Designation:E6–06
Standard Terminology Relating to
Methods of Mechanical Testing1
This standard is issued under thefixed designation E6;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1.Scope
1.1This terminology covers the principal terms relating to methods of mechanical testing of solids.The general defini-tions are restricted and interpreted,when necessary,to make them particularly applicable and practicable for use in stan-dards requiring or relating to mechanical tests.These defini-tions are published to encourage uniformity of terminology in product specifications.
1.2Terms relating to fatigue and fracture testing are defined in Terminology E1823.
2.Referenced Documents
2.1ASTM Standards:2
E8Test Methods for Tension Testing of Metallic Materials E8M Test Methods for Tension Testing of Metallic Mate-rials[Metric]
E796Test Method for Ductility Testing of Metallic Foil E1823Terminology Relating to Fatigue and Fracture Test-ing
3.Index of Terms
3.1The definitions of the following terms,which are listed alphabetically,appear in the indicated sections of
4.1.
Term Section
accuracy G
alignment B
angle of bend D
angle of twist B
angular strain see strain
axial strain see strain
bearing area F
bearing force F
bearing strain F
bearing strength F bearing stress F
bearing yield strength F
bend test D
bending strain see strain
bias,statistical G
biaxial stretching D
break elongation see maximum elongation breaking load B
Brinell hardness number C
Brinell hardness test C
calibration G
calibration factor G
chord modulus see modulus of elasticity compressive strength B
compressive stress see stress compressometer G
constraint A
creep E
creep recovery E
creep rupture strength E
creep strength E
deep drawing D
deflectometer G
direct verification G
discontinuous yielding B
discontinuous yielding stress B
ductility A
钢段
dynamic mechanical measurement G
eccentricity B
edge distance F
edge distance ratio F
elastic calibration device G
elastic constants see modulus of elasticity and Poisson’s
ratio
elastic force-measurement device G
elastic limit A
elastic modulus see modulus of elasticity
elastic true strain A
elongation B
engineering strain see strain
engineering stress see stress extensometer G
extensometer system G
fatigue ductility D
fatigue ductility exponent D
fatigue life B
forming limit curve D
forming limit diagram D
fracture ductility A
fracture strength A
fracture stress see stress
free bend D
force A
gage length G
guided bend D
hardness C
indentation hardness C
1This terminology is under the jurisdiction of ASTM Committee E28on
Mechanical Testing and is the direct responsibility of Subcommittee E28.91on
Editorial and Terminology except where designated otherwise.A subcommittee
designation in parentheses following a definition indicates the subcommittee with
responsibility for that definition.
Current edition approved April1,2006.Published April2006.Originally
approved1923.Last previous edition approved2003as E6–03e1.
2For referenced ASTM standards,visit the ASTM website,,or
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
the ASTM website.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
indirect verification G
initial recovery E
initial strain E
initial stress E
Knoop hardness number C
Knoop hardness test C
limiting dome height D
linear(tensile or compressive)strain see strain
load A
lower yield strength B
macrostrain see strain malleability see ductility
mandrel(in bend testing)D
maximum elongation B性描写
mechanical hysteresis A
mechanical properties A
mechanical testing A
microstrain see strain
modulus of elasticity A
modulus of rigidity see modulus of elasticity modulus of rupture in bending D
modulus of rupture in torsion B
necking B
nominal stress see stress
normal stress see stress
physical properties see mechanical properties pin see mandrel(in bend testing) plastic true strain A
plunger see mandrel(in bend testing) precision G
primary force standard G
principal stress see stress Poisson’s ratio A
proportional limit A
radius of bend D
rate of creep E
reduction of area B
relaxation rate E常乐康
relaxed stress E
remaining stress E
residual strain see strain
residual stress see stress
Rockwell hardness number C
Rockwell hardness test C
Rockwell superficial hardness num-
ber
see Rockwell hardness number Rockwell superficial hardness test C
semi-guided bend D
Scleroscope hardness number C
Scleroscope hardness test C
secondary force standard G
set A
secant modulus see modulus of elasticity shear fracture B
shear modulus A
shear strain see strain
shear strength B
shear stress see stress slenderness ratio B
static fatigue strength see creep rupture strength strain A
strain gage fatigue life see fatigue life
strain hardening A
stress A
stress relaxation E
stress-rupture strength see creep rupture strength stress-strain diagram A
tangent modulus see modulus of elasticity tensile strength B
tensile stress see stress
tension testing machine A
testing machine A
torque A
torsional modulus see modulus of elasticity torsional stress see stress
total elongation B
transverse strain see strain true strain see strain
true stress see stress
ultimate elongation see maximum elongation uniform elongation B
upper yield strength B
verification G
Vickers hardness number C
Vickers hardness test C
wrap-around bend D
yield point B
yield point elongation B
yield strength B(also see upper yield strength and
lower yield strength)
Young’s modulus A
zero time E
4.Terminology
4.1Terms and Definitions:
A.GENERAL DEFINITIONS constraint,n—any restriction to the deformation of a body.
(E28.11) ductility,n—the ability of a material to deform plastically before fracturing.(E28.02)
D ISCUSSION—Ductility is usually evaluated by measuring(1)the
elongation or reduction of area from a tension test,(2)the depth of cup from a cupping test,(3)the radius or angle of bend from the bend test, or(4)the fatigue ductility from the fatigue ductility test(see Test Method E796).
D ISCUSSION—Malleability is the ability to deform plastically under
repetitive compressive forces.
elastic limit[FL–2],n—the greatest stress which a material is capable of sustaining without any perma
nent strain remain-ing upon complete release of the stress.
D ISCUSSION—Due to practical considerations in determining the
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elastic limit,measurements of strain,using a small force rather than zero force,are usually taken as the initial andfinal reference. fracture ductility,e f,n—the true plastic strain at fracture. fracture strength,S f[FL–2],n—the normal stress at the beginning of fracture.Fracture strength is calculated from the force at the beginning of fracture during a tension test and the original cross-sectional area of the specimen. force[F],n—in mechanical testing,a vector quantity of fundamental nature characterized by a magnitude,a direc-tion,a sense,and a discrete point of application,that acts externally upon a test object and creates stresses in it.
(E28.91)
D ISCUSSION—Force is a derived unit of the SI system.Units of force
in the SI system are newtons(N).
D ISCUSSION—Where applicable,the noun force is preferred to load in
terminology for mechanical testing.
least count,n—the smallest change in indication that can customarily be determined and reported.
D ISCUSSION—In machines with close graduations it may be the value
of a graduation interval;with open graduations or with magnifiers for reading,it may be an estimated fraction,rarely asfine as one tenth,of
a graduated interval;and with verniers it is customarily the difference
between the scale and vernier graduation measured in terms of scale units.If the indicating mechanism includes a stepped detent,the detent action may determine the least
count.
load[F],n—in mechanical testing,an external force or system of forces or pressures,or both,that act upon the test object.
(E28.91)
D ISCUSSION—Load is a deprecated term and,where applicable,it
should be replaced by force,particularly where it is used as a noun.For reasons of editorial simplicity or traditional usage,replacement of load by force may not always be desirable when used as a verb,adjective, or other part of speech(for example,to load a specimen,loading rate, load cell).
mechanical hysteresis,n—the energy absorbed in a complete cycle of loading and unloading.(E28.03)
D ISCUSSION—A complete cycle of loading and unloading includes
any stress cycle regardless of the mean stress or range of stress. mechanical properties,n—those properties of a material that are associated with elastic and inelastic reaction when force is applied,or that involve the relationship between stress and strain.
D ISCUSSION—These properties have often been referred to as“physi-
cal properties,”but the term“mechanical properties”is preferred. mechanical testing,n—the determination of mechanical prop-erties.(E28.90) modulus of elasticity[FL–2],n—the ratio of stress to corre-sponding strain below the proportional limit.
D ISCUSSION—The stress-strain relations of many materials do not
conform to Hooke’s law throughout the elastic range,but deviate therefrom even at stresses well below the elastic limit.For such materials the slope of either the tangent to the stress-strain curve at the origin or at a low stress,the secant drawn from the origin to any specified point on the stress-strain curve,or the chord connecting any two specified points on the stress-strain curve is usually taken to be the “modulus of elasticity.”In these cases the modulus should be desig-nated as the“tangent modulus,”the“secant modulus,”or the“chord modulus,”and the point or points on the stress-strain curve described.
Thus,for materials where the stress-strain relationship is curvilinear rather than linear,one of the four following terms may be used:
(a)initial tangent modulus[FL–2],n—the slope of the stress-strain
curve at the origin.
(b)tangent modulus[FL–2],n—the slope of the stress-strain curve at
any specified stress or strain.
(c)secant modulus[FL–2],n—the slope of the secant drawn from the
origin to any specified point on the stress-strain curve.
(d)chord modulus[FL–2],n—the slope of the chord drawn between
any two specified points on the stress-strain curve below the elastic limit of the material.E28.03
D ISCUSSION—Modulus of elasticity,like stress,is expressed in force
per unit of area(pounds per square inch,etc.).
Poisson’s ratio,µ,n—the negative of the ratio of transverse strain to the corresponding axial strain resulting from an axial stress below the proportional limit of the material.
(E28.03)
D ISCUSSION—Poisson’s ratio may be negative for some materials,for
example,a tensile transverse strain will result from a tensile axial strain.
D ISCUSSION—Poisson’s ratio will have more than one value if the
material is not isotropic.
proportional limit[FL–2],n—the greatest stress which a material is capable of sustaining without any deviation from proportionality of stress to strain(Hooke’s law).
D ISCUSSION—Many experiments have shown that values observed for
the proportional limit vary greatly with the sensitivity and accuracy of the testing equipment,eccentricity of loading,the scale to which the stress-strain diagram is plotted,and other factors.When determination of proportional limit is required,the procedure and the sensitivity of the test equipment should be specified.
set,n—strain remaining after complete release of the force producing the deformation.
D ISCUSSION—Due to practical considerations,such as distortion in the
specimen and slack in the strain indicating system,measurements of strain at a small force rather than zero force are often taken.
D ISCUSSION—Set is often referred to as permanent set if it shows no
further change with time.Time elapsing between removal of force and final reading of set should be stated.
shear modulus,G[FL–2],n—the ratio of shear stress to corresponding shear strain below the proportional limit,also called torsional modulus and modulus of rigidity.(E28.03)
D ISCUSSION—The value of the shear modulus may depend on the
direction in which it is measured if the material is not isotropic.Wood, many plastics and certain metals are markedly anisotropic.Deviations from isotropy should be suspected if the shear modulus differs from that determined by substituting independently measured values of Young’s modulus,E,and Poisson’s ratio,µ,in the relation:
G5E/[2~11µ!#
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D ISCUSSION—In general,it is advisable in reporting values of shear
modulus to state the range of stress over which it is measured. strain,e,n—the per unit change,due to force,in the size or shape of a body referred to its original size or shape.Strain is a nondimensional quantity,but it is frequently expressed in inches per inch,metres per metre,or percent.
D ISCUSSION—In this standard,“original”refers to dimensions or
shape of cross section of specimens at the beginning of testing.
D ISCUSSION—Strain at a point is defined by six components of strain:
three linear components and three shear components referred to a set of coordinate axes.
D ISCUSSION—In the usual tension,compression,or torsion test it is
customary to measure only one component of strain and to refer to this as“the strain.”In a tension or a compression test this is usually the axial component.
D ISCUSSION—Strain has an elastic and a plastic component.For small
strains the plastic component can be imperceptibly small.
D ISCUSSION—Linear thermal expansion,sometimes called“thermal
strain,”and changes due to the effect of moisture are not to be considered strain in mechanical testing.
angular strain,n—use shear strain.
axial strain,n—linear strain in a plane parallel to the longitu-dinal axis of the specimen.(E28.04) bending strain,n—the difference between the strain at the surface of the specimen and the axial strain.(E28.03,
E28.10 elastic true strain,e e,n—elastic component of the true strain. engineering strain,e,n—a dimensionless value that is the change in length(D L)per unit length of original linear dimension(L0)along the loading axis of the specimen;that is,e=(D L)/L0.(E28.02) linear(tensile or compressive)strain,n—the change per unit length due to force in an original linear dimension.
(E28.04)
D ISCUSSION—An increase in length is considered
positive.
macrostrain,n—the mean strain over anyfinite gage length of measurement large in comparison with interatomic dis-tances.(E28.13)
D ISCUSSION—Macrostrain can be measured by several methods,
including electrical-resistance strain gages and mechanical or optical extensometers.Elastic macrostrain can be measured by X-ray diffrac-tion.
D ISCUSSION—When either of the terms macrostrain or microstrain is
first used in a document,it is recommended that the physical dimension or the gage length,which indicate the size of the reference strain volume involved,be stated.
microstrain,n—the strain over a gage length comparable to interatomic distances.(E28.13)
D ISCUSSION—These are the strains being averaged by the macrostrain
measurement.Microstrain is not measurable by existing techniques.
Variance of the microstrain distribution can,however,be measured by X-ray diffraction.
D ISCUSSION—When either of the terms macrostrain or microstrain is
first used in a document,it is recommended that the physical dimension or the gage length,which indicate the size of the reference strain volume involved,be stated.
plastic true strain,e p,n—the inelastic component of true strain.
residual strain,n—strain associated with residual stress.
(E28.13)
D ISCUSSION—Residual strains are elastic.
shear strain,n—the tangent of the angular change,due to force,between two lines originally perpendicular to each other through a point in a body.(E28.04) transverse strain,n—linear strain in a plane perpendicular to the axis of the specimen.
D ISCUSSION—Transverse strain may differ with direction in anisotro-
pic materials.
true strain,e,n—the natural logarithm of the ratio of instan-taneous gage length,L,to the original gage length,L0;that is,e=1n(L/L0)or e=1n(1+e).(E28.02) strain hardening,n—an increase in hardness and strength caused by plastic deformation.(E28.02) stress[FL–2],n—the intensity at a point in a body of the forces or components of force that act on a given plane through the point.Stress is expressed in force per unit of area(for example,pounds-force per square inch,megapascals.).
D ISCUSSION—As used in tension,compression,or shear tests pre-
scribed in product specifications,stress is calculated on the basis of the original dimensions of the cross section of the specimen.This stress is sometimes called“engineering stress,”to emphasize the difference from true stress.
compressive stress[FL–2],n—normal stress due to forces directed toward the plane on which they act.(E28.04) engineering stress,S[FL−2],n—the normal stress,expressed in units of applied force,F,per unit of original cross-sectional area,A0;that is,S=F/A0.(E28.02) fracture stress[FL–2],n—the true normal stress on the mini-mum cross-sectional area at the beginning of fracture.
D ISCUSSION—This term usually applies to tension tests of unnotched
principal stress(normal)[FL–2],n—the maximum or mini-mum value of the normal stress at a point in a plane considered with respect to all possible orientations of the considered plane.On such principal planes the shear stress is zero.
D ISCUSSION—There are three principal stresses on three mutually
perpendicular planes.The states of stress at a point may be:
(1)uniaxial[FL–2],n—a state of stress in which two of the three
principal stresses are zero,
(2)biaxial[FL–2],n—a state of stress in which only one of the three
principal stresses is zero,or
(3)triaxial[FL–2],n—a state of stress in which none of the principal
stresses is zero.
(4)multiaxial[FL–2],n—biaxial or triaxial.
residual stress[FL–2],n—stress in a body which is at rest and in equilibrium and at uniform temperature in the absence of external and mass forces.(E28.13) shear stress[FL–2],n—the stress component tangential to the plane on which the forces act.(E28.04) tensile stress[FL–2],n—normal stress due to forces directed away from the plane on which they act.(E28.04) torsional stress[FL−2],n—the shear stress in a body,in a plane normal to the axis of rotation,resulting from the application of torque.(E28.03) true stress,s[FL−2],n—the instantaneous normal stress, calculated on the basis of the instantaneous cross-sectional area,A;that is,s=F/A;if no necking has occurred,s= S(1+e).(E28.02) stress-strain diagram,n—a diagram in which corresponding values of stress and strain are plotted against each other. Values of stress are usually plotted as ordinates(vertically) and values of strain as abscissas(horizontally).(E28.04) tension testing machine,CTR(constant rate of traverse), n—a mechanical device for applying a load(force)to a specimen and in which the force is measured by means of a pendulum.(E28.01) testing machine(force-measuring type),n—a mechanic
al device for applying a force to a specimen.(E28.01) torque[FL],n—a moment(of forces)that produces or tends to produce rotation or torsion.(E28.03) Young’s modulus,E[FL–2],n—the ratio of tensile or com-pressive stress to corresponding strain below the propor-tional limit of the material.(E28.03)
B.TENSION,COMPRESSION,SHEAR,AND
TORSION TESTING
alignment,n—the condition of a testing machine and load train(including the test specimen)that influences the intro-duction of bending moments into a specimen during tensile loading.(E28.04) angle of twist(torsion test),n—the angle of relative rotation measured in a plane normal to the torsion
specimen’s
longitudinal axis over the gage length.(E28.03) breaking force[F],n—the force at which fracture occurs.
(E28.04)
D ISCUSSION—When used in connection with tension tests of thin
materials or materials of small diameter for which it is often difficult to distinguish between the breaking force and the maximum force developed,the latter is considered to be the breaking force. compressive strength[FL–2],n—the maximum compressive stress which a material is capable of sustaining.Compressive strength is calculated from the maximum force during a compression test and the original cross-sectional area of the specimen.(E28.04)
D ISCUSSION—In the case of a material which fails in compression by
a shattering fracture,the compressive strength has a very definite value.
巴尔蒂斯In the case of materials which do not fail in compression by a shattering fracture,the value obtained for compressive strength is an arbitrary value depending upon the degree of distortion which is regarded as indicating complete failure of the material.
discontinuous yielding,n—a hesitation orfluctuation of force observed at the onset of plastic deformation,due to localized yielding.(E28.04)
D ISCUSSION—The stress-strain curve need not appear to be discon-
tinuous.
discontinuous yielding stress,n—the peak stress at the initiation of thefirst measurable serration on the curve of stress-versus strain.(E28.10) eccentricity,n—the distance between the line of action of the applied force and the axis of symmetry of the specimen in a plane perpendicular to the longitudinal axis of the specimen.
(E28.04) elongation,El,n—the increase in gage length of a body subjected to a tension force,referenced to a gage length on the body.Usually elongation is expressed as a percentage of the original gage length.(E28.04)
D ISCUSSION—The increase in gage length may be determined either at
or after fracture,as specified for the material under test.
D ISCUSSION—The term elongation,when applied to metals,generally
means measurement after fracture;when applied to plastics and elastomers,measurement at fracture.
Such interpretation is usually applicable to values of elongation reported in the literature when no further qualification is given.
D ISCUSSION—In reporting values of elongation the gage length shall
be stated.
D ISCUSSION—Elongation is affected by:specimen geometry;length,
width,thickness of the gage section and adjacent regions;and test procedure,such as alignment and speed of pulling.
fatigue life,N f,n—the numbers of cycles of stress or strain of a specified character that a given specimen sustains before failure of a specified nature occurs.(E28.04) strain gage fatigue life,n—the number of fully reversed strain cycles corresponding to the onset of degraded gage perfor-mance,whether due to excessive zero shift or other detect-able failure mode.(E28.14) lower yield strength,LYS[FL–2],n—the minimum stress recorded during discontinuous yielding,ignoring transient effects.See Figs.1and2.(E28.04) maximum elongation,El max,n—the elongation at the time of
fracture,including both elastic and plastic deformation of the tensile specimen.(E28.04)
D ISCUSSION—This definition is used for rubber,plastic,and some
metallic materials.
D ISCUSSION—Maximum elongation is also called ultimate elongation
or break elongation.
modulus of rupture in torsion[FL–2],n—the value of maximum shear stress in the extremefiber of a member of circular cross section loaded to failure in torsion computed from the equation:
S s5Tr/J(1) where:
T=maximum twisting moment,
r=original outer radius,and
J=polar moment of inertia of the original cross section.
(E28.04)
D ISCUSSION—When the proportional limit in shear is exceeded,the
modulus of rupture in torsion is greater than the actual maximum shear stress in the extremefiber,exclusive of the effect of stress concentration near points of application of torque.
D ISCUSSION—If the criterion for failure is other than fracture
or FIG.1Stress-Strain Diagram for Determination of Upper and Lower Yield Strengths and Yield Point Elongation in a Material
Exhibiting Discontinuous
Yielding
FIG.2Stress Strain Diagram Showing Yield Point Elongation and Upper and Lower Yield
Strengths
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