Comparative Destructive and Non-Destructive Residual Stress Measuring Methods for Steering Rack Bar Semi-Product

摘要

It is well known that residual stress is introduced within solid materials during many types of processing methods, including heat treatments, machining, grinding, casting, etc. The type and magnitude of the formed stress state can be various depending on the type and conditions of the treatment and the geometry of the sample. The presence of residual stress can either be harmful or useful. If undesired residual stress is arisen within a machine component during its manufacturing steps, it can lead to deformation. Since the geometry of automotive components must be kept strictly within tolerances, more and more attention is given to the importance of residual stress in the field of the automotive industry. Many methods have been developed to characterise the residual stress. In the present study, the results of a destructive and non-destructive residual stress measuring methods for induction hardened automotive rack bar semi-products were compared. The theory of non-destructive method associated with the distortion of the crystal lattice, from which, residual stress can be quantitatively calculated, while the destructive method that we have developed specially to test this product at the Lech-Stahl Veredelung GmbH is very fast, suitable for qualification, and easily inserted into the manufacturing line.