ASTM B557M-02a pdf free.Standard Test Methods of Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products [Metric]
Changes in the strain rate can effect the yieldstrength, tensile strength, and elongation values, especially formaterials which are highly strain-rate sensitive. In general,yield strength and tensile strength will increase with increasingstrain rate, although the effect on tensile strength is generallyless pronounced. Elongation values generally decrease as thestrain rate increases.Aluminum alloys at room temperature arenot highly strain-rate sensitive; some exhibit a slightly higheryield strength with increasing strain rate while others show theopposite effect.Brittle materials require careful specimen prepara-tion, high-quality surface finishes, large fillets at the ends of thegage length,oversize threaded grip sections,and cannottolerate punch or scribe marks as gage length indicators. Flattening of tubular products to permit testing doesalter the material properties,generally nonuniformly,in theflattened region which may affect test results.Measurement errors that can affect test results in-clude: verification of the test force,extensometers,microme-ters,dividers,and other measurement devices,alignment andzeroing of chart recording devices, and so forth. Measurement of the dimensions of as-cast, as-rolled,as-forged,and other fest specimens with non-machined sur-faces may be imprecise due to the irregularity of the surfaceflatness.If any portion of the fracture occurs outside of themiddle of the gage length, or in a punch or scribe mark withinthe gage length, the elongation may not be representative of thematerial. Wire specimens that break at or within the grips maynot produce test results representative of the material.Because standard reference materials with certifiedtensile property values are not available, it is not possible torigorously define the bias of tension tests.However, by the useof carefully designed and controlled interlaboratory studies, areasonable definition of the precision of tension test results canbe obtained.
The consistency of agreement for repeated tests of thesame material is dependent on the homogeneity of the material,and the repeatability of specimen preparation, test conditions,and measurements of the tension test parameters.Instrumental factors that can affect test results in-clude: the stiffness,damping capacity,natural frequency,andmass of the tensile test machine,the accuracy of forceindication and the use of forces within the verified range for themachine,rate of force application,alignment of the testspecimen with the applied force, parallelism of the grips,grippressure, nature of the force control used, appropriateness andcalibration of extensometers used, and so forth.ASTM B557M pdf download.
ASTM B557M-02a pdf free
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