Add a Sense of Reality to Your Simulation
I have seen many simulation results which do not make sense to a normal engineer. It is usually not because the theories or corresponding simulation codes are wrong, but because the inputs are not real, or not in consistent units. For example, I have seen students obtain a strain of 0.5 from a linear elastic model and stress of a few Pascals in a loading-bearing solid. There are a few tips a simulator should keep in mind:
- Make your inputs as real as possible. Don't just give a random number. For example, if you are analyzing a composite laminate with each layer assumed to be homogeneous, find the lamina constants from a trustworthy database such as the NIAR' AGATE database at shttp://www.niar.wichita.edu/agate/. And also not only lamina constants, also use realistic layer thickness. A layer thickness of 0.1 meter is laughable.
- Make sure that you use a consistent unit system. Most software does not care which unit system you uses, For example, if you have Young's modulus E=73 GPa. You can input Young's modulus as 73E9, geometry of your model in terms of meter, and load in terms of Newton. However, if your structure is very small, such as in the size of milimeter, and you would like to use milimeter as the unit for the geometry, and Newton for the load, then you need to input E=73e3 MPa, and the stress results will be in MPa for a elastic analysis. For multifunctional analysis which involves different physics, then using consistent units become even more important.
- Make sure you indicate the units for your tables and plots so that others don't have to ask. And also ask yourself whether the results make realistic sense or not. For example, if the results has stresses in the order of hundreds of GPa, these should cause to re-think your results as most materials cannot sustain such a high stress. For a linear elastic model, if you have a strain of 0.5, it does not make sense either. Even a strain of 0.1 should cause a read flag for a linear elastic problem.