Nonlinear static stress study

Static stress analyses are one of the most common types of finite element structural analyses. The component or assembly is subjected to a range of load conditions and the resultant stress, strain, and deformation results analyzed to determine the likelihood of failure of the design.

A Nonlinear Static Stress study should be used whenever a source of nonlinearity is introduced into the solution, and the assumptions of the linear Static Stress Analysis are no longer valid. There are four common forms of nonlinearity: material, geometric, load, and boundary condition nonlinearity.

• Material nonlinearity, where the material does not have a complete linear stress-strain curve, as seen in plastic and rubber materials. Material nonlinearity occurs when the material stiffness is inherently nonlinear (such as hyperelastic materials) or when a material is loaded beyond its elastic range. Examples of material nonlinearity include softening, stiffening, hysteresis, plasticity, viscoelasticity, creep, and failure.
• Geometric nonlinearity occurs when the deformation of the structure results in large displacements or rotations. Examples of geometric nonlinearity include the bending of a fishing pole or the buckling of a structure.
• Load nonlinearities occur when the area over which a load is applied or the orientation of the load vary significantly as the structure deforms (follower forces). Currently, Fusion does not support Load nonlinearities.
• Boundary condition nonlinearity occurs when the loads or constraints on the model are a function of the current structural displacements, surface interactions, or temperature. Contact surfaces that change throughout the simulation is an example. Currently, Fusion does not support boundary condition nonlinearity.

Another distinguishing feature of a Nonlinear Static Stress analysis is that the load is applied gradually over multiple increments. Incremental loading allows the solver to account for changing material stiffness, geometric changes, and changing boundary conditions.

Nonlinear Static Stress analysis examples

The following list contains a few examples for which a Nonlinear Static Stress analysis might be appropriate:

• Plastic (nonelastic/permanent) deformation of a material (for example, steel or aluminum loaded beyond the yield strength).
• Large deformation cases (such as the bending of a fishing pole).
• To determine stresses and displacements of hyperelastic materials (such as rubber).