Abstract Many structural materials exhibit stress-regime-dependent anisotropy of inelastic responses. Examples are age-hardening aluminium alloys forgings. Experimental creep curves indicate that inelastic strain rates depend significantly on the loading direction within the power law regime, while in the power law breakdown range the anisotropy is weak and can be neglected. The aim of this paper is to analyze anisotropic behavior of forged AA2014 alloy and to develop a constitutive model to describe inelastic response under multi-axial stress state. Microstructural observations suggest that the anisotropy is primarily caused by elongated grains and coarse particles on grain boundaries. To account for inhomogeneous inelastic deformation and stress redistribution in different microstructural zones a composite model is developed. Constitutive equations for inelastic-hard and inelastic-soft constituents and anisotropic rules for mechanical interactions between them are elaborated. Hardening/recovery and overageing processes in grain interiors are characterized by internal state variables and kinetic equations. The model is calibrated against families of creep curves for two loading directions in a wide stress and temperature ranges. For the validation, creep tests under the loading with the angle of 30∘ relative to the longitudinal grain axis as well as tensile tests are simulated by the model and results are compared with experimental data.

中文翻译：

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高温锻造时效硬化铝合金非弹性各向异性的应力状态依赖性。本构建模、识别和验证

摘要 许多结构材料表现出非弹性响应的应力状态相关的各向异性。例子是时效硬化铝合金锻件。实验蠕变曲线表明，非弹性应变率在幂律范围内显着取决于加载方向，而在幂律击穿范围内，各向异性很弱，可以忽略不计。本文的目的是分析锻造 AA2014 合金的各向异性行为，并开发一个本构模型来描述多轴应力状态下的非弹性响应。微观结构观察表明，各向异性主要是由晶粒边界上的细长晶粒和粗颗粒引起的。为了说明不同微观结构区域中的非均匀非弹性变形和应力重新分布，开发了一个复合模型。详细阐述了非弹性硬和非弹性软成分的本构方程以及它们之间机械相互作用的各向异性规则。晶粒内部的硬化/恢复和过时效过程由内部状态变量和动力学方程表征。该模型是针对宽应力和温度范围内的两个加载方向的蠕变曲线族进行校准的。为了验证，模型模拟了与纵向晶粒轴成30∘角的加载蠕变试验以及拉伸试验，并将结果与​​实验数据进行了比较。晶粒内部的硬化/恢复和过时效过程由内部状态变量和动力学方程表征。该模型是针对宽应力和温度范围内两个加载方向的蠕变曲线族进行校准的。为了验证，模型模拟了与纵向晶粒轴成30∘角的加载蠕变试验以及拉伸试验，并将结果与​​实验数据进行了比较。晶粒内部的硬化/恢复和过时效过程由内部状态变量和动力学方程表征。该模型是针对宽应力和温度范围内两个加载方向的蠕变曲线族进行校准的。为了验证，模型模拟了与纵向晶粒轴成30∘角的加载蠕变试验以及拉伸试验，并将结果与​​实验数据进行了比较。