Yu Jun Cai

Microcosmic mechanism of material softening and fracture in primary shear zone during high speed machining of hardened steel

The metallurgical observations of microstructure and fracture characteristics of the adiabatic shear bands, within the primary shear zones of the serrated chips produced during high speed machining 30CrNi3MoV hardened high strength steel, have been performed using optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The microstructure observations showed that the material softening occurred in the primary shear zones during high speed machining. A microcosmic model of microstructure development and rotational dynamic recrystallisation in the primary shear zone during high speed machining high strength steel was suggested by analysis of material softening mechanism. The fracture observations showed that adiabatic shear fracture was the primary reason of serrated chip formation during high speed machining. A microcosmic fracture model during adiabatic shear was proposed.

Study on the Formability Rules with Precise Die Face for the Inner Clutch Shell of Automobile

The ultimate goal of the metal forming industry is to form components made of a specific material into a required shape without experiencing wrinkling, bifurcation and spring-back. This study is devoted to develop the whole process by making rules of precision for specific part geometry. For inner clutch shell a computer simulation system and the general procedure of dynamic simulation in sheet metal forming are presented. Finally compute all simulation results with reference to the original part property and recommend the appropriate process flow to produce the part, the comparison with tryout results shows that the formality simulation of thick panel with precise die face is reliable and accurate.

Simulation of Die Gap Variation in Temperature Field Distribution of High Strength Steel Hot Stamping Process

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.

Cooling System CAE Analysis and Optimization Design of Hot Stamping for High Strength Steel Sheet

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.

Experiment Study of Chip Formation and Cutting Force of Hardened AISI 1045 Steel in High Speed Machining

Orthogonal cutting experiments of hardness AISI1045 steel( HRC45) are performed. The change of chip formation and cutting force with cutting conditions are investigated through metallurgical observation, and the critical cutting speed of adiabatic shear of AISI1045 steel at different cutting depths and rake angles are given. In addition, the saw-frequency and space length of serrated chip and the influence of serrated chip on cutting force are also studied. The critical cutting speed decreases with the increase of cutting depth, but increases with the increase of rake angle. The saw-frequency of serrated chip is found to be independent of the cutting depth, and increases with the increase of cutting speed and rake angle. The cutting force decreases with the increase of cutting speed and rake angle, but increases with the increase of cutting depth, and there isn’t a sudden change of cutting force at the onset of adiabatic shear.

A Strategy of Toolpath Generation for Finish Machining of Mold Cavity Based on Tool-Zmap Model

A strategy of toolpath generation based on Tool-Zmap geometric model has been proposed to achieve efficient finish machining of mold cavity. Considering cutting tool wear, the finish machining of mold cavity was performed using variable cutting tools of different diameter. Each cutting tool only cuts the corresponding area to avoid identifying machining characteristic and poor rigidity of cutting tool during high speed machining. Finally, the validity of presented strategy was experimentally affirmed by a machining example.

Study on the Laser Shock Processing with Square Spot of Titanium Alloy Based on ABAQUS

Laser shock processing is a new kind of technology to improve the physical and mechanical properties of the metal surface. It uses the high-amplitude stress wave produced by the interaction of short-pulse laser and material, to make the material produce the compressive residual stress and refinement internal structure, and lead to the improved hardness and strength of material. In this paper, the simulation of laser shocking process with square spot of Titanium alloy plate was carried out through ABAQUS. The influences of the shock time, laser energy, plate thickness and spot size on the strengthening are investigated from the view of residual stress. The results show that: There are the compression residual stress in the workpiece surface after laser shcok processing, and its amplitude is about 300-400Mpa. With the increase of shock time, the surface residual stress increases, the area and depth of strengthening zone also increase. The strengthening area becomes a circular, while the distribution of residual stress becomes unhomogeneous. The surface residual stress increases as the laser energy increasing, but the amplitude is smaller. The plate thickness does not affect the amplitude of the surface residual stress. When the shock pressure is constant, surface residual stress does not change with the spot size. However, if the laser energy is constant, due to the shock pressure will decrease with the increase of spot size. Therefore, there should be an optimized spot size when the strengthening effectiveness and efficiency are both considered.

Experiment Study of Serrated Chip and Surface Roughness of High Speed Cutting of Ti6Al4V

Under the condition of cutting speed 10-300m/min, rake angle -10°、0°、10°and cutting depths 0.05mm、0.1mm and 0.2mm, the experiment study of adiabatic shear serrated chip and surface roughness are carried out. The influence of cutting condition on serrated chip is analyzed through the metallographic observation of obtained chip. By the measurement of finished surface, the influenc of cutting condition and adiabatic shear on surface roughness is also investigated. The rusults show that the reason lead to serrated chip in high speed cutting of Ti6Al4V is adiabatic shear, not the periodic fracture.The adiabatic shear serrated chip is easier appear and the degree of segment is more large under the condition of higher cutting speed, larger cutting depth and smaller rake angle. The surface roughness is smaller when the cutting speed is higher, cutting depth is larger, and rake angle is smaller.

3D Finite Element Simulation of Inclined Cutting of Hardened 45 Steel

The research of the simulation for high speed cutting is usually based on 2D modeling by now, and the 3D simulation is few. Because the cutting process is a 3D deformation of workpiece, its badly in need of the research on 3D finite element simulation of cutting process for further reveal the mechanism of high speed cutting. The 3D simulation of inclined cutting of hardened 45 steel (45HRC) is carried out base on ABAQUS. The forming process of serrated chip is simulated by adopting the Johnson-cook material modeling and separation criterion of shear failure. The change of chip morphology, chip flow angle and deformation coefficient of width under different rake angle and cutting depth are analyzed. The results show that the segment degree of chip becomes larger with the decrease of rake angle and increase of cutting depth. The chip flow angle is not effected by rake angle and its value is approximately equal to tool cutting edge inclination angle, an it increases with the increase of cutting depth. The deformation coefficient of width increase with the decrease of rake angle and increase of cutting depth.

Factors and Optimization Methods of Error in Reverse Engineering Practical Application

This article states the error factors in parts of data acquisition and data processing of reverse engineering, and gives optimization suggestions in practical applications. It provides a more practical method for manufacturing products closer to the samples.