and thin portions of a casting, or between longitudinal and transverse properties in a wrought material. Note that a material can be shown to meet the properties required or specified (i.e, a separately cast tensile bar used to certify a casting, or the longitudinal tensile properties to certify a complex aluminum extrusion), but the specific properties required for the application may rely on the strength, toughness, or stress-corrosion cracking resistance in a direction other than longitudinal Design-caused failures include inappropriate geometries(as defined on the engineering drawing), which may lead to a compromise of component or system capabilities. Examples of inappropriate geometries include improper joint preparation for welding or brazing, such as an insufficient or missing groove for a groove weld, insufficient fit-up relief in a socket weld, or inadequate joint overlap in a brazed joint. Other geometry-caused failures can result from insufficient section thickness for a failure based on gross yielding, excessive section thickness in the presence of a flaw for a material of limited fracture toughness, or a fabrication configuration with an excessively sharp forming bend, with the resulting high residual stresses causing a reduction in the fatigue life For the example of the excessively tight cold-formed bend radius described previously, an application-life diagram can be constructed as shown in Fig. 6. The service condition considered is stress, and the characteristic that is varied is the radius of the cold-formed bend. Upon examination of the relationship between the characteristic curves and the intended service life, the components having the large and moderate bend radii are found to meet the intended service life at the severity of stress that is anticipated in the specific application. However, in this illustration, the component with the small bend radius sustained a premature failure at the anticipated stress level in the application, since the curve intersects the severity of stress line prior to reaching the intended service life Cold-formed products og0o66go6 Large bend radius Anticipated severity Moderate bend radius 十 Premature failure smal‖ bend radius Increasing service life Intended life Fig 6 Application-life diagram for design deficiency Some of the aforementioned deficiencies in design as well as application-life diagram concepts are illustrated in the following two case histories Example 1: Ice Cream Drink Mixer Blade Failures. Excessive assembly stresses and inappropriate detail design caused the premature failures of ice cream drink mixer blades shortly after the mixing machines were introduced into service. A mixer blade as-manufactured is shown on the left side of Fig. 7. As assembled(right side of Fig. 7), the mixer blade is slightly deformed by the contact between the wavy washer at the bottom of the assembly and the bends at the bottom shoulders of the two mixer arms. When properly torqued, the screw that fastens the wavy washer and the mixer blade to the spindle in the center of the assembly places an upward force on the bottoms of the arms(as indicated by the pair of pward facing arrows in Fig. 7). This results in the observed inward deflection of the arms(as indicated by the right and left facing arrows). More significantly, this bending force places the inside radii of the two shoulders of the mixing blade Thefileisdownloadedfromwww.bzfxw.comand thin portions of a casting, or between longitudinal and transverse properties in a wrought material. Note that a material can be shown to meet the properties required or specified (i.e., a separately cast tensile bar used to certify a casting, or the longitudinal tensile properties to certify a complex aluminum extrusion), but the specific properties required for the application may rely on the strength, toughness, or stress-corrosion cracking resistance in a direction other than longitudinal. Design-caused failures include inappropriate geometries (as defined on the engineering drawing), which may lead to a compromise of component or system capabilities. Examples of inappropriate geometries include improper joint preparation for welding or brazing, such as an insufficient or missing groove for a groove weld, insufficient fit-up relief in a socket weld, or inadequate joint overlap in a brazed joint. Other geometry-caused failures can result from insufficient section thickness for a failure based on gross yielding, excessive section thickness in the presence of a flaw for a material of limited fracture toughness, or a fabrication configuration with an excessively sharp forming bend, with the resulting high residual stresses causing a reduction in the fatigue life. For the example of the excessively tight cold-formed bend radius described previously, an application-life diagram can be constructed as shown in Fig. 6. The service condition considered is stress, and the characteristic that is varied is the radius of the cold-formed bend. Upon examination of the relationship between the characteristic curves and the intended service life, the components having the large and moderate bend radii are found to meet the intended service life at the severity of stress that is anticipated in the specific application. However, in this illustration, the component with the small bend radius sustained a premature failure at the anticipated stress level in the application, since the curve intersects the severity of stress line prior to reaching the intended service life. Fig. 6 Application-life diagram for design deficiency Some of the aforementioned deficiencies in design as well as application-life diagram concepts are illustrated in the following two case histories. Example 1: Ice Cream Drink Mixer Blade Failures. Excessive assembly stresses and inappropriate detail design caused the premature failures of ice cream drink mixer blades shortly after the mixing machines were introduced into service. A mixer blade as-manufactured is shown on the left side of Fig. 7. As assembled (right side of Fig. 7), the mixer blade is slightly deformed by the contact between the wavy washer at the bottom of the assembly and the bends at the bottom shoulders of the two mixer arms. When properly torqued, the screw that fastens the wavy washer and the mixer blade to the spindle in the center of the assembly places an upward force on the bottoms of the arms (as indicated by the pair of upward facing arrows in Fig. 7). This results in the observed inward deflection of the arms (as indicated by the right and left facing arrows). More significantly, this bending force places the inside radii of the two shoulders of the mixing blade The file is downloaded from www.bzfxw.com