Microstructure-informed, predictive crystal plasticity finite element model of fatigue-dwells

Abstract

Crystal plasticity finite element (CPFE) modelling is an effective tool from which detailed information on the meso-scale behaviour of crystalline metallic systems can be extracted and used, not only to enhance the understanding of material behaviour under different loading conditions, but also to improve the structural integrity assessment of engineering components. To be of full benefit however it must be demonstrated to not only predict the average global response of the material, but also the local behaviour, to provide insight into localised regions of stress and plastic strain. In this study, a slip system based constitutive model is developed to improve the simulation capability of time independent and time dependent plasticity. Comparison has been made between the macro-mechanical behaviour predicted by the model and previous experiments carried out at engineering length scale. Critically, the macromechanical behaviour predicted by the model has been examined against the behaviour of the materials at the meso-scale crystalline level measured by previous diffraction experiments. The robustness of the model is demonstrated on both the macro-and meso-scale through the successful prediction of macro-scale behaviour and lattice strain evolution under a variety of loading conditions. The model not only effectively recognised the influence of prior deformation on subsequent loading, but also complemented neutron diffraction data to enrich the understanding of the influence of an important loading condition on the deformation of grains within the material.

Investigation into the Effects of Prior Plasticity on Creep Accumulation in 316H Stainless Steel

“…Sci. Forum 2022, 4, 16 4 of 8 results are similar to previous experimental findings, although the yield stress is slightly lower. This may be due to the 316H in the literature being ex-service steel; hence, it may have hardened throughout its lifetime [8].…”

“…These elements represent 97 grains which simulate the twelve slip systems of an FCC material. Microstructure data from [16] was utilized to generate this RVE. The model can incorporate calculations based on the grainsize; however, this appeared unnecessary for these simulations and hence a untextured, randomly oriented, RVE was used (depicted in Figure 5a).…”

Influence of Microstructure on Synchrotron X-ray Diffraction Lattice Strain Measurement Uncertainty

“…Integrating across 10 • azimuthal slices nominally results in 36 1D line profiles. The notable exception to this is for the 316H stress relaxation experiment, SR [18,24] and the associated, previously unpublished, stress relaxation data acquired for a high temperature ferritic steel, P91. In both cases, approximately half the outgoing Debye-Scherrer cone was blocked by auxiliary heating equipment, with the number of azimuthal bins being reduced in proportion to this, i.e., just 18 slices were analyzed.…”

“…For completeness, the process followed by pyXe is briefly described in detail in Section 2.2. The software has been used previously to analyze the data from a number of synchrotron experiments (e.g., see [14][15][16][17]24]) results of which were possible compared with widely used software such as Fit2D [23]. While the code was evaluated against other results to the best of authors' ability, it is difficult to carry out a full evaluation of the code without significant resources thus care should be taken when using it.…”

Creep-fatigue interactions in type 316H under typical high-temperature power plant operating conditions

“…Recently, crystal plasticity finite element (CPFE) models have been used to predict the creep strain accumulation in austenitic stainless steels under creep-fatigue describing the link between macroscopic response and evolution of internal residual stress state, e.g. [10]. Phenomenological constitutive models are typically employed at the slip system level of such CPFE models which brings inherit uncertainty in calibration and difficulty to capture the response dependence on microstructure evolution.…”