AbstractA method for determining the surface yield point and surface work hardening exponent by means of X-ray stress analysis and strain gauge techniques is proposed in the present paper. The reliability of the method is discussed. The test results of the annealed medium carbon high strength steel 40Si–Mn–Cr–Mo–Ni–V show that the proof stress corresponding to 0·1% permanent effective strain of the electrolytically polished surface is about 100 MN m−2less than the bulk yield point of the material, and the work hardening induced by shot peening raises the 0·05 and 0·1% surface proof stresses by about 400 MN m−2. The proof stresses of the shot peened surface under both bending–tension and bending–compression loading even exceed the ultimate tensile strength of the material.MST/3114