Reduction of development costs through improved calculation methods

Lifetime Concepts, Thermomechanics

Motor components, aircraft turbines, power station and plant components are all subject to high thermal and mechanical loads. It often takes numerous expensive and time-consuming laboratory and field tests to design such a component. Our understanding of damage mechanisms and the subsequent development of improved material models enable us to carry out an increasing proportion of component development at the computer. This saves our clients development costs and time, and increases component quality.

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© Photo Fraunhofer IWM

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During fatigue trials, materials are subjected to cyclical mechanical loads until a crack forms. Crack formation and propagation depend strongly on both the sample temperature and the surrounding media. This test rig enables us to test the reaction of sample pipes to up to 600° C hot liquid media. This in turn enables us to perform tests on, for example, materials for future solar thermal power stations.

Image on left: Test bed for mechanical fatigue trials with superimposed corrosive loading from molten salt.

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Characterization and modeling of metals under thermal and mechanical loads at temperatures ranging from -180 °C to over 1000 °C

Performance of isothermal and non-isothermal fatigue tests: LCF and CLCF, TMF, superimposed LCF/HCF and TMF/HCF tests, cryogenic fatigue tests with liquid nitrogen, high-cycle thermoshock tests as well as superimposed low-cycle fatigue loads, fatigue tests in corrosive media (liquid salt)

Performance of crack propagation tests under isothermal and non-isothermal conditions with potential drop systems and short crack growth measurements using the replica technique

Performance of creep fatigue tests, relaxation tests, creep tests on hollow cylinders under internal pressure and hot tensile tests.

Performance of registered indentation tests at higher temperatures Development of customized testing technology and execution for the automobile, turbine and plant engineering industries

Topics

 

Material characterization for thermal and mechanical loads


We have developed sophisticated tests with which to characterize the cast, forged and sheet metals used in components, which are subject to high thermal and mechanical loads. The testing temperatures range from -180 °C to >1000 °C, depending on the specifications. Mechanical loads can be applied monotonously or cyclically. The test results help to better understand material behavior and form the basis for the development and modification of...

 

Identification of deformation and damage mechanisms


Thermal and mechanical loading can lead to the transcrystalline and intercrystalline cracks and creep pores forming and growing. Oxidation and corrosion processes can also damage the material and change the microstructure to such an extent that the mechanical properties are significantly altered. When developing material models and designing components, it is therefore important to understand which deformation and damage mechanisms dominate...

 

Mechanism-based models for time and temperature dependent plasticity and damage


Sophisticated deformation models can describe typical material phenomena such as strain hardening, creep, relaxation and strain rate effects, taking account of microstructural changes and their effects on the mechanics. The mechanism-based damage models can describe crack growth under fatigue and creep fatigue loads. The models account for material properties that change with temperature ...

 

ThoMat computational software for finite element programs


The deformation and damage models developed at the Fraunhofer IWM have been incorporated into the ThoMat computational software. ThoMat can be used together with the finite element programs ABAQUS and ANSYS for component calculations. The ThoMat computational software is permanently undergoing further development and being adapted to suit users’ needs in order to provide users with the latest research findings...

 

Publications regarding Lifetime Concepts, Thermomechanics


Contributions to newspapers, books and conferences as well as dissertations and project reports...