7th March 2016
FATIGUE-BASED CONCEPT DESIGN AND OPTIMIZATION
A recent development in optimization simulations codes is the ability to use stress-life and strain-life fatigue analysis as design criteria. This allows concept optimization analysis to generate designs which are more robust and more mature earlier in the development process as the early freeform optimization results take further real world loading and use conditions into account. Optimizing designs in using this technology ensures that the effort to reduce mass and weight out of products does not mean that performance and use life has to be affected and in many cases, can actually be enhanced.
EQUIVALENT STATIC LOAD METHOD (ESLM)
The equivalent static load method, originally published by Dr. Park, Hanyang University, is a technique suitable for optimization of designs undergoing dynamic loads. The equivalent static load is that load which creates the same response field as that of the dynamic/nonlinear analysis at a given time step. The method has been implemented for the optimization of the following solutions:
• Multi-body dynamics problems including flexible bodies.
• Non-linear responses from implicit static analysis, implicit dynamic analysis and explicit dynamic analysis.
The calculated equivalent static loads from the analysis (as explained above) are considered as separate load cases, and these multiple load cases are used in the linear response optimization loop. An updated design from the optimization loop is then passed back to the analysis for validation and overall convergence. The design is validated against the original dynamic/non-linear analysis. Based on the outcome of this validation, the solution converges or an updated set of equivalent static loads is calculated for the updated geometry, and the entire process is repeated till convergence.
Apart from others, the equivalent static load method offers the following benefits:
• It can be applied at the concept design phase as well as design fine tuning phase, i.e. it can be used with topology, free sizing, topography, size, shape and free shape optimization.
• A design is optimized for updated loads due to an updated design during the optimization process.