Cushioned Impact

 
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Dynamic Contact:
Determine the stresses in a piece of conveyance/packaging equipment for fatigue susceptibility.

Special features:
3D CAD model setup with elastic material model using bricks, shells, beams, trusses, surface to surface contact, contact elements and time-based prescribed displacement for sinusoidal crank motion, whew!

Output:
Maximum principal stresses, displacements, etc.

Comments:
This was a unique problem. First, the easy part was determining the stresses and making changes to the equipment design. The REAL problem was simulating the dynamic impact event. Obviously, the developed stresses were largely a function of stiffness not only of the machine, but of the material being conveyed and packaged. It turned out that the material was not stiff at all, but very spongy. So, several models were built to simulate the stiffness of the material. It's density, mass, size, loft, compression rate, and its crush-to-solid height was measured experimentally. It was then a matter of constructing a finite element structure, which gave back those properties. The animation above (click on graphic thumbnails to access) shows this material in action. It was constructed largely of elastic beams. Once this was done and verified, the machine was set up to impact it in the virtual FEA world.