz's equations for deformation. The theoretical area of contact between two nonconforming surfaces is frequently small. The interaction between these surfaces is often described as either point or line contact. Common examples of point contact are mating helical gears, cams and crowned followers, ball bearings and their races, and train wheels and rails. If the mating parts can be considered semiinfinite and if material behavior is linearly elastic, then the local stress state can be described by Hertzian theory, as long as the contacting surfaces can be modeled as quadratic functions of those spatial coordinates defining the surfaces. Even in the absence of friction, the resulting three-dimensional stress state is quite complex, and although the local stress state is compressive, that is, the principal stresses beneath the load are negative. large subsurface shear stresses which can serve as crack initiation sites exist beneath the load The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. See also corrosion fatigue, crevice corrosion. denickelification dezincification erosion-corrosion. exfoliation filiform corrosion fretting corrosion galvanic corrosion, general corrosion, graphitic corrosion, impingement attack, interdendritic corrosion, intergranular corrosion, internal oxidation, oxidation, parting, pitting, poultice corrosion, rust, selective leaching, stray-current corrosion, stress-corrosion cracking, and sulfide stress cracking corrosion fatigue Cracking produced by the combined action of repeated or fluctuating stress and a corrosive corrosive wear Wear in which chemical or electrochemical reaction with the environment is significant Coulomb-Mohr fracture criterion a theory of fracture based on experimental values for both tensile and compressive strength in which acture on a plane is hypothesized to occur when a critical combination of normal and shear stress occur on the plane(maximum pressure reduced shear stress). The critical combination of stresses is assumed to be a linear relationship r|+=τ( uniaxial load)
A coarse structure of parallel, high-aspect-ratio grains formed by directional growth that is most often observed in castings. Similar structures are sometimes seen in steels subjected to extensive surface decarburization. composite material A heterogeneous, solid structural material consisting of two or more distinct components that are mechanically or metallurgically bonded together, such as a wire, filament, or particles of a highmelting-point substance embedded in a metal or nonmetal matrix. compression Pertaining to forces on a body or part of a body that tend to crush, or compress, the body. There is contraction in the direction of the force and expansion perpendicular to the force. compressive strength The maximum compressive stress a material is capable of developing. With a brittle material that fails in compression by fracturing, the compressive strength has a definite value. In the case of ductile, malleable, or semiviscous materials (which do not fail in compression by a shattering fracture), the value obtained for compressive stength is an arbitrary value dependent on the degree of distortion that is regarded as effective failure of the material. compressive stress A stress that causes a body to deform (shorten) in the direction of the applied load. Contrast with tensile stress. contact fatigue Cracking and subsequent pitting of a surface subjected to alternating Hertzian (contact stresses), such as those produced under rolling contact or combined rolling and sliding. The phenomenon of contact fatigue is encountered most often in rolling-element bearings or in gears, where the surface stresses are high due to the concentrated loads and are repeated many times during normal operation. Fracture is at the subsurface location of the maximum Hertzian shear stress. contact (Hertzian) stress The pressure at a contact between two solid bodies calculated according to Hertz's equations for elastic deformation. The theoretical area of contact between two nonconforming surfaces is frequently quite small. The interaction between these surfaces is often described as either point or line contact. Common examples of point contact are mating helical gears, cams and crowned followers, ball bearings and their races, and train wheels and rails. If the mating parts can be considered semiinfinite and if material behavior is linearly elastic, then the local stress state can be described by Hertzian theory, as long as the contacting surfaces can be modeled as quadratic functions of those spatial coordinates defining the surfaces. Even in the absence of friction, the resulting three-dimensional stress state is quite complex, and although the local stress state is compressive, that is, the principal stresses beneath the load are negative, large subsurface shear stresses, which can serve as crack initiation sites, exist beneath the load. corrosion The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. See also corrosion fatigue, crevice corrosion, denickelification, dezincification, erosion-corrosion, exfoliation, filiform corrosion, fretting corrosion, galvanic corrosion, general corrosion, graphitic corrosion, impingement attack, interdendritic corrosion, intergranular corrosion, internal oxidation, oxidation, parting, pitting, poultice corrosion, rust, selective leaching, stray-current corrosion, stress-corrosion cracking, and sulfide stress cracking. corrosion fatigue Cracking produced by the combined action of repeated or fluctuating stress and a corrosive environment. corrosive wear Wear in which chemical or electrochemical reaction with the environment is significant. Coulomb-Mohr fracture criterion A theory of fracture based on experimental values for both tensile and compressive strength in which fracture on a plane is hypothesized to occur when a critical combination of normal and shear stress occur on the plane (maximum pressure reduced shear stress). The critical combination of stresses is assumed to be a linear relationship: |τ| + μσ = τi(uniaxial load)
where t and o are shear and normal stress, respectively, and u and t; are material constants crack (1)a pair of surfaces and the associated discontinuity created by separation under stress of atoms previously bonded. This does not include internal free surfaces created by corrosion processes or olidification imperfections.(2) The process by which a solid object becomes fragmented due to crack Separation of atomic bonds under stress Cracking is often accompanied by or preceded by deformation The spliting of a crack into two paths, or the intersection of a crack with a preexisting crack crack extension An incremental increase in crack size. See also crack length(a) or depth, effective crack size, and physical crack si crack extension force The elastic energy per unit of new separation area that is made available at the front of an ideal crack in an elastic solid during a virtual increment of forward crack extension. Also described as the strain energy release rate crack length(a)or depth In fracture-mechanics-based analyses, the physical crack size used to determine the crack growth and the stress-intensity factor. For a compact-type specimen, crack length is measured from the connecting the bearing points of load application. For a center-crack tension specimen, crack length is measured from the perpendicular bisector of the central crack crack mouth opening displacement(CMOD) See crack tip opening di placement (CTOD) crack opening displacement (COD) See crack tip opening displacement (CTOD) crack plane orientation and growth direction three-letter identification system used to identify the longitudinal(L), transverse (T), and short transverse(S)direction of the applied stress normal to the plane on which the crack propagates and the direction of crack growth. Used for both prismatic and cylindrical sections. For example, a L-t orientation indicates a stress in the longitudinal (or rolling) direction, and crack propagation is in the wide transverse direction. See ASTME 399 for a complete descriptio crack size(a) A lineal measure of a principal planar dimension of a crack. This measure is commonly used in the EAlculation of quantities descriptive of the stress and displacement fields. In practice, the value of crack size is obtained from procedures for measurement of physical crack size, original crack size, or effective crack size, as appropriate to the situation under consideration. See also crack length(a)or depth crack tip opening displacement (CTOD) The crack displacement resulting from the total deformation(elastic plus plastic) at variously defined locations near the original crack tip crack-tip plane strain A stress-strain field near a crack tip that approaches plane strain to the degree required by an empirical criterion Time-dependent strain occurring under stress. The creep strain occurring at a diminishing rate is called primary or transient creep(stage D); that occurring at a minimum and almost constant rate, secondary or teady- rate creep(stage ID); and that occurring at an accelerating rate, tertiary creep (stage Il cree The slope of the creep-time curve at a given time. See also minimum creep rate creep-rupture strength The stress that causes fracture in a creep test at a given time in a specified constant environment. Also nown as stress-rupture strength creep strain The time-dependent total strain(including the initial instantaneous elastic strain) produced by applied stress during a creep test creep strength Thefileisdownloadedfromwww.bzfxw.com
where τ and σ are shear and normal stress, respectively, and μ and τi are material constants. crack (1) A pair of surfaces and the associated discontinuity created by separation under stress of atoms previously bonded. This does not include internal free surfaces created by corrosion processes or solidification imperfections. (2) The process by which a solid object becomes fragmented due to separation of atomic bonds under stress. Cracking is often accompanied by or preceded by deformation. crack bifurcation The spliting of a crack into two paths, or the intersection of a crack with a preexisting crack. crack extension An incremental increase in crack size. See also crack length (a) or depth, effective crack size, and physical crack size. crack extension force The elastic energy per unit of new separation area that is made available at the front of an ideal crack in an elastic solid during a virtual increment of forward crack extension. Also described as the strain energy release rate. crack length (a) or depth In fracture-mechanics-based analyses, the physical crack size used to determine the crack growth rate and the stress-intensity factor. For a compact-type specimen, crack length is measured from the line connecting the bearing points of load application. For a center-crack tension specimen, crack length is measured from the perpendicular bisector of the central crack. crack mouth opening displacement (CMOD) See crack tip opening displacement (CTOD). crack opening displacement (COD) See crack tip opening displacement (CTOD) crack plane orientation and growth direction A three-letter identification system used to identify the longitudinal (L), transverse (T), and short transverse (S) direction of the applied stress normal to the plane on which the crack propagates and the direction of crack growth. Used for both prismatic and cylindrical sections. For example, a L-T orientation indicates a stress in the longitudinal (or rolling) direction, and crack propagation is in the wide transverse direction. See ASTM E 399 for a complete description. crack size (a) A lineal measure of a principal planar dimension of a crack. This measure is commonly used in the calculation of quantities descriptive of the stress and displacement fields. In practice, the value of crack size is obtained from procedures for measurement of physical crack size, original crack size, or effective crack size, as appropriate to the situation under consideration. See also crack length (a) or depth. crack tip opening displacement (CTOD) The crack displacement resulting from the total deformation (elastic plus plastic) at variously defined locations near the original crack tip. crack-tip plane strain A stress-strain field near a crack tip that approaches plane strain to the degree required by an empirical criterion. creep Time-dependent strain occurring under stress. The creep strain occurring at a diminishing rate is called primary or transient creep (stage I); that occurring at a minimum and almost constant rate, secondary or steady-rate creep (stage II); and that occurring at an accelerating rate, tertiary creep (stage III). creep rate The slope of the creep-time curve at a given time. See also minimum creep rate. creep-rupture strength The stress that causes fracture in a creep test at a given time in a specified constant environment. Also known as stress-rupture strength. creep strain The time-dependent total strain (including the initial instantaneous elastic strain) produced by applied stress during a creep test. creep strength The file is downloaded from www.bzfxw.com
The stress that causes a given creep strain in a creep test at a given time in a specified constant environment creep stres The constant load divided by the original cross-sectional area of the specimen crevice corrosion Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and the surface of another material cross direction See transverse direction crush (1) An indentation in a casting surface due to displacement of sand into the mold cavity when the mold is closed. (2) Permanent localized compressive deformation. (3)The spalling of (usually thin) surface- treated cases on gears due to overload also known as case crushing cumulative damage In fatigue loading, a measure of damage, as expressed as a fraction of life to failure, as it accumulates with the number of cycles. When the stress level is changed, the life is changed. Therefore, damage accumulates according to the stress level and number of cycles spent at a given stress. The most common(but not only)model for linear cumulative damage is the Palmgren-Miner cumulative damage model. In the following equation, ni is the number of load cycles spent at a stress for which the life is ni Failure is assumed to occur when the damage summation becomes unity D cup fracture(cup-and-cone fracture) A mixed-mode fracture, often seen in cylindrical-shaped components or tension test specimens of a ductile material, where the core of the necked region undergoes fracture by microvoid coalescence, creating the cup bottom. As the crack grows from this central region, the degree of constraint is reduced and fracture continues in the remaining outer ring under conditions of plane stress, creating the slanted cup walls. Closely related fracture appearance also is seen in small width-to-thickness-ratio prismatic tensile specimens. One of the mating fracture surfaces looks similar to a miniature cup, having a central depressed flat-face region surrounded by a shear lip. The other fracture surface looks similar to a miniature truncated cone The condition sometimes occurring in heavily cold-worked rods and wires in which the outside fibers are still intact and the central zone has failed in a series of cup -and-cone fractures cut A raised, rough surface on a casting due to erosion by the metal stream of part of the sand mold or core cyclic loading (1)Repetitive loading, as with regularly recurring stresses on a part, that sometimes leads to fatigue fracture.(2) Loads that change value by following a regular or irregular repeating sequence of change dealloying The selective corrosion of one or more components of a solid-solution alloy. Also called parting or selective leaching. See also decarburization, denickelification, dezincification, and graphitic corrosion decarburization Loss of carbon from a free surface(component surface or surface of a crack intersecting the surface)of a carbon-containing alloy due to reaction with one or more chemical substances in a medium that contacts the surface decohesion The process of creating a pair of free surfaces where a grain boundary or second-phase boundary existed
The stress that causes a given creep strain in a creep test at a given time in a specified constant environment. creep stress The constant load divided by the original cross-sectional area of the specimen. crevice corrosion Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and the surface of another material. cross direction See transverse direction. crush (1) An indentation in a casting surface due to displacement of sand into the mold cavity when the mold is closed. (2) Permanent localized compressive deformation. (3) The spalling of (usually thin) surfacetreated cases on gears due to overload; also known as case crushing. cumulative damage In fatigue loading, a measure of damage, as expressed as a fraction of life to failure, as it accumulates with the number of cycles. When the stress level is changed, the life is changed. Therefore, damage accumulates according to the stress level and number of cycles spent at a given stress. The most common (but not only) model for linear cumulative damage is the Palmgren-Miner cumulative damage model. In the following equation, ni is the number of load cycles spent at a stress for which the life is Ni. Failure is assumed to occur when the damage summation becomes unity: i i n D N = å cup fracture (cup-and-cone fracture) A mixed-mode fracture, often seen in cylindrical-shaped components or tension test specimens of a ductile material, where the core of the necked region undergoes fracture by microvoid coalescence, creating the cup bottom. As the crack grows from this central region, the degree of constraint is reduced, and fracture continues in the remaining outer ring under conditions of plane stress, creating the slanted cup walls. Closely related fracture appearance also is seen in small width-to-thickness-ratio prismatic tensile specimens. One of the mating fracture surfaces looks similar to a miniature cup, having a central depressed flat-face region surrounded by a shear lip. The other fracture surface looks similar to a miniature truncated cone. cupping The condition sometimes occurring in heavily cold-worked rods and wires in which the outside fibers are still intact and the central zone has failed in a series of cup-and-cone fractures. cut A raised, rough surface on a casting due to erosion by the metal stream of part of the sand mold or core. cyclic loading (1) Repetitive loading, as with regularly recurring stresses on a part, that sometimes leads to fatigue fracture. (2) Loads that change value by following a regular or irregular repeating sequence of change. D dealloying The selective corrosion of one or more components of a solid-solution alloy. Also called parting or selective leaching. See also decarburization, denickelification, dezincification, and graphitic corrosion. decarburization Loss of carbon from a free surface (component surface or surface of a crack intersecting the surface) of a carbon-containing alloy due to reaction with one or more chemical substances in a medium that contacts the surface. decohesion The process of creating a pair of free surfaces where a grain boundary or second-phase boundary existed previously
defect (1)An imperfection(deviation from perfection) that can be shown to cause failure by a quantitative analysis and that would not have occurred in the absence of the imperfection.(2)(Legal) Manufacturing defect:(a) a failure to conform to stated specifications; (b) nonsatisfaction of user requirements;(c) deviation from the norm;(d) when a product leaves the assembly line in substandard condition, differs from the manufacturer's intended result, or differs from other ostensibly identical units of the same product line. (3)(Legal) Design defect: (a) less safe than expected by the ordinary consumer;(b) excessive preventable danger.(4)(Legal) Marketing defect: failure to warn or inadequate warning of hazard and risk involved with use of a product. Note: Legal definitions may vary from jurisdiction to jurisdiction. Those legal definitions cited here are from the article"Product Liability and Design"in this Volume and also in Materials Selection and Design, Volume 20, ASM Handbook, page 147.An example is a deviation from specification. It can be the cause of a failure that makes the part unsuitable for its intended purpose. However, just because a part fails does not imply that it contained a defect, and not all defects are a cause for failure. (2) Laws of various jurisdictions may also define what constitutes a defect of defective product deformation a change in the shape of a body due to stress, thermal change, change in moisture, or other causes deformation bands Bands produced within individual grains during cold working that differ in orientation from the matrix deformation twin See mechanical twin(deformation twin) and Neumann bands a crystal with a treelike branching pattern. dendrites are most evident in cast metals slowly cooled through the solidification range denickelification Corrosion in which nickel is selectively leached from nickel-containing alloys. Most commonly observed in copper-nickel alloys after extended service in fresh water. See also selective leaching depletion Selective removal of one component of an alloy, usually from the surface or preferentially from grain- boundary regions. See also selective leaching deposit attack or corrosion See poultice corrosion deviatoric stress The nonhydrostatic component of the state of stress on a body It is the deviatoric component that causes shape change(plastic deformation) dezincification Corrosion in which zinc is selectively leached from zinc-containing alloys. Most commonly found in copper-zinc alloys containing less than 85% Cu after extended service in water containing dissolved oxygen. See also selective leaching diamond pyramid hardness test See vickers hardness test diffuse necking The nonuniform strain distribution along the length of a member loaded in tension that develops at the maximum load The term"diffuse"is used because the neck develops slowly, with little change in load but an increase in axial strain near the load maximum Contrast to local necking dimpled rupture fracture Ductile fracture that occurs through the formation and coalescence of microvoids(dimples)along the fracture path. The fracture surface of such a ductile fracture appears dimpled when observed at high magnification and usually is most clearly resolved when viewed in a scanning electron microscope distortion Any deviation from an original size, shape, or contour that occurs because of the application of stress or duchie the release of residual stress and may be associated with exposure to high or low temperature Capable of being plastically deformed before fracturing Thefileisdownloadedfromwww.bzfxw.com
defect (1) An imperfection (deviation from perfection) that can be shown to cause failure by a quantitative analysis and that would not have occurred in the absence of the imperfection. (2) (Legal) Manufacturing defect: (a) a failure to conform to stated specifications; (b) nonsatisfaction of user requirements; (c) deviation from the norm; (d) when a product leaves the assembly line in substandard condition, differs from the manufacturer's intended result, or differs from other ostensibly identical units of the same product line. (3) (Legal) Design defect: (a) less safe than expected by the ordinary consumer; (b) excessive preventable danger. (4) (Legal) Marketing defect: failure to warn or inadequate warning of hazard and risk involved with use of a product. Note: Legal definitions may vary from jurisdiction to jurisdiction. Those legal definitions cited here are from the article “Product Liability and Design” in this Volume and also in Materials Selection and Design, Volume 20, ASM Handbook, page 147. An example is a deviation from specification. It can be the cause of a failure that makes the part unsuitable for its intended purpose. However, just because a part fails does not imply that it contained a defect, and not all defects are a cause for failure. (2) Laws of various jurisdictions may also define what constitutes a defect of defective product. deformation A change in the shape of a body due to stress, thermal change, change in moisture, or other causes. deformation bands Bands produced within individual grains during cold working that differ in orientation from the matrix. deformation twin See mechanical twin (deformation twin) and Neumann bands. dendrite A crystal with a treelike branching pattern. Dendrites are most evident in cast metals slowly cooled through the solidification range. denickelification Corrosion in which nickel is selectively leached from nickel-containing alloys. Most commonly observed in copper-nickel alloys after extended service in fresh water. See also selective leaching. depletion Selective removal of one component of an alloy, usually from the surface or preferentially from grainboundary regions. See also selective leaching. deposit attack or corrosion See poultice corrosion. deviatoric stress The nonhydrostatic component of the state of stress on a body. It is the deviatoric component that causes shape change (plastic deformation). dezincification Corrosion in which zinc is selectively leached from zinc-containing alloys. Most commonly found in copper-zinc alloys containing less than 85% Cu after extended service in water containing dissolved oxygen. See also selective leaching. diamond pyramid hardness test See Vickers hardness test. diffuse necking The nonuniform strain distribution along the length of a member loaded in tension that develops at the maximum load. The term “diffuse” is used because the neck develops slowly, with little change in load, but an increase in axial strain near the load maximum. Contrast to local necking. dimpled rupture fracture Ductile fracture that occurs through the formation and coalescence of microvoids (dimples) along the fracture path. The fracture surface of such a ductile fracture appears dimpled when observed at high magnification and usually is most clearly resolved when viewed in a scanning electron microscope. distortion Any deviation from an original size, shape, or contour that occurs because of the application of stress or the release of residual stress and may be associated with exposure to high or low temperature. ductile Capable of being plastically deformed before fracturing. The file is downloaded from www.bzfxw.com