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Figure 3 Steps for defining materials used in a subcomponent in connection with a location for analysis LAi
[1] "Major Nominal Alloy Composition" includes those species added in relatively large concentrations such as the iron, chromium, nickel and molybdenum in Type 316 stainless steel.
[2] "Minor Nominal Alloy Composition" includes species such as sulfur, nitrogen, phosphorous, silicon and manganese usually found in steels or the oxygen and nitrogen usually found in titanium.
[3] "Impurities" includes species such as arsenic, selenium and similar elements that contribute to temper brittleness or to excess oxygen and nitrogen picked up during welding of titanium.
[4] "Processing" includes fabrication to shape with associated times and temperatures of hot deformation and heat treatments, cold deformation to size, welding, machining, and grinding.
Processing together with the initial chemistry of the material as in [1], [2] and [3] are the first four steps that interact to control properties in the next four steps [5] - [8].
[5] "Structure" includes single and multiple phases, anisotropy, second phases, and grain size.
[6] "Embrittlement" includes grain boundary composition and the formation of phases that embrittle such as sigma phases in iron-chromium base alloys.
[7] "Surface" includes surface machining, surface stresses that result from thermal gradients, grinding, shot peening, and impurities absorbed at the surface.
[8] "Mechanical" includes the mechanical properties of tensile strength, ductility and toughness.
[9] Once these eight steps are defined they, like the result of "Environmental Definition," provide inputs to [9], the LAM, which is discussed in connection with Figure 4.
Lifetime Prediction, Roger W. Staehle, Adjunct Professor, Department of Chemical Engineering and Materials Science, University of Minnesota, Staehle Consulting Co.