An holistic view is attempted towards prediction of the effect of residual stresses induced by full-forward extrusion on fatigue life of workpieces during operation. To study the effect of constitutive model on the accuracy of forming simulations, a combined nonlinear isotropic/kinematic hardening model as well as the isotropic hardening part of the same model are calibrated based on five compression-tension-compression uniaxial stress experiments. A full-forward extrusion finite element model is developed adapting both the aforementioned hardening plasticity models and the predicted residual stress states at the surface of the workpiece are compared against that of a corresponding forming experiment. Results show residual stress predictions of remarkable accuracy by the FE-models with the isotropic hardening model. The effect of residual stresses on fatigue life of the workpiece is qualitatively studied by uncoupled multiscale simulations featuring gradient crystal plasticity at the microscale. While the effective (homogenized) macroscale response indicates elastic response during a macroscopically cyclic loading, plasticity accompanying reduction of residual stresses is still present at the microscale within, e.g. grain boundaries.

试图从整体角度来预测由全向挤压引起的残余应力对操作过程中工件的疲劳寿命的影响。为了研究本构模型对成形模拟精度的影响，基于五个压缩-拉伸-压缩单轴应力实验，对非线性各向同性/运动硬化组合模型以及该模型的各向同性硬化部分进行了校准。利用上述硬化塑性模型，开发了全前向挤压有限元模型，并将工件表面的预测残余应力状态与相应的成形实验进行了比较。结果表明，采用各向同性硬化模型的有限元模型预测了具有显着精度的残余应力。通过在微观尺度上具有梯度晶体可塑性的无耦合多尺度模拟，定性地研究了残余应力对工件疲劳寿命的影响。尽管有效的（均质的）宏观响应表示在宏观循环加载过程中的弹性响应，但伴随残余应力降低的可塑性仍存在于例如晶粒边界内的微观尺度上。