Correct Answer - Option 4 : material non linearity
Concepts:
Nonlinear means, the force versus displacement plot is not as straight line. The stiffness of the structure is no longer constant but varies with respect to loading. A structure is said to be nonlinear, if the loading causes the significant changes in the stiffness. The reasons for stiffness changes are:
- Material does no obeys hooks law, material plastically deform after elastic limit.
- Large deformation due small or larger loads.
- Contact status abrupt change.
There are three basic types of nonlinearity; the first one is geometry based nonlinearity, second one is material based and third one is contact & boundary condition based nonlinearity.
Material non-linearity’s occur in solid mechanics when the relationship between stress and strain is no longer linear. The non-linear material behavior in solid mechanics may be rate independent and rate dependent. Plasticity, creep, visco-plasticity or visco-elasticty are some characteristics of materials which posses this kind of material non-linear behavior.
Geometric Non-Linearity means changes in the geometry of the structure during the analysis. This is caused by large deflections or rotations and higher loads. Geometry buckling is also cause of geometric non linearity i.e. huge compressive load causes the structural member to buckle resulting higher displacement.
Contact nonlinearity means abrupt change in stiffness, which may occur when bodies come into or out of contact each other. Friction coefficient can be used to decide the amount of resistance between the contact bodies. Sometimes boundary conditions can also be treated as nonlinear analysis like elastic support.
