CONSEQUENCES OF TRANSFORMATION PLASTICITY ON THE DEVELOPMENT OF RESIDUAL-STRESSES AND DISTORTIONS DURING MARTENSITIC HARDENING OF SAE-4140 STEEL CYLINDERS

Residual stresses and distortions developing during martensitic hardening of steel can be quantitatively determined by finite element calculations, if the underlying processes are adequately modelled and the materials and process data necessary are known. In this context also transformation plasticity effects have to be taken into account. Model calculations for SAE 4140 steel cylinders demonstrate the influence of these effects on the developing residual stresses. Using a special device which allows martensitic transformation under constant external loads, for SAE 4140 the transformation plasticity constant K = 4.2 . 10(-5)mm(2)/N is determined. With this constant and assuming realistic heat transfer conditions, the development of residual stresses and distortions of SAE 4140 cylinders with a diameter of 30 mm and a length of 90 mm is modelled. The calculated results are in good agreement with experimental findings.