| Abstrakt: |
The use of a laser beam in forming processes was introduced at the end of 20th century and is still under development. The laser beam makes forming technology applicable for industrial use, which formerly had to be done manually due to the lack of reproducibility or flexibility of the heat source used (e.g. straightening of distortion by heating with a gas torch). The main advantages of thermal formingprocesses are the fact that there's no spring-back effect and that tool and work piece are not in contact during the process. The latter fact also increases the flexibility of the processes, because no special tool is needed. Different geometries, therefore, canbe produced by using the same set-up and changing only the process parameters. Thermal forming is based on the generation of stress and strain fields by elevated local temperatures. The different mechanisms can be grouped as direct thermal forming mechanisms (temperature gradient, residual stress point, upsetting and buckling mechanisms) and indirect thermal forming mechanisms (residual stress relaxation and martensite expansion mechanisms), where the distinguishing criterion is the driving force for the forming process. In addition to the thermal forming mechanisms a non-thermal laser beam forming mechanism (shock wave mechanism) is described in this chapter. Potential applications arise in the fields of forming, straightening and adjustment for both macro and micro components. Some examples are: rapid prototyping,precision adjustment, removing distortion and creating 3D complex shapes. Current research is concentrating on the mechanisms of thermal forming, on the prediction of the strains and on the heating strategies and path planning in order to obtain a given shape. For the latter especially, a precise prediction of the forming results is necessary. This can be done by modelling the process numerically, which is often done by finite element methods nowadays. The calculation results of FEM simulation of thermal forming processes have a high degree of accuracy if the materialparameters and the boundary conditions are defined correctly. A list of notation and abbreviations is given in Table 9.1. [ABSTRACT FROM AUTHOR] |
