【英文标准名称】: Standard Test Method for Tensile Strain-Hardening Exponents (n -Values) of Metallic Sheet Materials 【原文标准名称】: 金属薄板材拉伸应变硬化指数(n值)的标准试验方法 【标准号】: ASTM E646-2007 【标准状态】: 现行 【国别】: 【发布日期】: 2007 【实施或试行日期】: 【发布单位】: 美国材料与试验协会(US-ASTM)【起草单位】: E28.02【标准类型】: (Test Method)【标准水平】: ()【中文主题词】: 指数;机械测试;金属;薄板材;拉伸应变;测试【英文主题词】: 【摘要】: This test method is useful for estimating the strain at the onset of necking in a uniaxial tension test (1). Practically, it provides an empirical parameter for appraising the relative stretch formability of similar metallic systems. The strain-hardening exponent is also a measure of the increase in strength of a material due to plastic deformation. The strain-hardening exponent may be determined over the entire plastic stress-strain curve or any portion(s) of the stress-strain curve specified in a product specification. Note 38212;The strain interval 10x2013;20% is commonly utilized for determining the n-value of formable low carbon steel products. This test method is not intended to apply to any portion of the true-stress versus true-strain curve that exhibits discontinuous behavior; however, the method may be applied by curve-smoothing techniques as agreed upon. Note 48212;For example, those portions of the stress-strain curves for mild steel or aluminum alloys which exhibit yield-point elongation or Luuml;ders bands may be characterized as behaving discontinuously. Note 58212;Caution should be observed in the use of curve-smoothing techniques as they may affect the n-value. This test method is suitable for determining the tensile stress-strain response of metallic sheet materials in the plastic region prior to the onset of necking. The n-value may vary with the displacement rate or strain rate used, depending on the metal and test temperature.1.1 This test method covers the determination of a strain-hardening exponent by tension testing of metallic sheet materials for which plastic-flow behavior obeys the power curve given in the Introduction. Note 18212;A single power curve may not fit the entire stress-strain curve between yield and necking. If such is the case, more than one value of the strain-hardening exponent can be obtained (2). 1.2 This test method is for metallic sheet materials with thicknesses of at least 0.005 in. (0.13 mm) but not greater than 0.25 in. (6.4 mm). 1.3 The values stated in inch-pound units are to be regarded as the standard. The SI equivalents shown may be approximate. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 【中国标准分类号】: H22【国际标准分类号】: 77_140_50【页数】: 9P.;A4【正文语种】: 作者: lj1993qf 时间: 2016-12-28 16:34:59