Study On Surface Residual Stress Of Hot Work Die Steel For Ball-end Milling

Mold and die have large consumption and wide influence, their quality is directly related to the production efficiency and production cost. Recently, high speed cutting has become the main method of mold and die manufacturing instead of the traditional processing method. The study of die's surface quality which is based on high speed cutting has became focus of attention.The formation mechanisms of surface residual stress of hot work die steel H13 during ball-end milling have been investigated in this thesis by using experiment and finite element method. By adding the changes of tool-orientation into the influencing factors of surface residual stress, the influencing mechanism of tool-orientations on surface residual stress is analyzed. Prediction model of surface residual stress is established by using BP neural network method.The residual stress formation mechanisms on machined surface of hot work die steel H13 are investigated. The experimental and finite element simulation results indicate that cutting force is the most important influencing factor of machined surface residual stress, and the burnishing effect is the dominant cause of machined surface residual stress. The deformation of machined part of the workpiece during the machining process would influence the stress distribution of the part to be machined, leading to a gradient distribution characteristic of residual stress.The influencing mechanisms of tool-orientation on machined surface residual stress and the change in residual stress under different tool-orientations are analyzed. It is found that the tool-orientation influences the residual stress by changing the real cutting speed of the cutting edge segment engaged in milling.The influences of cutting parameters on machined surface residual stress are analyzed, and the results reveal that axial depth of cut and spindle speed are two main influencing factors. They influence the residual stress by changing the real cutting speed too. With the increase in cutting speed the machined surface compressive residual stress increases at first and then decreases.A new model based on BP net of artificial neural network (ANN) is established to predict the residual stress on ball-end milled surface of H13 steel. The predicted values agreed well with the measured ones by using a large amount of training data.