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 harden ing of steel can be quantitatively determined by finite element calcul ations, if the underlying processes are adequately modelled and the ma terials and process data necessary are known. In this context also tra nsformation plasticity effects have to be taken into account. Model ca lculations for SAE 4140 steel cylinders demonstrate the influence of t hese effects on the developing residual stresses. Using a special devi ce which allows martensitic transformation under constant external loa ds, for SAE 4140 the transformation plasticity constant K = 4.2 . 10(- 5)mm(2)/N is determined. With this constant and assuming realistic hea t transfer conditions, the development of residual stresses and distor tions of SAE 4140 cylinders with a diameter of 30 mm and a length of 9 0 mm is modelled. The calculated results are in good agreement with ex perimental findings.