Turning tool is one of the most widely used metal cutting tools, which is mainly used for turning all kinds of revolving surfaces and end faces of revolving bodies. Taking a typical cylindrical turning tool as an example, the finite element numerical simulation analysis of tool strength is carried out by ANSYS.
(1) test parameters
Turning test of carbide turning tool on C630 horizontal lathe. The workpiece material is carbon steel. Select the geometric parameters of the tool: tool holder material: 45 steel; Geometric dimensions of tool rest: B×H=20mm×25mm, L= 150mm. Blade material: YT15; ; Main turning angle: rake angle, mechanical properties of cutting tool material: strength limit: 600Mpa；; Yield limit: 355MPa；; Elastic modulus e = 206 GPA Poisson's ratio =0.27. Cutting dosage: cutting speed) vc= 100m/min, feed speed (or feed speed) f=0.5mm/r, and back feed.
(2) splinter cell
According to the geometric dimensions of the tool, the finite element solid model of the tool is established in ANSYS interactive mode.
Fig. 2 finite element mesh diagram
The element length is defined by the adaptive grid division method of ANSYS. The turning tool is divided into 1569 nodes and 6934 elements by using the eight-node hexahedral Solid45 element type (easy to apply load and high in calculation accuracy) (see Figure 2, the element division is denser to show the stress concentration area more clearly), and the following assumptions are made:
* The arbor and blade materials are regarded as a whole, which is convenient for simulation loading analysis and calculation.
* In the calculation, it is assumed that the material is linear elastic, that is, it does not yield.
* Tool will be impacted and vibrated during cutting. Considering the limitations of this impact and vibration, in order to simplify the calculation, the tool is regarded as the static stress distribution at a certain moment in the cutting process.
* In the process of cutting, the tool will produce high temperature due to severe friction, but for the convenience of calculation, the influence of temperature field is temporarily ignored.
(3) Simulation loading scheme
Because there are many factors that affect the cutting force and the calculation is complicated, the theoretical calculation formula of cutting force currently used is derived under the condition of ignoring the temperature, normal stress, deformation and friction in the third deformation zone, which is quite different from the actual cutting state, and can only be used for qualitative analysis of cutting force and is not suitable for actual calculation. Therefore, according to the original test data of this example and an experimental formula in the literature, the empirical values of the three cutting components are calculated as follows:
According to the above analysis, the simulation loading is carried out according to the worst limit of cutting conditions (that is, concentrated on the tip of the tool), and all constraints are imposed on the end of the tool (this will not affect the analysis results).
(4) result analysis
Through the static load calculation of ANSYS, we can get the stress distribution inside the tool as shown in Figure 3, the strain distribution at the tip of the tool as shown in Figure 4 and the USUM distribution (displacement contour map) of each degree of freedom solution as shown in Figure 5.
Figure 3 Schematic diagram of stress distribution of turning tool Figure 4 Strain distribution of tool tip Figure 5 Displacement contour map
As can be seen from Figure 3, the maximum stress point of the turning tool is located at the tool tip (node 2 1), the maximum stress value is 676MPa, and the coordinates of the maximum stress point are (-0.025, -0.008, 0.002). In a similar way, the maximum strain of the tool tip can be calculated to be 0.00426 meters. As can be seen from Figure 5, the maximum composite displacement DMX=0.609, and the calculation result is consistent with the actual situation.
Because the above analysis results are obtained under the limit condition (cutting force is concentrated on the tip) and ANSYS linear analysis is adopted, the maximum stress value obtained is slightly larger than the strength limit value, which should still be within the allowable range. If ANSYS nonlinear analysis is carried out, the maximum stress value should be within the allowable stress range, and the analysis result will be more accurate.
Because the tip of the knife is the maximum stress point, it can be seen that the main forms of tool damage are the tip and blade damage, so it is necessary to choose high-strength blade materials to increase the strength of the tool. Because of the high temperature in the cutting process, there is a great pressure between the tool and the workpiece material. When the temperature and stress reach a certain level, pitting corrosion of the tool and plastic deformation of the tool material may occur under the maximum stress, and it is difficult to ensure the machining accuracy. Therefore, it is necessary to adjust the cutting parameters to reduce the stress and ensure that the tool works in a stable cutting state. In addition, due to the greatest stress and serious wear of the tool tip, it will directly affect the machining quality, so it is necessary to check the tool condition in time and compensate the tool.
Through the above analysis, we can choose and use tools correctly in cutting and adjust cutting parameters reasonably.
In order to explain the stress distribution at the stress concentration more clearly, ANSYS can also be used to slice the surface nodes along the longitudinal section with the greatest stress to show the stress change curve of the section. Because the lathe tool analyzed in this paper has a simple structure, it is omitted.
5. Conclusion
Using ANSYS, a large-scale finite element numerical analysis software, the numerical simulation analysis of tool strength can accurately grasp the stress situation of each point on the tool, understand the stress and strain distribution law inside the tool, obtain the stress and strain distribution map, and find out the dangerous points conveniently. This method can provide theoretical basis for improving tool stress, rationally designing tool structure and analyzing tool failure, and provide a new method for analyzing and calculating tool strength and life.
In this paper, the cylindrical turning tool is taken as an example, and the strength of the tool is numerically simulated and analyzed. This method can also be applied to the strength and failure analysis of other types of tools, spindles and other parts. The nonlinear dynamic analysis method can be used for the analysis object with complex stress situation, which makes the analysis result more accurate. The analysis results of this paper show that ANSYS finite element numerical analysis software can complete the strength simulation analysis and calculation work which is difficult to be completed by traditional calculation methods (or the effect is not good), and it has important practical value.