Plastisuuskäyttäytymismallit

Plastisuuskäyttäytymismallit, known in English as plasticity models or constitutive models of plasticity, are mathematical frameworks used in continuum mechanics to describe the mechanical behavior of materials that undergo permanent deformation. When a material is subjected to stress beyond its elastic limit, it enters the plastic regime where the deformation is irreversible. Plastisuuskäyttäytymismallit aim to capture this transition and the subsequent plastic flow.

These models typically consist of several key components. A yield criterion defines the stress state at which plastic deformation begins. Common yield criteria include the Tresca criterion and the von Mises criterion, which depend on the principal stresses or stress invariants. Following the yield criterion, a flow rule dictates the direction of the plastic strain increment. The associated flow rule, a common assumption, posits that the plastic strain increment is normal to the yield surface in stress space. Non-associated flow rules are also used when the plastic potential differs from the yield function. Finally, a hardening rule describes how the yield surface evolves with plastic deformation. This can be isotropic hardening, where the yield surface expands uniformly, or kinematic hardening, where the yield surface translates in stress space.

Plastisuuskäyttäytymismallit are crucial in simulating a wide range of engineering applications, including the design of structures, manufacturing processes like metal forming, and the analysis of material failure. The choice of a particular model depends on the material being studied and the accuracy required for the analysis.