Designation:D256–06
Standard Test Methods for
Determining the Izod Pendulum Impact Resistance of Plastics1
This standard is issued under thefixed designation D256;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
1.Scope*
1.1The test methods cover the determination of the resistance of plastics to“standardized”(e Note1)pendulum-type hammers,mounted in“standardized”machines,in break-ing standard specimens with one pendulum swing(e Note2). The standard tests for the test methods require specimens made with a milled notch(e Note3).In Test Methods A,C, and D,the notch produces a stress concentration that increas the probability of a brittle,rather than a ductile,fracture.In Test Method E,the impact resistance is obtained by reversing the notched specimen180°in the clamping vi.The results of all test methods are reported in terms of energy absorbed per unit of specimen width or per unit of cross-ctional area under the notch.(See Note4.)
N OTE1—The machines with their pendulum-type hammers have been “standardized”in that they must comply with certain requirements, including afixed height of hammer fall that results in a substantiallyfixed velocity of the hammer at the moment of impact.However,hammers of different initial energies(produced by varying their effective weights)are recommended for u with specimens of different impact resistance. Moreover,manufacturers of the equipment are permitted to u different lengths and constructions of pendulums with possible differences in pendulum rigidities resulting.(See Section5.)Be aware that other differences in machine design may exist.The specimens are“standard-ized”in that they are required to have onefixed length,onefixed depth, and one particular design of milled notch.The width of the specimens is permitted to vary between limits.
N OTE2—Results generated using pendulums that utilize a load cell to record the impact force and thus impact energy,may not be equivalent to results that are generated using manually or digitally encoded testers that measure the energy remaining in the pendulum after impact.
N OTE3—The notch in the Izod specimen rves to concentrate the stress,minimize plastic deformation,and direct the fracture to the part of the specimen behind the notch.Scatter in energy-to-break is thus reduced. However,becau of differences in the elastic and viscoelastic properties of plastics,respon to a given notch varies among materials.A measure of a plastic’s“notch nsitivity”may be obtained with Test Method D by comparing the energies to break specimens having different radii at the ba of the notch.
N OTE4—Caution must be exercid in interpreting the results of the standard test methods.The following testing parameters may affect test results significantly:
Method of fabrication,including but not limited to processing
technology,molding conditions,mold design,and thermal
treatments;
Method of notching;
Speed of notching tool;
Design of notching apparatus;
Quality of the notch;
Time between notching and test;
Test specimen thickness,
Test specimen width under notch,and
Environmental conditioning.
1.2The values stated in SI units are to be regarded as standard.The values given in brackets are for information only.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health prac
tices and determine the applica-bility of regulatory limitations prior to u.
N OTE5—The test methods remble ISO180:1993in regard to title only.The contents are significantly different.图片转换成excel文件
2.Referenced Documents
2.1ASTM Standards:2
D618Practice for Conditioning Plastics for Testing
D883Terminology Relating to Plastics
D3641Practice for Injection Molding Test Specimens of Thermoplastic Molding and Extrusion Materials
D4066Classification System for Nylon Injection and Ex-trusion Materials(PA)
D5947Test Methods for Physical Dimensions of Solid Plastics Specimens
E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2ISO Standard:
ISO180:1993Plastics—Determination of Izod Impact
1The test methods are under the jurisdiction of ASTM Committee D20on Plastics and are the direct responsibility of Subcommittee D20.10on Mechanical Properties.
红岭社区
Current edition approved March15,2006.Published March2006.Originally approved in1926.Last previous edition approved in2005as D256-05a.
借物喻人的古诗2For referenced ASTM standards,visit the ASTM website,www.astm,or contact ASTM Customer Service at rvice@astm.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes ction appears at the end of this standard. Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
Strength of Rigid Materials3
3.Terminology
3.1Definitions—For definitions related to plastics e Terminology D883.
3.2Definitions of Terms Specific to This Standard:
3.2.1cantilever—a projecting beam clamped at only one end.
3.2.2notch nsitivity—a measure of the variation of impact energy as a function of notch radius.
4.Types of Tests
4.1Four similar methods are prented in the test meth-ods.(See Note6.)All test methods u the same testing machine and specimen dimensions.There is no known means for correlating the results from the different test methods.
N OTE6—Test Method B for Charpy has been removed and is being revid under a new standard.
4.1.1In Test Method A,the specimen is held as a vertical cantilever beam and is broken by a single swing of the pendulum.The line of initial contact is at afixed distance from the specimen clamp and from the centerline of the notch and on
the same face as the notch.
4.1.2Test Method C is similar to Test Method A,except for the addition of a procedure for determining the energy ex-pended in tossing a portion of the specimen.The value reported is called the“estimated net Izod impact resistance.”Test Method C is preferred over Test Method A for materials that have an Izod impact resistance of less than27J/m[0.5 ft·lbf/in.]under notch.(See Appendix X4for optional units.) The differences between Test Methods A and C become unimportant for materials that have an Izod impact resistance higher than this value.
4.1.3Test Method D provides a measure of the notch nsitivity of a material.The stress-concentration at the notch increas with decreasing notch radius.
4.1.3.1For a given system,greater stress concentration results in higher localized rates-of-strain.Since the effect of strain-rate on energy-to-break varies among materials,a mea-sure of this effect may be obtained by testing specimens with different notch radii.In the Izod-type test it has been demon-strated that the function,energy-to-break versus notch radius, is reasonably linear from a radius of0.03to2.5mm[0.001to 0.100in.],provided that all specimens have the same type of break.(See
5.8and22.1.)
4.1.3.2For the purpo of this test,the slope,b(e22.1), of the line between radii of0.25and1.0mm[0.010and0.040 in.]is ud,unless tests with the1.0-mm radius give“non-break”results.In that ca,0.25and0.50-mm[0.010and 0.020-in.]radii may be ud.The effect of notch radius on the impact energy to break a specimen under the conditions of this test is measured by the value b.Materials with low values of b, whether high or low energy-to-break with the standard notch, are relatively innsitive to differences in notch radius;while the energy-to-break materials with high values of b is highly dependent on notch radius.The parameter b cannot be ud in design calculations but may rve as a guide to the designer and in lection of materials.
4.2Test Method E is similar to Test Method A,except that the specimen is reverd in the vi of the machine180°to the usual striking position,such that the striker of the apparatus impacts the specimen on the face opposite the notch.(See Fig. 1,Fig.2.)Test Method E is ud to give an indication of the unnotched impact resistance of plastics;however,results ob-tained by the reverd notch method may not always agree with tho obtained on a completely unnotched specimen.(See 28.1.)4,5
5.Significance and U
5.1Before proceeding with the test methods,reference should be made to the specification of the material being tested. Any test specimen preparation,conditioning,dimensions,and testing parameters covered in the materials specification shall take precedence over tho mentioned in the test methods.If there is no material specification,then the default conditions apply.
5.2The pendulum impact test indicates the energy to break standard test specimens of specified size under stipulated parameters of specimen mounting,notching,and pendulum velocity-at-impact.
5.3The energy lost by the pendulum during the breakage of the specimen is the sum of the following:
5.3.1Energy to initiate fracture of the specimen;
5.3.2Energy to propagate the fracture across the specimen;
3Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036.
4Supporting data giving results of the interlaboratory tests are available from ASTM Headquarters.Request RR:D20-1021.
5Supporting data giving results of the interlaboratory tests are available from ASTM Headquarters.Request RR:
D20-1026.
FIG.1Relationship of Vi,Specimen,and Striking Edge to Each Other for Izod Test Methods A and
C
5.3.3Energy to throw the free end (or ends)of the broken specimen (“toss correction”);
5.3.4Energy to bend the specimen;
5.3.5Energy to produce vibration in the pendulum arm;5.3.6Energy to produce vibration or horizontal movement of the machine frame or ba;
5.3.7Energy to overcome friction in the pendulum bearing and in the indicating mechanism,and to overcome windage (pendulum air drag);
5.3.8Energy to indent or deform plastically the specimen at the line of impact;and
5.3.9Energy to overcome the friction caud by the rubbing of the striker (or other part of the pendulum)over the face of the bent specimen.
5.4For relatively brittle materials,for which fracture propa-gation energy is small in comparison with the fracture initiation energy,the indicated impact energy absorbed is,for all practical purpos,the sum of factors 5.3.1and 5.3.3.The toss correction (e 5.3.3)may reprent a very large fraction of the total energy absorbed when testing relatively den and brittle materials.Test Method C shall be ud for materials that have an Izod impact resistance of less than 27J/m [0.5ft·lbf/in.].(See Appendix X4for optional units.)The toss correction obtained in Test Method C is only an approximation of the toss error,since the rotational and rectilinear velocities may not be the same during the re-toss of the specimen as for the original toss,and becau stored stress in the specimen may have been relead as kinetic energy during the specimen fracture.5.5For tough,ductile,fiber filled,or cloth-laminated mate-rials,the fracture propagation energy (e 5.3.2)may be large compared to the fracture initiation energy (e 5.3.1).When testing the materials,factors (e 5.3.2,5.3.5,and 5.3.9)can become quite significant,even when the specimen is accurately machined and positioned and the machine is in good condition
红头文件制作with adequate capacity.(See Note 7.)Bending (e 5.3.4)and indentation loss (e 5.3.8)may be a
ppreciable when testing soft materials.
N OTE 7—Although the frame and ba of the machine should be sufficiently rigid and massive to handle the energies of tough specimens without motion or excessive vibration,the design must ensure that the center of percussion be at the center of strike.Locating the striker precily at the center of percussion reduces vibration of the pendulum arm when ud with brittle specimens.However,some loss due to pendulum arm vibration,the amount varying with the design of the pendulum,will occur with tough specimens,even when the striker is properly positioned.
5.6In a well-designed machine of sufficient rigidity and mass,the loss due to factors 5.3.6and 5.3.7should be very small.Vibrational loss (e 5.3.6)can be quite large when wide specimens of tough materials are tested in machines of insufficient mass,not curely fastened to a heavy ba.
5.7With some materials,a critical width of specimen may be found below which specimens will appear ductile,as evidenced by considerable drawing or necking down in the region behind the notch and by a relatively high-energy absorption,and above which they will appear brittle as evidenced by little or no drawing down or necking and by a relatively low-energy absorption.Since the methods permit a variation in the width of the specimens,and since the width dictates,for many materials,whet
竹鸡是保护动物吗her a brittle,low-energy break or a ductile,high energy break will occur,it is necessary that the width be stated in the specification covering that material and that the width be reported along with the impact resistance.In view of the preceding,one should not make comparisons between data from specimens having widths that differ by more than a few mils.
5.8The type of failure for each specimen shall be recorded as one of the four categories listed as follows:
C =Complete Break —A break where the specimen parates into two or more pieces.
H =
Hinge Break —An incomplete break,such that one part of the specimen cannot support itlf above the horizontal when the other part is held vertically (less than 90°included angle).
P =
Partial Break —An incomplete break that does not meet the definition for a hinge break but has frac-tured at least 90%of the distance between the vertex of the notch and the opposite side.
NB =
Non-Break —An incomplete break where the frac-ture extends less than 90%of the distance be-tween the vertex of the notch and the opposite side.
For tough materials,the pendulum may not have the energy necessary to complete the breaking of the extreme fibers and toss the broken piece or pieces.Results obtained from “non-break”specimens shall be considered a departure from stan-dard and shall not be reported as a standard result.Impact resistance cannot be directly compared for any two materials that experience different types of failure as defined in the test method by this code.Averages reported must likewi be derived from specimens contained within a single failure category.This letter code shall suffix the reported impact identifying the types of failure associated with the reported value.If more than one type of failure is obrved for a sample material,then the report will indicate the average
impact
FIG.2Relationship of Vi,Specimen,and Striking Edge to Each
Other for Test Method
E
resistance for each type of failure,followed by the percent of the specimens failing in that manner and suffixed by the letter code.
5.9The value of the impact methods lies mainly in the areas of quality control and materials specification.If two groups of specimens of suppodly the same material show significantly different energy absorptions,types of breaks,critical widths,or critical temperatures,it may be assumed that they were made of different materials or were expod to different processing or conditioning environments.The fact that a material shows twice the energy absorption of another under the con
ditions of test does not indicate that this same relationship will exist under another t of test conditions.The order of toughness may even be reverd under different testing conditions.
N OTE8—A documented discrepancy exists between manual and digital impact testers,primarily with thermot materials,including phenolics, having an impact value of less than54J/m[1ft-lb/in.].Comparing data on the same material,tested on both manual and digital impact testers, may show the data from the digital tester to be significantly lower than data from a manual tester.In such cas a correlation study may be necessary to properly define the true relationship between the instruments.
TEST METHOD A—CANTILEVER BEAM TEST
6.Apparatus
6.1The machine shall consist of a massive ba on which is mounted a vi for holding the specimen and to which is connected,through a rigid frame and bearings,a pendulum-type hammer.(See 6.2.)The machine must also have a pendulum holding and releasing mechanism and a mechanism for indicating the breaking energy of the specimen.
6.2A jig for positioning the specimen in the vi and graphs or tables to aid in the calculation of the correction for friction and windage also should be included.One type of machine is shown in Fig.3.One design of specimen-positioning jig is illustrated in Fig.4.Detailed requirements are given in subquent paragraphs.General test methods for checking and calibrating the machine are given in Appendix X2.Additional instructions for adjusting a particular machine should be supplied by the manufacturer.
6.3The pendulum shall consist of a single or multi-membered arm with a bearing on one end and a head, containing the striker,on the other.The arm must be suffi-ciently rigid to maintain the proper clearances and geometric relationships between the machine parts and the specimen and to minimize vibrational energy loss that are always included in the measured impact resistance.Both simple and compound pendulum designs may comply with this test method.
6.4The striker of the pendulum shall be hardened steel and
shall be a cylindrical surface having a radius of curvature of 0.8060.20mm[0.03160.008in.]with its axis horizontal and perpendicular to the plane of swing of the pendulum.The line of contact of the striker shall be located at the center of percussion of the pendulum within62.54mm[60.100in.] (See N
ote9.)Tho portions of the pendulum adjacent to the cylindrical striking edge shall be recesd or inclined at a suitable angle so that there will be no chance for other than this cylindrical surface coming in contact with the specimen during the break.
N OTE9—The distance from the axis of support to the center of percussion may be determined experimentally from the period of small amplitude oscillations of the pendulum by means of the following equation:
L5~g/4p2!p2
where:
L=distance from the axis of support to the center of percussion,m or
[ft],
FIG.3Cantilever Beam(Izod-Type)Impact
Machine FIG.4Jig for Positioning Specimen for
Clamping
g=local gravitational acceleration(known to an accuracy of one part in one thousand),m/s2or[ft/s2],
p= 3.1416(4p2=39.48),and
p=period,s,of a single complete swing(to and fro)determined by averaging at least20concutive and uninterrupted swings.The
angle of swing shall be less than5°each side of center.日记格式图片
6.5The position of the pendulum holding and releasing mechanism shall be such that the vertical height of fall of the striker shall be61062mm[24.060.1in.].This will produce a velocity of the striker at the moment of impact of approxi-mately3.5m[11.4ft]/s.(See Note10.)The mechanism shall be so constructed and operated that it will relea the pendulum without imparting acceleration or vibration
to it.
N OTE10—
V5~2gh!0.5
where:
V=velocity of the striker at the moment of impact(m/s),
g=local gravitational acceleration(m/s2),and
h=vertical height of fall of the striker(m).
This assumes no windage or friction.
6.6The effective length of the pendulum shall be between 0.33and0.40m[12.8and16.0in.]so that the required elevation of the striker may be obtained by raising the pendulum to an angle between60and30°above the horizontal.
6.7The machine shall be provided with a basic pendulum capable of delivering an energy of2.760.14
J[2.0060.10 ft·lbf].This pendulum shall be ud with all specimens that extract less than85%of this energy.Heavier pendulums shall be provided for specimens that require more energy to break. The may be parate interchangeable pendulums or one basic pendulum to which extra pairs of equal calibrated weights may be rigidly attached to opposite sides of the pendulum.It is imperative that the extra weights shall not significantly change the position of the center of percussion or the free-hanging rest point of the pendulum(that would conquently take the machine outside of the allowable calibration tolerances).A range of pendulums having energies from2.7to21.7J[2to16 ft·lbf]has been found to be sufficient for u with most plastic specimens and may be ud with most machines.A ries of pendulums such that each has twice the energy of the next will be found convenient.Each pendulum shall have an energy within60.5%of its nominal capacity.
6.8A vi shall be provided for clamping the specimen rigidly in position so that the long axis of the specimen is vertical and at right angles to the top plane of the vi.(See Fig.
1.)This top plane shall bict the angle of the notch with a tolerance of0.12mm[0.005in.].Correct positioning of the specimen is generally done with a jig furnished with the machine.The top edges of thefixed and moveable jaws shall have a radius of0.2560.12mm[0.01060.005in.].For specimens who thickness approaches the lower limiting value of3.00mm[0.118in.],means shall be provided to
prevent the lower half of the specimen from moving during the clamping or testing operations(e Fig.4and Note11.)
N OTE11—Some plastics are nsitive to clamping pressure;therefore, cooperating laboratories should agree upon some means of standardizing the clamping force.One method is using a torque wrench on the screw of the specimen vi.If the faces of the vi or specimen are notflat and parallel,a greater nsitivity to clamping pressure may be evident.See the calibration procedure in Appendix X2for adjustment and correction instructions for faulty instruments.
6.9When the pendulum is free hanging,the striking surface shall come within0.2%of scale of touching the front face of a standard specimen.During an actual swing this element shall make initial contact with the specimen on a line22.0060.05 mm[0.8760.002in.]above the top surface of the vi. 6.10Means shall be provided for determining the energy expended by the pendulum in breaking the specimen.This is accomplished using either a pointer and dial mechanism or an electronic system consisting of a digital indicator and nsor (typically an encoder or resolver).In either ca,the indicated breaking energy is determined by detecting the height of ri of the pendulum beyond the point of impact in terms of energy removed from that specific pendulum.Since the indicated energy must be corrected for pendulum-bearing friction, pointer friction,pointer inertia,and pendulum windag
e,in-structions for making the corrections are included in10.3and Annex A1and Annex A2.If the electronic display does not automatically correct for windage and friction,it shall be incumbent for the operator to determine the energy loss manually.(See Note12.)
N OTE12—Many digital indicating systems automatically correct for windage and friction.The equipment manufacturer may be consulted for details concerning how this is performed,or if it is necessary to determine the means for manually calculating the energy loss due to windage and friction.
压岁钱英文6.11The vi,pendulum,and frame shall be sufficiently rigid to maintain correct alignment of the hammer and speci-men,both at the moment of impact and during the propagation of the fracture,and to minimize energy loss due to vibration. The ba shall be sufficiently massive that the impact will not cau it to move.The machine shall be so designed,con-structed,and maintained that energy loss due to pendulum air drag(windage),friction in the pendulum bearings,and friction and inertia in the indicating mechanism are held to a minimum.
6.12A check of the calibration of an impact machine is difficult to make under dynamic conditions.The basic param-eters are normally checked under static conditions;if the machine pas
s the static tests,then it is assumed to be accurate.The calibration procedure in Appendix X2should be ud to establish the accuracy of the equipment.However,for some machine designs it might be necessary to change the recommended method of obtaining the required calibration measurements.Other methods of performing the required checks may be substituted,provided that they can be shown to result in an equivalent accuracy.Appendix X1also describes a dynamic test for checking certain features of the machine and specimen.
6.13Micrometers—Apparatus for measurement of the width of the specimen shall comply with the requirements of Test Methods D594
7.Apparatus for the measurement of the depth of plastic material remaining in the specimen under the notch shall comply with requirements of Test Methods D5947, provided however that the one anvil or presr foot shall be a tapered blade conforming to the dimensions given in Fig.5新津黄辣丁
.
