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许多材料由于物理屈服点不明显,所以根据材料在服役中的不同要求,人为地规定在拉伸过程中标距部分的残余伸长达到原标距长度的0.1％或0.2％时的应力为这种材料的屈服强度。 由于σ_(0.1)和σ_(0.2)的测定方法相同,只是引伸计放大倍数和残余变形量△L不同,所以仅以测σ_(0.2)为例,对这种测量方法加以说明。 在国家标准GB228-76中,用引伸计法测σ_(0.2)有两种方法,一种是卸荷法,另一种是直接加荷法。直接加荷法测起来速度快、失误少,可靠性高,但是由于在测试当中计
Many materials due to the physical yield point is not obvious, so according to the different requirements of the material in service, artificially stipulated in the stretching process of the gauge length of the residual elongation reaches the original gauge length of 0.1% or 0.2% of the stress when this Yield strength of the material. Since the methods of measuring σ_ (0.1) and σ_ (0.2) are the same, only the magnification of extensometer and the residual deformation ΔL are different, so this measurement method will be described only by taking σ_ (0.2) as an example. In the national standard GB228-76, with extensometer method σ_ (0.2) there are two ways, one is the unloading method, and the other is the direct loading method. Direct loading method measured speed, fewer errors, high reliability, but as in the test