Abstract

The abnormal behavior of monotonic stress-strain curves of aluminum alloys induced by the yield drop with increasing strain rate or decreasing temperature is considered based on the relaxation model of plasticity. The plastic deformation of 2519A and 2519A-T87 aluminum alloys within the strain rate range from 0.001 to 6000 s^–1 and temperature range from –45 to 450°С is analyzed from the standpoint of determining the structural and temporal characteristics of the material invariant to the strain rate. It is proposed to determine the change in the structural and temporal characteristics caused by the test temperature choice by analyzing a set of strain rate dependences of the material constructed at a fixed temperature. The temperature dependences of the characteristic relaxation time as a rate sensitivity factor of the relaxation plasticity model are compared for 2519A and 2519A-T87 aluminum alloys. Theoretical nonmonotonic stress-strain curves in a wide strain rate range of 0.001–6000 s^–1 are constructed at –45, 0, 20, 150°С, and nonmonotonic stress-strain curves at a fixed strain rate of 4300 s^–1 are plotted at temperatures of 150, 300, 450°С. The relaxation model of plasticity is shown to predict the yield stress within a wide range of temperatures and strain rates in accordance with the temperature-time superposition principle. The model also identifies the temperature-strain rate conditions of deformation in which monotonic curves (without the yield drop) are not observed with increasing strain rate.

中文翻译：

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2519A铝合金不可逆形变的温度-时间效应的预测

摘要

基于塑性松弛模型，考虑了屈服强度随应变率升高或温度降低而引起的铝合金单调应力-应变曲线的异常行为。2519A和2519A-T87铝合金在0.001至6000 s ^–1的应变速率范围内的塑性变形从确定应变速率不变的材料的结构和时间特性的角度分析了–45至450°С的温度范围。建议通过分析在固定温度下构造的材料的一组应变率依赖性来确定由测试温度选择引起的结构和时间特性的变化。对于2519A和2519A-T87铝合金，比较了特征驰豫时间的温度依赖性（作为驰豫塑性模型的速率敏感性因子）。在0.001-6000秒的宽应变速率范围理论非单调应力-应变曲线^-1在-45，0，20构成，150°С，和在4300秒的固定应变速率非单调应力-应变曲线^-1在150、300、450°С的温度下绘制曲线。根据温度-时间叠加原理，可塑性的松弛模型显示出可在宽温度和应变率范围内预测屈服应力。该模型还确定了变形的温度-应变速率条件，在该条件下，随着应变速率的增加，未观察到单调曲线（无屈服下降）。