Advantages, Limitations and Error Estimation of Mixed Solid Axisymmetric Modeling

The key to successful analysis of large structures often depends upon the analyst's ability to minimise the computational effort. An efficient method to reduce the computational effort is the mixed modeling of axisymmetric and 3D solid elements in ANSYS. This approach can be adopted for geometries possessing significant axisymmetric regions like turbine and compressor disks. The model size in these cases is large and consequently a large memory and disk space are needed to solve these models. Also, a variety of analyses are required to be executed on these models, like, thermal, structural, modal, etc. The finite element model building exercise is operationally more intensive than conventional method, which involves full 3D sectorial modeling, but it is more than offset by the time saved while running model for different analyses. However one needs to fully comprehend the limitations and errors that might be introduced and equate them with the advantages, while adopting this technique. The scope of this study is to investigate the advantages and limitations of this approach for different analyses. A study is conducted to establish the validity of the interface conditions, material and load scaling by comparing with a sectored 3D model for a simple model where results are easy to comprehend. The model was also analysed for determining the various limitations and drawbacks the methodology can impose for different analyses and the conclusions in this regard are made. In this approach, the section of the model which is completely axisymmetric is modeled using axisymmetric elements, sections which are cyclic symmetric are modeled with 3D elements as one sector with symmetry boundary conditions and sections which are not cyclically symmetric are modeled in full.

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