Loading and Calculating Apply a horizontal to right displacement at the right end of the tool. The tool moves to the right at a given speed and different displacement boundaries to form a cutting process. The calculation is then performed by the solver of the calculation software.
Through the ANSYS post-processor, the formation of the shear angle during the cutting process (as shown in Figure 3) and the change in the effective stress of the tool (see Figure 4) can be observed. Thus, the size of the shear angle can be measured by means of AutoCAD software. At the same time, the instantaneous effective stress of the tool at any time can be obtained.
Effective stress analysis of the rake face of the toolIt can be seen from the distribution of stress lines such as the tool of Fig. 4 that the effective stress at the tool tip is the largest, and gradually decreases along the front face. The relationship between the effective stress at each point on the tool rake face and the distance from the tool tip is shown in Fig. 5. This result is consistent with the conclusions in BA Ostafefev's "Chip Dynamic Strength Calculation" (Machine Industry Press, 1982).
2 Lee & Shaffer shear angle theory verification
After the Lee & Shaffer shear angle theory material enters the yield state, the points in the plastic zone are plastically sheared along the mutually orthogonal maximum shear stress directions, and the maximum shear stress directions of the points are connected to form an orthogonal network. It is the slip line field of plastic shear. Thus, the slip line field in the cutting layer in front of the rake face of the tool can be constructed as shown in Fig. 6. AB in the chip layer is the boundary line between the plastic zone and the rigid zone, that is, the shear plane, and the angle between the shear plane and the tool displacement direction is the shear angle. Available from Figure 6 geometric relationship| f +bg 0 =45° | (2) |
Where f - shear angleB——friction angle
g 0 ——tool rake angle
It can be seen from equation (2) that as the tool rake angle g 0 increases, the shear angle f increases, and the thinner the chip is formed, the smaller the deformation, and vice versa. This is the Lee & Shaffer shear angle theory. If the shear angle and the yield shear stress of the material being sheared are known, the cutting force can be calculated. Therefore, studying the shear angle is an important way to study the cutting mechanism.
The virtual design approach provides a more concise approach to the study of shear angles. Based on the above research, we keep the other factors in the cutting process unchanged, change the tool rake angle in the range of -15 ° ~ 15 °, establish different cutting simulation models for calculation, and measure the shear angle range of 38 ° ~ 56°. The calculation results of the shear angle corresponding to the rake angles of different tools are shown in the table.
The calculation results show that as the rake angle of the tool increases, the shear angle increases and the deformation decreases. This verifies the correctness of the conclusion.
3 ConclusionThrough the finite element simulation and analysis of the results of the metal cutting process, the following conclusions can be drawn:
The finite element method was used to successfully simulate the formation process of the cutting layer and the stress-strain change process of the entire shear deformation zone during metal cutting. The simulation of the formation process of the three deformation zones during cutting proves that it is feasible to simulate large strain plastic deformation by this method.When studying the tool strength, you must first understand the load condition of the tool, and the boundary conditions of the tool force during the cutting process are very complicated. The finite element method can apply instantaneous boundary conditions to the tool through the simulation experiment process, and can obtain various stress and strain values ​​of any part of the tool at any time during the cutting process, thus providing a series of numerical solutions for the optimal design of the tool. Therefore, numerical simulation method, as an important part of computer-aided engineering system, will become a more effective and reliable research method in tool theory research and product development.
This paper is only a preliminary attempt to apply numerical simulation methods to tool research. On this basis, the distribution of temperature field during cutting and its influence on the cutting performance of the tool can be further studied. The fracture mechanics and wear analysis can be carried out by means of fracture mechanics theory. On the basis of comprehensive numerical analysis results, Optimize tool structure and geometry parameters. In addition, a 3D finite element model can be applied to perform a more comprehensive structural and performance analysis of some complex tools.
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