Infrared and ultraviolet spectroscopy are used in analyzing organic materials. When the organic materials are present in a complex mixture(such as, for example, solvents, oils, greases, rubber, and plastics), the mixture is first separated into its components by gas chromatography Analysis of Surfaces and Deposits. Wavelength-dispersive x-ray spectrometers(WDSs) and edSs are frequently used for providing information regarding the chemical composition of surface constituents. They are employed as accessories for SEMs and permit simultaneous viewing and chemical analysis of a surface. The Auger electron spectrometer is useful for detecting the elements in extremely thin surface layers. The Auger electron spectrometer can provide semiquantitative determinations of elements with atomic numbers down to 3 (lithium). The size of the area examined varies greatly with the test conditions; it may be from I to 50 um in diameter For chemical analysis of surface areas as small as I um in diameter, the electron-microprobe analyzer is widely used. This instrument can determine the concentration of all but the low atomic number elements with a limit of detection below 0. 1%. The area examined with the ion-microprobe analyzer is a few microns in diameter larger than that examined with the electron-microprobe analyzer. The ion-microprobe analyzer has the advantage of being able to detect nearly all elements(including those of low atomic weights) in concentrations as low as 100 ppm. It is sometimes used to volatilize materials, which are then passed through a mass spectrometer Electron microprobes and other modern analytical instruments are described in greater detail in Materials Characterization. Volume 10 of the ASM Handbook. The instruments discussed previously are used for direct analysis of surfaces other techniques can be used for analyzing material that has been removed from the surface. For example, if material is removed in a replica(perhaps chemically extracted), it can be analyzed structurally by x-ray diffraction or electron diffraction. Also, depending on the quantity of material extracted, many of the routine chemical analysis techniques may be applicable Spot testing uses chemical tests to identify the metal, the alloying elements present, deposits, corrosion products, and soil Spot tests can be performed both in the laboratory and in the field; they do not require extensive training in analytical chemistry. The only requirement is that the substance be dissolvable, hydrochloric acid or even aqua regia may be used to dissolve the material Spot tests for metallic elements such as chromium, nickel, cobalt, iron, and molybdenum are usually done by dissolving a small amount of the alloy in acid and mixing a drop of the resulting solution with a drop of a specific reagent on absorbent paper or a porcelain plate. Spot colorings produced in this way indicate the presence or absence of the metallic radical under test. Samples may be removed from gross surfaces by spotting the specimen with a suitable acid, allowing time for solution and collecting the acid spot with an eyedropper Simulated-Service Testing During the concluding stages of an investigation, it may be necessary to conduct tests that simulate the conditions under which failure is believed to have occurred. Often, simulated-service testing is not practical because elaborate equipment is required, and even where practical it is possible that not all of the service conditions are fully known or understood Corrosion failures, for example, are difficult to reproduce in a laboratory, and some attempts to reproduce them have iven misleading results. Serious errors can arise when attempts are made to reduce the time required for a test by artificially increasing the severity of one of the factorssuch as the corrosive medium or the operating temperature Similar problems are encountered in wear testing On the other hand, when its limitations are clearly understood, the simulated testing and statistical experimental design analysis of the effects of certain selected variables encountered in service may be helpful in planning corrective action or at least, may extend service life. The evaluation of the efficacy of special additives to lubricants is an example of the uccessful application of simulated-service testing. The aircraft industry has made successful use of devices such as the wind tunnel to simulate some of the conditions encountered in flight, and naval architects have employed tank tests to evaluate hull modifications, power requirements, steerage, and other variables that might forestall component failure or promote safety at sea Taken singly, most of the metallurgical phenomena involved in failures can be satisfactorily reproduced on a laboratory scale, and the information derived from such experiments can be helpful to the investigator, provided the limitations of the tests are fully recognized. However, many company managers prefer to conduct trials to verify improvements before major conversions are approved. This is a more conservative approach, but it only takes one improper recommendation that results in an adverse result to justify trials of major changes Reference cited in this section P.M. Mumford, Test Methodology and Data Analysis, Tensile Testing, P. Han, Ed, ASM International, 1992, Thefileisdownloadedfromwww.bzfxw.comInfrared and ultraviolet spectroscopy are used in analyzing organic materials. When the organic materials are present in a complex mixture (such as, for example, solvents, oils, greases, rubber, and plastics), the mixture is first separated into its components by gas chromatography. Analysis of Surfaces and Deposits. Wavelength-dispersive x-ray spectrometers (WDSs) and EDSs are frequently used for providing information regarding the chemical composition of surface constituents. They are employed as accessories for SEMs and permit simultaneous viewing and chemical analysis of a surface. The Auger electron spectrometer is useful for detecting the elements in extremely thin surface layers. The Auger electron spectrometer can provide semiquantitative determinations of elements with atomic numbers down to 3 (lithium). The size of the area examined varies greatly with the test conditions; it may be from 1 to 50 μm in diameter. For chemical analysis of surface areas as small as 1 μm in diameter, the electron-microprobe analyzer is widely used. This instrument can determine the concentration of all but the low atomic number elements, with a limit of detection below 0.1%. The area examined with the ion-microprobe analyzer is a few microns in diameter larger than that examined with the electron-microprobe analyzer. The ion-microprobe analyzer has the advantage of being able to detect nearly all elements (including those of low atomic weights) in concentrations as low as 100 ppm. It is sometimes used to volatilize materials, which are then passed through a mass spectrometer. Electron microprobes and other modern analytical instruments are described in greater detail in Materials Characterization, Volume 10 of the ASM Handbook. The instruments discussed previously are used for direct analysis of surfaces; other techniques can be used for analyzing material that has been removed from the surface. For example, if material is removed in a replica (perhaps chemically extracted), it can be analyzed structurally by x-ray diffraction or electron diffraction. Also, depending on the quantity of material extracted, many of the routine chemical analysis techniques may be applicable. Spot testing uses chemical tests to identify the metal, the alloying elements present, deposits, corrosion products, and soil. Spot tests can be performed both in the laboratory and in the field; they do not require extensive training in analytical chemistry. The only requirement is that the substance be dissolvable; hydrochloric acid or even aqua regia may be used to dissolve the material. Spot tests for metallic elements such as chromium, nickel, cobalt, iron, and molybdenum are usually done by dissolving a small amount of the alloy in acid and mixing a drop of the resulting solution with a drop of a specific reagent on absorbent paper or a porcelain plate. Spot colorings produced in this way indicate the presence or absence of the metallic radical under test. Samples may be removed from gross surfaces by spotting the specimen with a suitable acid, allowing time for solution and collecting the acid spot with an eyedropper. Simulated-Service Testing During the concluding stages of an investigation, it may be necessary to conduct tests that simulate the conditions under which failure is believed to have occurred. Often, simulated-service testing is not practical because elaborate equipment is required, and even where practical it is possible that not all of the service conditions are fully known or understood. Corrosion failures, for example, are difficult to reproduce in a laboratory, and some attempts to reproduce them have given misleading results. Serious errors can arise when attempts are made to reduce the time required for a test by artificially increasing the severity of one of the factors—such as the corrosive medium or the operating temperature. Similar problems are encountered in wear testing. On the other hand, when its limitations are clearly understood, the simulated testing and statistical experimental design analysis of the effects of certain selected variables encountered in service may be helpful in planning corrective action or, at least, may extend service life. The evaluation of the efficacy of special additives to lubricants is an example of the successful application of simulated-service testing. The aircraft industry has made successful use of devices such as the wind tunnel to simulate some of the conditions encountered in flight, and naval architects have employed tank tests to evaluate hull modifications, power requirements, steerage, and other variables that might forestall component failure or promote safety at sea. Taken singly, most of the metallurgical phenomena involved in failures can be satisfactorily reproduced on a laboratory scale, and the information derived from such experiments can be helpful to the investigator, provided the limitations of the tests are fully recognized. However, many company managers prefer to conduct trials to verify improvements before major conversions are approved. This is a more conservative approach, but it only takes one improper recommendation that results in an adverse result to justify trials of major changes. Reference cited in this section 1. P.M. Mumford, Test Methodology and Data Analysis, Tensile Testing, P. Han, Ed., ASM International, 1992, p 55 The file is downloaded from www.bzfxw.com