RESIDUAL STRESSES GENERATED DURING HARDENING OF MEDIUM CARBON STEEL BAR, FINITE ELEMENT SIMULATION AND EXPERIMENTAL VERIFICATION

Abstract

The aim of this work is to analyze the distribution of residual stresses resulting from combination of volumetric changes due to heat gradients and phase changes occurring during the quenching process of 4340 steel cylinder. The mathematical model  used  for  this  objective  uses  the  AC3  program  for  modeling  thermal  treatments  which provides  transformation curves,  cooling  curves,  microstructure  and  material  hardness  in  20  positions  between  the  surface  and  the  center  of  the cylinder,  whose  results  were  fed  into  a  finite  element  model,  considering  thermal-mechanical  coupling  and  non-linear elastic-plastic behavior. The values of the physical and mechanical properties required in the model, were included taking into  account  the  temperature  dependence  and  the  phases  present,  depending  on  the  treatment  time. The results  of  the modeling  have  been  compared  to  experimental  measurements  of  the  residual  stresses  at  the  surface,  through  X-Ray diffraction techniques and  using the sin2ψ  method. The results obtained  from the  numerical  model  showed a  significant correspondence in comparison with the experimental results and indicates that the most significant stresses are tangential.