The nature of yielding and anelasticity in metals
The nature of yielding and anelasticity in metals
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金属屈服和迟弹性的本质
DOI：
10.1016/j.actamat.2021.116625
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发表时间：
2021-03-01
期刊：
影响因子：
9.4
通讯作者：
Wagoner, Robert H.
中科院分区：
文献类型：
--
作者：
Li, Dayong;Wagoner, Robert H.
最近的文献报告指出，在几乎所有应力下，金属中都会出现屈服前应力应变非线性和滞后(滞弹性)。这些观察结果提出了关于金属变形的基本问题。位错不能移动的临界应力是否存在？是否存在发生永久变形的临界应力？滞弹性不同于弹性和塑性吗？为了回答这些问题，对11种商业板材合金进行了不同预应变后加卸载循环的特殊拉伸试验：9种先进高强度钢和2种镁合金。推导了滞弹性的位错退出耗散模型，该模型能较好地再现实验结果，并与滞弹性演化的实验图像相一致。在预应变后，发现存在有限屈服应力，低于该屈服应力不会发生永久变形或硬化。滞弹性不同于弹性和可塑性：它是可恢复和耗散的；机械上是可逆的，热力学上是不可逆的。相应的初始载荷测试得出了截然不同的结论。在没有预应变的情况下，即没有发展的内应力模式，塑性变形发生在零应力附近。提出了考虑弹性、塑性和滞弹性变形的局部和非局部相互作用的假设。(C)《2021年》，由爱思唯尔有限公司代表Acta Materialia Inc.出版。
Recent reports in the literature identified pre-yield stress-strain nonlinearity and hysteresis (anelasticity) as occurring in metals at virtually all stresses. These observations raise foundational questions about metal deformation. Does a critical stress exist below which dislocations are immobile? Is there a critical stress for which permanent deformation occurs? Is anelasticity distinct from elasticity and plasticity? To answer such questions, special tensile tests with loading-unloading cycles after various prestrains were performed for 11 commercial sheet alloys: 9 AHSS (advanced high strength steels) and two Mg alloys. A dissipative dislocation bow-out model of anelasticity was derived that closely reproduces the experimental results and is consistent with the evolving experimental picture of anelasticity. Following prestrain, a finite yield stress was found to exist, below which no permanent deformation or hardening occurs. Anelasticity is distinct from elasticity and plasticity: it is recoverable and dissipative; mechanically reversible and thermodynamically irreversible. Corresponding tests of initial loading suggest radically different conclusions. Without prestrain, i.e. without a developed internal stress pattern, plastic deformation occurs near zero stress. A postulate of local and nonlocal interactions accounting for elastic, plastic and anelastic deformation was proposed. (C) 2021 Published by Elsevier Ltd on behalf of Acta Materialia Inc.