jericho2009
Mechanical
Does anyone have a reference( or online documentation) that provides a guideline when a small displacement FEA solution must be abandoned and a large displacement solution must be used?
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Small vs. Large Displacement FEA
- Thread starter jericho2009
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When the displacements (or rotations) become so large that they have significant effect on the stiffness, etc. In many cases this is quite a bit more than most people think...It really does depend on the problem...Consider..
A problem that is essentially a bar loaded axially...If the meshing is such that strains within elements can be kept "small" (which is also subject to interpretation) then a good solution can be obtained for displacements which are quite large overall....
Also, depending on the problem, rotations up to 10-15 degrees can be tolerated without totally trashing a solution (Which also depends on your individual tolerance for error)...Some people think any error over 1-2% is excessive while others may accept errors of 50-100% depending on the type of problem and known loads, material properties, etc....
Hope this helps.....
Ed.R.
A problem that is essentially a bar loaded axially...If the meshing is such that strains within elements can be kept "small" (which is also subject to interpretation) then a good solution can be obtained for displacements which are quite large overall....
Also, depending on the problem, rotations up to 10-15 degrees can be tolerated without totally trashing a solution (Which also depends on your individual tolerance for error)...Some people think any error over 1-2% is excessive while others may accept errors of 50-100% depending on the type of problem and known loads, material properties, etc....
Hope this helps.....
Ed.R.
There are no hard and fast rules for this. In my experience, thin shell structures with no obvious symmetry axes subject to pressure loads are the most sensitive to NL effects.
If you want to get a feel for the effect try pressurising a 300mm diameter aluminium alloy plate, 1mm thick, with pinned boundary restraints. Run linear and nonlinear analyses with ramped loads and graph the bending stresses and centre point deflection against load. For high yet sensible pressures the NL analysis will give bending stresses significantly lower than the linear analysis.
gwolf
If you want to get a feel for the effect try pressurising a 300mm diameter aluminium alloy plate, 1mm thick, with pinned boundary restraints. Run linear and nonlinear analyses with ramped loads and graph the bending stresses and centre point deflection against load. For high yet sensible pressures the NL analysis will give bending stresses significantly lower than the linear analysis.
gwolf
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