Use of creep-plastic analysis methods to predict complex non-isothermal loading cycle crack growth and nucleation behaviour

由RR开发的蠕变和塑性模型已被证明为名义上复杂的疲劳和裂纹扩展行为提供了有价值的见解。使用蠕变塑性有限元分析预测的稳定应力作为寿命相关性的基础，解决了疲劳试验中观察到的许多不寻常的趋势，例如在极端温度以外的任何温度下，更长的停留时间都能提供更高的疲劳寿命。裂纹尖端应力场的蠕变塑性模型允许开发高温延迟模型，预测从高应力水平卸载到中等应力水平后没有时间依赖性裂纹扩展的潜伏期。该项目建议进一步探索裂纹尖端和缺口的非线性应力分析能力，以解决与复杂加载循环相关的许多长期问题，如阈值行为，低温和高温迟滞、疲劳散射和平均应力效应。从非线性有限元分析中获得的理解将用于开发适合组件寿命的上述影响的模型。

Models developed by RR for creep and plasticity have been shown to provide a valuable insight into nominally complex fatigue and crack growth behaviour. Using stabilised stresses predicted by creep-plastic finite element analyses as the basis for lifing correlations has resolved many of the unusual observed trends in fatigue tests such as longer dwell times giving higher fatigue lives at all but extreme temperatures. Creep-plastic modelling of crack tip stress fields has allowed high temperature retardation models to be developed that predict incubation periods where no time dependent crack growth occurs following unloading from a high to an intermediate stress levelThis project proposes to explore the capabilities of non-linear stress analyses of crack tips and notches further to resolve a number of long-standing issues related to complex loading cycles such as threshold behaviour, low and high temperature retardation, fatigue scatter and mean stress effects. The understanding gained from the non-linear FE analyses will be used to develop models for the above effects that will be suitable for component lifing.