Distortion and residual stress generation in laser beam welding calculated by the finite element method
The laser beam opens new industrially relevant welding applications under different aspects: precision welding, welding of complex structures, joining of conventionally nonweldable materials, high speed welding, etc. On the other hand, the resulting weld quality depends on a large number of process parameters which have to be optimized for each application. Since trial-and-error developments are often very time and cost intensive, powerful techniques of numerical process simulations are necessary, especially in this field. The physically very complicated mechanism of beam absorption within the keyhole is modeled by a special version of load steps which are capable of simulating the continuous wave (CW) as well as the pulsed laser operation. All physical properties of the material are considered to be temperature-dependent quantities, also including latent heat. For the mechanical properties of the material, plasticity is incorporated into the code by using a bilinear approximation of the stress-strain curve. Special effort is given to the generation of the FEM net, so that its structure is well adapted to the extremely steep gradients of the moving temperature profile which are typically for high-energy-density beam welding. Since the geometry of a laser beam weld itself with nearly parallel melting lines and narrow heat-affected zones on both sides is quite simple, for the first time simulation of the complete welding process and especially its influence to the material is possible. Since the FEM calculation includes the full time development, not only the stationary process behavior but also transient effects can be studied. The influence of solid-state phase transitions (austenite/martensite) to the residual stress pattern and the workpiece distortion have not been considered, up to now.
- OSTI ID:
- 115507
- Report Number(s):
- CONF-9404233-; TRN: 95:002927-0085
- Resource Relation:
- Conference: 75. American Welding Society (AWS) annual meeting, Philadelphia, PA (United States), 10-15 Apr 1994; Other Information: PBD: 1994; Related Information: Is Part Of 75th Diamond anniversary American Welding Society annual meeting; PB: 273 p.
- Country of Publication:
- United States
- Language:
- English
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