Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

Welding simulations for distortion and residual stress determination

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Material behavior considering multiaxial loading

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Fatigue

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Fatigue Fracture
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Shot Peening Simulations

Load-bearing components and structures in all industrial sectors such as automotive, vehicle, railway, aerospace, steel and bridge constructions are exposed to complex stresses. Many technical cases of damage can be attributed to material fatigue due to cyclic mechanical loading. In order to ensure the reliable use of critical components, the assessment of material fatigue is of decisive importance.

In order to fulfill the requirement for lightweight, resource-efficient and fatigue-resistant components, it is necessary to consider the properties of the component surface layer during the design phase of a construction. On the basis of our material and damage models for components and structures subjected to fatigue loading, we perform reliable service lifetime calculations so our customers are able to fully benefit from the potential of the strength reserves of their construction materials under extreme loads.

Controlling material fatigue

 

We:

  • determine the static and fatigue strength as well as the safety of components
  • support you in material selection and design optimization for cyclic loaded components
  • investigate the lightweight potential of load-bearing components and structures thus avoiding over-dimensioning and thereby saving costs for material, production and transport
  • support you in the material substitution for existing and new constructions
  • help you to improve the endurance limit of metallic components by mechanical surface treatment and to avoid fatigue fractures
  • assist you to handle production-related material defects in a safe and reliable way
  • advise you with respect to continuation of component operation and the lifetime extension of metallic structures
  • support you with numerical welding simulation to determine the residual stress state and the distortion of your components in order to evaluate their lifetime

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What we offer

 

  • Numerical and experimental stress and strain analysis of components under static and cyclic loading
  • Numerical component assessment under static and cyclic loading experimentally supported by component tests
  • Numerical and experimental strength and safety analysis
  • Welding simulation and strength analysis of welded joints under consideration of residual stress and distortion
  • Numerical simulation of shot-peening, deep rolling and high frequency mechanical impact and resulting residual compressive stresses in the surface-near layer of metallic structural materials
  • Calculation of service lifetime of mechanical surface-treated (such as shot-peened, deep rolled and high frequency mechanical impact) components including the quantification of the lifetime improvement and the estimation of the cost-benefit ratio
  • Material qualification
  • Vibrations and shock tests and experimental modal analysis
  • Microstructure and failure analysis

Selection of measurement and equipment highlights

 

  • Electromechanical, servo-hydraulic and resonance testing machines (N to MN) to carry out static and cyclic material and component tests
  • Equipment to perform fracture mechanical tests (i.e. ASTM E399, E1820, E1921 and E647) over large force and temperature ranges
  • Multi-axial loading devices (tension-torsion; span) for multiaxial component testing
  • Air-conditioned shock and vibrations tests
  • Metallography and fracture surface analysis

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Topics

 

© Fraunhofer IWM

Welding simulation, residual stresses, component distortion and microstructure

 

For the assessment of the fatigue strength of welded joints a realistic estimation of the damaging effect of welding residual stresses are of fundamental importance. A necessary element is the evaluation of the welding residual stress field and its possible degradation under mechanical loading. By means of validated numerical evidence the influence of residual stresses...

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Mechanical surface layer strengthening

 

The surface layer of metallic components and structures is of decisive importance for their lifetime. In all industrial sectors, where components are exposed to high stress such as automotive, vehicle and railway construction, aerospace, steel and bridge construction, drive technology and gear manufacturing, combustion engines, steam and gas turbines, compressor and pump manufacturing, tool and mold making...

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Increasing the lifetime of welded joints by high frequency mechanical impact

 

In general welds have significantly lower fatigue strength in comparison to the adjacent base material. This is mainly caused by the notch effect due to the weld seam geometry. Furthermore changing material and microstructure conditions in the weld zone (metallurgical notch effect) and tensile residual stress in regions which are susceptible to cracking reduce the fatigue strength of welded joints.

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Microstructure-based description of the formation of cracks in welded joints

 

As part of the DFG-AiF cluster project IBESS "Integral fracture mechanics determination of the fatigue strength of welded joints" Fraunhofer IWM has developed a fracture mechanics substitute model for the formation of cracks on the basis of real micromechanical structures to determine initial crack sizes for macroscopic fracture mechanics lifetime predictions.

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The influence of production-related defects on the strength behavior of cast steel components

 

The evaluation of faults in cast steel components is a vital part of strength calculation. Using the examples of materials G20Mn5 and G22NiMoCr5-6, a validated assessment concept was provided in the course of an Industrial Collective Research (IGF) project. Critical to this project were the validation of different non-destructive test methods, strength tests of samples with defects...

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Damage analysis: metals

 

We answer questions that occur during the quality assurance phase of industrial production or due to failure during service. The scientific investigation of damage to and failures of metals and metallic components is well established within the Fraunhofer IWM. We will build an expert project team customized for your individual task, which will assess the situation and discuss the next steps with you to reach an effective solution.

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Fatigue publications

 

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

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