The metal cutting process is the process of the interaction between the tool and the workpiece. In the machining system composed of machine tools—fixtures—tools—workpieces, it is very important to use tools properly. The overall structure of the tool, cutting edge material and geometry will directly affect the tool life, workpiece machining quality and cutting production efficiency. Therefore, in the cutting process, the tool should have high strength, good toughness, long life, and good processability. Theoretical analysis of the tool strength to understand the state of internal stress and strain of the tool is not only conducive to the reasonable selection of the tool in the machining process, but also provides a theoretical basis for further improving the internal force state of the tool and improving the service life of the tool. 2. Introduction to finite element numerical analysis software ANSYS The finite element numerical analysis software (ANSYS) combines the basic theories of modern mathematics and mechanics with finite element analysis techniques, computer graphics, and optimization techniques. It has a rich and complete cell library, material model library, and solver that can be used for numerical simulation. The technology efficiently solves all kinds of structural dynamics, static forces, linear and nonlinear problems. As a finite element analysis software, ANSYS has become an effective tool for CAE and engineering numerical simulation. It is one of the mainstream products in CADFCAEFCAM software today. When ANSYS is used for the mechanical analysis of the finite element structure, the stress and strain concentration area is analyzed through the numerical simulation of the applied load, so as to achieve the purpose of strength analysis and optimization design. The three main steps of the ANSYS solution are: creating a finite element model (preprocessing) → applying a load and solving (solving) → viewing the analysis results (postprocessing). 3, the establishment of tool mechanics model In the metal cutting process, when the tool cuts into the workpiece, the force required to deform the material to be machined and form the chip is called the cutting force. The size of the cutting force directly affects the design and use of tools, machine tools, and fixtures. The cutting force includes the resistance to elasticity and plastic deformation generated when the material to be processed is deformed, the frictional force of the rake face of the tool against the chip, and the frictional force between the face and the machined surface of the back face of the tool. Figure 1 Tool Force Analysis In order to facilitate the analysis, calculation and measurement of the tool force conditions, a space rectangular coordinate system can be established according to the direction of the main cutting speed, depth of cut and feed direction. The main cutting force Fz is the largest component force, and it is also the main basis for the design and use of tools. It can also be used to check the strength and stiffness of the main components of the machine tools and fixtures, as well as the machine motor power. The deep-cut resistance Fy does not consume power. It mainly affects the deformation of the process system and the machining quality of the parts. However, when the rigidity of the process system consisting of machine tools, fixtures, tools, and workpieces is insufficient, Fy is the main cause of part deformation and machining vibration. factor. The feed resistance Fx mainly acts on the machine tool feed system and is an important basis for checking the strength and rigidity of the main parts of the machine tool feed system. The turning tool is one of the most widely used metal cutting tools and is mainly used for turning various rotary surfaces and rotary body end surfaces. The following is an example of a typical external turning tool. ANSYS is used to perform finite element numerical simulation analysis on tool strength. (1) Test parameters Carbide turning tools were used for turning tests on a C630 horizontal lathe. Workpiece material is (2) Divide the cell According to the geometry of the tool, create a tool FEM solid model in ANSYS interactive mode. Figure 2 Finite element grid Through ANSYS self-adaptive mesh division method for cell division, custom unit length. Using an eight-node hexahedron Solid45 unit type (this unit type is easy to apply load, and the calculation accuracy is high), the turning tool is divided into 1569 nodes and 6,934 units (see Figure 2). The unit is denser to show the stress more clearly. Concentrated area) and make the following assumptions: * Assemble the tool bar and blade material for simulation load analysis and calculations. (3) Simulated loading solution There are many factors affecting the cutting force and the calculation is more complicated. In addition, the theoretical calculation formula of the cutting force currently used is deduced under the conditions of ignoring temperature, normal stress, deformation and friction of the III deformation zone, etc. The difference between the actual cutting condition and the actual cutting condition can only be used for the qualitative analysis of the cutting force and should not be used for the actual calculation. Therefore, according to the original experimental data of this example, using empirical formulas in a literature, the empirical values ​​of the three cutting force components are calculated as: According to the above analysis, the worst case of cutting conditions (ie Fig. 3 Schematic diagram of the stress distribution of the turning toolFig. 4 Strain distribution diagram of the tool tipFig. 5 Displacement contour map According to Fig. 3, the maximum stress point of the turning tool is located at the tool nose (at node 21), the maximum stress value is 676 MPa, and the coordinates of the maximum stress point are (-0.025, -0.008, 0.002). Using a similar method, the maximum strain value at the tool tip can be calculated as 0.00426m. From Figure 5 we can see that the maximum combined displacement DMX = 0.609, the calculation results and the actual situation. Since the above analysis results are obtained under the extreme conditions (the cutting force is concentrated on the tool tip) and the linear analysis is performed using ANSYS, the maximum stress obtained is slightly greater than the strength limit and should still be within the allowable range. For ANSYS nonlinear analysis, the maximum stress value should be within the allowable stress range, and the analysis result will be more accurate. Since the tool tip position is the maximum stress point, it can be seen that the main form of tool failure is the destruction of the tool tip and the blade edge, so the use of high-strength blade material is very necessary for increasing the tool strength. Due to the high temperature during the cutting process and the large pressure between the tool and the workpiece material, when the temperature and stress reach a certain level, the blade edge pitting and the plastic deformation of the tool material may occur at the point where the stress is greatest, making the machining precision difficult. Ensure that the cutting parameters must be adjusted to reduce the stress in order to ensure that the tool works in a stable cutting condition. In addition, due to the maximum stress at the tool tip and severe wear, it will directly affect the machining quality. Therefore, it is necessary to check the tool status and perform tool compensation in time. Based on the above analysis as a theoretical basis, the tool can be correctly selected and used in the cutting process, and the cutting parameters can be reasonably adjusted. In order to more clearly explain the stress distribution in the stress concentration area, ANSYS can also be used to slice along the surface node of the longitudinal section where the stress is greatest to show the stress change curve of the section. Because the structure of the turning tool analyzed in this paper is relatively simple, it is omitted. 5 Conclusion Application of large-scale finite element numerical analysis software ANSYS to numerical simulation analysis of tool strength can accurately grasp the force conditions of each point on the tool, understand the distribution law of stress and strain inside the tool, obtain the stress-strain distribution diagram and easily find the danger point. The method can provide a theoretical basis for improving the force condition of the tool, designing the tool structure reasonably and failure analysis of the tool, and providing a new method for the analysis and calculation of the tool strength and life. The numerical simulation analysis of the tool strength performed by the round turning tool as an example has certain typical characteristics. This method can also be applied to strength and failure analysis of other types of tools and spindles and other components. For the analysis object with more complex stress conditions, nonlinear dynamic analysis method can be used to make the analysis result more accurate. The analysis results of this paper show that the ANSYS finite element numerical analysis software can accomplish the strength simulation analysis and calculation work that is difficult to complete (or the effect is not good) by traditional calculation methods, and therefore has important practical value.
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The total cutting force Fr is decomposed into three components in this coordinate system, namely, the main cutting force Fz - the cutting speed direction component force (tangential force), the depth of cut resistance Fy - the force in the depth direction (radial force ) and feed resistance Fx - component force (axial force) in the direction of feed (see Figure 1).
4, the tool strength finite element analysis example 
Carbon steel. Select tool geometric parameters: Arbor material: 45 steel; Arbor geometry: B×H=20mm×25mm, L=150mm. Blade material: YT15; turning tool main angle: front angle 
, 
Tool material mechanical properties: strength limit: 600Mpa; yield limit: 355MPa; elastic modulus E = 206GPa; Poisson's ratio 
= 0.27. Cutting amount: cutting speed) vc = 100m/min, feed (or feed rate) f = 0.5mm/r, back knife 
* It is assumed in the calculation that the material is linearly elastic, ie no yield occurs.
* The tool will be subject to certain shocks and vibration during the cutting process. Considering the limited impact and vibration, in order to simplify the calculation, depending on the tool at some moment in the cutting process is the static stress distribution.
* In the cutting process, the cutter will produce high temperatures due to severe friction, but for ease of calculation, the influence of the temperature field is not considered. 
Concentrically acting on the tip of the tool. Load the simulation and apply all constraints at the end of the tool (this does not affect the results of the analysis).
(4) Analysis of the results Through the static load calculation of ANSYS, the internal stress distribution diagram of the tool shown in Fig. 3, the strain distribution diagram of the tool tip shown in Fig. 4, and the total freedom solution USUM distribution diagram shown in Fig. 5 (displacement equivalent) can be obtained. line graph). 
Finite Element Numerical Simulation Analysis of Tool Strength
1 Introduction