MF GenYld + CrachFEM

MF GenYld + CrachFEM is a comprehensive material and failure model that can be used in combination with commercial explicit finite element codes. It can characterize various metallic and polymer materials for shell and solid element models.

MF GenYld + CrachFEM is:


MF GenYld + CrachFEM aims to predict the material behaviour under arbitrary load cases. Therefore, a com­prehen­sive suite of well-defined elemental tests should be carried out to feed the material model. This technique is opposed to iteratively adjusting data in calibration cycles of a component simulation.


The principal building block of the material and fracture model MF GenYld + CrachFEM is the module. Each module describes one physical property. Modules are independent of each other and may be combined freely depending on the characteristics of the material.


MF GenYld + CrachFEM may be coupled to various explicit finite-element solvers. Material data is input in the solvers’ native format. It can easily be converted, though, and data for one material can be used nearly interchangeably between different solvers: The attached model is the same in all solvers.

The material model MF GenYld describes the elasto-plastic deformation of the material. It can model many physical effects of plasticity and allows to model a wide range of materials.

The failure model CrachFEM uses the calculated stresses and deformations to assess various modes of ductile and brittle failure, either as post-processing value or transiently with element elimination and post-critical models.

MF GenYld + CrachFEM can be coupled to various explicit finite-element solvers. Support for implicit solvers is in progress.

orthotropic elasticity viscoelasticity orthotropic elasticity orthotropic yield locus non-associated flow orthotropic yield locus orthotropic yield locus yield-locus correction asymmetric hardening yield-locus correction Bauschinger effect ductile normal fracture ductile shear fracture tensile instability orthotropy of fracture post-critical failure evolution of porosity brittle fracture interpolation between states stochastic scatter local initialization Composite modelling Composite modelling plastic compressibility plastic compressibility temperature dependence plastic compressibility plastic compressibility plastic compressibility plastic compressibility

Elasto-plastic model

The material model MF GenYld describes the elasto-plastic deformation of the material.

The elastic behaviour of most materials is isotropic, but orthotropic and strain-rate dependent elasticity are important to model polymers correctly.

Strain-rate dependent hardening is a basic requirement for modelling nearly all materials. The hardening can also depend on temperature or other locally distributed values such as hardness or the degree of anisotropy.

A variety of base yield criteria cover a wide range of materials, especially sheet metals. These base yield criteria can be scaled for different stress states and they can be different in tension and compression.

Isotropic-kinematic hardening can describe the Bauschinger effect where the yield stress changes after load reversal.

Some polymers cannot be considered incompressible. The compressibility module can model volume changes under plastic deformation.

With a few exceptions, the elasto-plastic behaviour of the material can be modelled consistently with shell and solid elements.

Comprehensive failure model

The failure model CrachFEM describes the onset of material failure. It includes:

Failure is evaluated as failure risk, which can be used as criterion for element elimination. If statistical data is available, failure probabilities can be assessed.

CrachFEM distinguishes between the ductile fracture modes normal fracture due to microvoids under tensile loads and shear fracture due to shear band localization. These models are complemented by optional post-critical models.

Thin-walled metal parts are subject to tensile instability. The instability itself does not constitute failure. Post-instability models can model the subsequent fracture.

A stress-based fracture criterion can model brittle fracture in metals or polymers. In glass and ceramics, this is the only fracture mode.

Depending on the material, damage accumulation can be linear or tensorial. In addition, there is a true anisotropic fracture model that determines the fracture direction.

Porosity in castings contributes to a higher risk against normal fracture. The porosity can evolve during the simulation starting from an initial porosity.

Process chains and manufacturig

CrachFEM can model the material throughout process chains by mapping results from one stage to the next.

Local variations in the material behaviour of manufactured parts can be accounted for with suitable initialization methods.

A rich ecosystem

MF GenYld + CrachFEM is mature and has a broad user base. The material and failure models are under steady development. New features are being integrated according to our experience with industry and research projects.

MF GenYld + CrachFEM is complemented by a rich ecosystem of utilities: