Computer aided design and analysis is widely being practiced in the engineering community. However, as new FEA tools continue to make simulation process easier, it has been increasingly tried and tested by novices. While modern tools have attempted to make the life of an analyst much easier, it is simultaneously raising the threat of its misuse.
The results obtained through finite element analysis largely depend on the engineering judgment of the engineer, his assumptions and careful application of loading conditions. As such, FEA in wrong hands can produce destructive outcomes, especially when someone relies on the results completely and do not opt for an experimental test.
For the FE method to be meaningful, there are few points one should take care of, before executing the analysis. Let’s take an example of developing a piston through FE technique and figure out important points that would make the simulation results more meaningful.
Identify and Define the Problem
The foremost requirement is to identify the problem and its definition. In case of a piston, the problem could be optimizing its weight or design to save material. For this requirement, it is important to figure out necessary parameters that affect the piston design, such as maximum gas pressure acting on the crown, lubrication effects, thermal loadings, etc. Obtaining information about each parameter is equally important to obtain results without many deviations.
Perform Theoretical Calculations
Before letting the computer do everything for you, make sure to perform theoretical calculations to ensure that the FEA solver yields appropriate results. Make use of empirical relations to obtain results that can be compared against the ones obtained through FEA.
Ensure that Results are Independent of Mesh
The problem with FEA is that the results heavily rely on the mesh quality. Solution obtained with a coarse mesh will be entirely different from the one obtained with a finer one. Make sure that the mesh quality selected is adequate enough to capture the physics accurately, especially around edges and corners. In case of piston, it is important to have finer mesh near piston pin area as well as the edges of piston ring grooves.
Determine Alternative Failure Conditions
It is not always right to finalize the design with one failure condition as in reality there could be many other possibilities of failure as well. A piston design with an optimized geometry and a light weight material might resist stress and deformation quite well, but its fatigue life could have been affected too. It is better to perform a fatigue analysis in such case before finalizing the design.
Despite considering every parameter required to study the design behavior, there are always certain assumptions present in finite element analysis. As a design engineer, it is important to make a note of every assumption made during the analysis process, as it will assist in performing experimental validations.
A structural analysis on a piston will consist of assumptions such as isotropic material, uniform lubrication film thickness and neglecting of frictional forces. Documenting these assumptions in the FEA report will help the end user better comprehend the solution and trust the results obtained through simulation.