Abstract: The effect of residual shear stress on the hardness of materials was considered and the relationship between the residual shear stress and the maximum shear strss
induced by hardness pressure head was also deduced. The analysis indicates that the residual shear stress reduces the hardness of materials whatever its direction
which is different from the residual normal stress. The decease value of hardness by residual shear stress is larger than the increase value of hardness by compressive
stress near the interface of the ceramic/cemented carbide compact. According to this, it is considered that the hardness of the ceramic surface not only can’t increase
but also decrase due to the effect of the residual shear stress, although larger residual compressive stress can be formed in the ceramic when the ceramic is too thin
and its thermal expansion coefficient is smaller than that of the cemented carbide.

Key words: residual stresses, hardness, ceramic/cemented carbide, hot-press