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单轴载荷下X80钢的包申格效应研究 总被引:2,自引:0,他引:2
本文通过单轴拉伸和压缩试验研究了X80管线钢的包申格效应(BE)。采用正向与反向加载方法研究材料变形历史特性。测定了X80钢的简单拉伸试验曲线,其应力-应变关系表明,该材料具有理想弹塑性特点。为了得到X80钢的BE,在不同预变形下对几个试件分别进行加载,并当给定的预应变值分别达到0.63%,0.67%,0.95%,1.27%和1.55%时就卸载。随后再进行反向加载实验,并记录应力应变曲线。该钢材反向加载时出现加工硬化,且屈服强度比正向加载时要低。正反向加载之间的屈服强度差值随着预应变增加而增大;当预应变超过0.95%时,反向屈服强度达到恒量。实验表明,X80钢的反向加载特性可用Remberg-Osgood关系拟合。最后给出了屈服强度降和预塑性应变之间的经验公式。 相似文献
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Summary A viscoelastic constitutive equation of rubber that is under small oscillatory load superimposed on large static deformation
is proposed. The model is derived through linearization of Simo's nonlinear viscoelastic constitutive model and reference
configuration transformation. Most importantly, in this model, static deformation correction factor is introduced to consider
the influence of pre-strain on the relaxation function. Natural statically pre-deformed state is served as reference configuration.
The proposed constitutive equation is extended to a generalized viscoelastic constitutive equation that includes widely used
Morman's model as a special case using objective stress increment. The proposed constitutive model is tested for dynamic behavior
of rubber specimens with different carbon black content. It is concluded from the test that the assumption that the effects
of static deformation can be separated from time effects, which is the basis of Morman's model, is only applicable to unfilled
rubber. The viscoelastic constitutive equation for filled rubber must include, therefore, the influence of the static deformation
on the time effects. The suggested constitutive equation with static deformation correction factor shows good agreement with
test values.
Received 4 January 2001; accepted for publication 13 June 2001 相似文献
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金属材料的中子辐照硬化和脆化一直都是核能安全领域十分关注的重要问题之一. 为了进一步认识预应变对中子辐照金属材料塑性形变和最终断裂特性的影响规律, 及其微观机理, 本文研究了10%拉伸预应变高纯铝的拉伸应力-应变曲线、失稳应力和失稳应变等随辐照剂量的变化规律. 结果表明, 辐照剂量越高, 预应变高纯铝内部孔洞的尺寸和数密度越高, 导致屈服强度和极限拉伸强度越高, 均匀延伸率和失稳应变越小, 表现出典型的辐照硬化和脆化效应, 但失稳应力与辐照剂量几乎无关. 相同辐照剂量条件下, 预应变引入的高密度位错能够显著降低辐照孔洞的尺寸和数密度, 加之辐照退火效应的综合影响, 导致预应变能够降低高纯铝屈服强度的增长率和失稳应变的下降率, 从而表现出一定的抑制辐照硬化和脆化的能力, 预应变还能够提高高纯铝的失稳应力, 但整体而言预应变并不能提高高纯铝的延性. 最后, 基于J-C本构模型的中子辐照退火态金属材料的脆化模型能够直接应用于预应变金属材料, 且模型预测结果与实验结果吻合较好. 相似文献
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对3种不同预应变量的碳素钢实施时效处理,并进行弯曲疲劳实验,实验结果表明:材料的疲劳极限同时受预应变量和时效处理温度的影响,使其疲劳极限为最大值时所对应的最优时效处理温度随预应变量的增大而降低。 相似文献
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