Papers by Author: Yu Jun Cai

Abstract: In the hot stamping process, die gap may affect cooling efficiency of the die and the condition of stress-strain. When other conditions are same, die gap were taken for 0.9t, t, 1.1 t, 1.2 t, t is sheetthickness. Temperature field and thickness distribution of the parts are simulated by ANSYS/LS-DYNA module, it is discovered that the distribution of temperature and thickness is uniform when the die gap is 1t and 1.1t. Finally, an experimental is designed to verify the simulation accuracy.

Abstract: The thin-walled blade of aero engine has low stiffness, during machining, it easily generates deflection due to the milling force, but because high accuracy of such component is required, the prediction of the deflection exactly becomes extremely important. Therefore, this paper analyzes the milling process, and simplifies it reasonably. The deformation of the blade is predicted based on ABAQUS using FEM, and then the machining deflection curves of the blade is got. The result is analyzed soon afterwards, and deflection law is summarized. Finally, an experiment has been designed. The reliability of the method of predicting deflection is proved by comparing the measurement results and the simulation ones.

Abstract: This paper has done CAE analysis of hot stamping, and optimized the water-cooled system which takes the degree of uniform temperature of blank as the objective function of optimization. The aim is to find a method of optimizing hot stamping mold cooling system based on ANSYS Parametric Design Language (APDL) with ANSYS Mechanical/LS-DYNA software and lay the foundation for designing hot stamping mold. And the work mainly consists of three sections, building parametric finite element model, simulating the process of quenching and optimizing the location parameters and radiuses of each coolant duct. Finally, contrast the optimal result with the initial result and get the conclusion, and moreover, point out the future work.

Abstract: The development of chip morphology, critical cutting condition of adiabatic shear during serrated chip formation and cutting forces were observed and measured by high speed turning experiment for 30CrNi3MoV hardened steel. Results show that the cutting speed and rake angle are leading factors to influence chip morphology and cutting forces. With the increase of cutting speed, the continuous band chip transforms into serrated chip at a certain critical value. As the rake angle is changed from positive to negative, the critical cutting speed of adiabatic shear significantly decreases, the cutting forces abruptly reduces when the serrated chip forms. The results from predicting critical cutting speed using the critical cutting condition criterion of adiabatic shear in metal cutting process show that the leading reason of serrated chip formation is that the adiabatic shear fracture repeatedly occurs in the primary shear zone.

Abstract: As an advanced manufacturing technology which has been developed rapidly in recent years, high speed machining is widely applied in many industries. The chip formation during high speed machining is a complicated material deformation and removing process. In research area of high speed machining, the prediction of chip morphology is a hot and difficult topic. A finite element method based on the software ABAOUS which involves Johnson-Cook material model and fracture criterion was used to simulate the serrated chip morphology and cutting force during high speed cutting of AISI 1045 hardened steel. The serrated chip morphology and cutting force were observed and measured by high speed cutting experiment of AISI 1045 hardened steel. The effects of rake angle on cutting force, sawtooth degree and space between sawteeth were discussed. The investigation indicates that the simulation results are consistent with the experiments and this finite element simulation method presented can be used to predict the chip morphology and cutting force accurately during high speed cutting of hardened steel.

Abstract: The chip morphology and the formation and development of the adiabatic shear band within the serrated chips formed in high speed cutting of 30CrNi3MoV steel with two tempering hardness were observed and analyzed using optical microscope and SEM. The investigation shows that as the adiabatic shear phenomenon occurs and develops, the chip morphology changes as follows: ribbon chip→serrated chip with deformed band→serrated chip with transformed band→fractured chip. The cutting speed and tempering hardness is the two main factors affecting adiabatic shear, in the case of lower cutting speed the formation and development of adiabatic shear band are more sensitive to tempered hardness increase. The deformed shear bands are constituted by large deformed microstructure, while the formation of the transformed shear bands has experienced the large plastic deformation and grain refinement.