Fracture Property Test Of Cold Work Die Steel DC53 And Crack Propagation Analysis For Tooth Of Rolling Tool

The processing method of gear generated rolling is an advanced plastic forming technology,which has attracted more and more attention.It has better processing efficiency,and better use ratio of materials.Due to the forming line of the formed parts has not been cut off,the formed parts have better mechanical properties.However,as the key part of the gear rolling forming bench,the rolling load of rolling tool is much greater than the cutting load of the cutting tool in the processing of steel gear generated rolling.If the rolling process is improperly controlled,the phenomenon of fatigue fracture of rolling tool often occurs during the gear production process,due to the impact load is great,which seriously affected the quality of the forming parts,equipment and the normal production.To solve the problem,it is necessary to carry out the research on the performance test of material of the rolling tool and the crack propagation of rolling tool.In this work,the current common rolling tool material-DC53 is chosen be the research object,and this paper will study on the following aspects:(1)The fatigue fracture behavior of metal materials,the forming mechanism of each stage of fatigue fracture,elastic fracture mechanics theory and the criterions of different kinds of fracture are briefly introduced;(2)Some mechanical properties parameters of cold work die steel DC53,such as elastic modulus E,yield Strength0.2?,tensile strengthb? are obtained by uniaxial tensile test;The fracture toughness of DC53 is obtained by fracture toughness test;The crack propagation curves da/ d N-(35)K are obtained by fatigue crack propagation test with different stress ratio,and the expression of fatigue crack propagation rate also be obtained by the Paris fitting;(3)Using the software FRANC3 D,based on the linear elastic fracture mechanics,the boundary element method,the stress intensity factors and fatigue crack propagation lifetime of the standard CT specimen are calculated.The results are compared with the theoretical calculation and experimental results to validate the accuracy and feasibility of the numerical simulation method;(4)Boundary element analysis of rolling tool tooth model with a semi-ellipse initial crack is carried out with 3D fracture analysis software FRANC3 D to calculate stress intensity factors of rolling tool tooth crack front.Then the crack propagation path of the rolling tool tooth is simulated by the boundary element based crack automatic propagation function of FRANC3 D,and then compare the simulation result with the fracture appearance in operating condition;(5)Applying fracture mechanics based on the theory of damage tolerance design,the fatigue crack propagation lifetime of the rolling tool tooth is estimated.Based on the combination of material test,numerical simulation and theoretical analysis,the fatigue fracture mechanism of the rolling tool will be analyzed from the material perspective.The problem of fatigue fracture of rolling tool is detailed analyzed,which can be a strong support for the design,repair and prediction of fatigue life of rolling tool,and optimization of process parameters of gear rolling.