Lifetime concepts and software tools for assessment of the operational behavior of components

© Fraunhofer IWM

What we offer:#

 

  • Material subroutines for cyclical changing plasticity (ABQUS and ANSYS)
  • Post processing tool for lifetime prediction with LCF and TMF loads (ABQUS, ANSYS and independent of FE code)
  • Customized development of software tools

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The ThoMat computational software for ABAQUS and ANSYS#

 

The deformation and damage models developed at the Fraunhofer IWM have been incorporated into the ThoMat computational software. The ThoMat computational software can currently be used together with the commercial finite element programs ABAQUS and ANSYS for thermomechanical analysis at component level. Through a modular separation into deformation and damage models, stresses and (in)elastic strains can initially be calculated via a user sub-routine in the context of the FEM. Along with temperature, these serve as (transient) input variables for local lifetime prediction in a subsequent post processing step with a mechanism-based damage model. For transient finite element analyses, an intelligent search algorithm allows calculation of the time related maximum damaging load cycle at the integration point.

 

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Lifetime prediction independent of finite element software#

 

In addition to post processing developed specifically for the finite element software ABAQUS, post-processing independent of the finite element program is also available. Here the (transient) variables at the element node previously calculated in the finite element simulation are made available in ASCII format and the lifetime is then predicted. For the ANSYS finite element software, there are interfaces for reading the calculated stresses and (in)elastic strains and for importing the calculated lifetime for visualization.

 

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Latest developments of the ThoMat computational software#

 

The ThoMat computational software is permanently undergoing further development and being adapted to suit users’ needs in order to provide them with the latest research findings. The latest developments relate, in particular, to being able to quantify the influence of microstructural changes in the material and their effect on the deformation and lifetime behavior of a component in operation. Model extensions for materials with asymmetrical stress-strain relationships, such as those for gray cast-iron materials, have also been integrated successfully and are in industrial use. Current research activities focus on the assessability of components that are subject to complex load cycles or have steep load gradients.

Attention has also been paid in the development of the ThoMat computational software to efficient implementation and its parallelization.

Manufacturers of the commercial finite element programs ABAQUS and ANSYS have also developed deformation models for cyclical changing plasticity under thermomechanical load. These include the key equations from the ThoMat computational software, so that the model parameters can be shared.

 

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Publications#

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  • Seifert, T.; Riedel, H.; Pramhas, G.; Bumberger, G.; Lifetime models for high temperature components; AutoTechnology 7 (2007) 34-38 Link
  • Metzger, M.; Seifert, T., On the exploitation of Armstrong-Frederik type nonlinear kinematic hardening in the numerical integration and finite-element implemantation of pressure dependent plasticity models, Computational Mechanics 52/3 (2013) 515-524 Link