铝合金筋板蠕变全过程的Graham改进模型研究

Research on the improved Graham model for aluminum-based alloy stiffened panel under the whole creep aging process

采用分离模型推导了铝合金筋板的循环弹塑性在蠕变全过程的应力-应变增量关系,并用塑性增量及蠕变理论分析了筋板在温度场及应力应变场作用下的热弹塑性-蠕变力学性质。将蠕变应变增量以初应变形式置入ANSYS隐式蠕变方程中,推导出包含初应力和初应变过程的Graham改进模型。用提出的Graham改进模型对四应力水平下的筋板蠕变实验数据进行拟合,并对比分析。结果表明,拟合结果能够较好地表征铝合金筋板在不同应力水平下不同蠕变阶段的蠕变特性,且对高应力水平的加速蠕变特性具有很好的适用性。同时,Graham改进模型和传统模型的有限元模拟预测结果进一步验证了在同一位置时改进模型的误差更小,拟合效果更好。

The stress-strain increment relationship on the cyclic elasto-plastic behaviors of stiffened panel in the whole creep process is derived by the separation model. Based on the theory of plastic increment and creep theory, the thermo-elastic-plastic-creep mechanical properties of aluminum alloy plates with ribs under the action of temperature field and stress strain field are analyzed. The creep strain increment is embedded into the implicit creep equation for ANSYS in the form of initial strain, and then, an improved Graham model with initial stress and initial strain is derived. Meanwhile, compared to the creep data of the stiffened plates under the four stress levels, the fitting results of the improved Graham model can well describe the creep characteristics of aluminum alloy plate with ribs under different creep stages at different creep levels, and it has better suitability to the tertiary creep characteristics at high stress levels. In addition, the prediction results of finite element simulation, Graham improved model and the traditional model verify that the errors between the fitting curves of simulation results and the experimental results at the same position are smaller and the corresponding fitting effect are better.