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