## Getting Acquainted with Complex Relationships in FEA

The Structural Performance Engineer role was developed with SOLIDWORKS users in mind: powerful nonlinear static analysis in a more designer-friendly environment.

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## Assuming Linearity: Linear Static vs. Nonlinear

Background
SolidWorks has several different tools available for analyzing structures. Static analysis (discussed in my previous blog article) is available with the purchase of SolidWorks Simulation (included in SolidWorks Premium). Nonlinear analysis is available with the purchase of SolidWorks Simulation Premium (see Figure 1).

Figure 1 – SolidWorks Simulation study types

When a force is applied to a structure (a pencil, a building, a fixture, etc.) the internal pressure in the structure builds up. We call this internal pressure, stress. As stresses rise, the structure gets longer or shorter. We call this elongation, strain. When we run a Static analysis, we are assuming that the relationship between stress and strain is a simple one; we assume the relationship is linear. By making this assumption, we can potentially make an otherwise difficult or sometimes impossible problem very easy to solve.

However, this assumption isn’t all true. In reality, the relationship between stress and strain is never “perfectly” linear. But this assumption is close enough for many scenarios, and the amount of error it introduces may be negligible.

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