Oberreiter Matthias, Horvath Michael, Stoschka Michael, Fladischer Stefan
Christian Doppler Laboratory for Manufacturing Process Based Component Design, Chair of Mechanical Engineering, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, 8700 Leoben, Austria.
Chair of Mechanical Engineering, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, 8700 Leoben, Austria.
Materials (Basel). 2023 Jun 30;16(13):4755. doi: 10.3390/ma16134755.
The endurance limit of structural mechanical components is affected by the residual stress state, which depends strongly on the manufacturing process. In general, compressive residual stresses tend to result in an increased fatigue strength. Post-manufacturing processes such as shot peening or vibratory finishing may achieve such a compressive residual stress state. But within complex components, manufacturing-process-based imperfections severely limit the fatigue strength. Thus, the interactions of imperfections, residual stress state and material strength are key aspects in fatigue design. In this work, cast steel and aluminium alloys are investigated, each of them in vibratory finished and polished surface condition. A layer-based fatigue assessment concept is extended towards stable effective mean stress state considering the elastic-plastic material behaviour. Murakami's concept was applied to incorporate the effect of hardness change and residual stress state. Residual stress relaxation is determined by elastic-plastic simulations invoking a combined hardening model. If the effective stress ratio within the local layer-based fatigue strength is evaluated as critical distance value, a sound calculation of fatigue strength can be achieved. Summing up, the layer-based fatigue strength design is extended and features an enhanced understanding of the effective stabilized mean stress state during cyclic loading.
结构机械部件的疲劳极限受残余应力状态的影响，而残余应力状态很大程度上取决于制造工艺。一般来说，压缩残余应力往往会提高疲劳强度。喷丸处理或振动光饰等制造后处理工艺可以实现这种压缩残余应力状态。但在复杂部件中，基于制造工艺的缺陷会严重限制疲劳强度。因此，缺陷、残余应力状态和材料强度之间的相互作用是疲劳设计的关键因素。在这项工作中，对铸钢和铝合金进行了研究，它们分别处于振动光饰和抛光的表面状态。考虑弹塑性材料行为，将基于层的疲劳评估概念扩展到稳定的有效平均应力状态。应用村上的概念来纳入硬度变化和残余应力状态的影响。残余应力松弛通过调用组合硬化模型的弹塑性模拟来确定。如果将基于局部层的疲劳强度内的有效应力比评估为临界距离值，则可以实现对疲劳强度的合理计算。总之，基于层的疲劳强度设计得到了扩展，并且对循环加载过程中的有效稳定平均应力状态有了更深入的理解。
