Roentgenographic measurement of residual stresses or residual stress profiles in component surface areas in order to receive crucial knowledge regarding strength and long life fatigue strength or regarding influences from mechanical or spark erosion manufacturing.
Every component, tool or any welded structure is under residual stresses. Even raw materials, which are used to manufacture and heat-treat components, are not free of residual stresses.
Residual stress is tension within a closed system which is shielded from external forces or moments. The residual stresses equalise each other over the cross-section of a component, for which reason residual tensile and compressive stresses always appear together.
On the other hand, residual compressive stresses in the surface area of the component can increase strength and long life fatigue strength decisively. Residual compressive stresses are targetedly introduced by means of the following processes:
It is possible to measure the residual stresses of a workpiece. Particularly for component optimisations aimed at increasing long life fatigue strength or for endurance strength calculations and for dynamic fatigue testing, etc., knowledge regarding the level and profile of residual stresses is absolutely crucial.
The most reliable and most accurate method for measuring residual stress is the X-ray diffractometer analysis (RDA) according to DIN EN 15305.