Investigations of a computational scheme for accelerated numerical simulations of cyclically loaded structures
Date
2010
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Publisher
University of Delaware
Abstract
Engineering structures are commonly subjected to cyclic loading. This leads to fatigue and unwanted, premature failures. Thermal barrier coatings (TBCs) are example of structures exposed to both thermal and mechanical cycles. Understanding the failure evolution in these structures during use is important to prevent the life-time limiting failures. To predict failures due to cyclic loading, finite element analysis (FEA) is commonly used, which can simulate and give the stress and strain distribution as a function of time. However, every single cycle of simulation may take significant computation time. For structures subjected to cyclic loadings, it is very time-consuming and inefficient to simulate the whole process of structural evolution. The goal with this work is to improve upon an existing numerical scheme that can, in combination with simple testing, predict the life-time of structures subjected to cyclic loading. The numerical scheme is the “cycle-jump technique” developed previously. The idea behind the cycle-jump technique is that there is no need to calculate each individual cycle in cyclically loaded structure. The cycle-jump technique predicts the overall structural behavior utilizing an extrapolation scheme. As part of the improvement of the numerical scheme, the simulations must be compared to experimental data. In order to do so, the cycle-jump technique code is modified to be used for real life experiments. The materials used in these experiments are materials used in high temperature applications with particular focus on TBCs. TBCs exhibits time dependent material response, thus creep properties are incorporated into the cycle-jump technique code. Furthermore, in order to allow for displacement controlled loading, “intermediate initiation simulation” is incorporated as a numerical tool to impose the necessary initial conditions in a time-economic manner. Suitable load sequences are established via numerical simulation so to develop experimental investigation suitable as verifying tests. In addition, sensitivity analyses are conducted to investigate the effect of expected variance of material properties in the real structure. Finally, preliminary experimental results are used to compare with the simulation results. Even though the experimental data is very limited, it appears as cycle-jump technique can predict the evolution of the test sample.