Measurement and Modeling of Transient Thermal-Mechanical Strain Field in High Strength S700 MC Steel During Gas Metal Arc Welding

Residual stress formation in welded joints of high strength steels is a well-studied topic and many methods of residual stress measurements are available. However, far less is known about the transient strains during welding. Transient strains are the direct cause for the development of ex-situ residual stresses which results in distortion of the welded plates. Modeling of weld formation usually includes the calculation of transient strains and stresses, but in general these models are verified with ex-situ experimentally measured residual stresses. There is a lack of published data covering strains in the transient regime. Study of welding transient strains and stresses will aid in the optimization of in-process methods to reduce welding residual stresses, such as transient thermal and mechanical tensioning.

In this study, electrical resistance strain gages are used to measure the transient strains during welding. The experimental results are then compared with the coupled temperature-displacement finite element model of the process. The welding process is simulated by a 3-dimensional deformable solid plate with a sub-routine for a Goldak’s double-ellipsoid heat source. The transient biaxial state of strain is measured during Gas Metal Arc Welding (GMAW) of S700 MC steel samples in a square butt welded configuration. Experimental results are found to be consistent between samples and show good agreement with the numerical results.