Experimental Study On Plastic Zone And Stress Field Of Hammering Deformation

With the continuous development of modern industry,the demand for high-value industrial equipment is increasing.The purpose of reducing the cost of production by prolonging the fatigue life through the surface treatment is the research target of all relevant researchers.The extent of the plastic zone and the distribution of the stress field after the surface treatment of the component are the key factors for improving the performance of the component.Compared with the method of finite element numerical simulation,how to obtain the distribution of plastic zone and stress field effectively,intuitively and accurately has become a hot research topic.In this paper,the hammering test device is designed by ourselves.Q235 steel is the main object of analysis and research.It proposes tight hammering method to study the plastic zone innovatively.The residual stress of the hammer trace profile multi-point residual stress method is used to measure the residual stress,and the finite element method is used to simulate tight hammer stroke experiment process.The experiment study the plastic zone by tight hammering method.Q235 steel and 45 steel which is quenched,heat treated are preferably fabricated into strips with a dimension of 170 mm × 20 mm × 30 mm(length × width × height).Six hammer strokes are 25 mm,50 mm,75 mm,100 mm,125 mm,150 mm;Hammer head shapes are SR5.5,SR8,the apex angle of 110 taper,?2 circular mesa hammer and the surface shape is flat and R8,R10,R12,R14,R16 Surface with five curvature radii.The results show that:1.We studied the plastic deformation zone of Q235 steel after hammering by the method of abutting and hammering,and successfully achieved the purpose of surface information of the plastic deformation zone.The shape of plastic zone by hammering is round under the various factors of the experimental design.Due to the space symmetry of the impact marks,it is determined that the plastic zone formed by the hammering inside the sample is almost spherical.2.No matter what the type of hammer head and the surface shape of the hammer,the plastic zone is much wider with the hammer stroke increasing.The area of the plastic zone of the hammer stroke of 75 mm and below with the SR5.5 hammer head is the largest and the plastic zone of the hammer stroke of 100 mm and above with the SR8 hammer head is the largest.The area of the plastic zone under various strokes with the 110° taper hammer head is the smallest and increasing trend is smooth.Although the plastic zone of the 110° taper hammer range is small,the deformation is high.3.When the surface is a plane,internal corner and external corner surface,the area of plastic zone obtained by the hammering is the smallest at the internal corner surface.The area of the plastic zone will not change significantly with the radius of curvature increasing when we hammer the curved surface.The area of the plastic zone obtained at the plane changes rapidly with the hammer stroke increasing,while the area of the plastic zone obtained at the internal and external corners changes more slowly with the hammer stroke increasing.4.The method of measuring the residual stress at multi-point of the hammer trace profile not only verifies the accuracy of the plastic zone shape and position of the material in the tight hammering experiment observed under the microscope,but also verifies the study of plastic zone using the tight hammering method that is scientific and it lays the foundation for further study of the stress distribution inside the hammering deformed plastic zone.5.The depth of the plastic zone obtained by the tight hammering method is greater than the depth obtained by the traditional shot peening,rolling shot,hole extrusion,and explosion methods,and the pre-compressive stress layer is maintained to a certain depth after finishing the parts.This will help to improve the fatigue life of finished parts.This study has opened up an effective and reasonable way to apply pre-compressive layer on metal surfaces.6.Compare the results obtained from the finite element simulation with the plastic zone data measured by the microscope.The deviation of the two results is small,which proves that the simulation results are trustworthy.