(College of Mechanical and Electrical Engineering,Central South University,Changsha 410083，China)
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Abstract:
Surface residual stress distributions and general rules of quenched 7075 aluminum alloy thick plates were acquired by nondestructive X ray diffraction method,in which effects of collimators were analyzed and the stress results were co MPared with measurements from center drilling method.The results show that both of the two surface stress measurement methods are effective and correct.But center drilling method is not suitable to conditions with large stress gradient while X ray method is not effective in conditions where there is no stress or very low initial stress level.In addition,surface residual stress measurements of the plates showing normal distributions which indicate credibility and correctness of the measured stress distributions.Edge effect causes residual stress relaxation near the edges of plates during quenching process,in which the maximum relaxation may amount to 40% of initial stress and the region size occurring stress relaxation would be equal to the thickness of the quenched plate.