It is a new method in recent years to improve material fatigue property by explosion treatment. In comparison with others, the explosion treatment has significant effect, wide range of application, easy operation, etc. But so far, studies of improving fatigue property by the explosion treatment were mainly focused on the adjustment of residual welding stress and the property improment of surface layer. Little was done to study the effect of the elasto-plastic explosion shock wave on the material inner behavior. Doing this work will be helpful to understand the macrostructure changes of the material and clear the reason why the fatigue property is improved under the explosion treatment. This will conduce to the establishment of an appropriate standard of explosion treatment for the improvement of the fatigue property and open up the way to a bright future of spreading the application in industries. In this research, rotational bending welded-joint fatigue specimen was used. The welded joints of he specimen in the same state of the initial microstructure and residual stress were subjected to different strength of the shock wave by changing the distance between the explosive and the specimen. S-N curves, tensile properties, changes of the residual stress and the fatigue fracture surfaces observed by SEM were determined prior to and after the explosion treatment. the effect of reflected tensile shock wave on the welded joints was studied getting rid of the tensile wave by attaching the momentum trap to the welded plate. The calculation of plastic zone produced by the shock wave and the location strongly acted on by the reflected tensile shock wave in steel 16Mn were calculated under the parameters used in this article, conforme to the test results. New mordel of the dislocation generation and glide was posed through TEM observation of the morphology of the dislocations under the different strength of the shock loading. The improvement of the fatigue property and the plasticity of steel 16Mn and why the reflected tensile shock wave lowers the fatigue property were analyzed. At last, the proper standard how to improve the fatigue property of metals efficiently in industries is suggested in this article according to the studies.
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