From the incremental theory and plastic flow law the stress-strainrelations were derived according to Mises-Mises,Mises-Tresca,and Tresca-Tresca models.Based on the thermal elasto-plastic-creep finite elementmethod an axisymmetric thermal creep computer program was developed andnon-linear finite element calculations of a diesel engine exhaust valve werecarried out at elevated temperature and high pressure.Calculated results werein good agreement with the creep deformation of the valve in a practicaldiesel e...