Weld Mechanics

Component test device and submerged arc tandem welding equipment

We investigate thermal and mechanical loading as well as corrosion exposure of joined components during fabrication and service. It is essential to understand both the weldability and the subsequent behaviour of joined components during service as component properties. Above all, inclusion of the design-specific boundary conditions of welded components are crucial factors. For weld integrity assessment we draw on component tests and laboratory specimens. In order to master the challenges of testing, advanced test procedures are required assuring transferability of the results to real joined structures, forming a link in a closed test chain. We have special three-dimensionally acting test facilities in place for various loading ranges up to a maximum of 16 MN.

The principal focus of our research is on quantification of the relationships between material and structure. Apart from investigating the cold and hot cracking behaviour we analyse the hydrogen transport behaviour in metallic materials and develop new simulation models for numerical calculation of welding-specific distortions and stresses or for numerical analysis of hydrogen-associated material degradation. We design new alloy concepts for welding filler materials in order to enable loading oriented high quality joining of innovative materials.

For crack resistance assessment we employ various available cold and hot cracking tests as well as our own large-scale test facilities with testing capacities up to 16 MN.

Research topics

• Component tests and full-scale tests with linear and orbital welding under defined restraint intensities
• Stress-strain analyses during welding of components
• Analysis and assessment of welding residual stresses in components
• Cold and hot cracking investigations using small and large specimens (DIN EN ISO 17641 and 17642)
• Further development of higher-strength welding filler materials
• Investigations relating to the transformation behaviour of innovative materials (LTT-alloys)
• Hydrogen analyses in conformance with ISO 3690
• Assessment of structural variables influencing hot cracking during welding
• Thermometric analyses during welding
• Determination of retained austenite
• 2D strain and stress field measurement during welding

Equipment

• Test facility with a maximum test force of 2 MN
• Large-scale test facility with a maximum test force of 16 MN
• Instrumented restraint welding (cracking) test (IRC-Test)
• MVT hot cracking test
• CTW hot cracking test
• Mobile X-ray diffractometer for residual stress analysis and retained austenite determination on component specimens
• Stationary X-ray diffractometer for residual stress analysis and retained austenite determination
• Incremental hole drilling method for residual stress analysis on component specimens
• High-resolution thermo vision camera
• Differential pyrometer
• Tandem submerged-arc (SA) welding gantry, narrow-gap welding systems
• Optical stress-strain analysis using the Digital Image Correlation (DIC) technique
• TEKKEN-, CTS-, Implant-cold cracking test
• Carrier gas hot extraction for determining hydrogen concentrations and effective diffusion coefficients at elevated temperatures in metals
• Permeation experiments following Devanathan-Stachursky for determining material- and microstructure-dependent diffusion coefficients
• Heat treatment furnaces with shielding gas atmosphere

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