Development of physical simulation technology for

2022-09-19
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The development of cutting physical simulation technology

virtualmachining has been born for a long time. With the progress of science and technology, three-dimensional computer-aided design is widely used in product design. In terms of engineering operation design, machining process design and product assembly degree, it is necessary to develop computer-aided technology, especially in Computer-Aided Engineering (CAE), The finite element method (FEM) is used to analyze and study the structure and thermal conductivity related to product performance in advance, and the programming technology of using computer aided manufacturing (CAM) to determine the tool path has penetrated into all fields of engineering and has been effectively used

the development trend of cutting simulation technology includes two aspects. One is to develop NC simulation software to display the tool trajectory and judge whether the tool, tool holder and workpiece and fixture interfere

in the process of end milling, the most basic task is to cut off the cutting edge envelope surface of the tool and make the remaining part become the machined surface. The software used to complete this kind of processing should include the following contents: the coordination of tools, tool collets, workpieces, fixtures, etc., the composition of machine tool spindles and their working range, and the plan to sign a specific agreement between edaso and Chery to start the production of these carbon fiber composite automotive parts in Wuhu, so as to truly simulate the actions of machine tools and tools. Especially in recent years, due to the continuous increase of five coordinate machining, the importance of NC simulation before actual machining has become increasingly prominent. Many of these NC simulation software have excellent performance, such as calculating the machining efficiency from the metal cutting volume; Judge whether the cutting process has overload according to the metal cutting volume; If the load is fixed and overload occurs due to high feed speed, the simulation software can adjust the feed speed to prevent overload and shorten the cutting time

Another development trend of the cutting simulation technology is to study and analyze the physical phenomena in the cutting process, such as the heat generated by the processed material due to plastic deformation, the cuttings formed by the cut-off material constantly rubbing against the tool rake face are discharged, and the machined surface is formed on the workpiece by cutting unnecessary materials by the tool cutting edge, and this series of cutting processes are simulated by computer, At present, there are few products that can achieve this ideal goal. Thirdwavesystems' advanced is a software product that uses the finite element method to carry out special optimization and analysis of cutting processing. Compared with the finite element method program package for structural analysis, its biggest advantage is that the user interface is excellent, and the machining technicians can analyze it conveniently. Deform of American scientificformingtechnologies is a finite element analysis program package for plastic deformation processing such as forging, which has recently been transferred to cutting processing. The cutting process is the deformation process of elastic deformation and plastic deformation of chips and processed materials. Compared with plastic deformation such as stamping and forging, the deformation speed (the amount of deformation generated per unit time) is very large. The resulting plastic deformation energy and the energy generated by friction on the rake face will cause heating, which will greatly increase the temperature, and the tool tip will destroy the processed materials in a continuous and narrow range It is a remarkable feature of the cutting process that it is separated into chips and machined surfaces. These phenomena have complex interactions with each other

if the finite element analysis method is used, the following contents need to be input: the physical properties of the processed material and the friction state; Cutting conditions, tool shape and other boundary conditions. Through the finite element analysis of the rigid equation, the cutting force, shear angle, cutting temperature and other quantitative parameters with chip formation state characteristics can be output. In this process, there is no need to establish a mathematical model or propose assumptions. According to the results of finite element analysis, it is also easy to visualize the chip generation process, stress, deformation and other physical quantities

in order to obtain high-precision analytical results, the most important input content is the material properties that reflect the relationship between the stress and deformation of the processed material in the actual development, and the acquisition of material properties is extremely laborious work. In the future, with the increase of computer power, this physical simulation technology of cutting process will be gradually popularized. The key to the rapid popularization lies in whether the material characteristics of the processed materials can be provided to users in time

develop cutting simulation technology software on demand

at present, many scientific and technological personnel are carrying out research on the most basic cutting technology in production engineering, most of which are aimed at predicting the machining process while understanding the machining phenomenon. If these research contents realize the computerization of the system, it means that a cutting simulation technology software can be formed. For example, the laboratory of Tokyo a & M University, which refers to the force value at the moment when the sample is completely broken and separated, is conducting several predictive research on cutting simulation technology software. The technological process and practical simulation adopt the research system of horizontal and vertical matching, which corresponds to the product design to the processing process; Vertically, the higher up, the better the practicability. Downward, it is not only practical, but also includes the analysis of processing phenomena and the realization of visualization

1. Cutting condition selection system combined with tool information database and analytical simulation technology

in the actual cutting process, the recommended cutting conditions provided by the tool factory should not be copied, but the cutting conditions should be corrected by repeated trial cutting according to the specific conditions of machine tools, tool systems, workpiece clamping, etc. At the same time, the effective reference data accumulated in the past processing should also be input into the database. While effectively using these data, the cutting conditions should be optimized with the help of analytical methods; For new machining without reference data, a cutting condition selection system related to the long-term development of Chinaplas should be developed. In this system, vibration, machining accuracy, tool temperature rise, tool life, residual stress and so on are set as the analysis content. On the basis of analysis, the best tool can be selected and the cutting conditions can be adjusted

the data of this system is roughly divided into three parts: tool information data, tool system composition, and cutting conditions. Effective cutting parameters can be accumulated in cutting conditions

this paper plans to use a legend to represent the optimal milling efficiency and the shape error of the optimized side of the flat end milling cutter. According to the database, select the required tools and tool holders, and predict the machining errors caused by the bending of end mills and tool holders and the rotation changes of the joint part of chuck and spindle taper. The cutting force is predicted by multiplying the cutting force at the tool tip by the specific cutting resistance. This is the simplest method, but the cutting force waveform is consistent with the measured value. Calculate the tool deflection caused by the cutting force at each instant, and connect it with the displacement of the cutting edge forming the machined surface to obtain the shape of the machined surface. Compared with the calculation of large-scale finite element method, the calculation time is very small. By inputting the tool information and cutting condition information, the machining error can be easily simulated. Although the database has indeed adapted to the cutting conditions, people still hope to further reduce machining errors and improve machining efficiency. The example shows that it is possible to modify the cutting conditions with this simulation and optimization method

2. In recent years, high-speed milling has been very common. From experience, it is suitable for milling conditions with small cutting depth and large feed, but it is quite difficult to grasp the best conditions. Milling is different from turning. The former belongs to intermittent cutting. In the process of machining, the tool heating and cooling are repeated at high speed. Because the heat conduction to the chip contact part of the tool is intermittent, the change of the tool temperature must be analyzed according to this feature. The heat conduction has a great influence on the prediction accuracy, but it is not necessary to calculate the deformation of chip formation state on a large scale in connection with thermal analysis, so the analysis results can be obtained quickly. The combination of cutting speed, cutting depth and feed will affect the maximum temperature. When the machining efficiency is certain, increasing the feed speed will reduce the tool temperature. The reduction of temperature will often make the increase of feed speed reach the limit, and increasing the feed speed will make the machining surface rough. Therefore, if the relationship between roughness and temperature can be well balanced, the cutting conditions that balance each other can be selected

3. Physical simulation of cutting process with finite element method

in the physical simulation of cutting process with finite element method, the input contents as cutting conditions include: cutting speed, cutting thickness, tool rake angle, tool rake angle, workpiece material characteristics, etc. After analyzing these parameters, the output results of physical characteristics such as cutting force, chip shape, temperature distribution, stress distribution, deformation distribution and residual stress distribution on the tool and chip can be obtained

this simulation is also applicable to special cutting conditions (such as dynamic cutting). Both the waveremoval process of cutting into wavy surface and the waveform generation process of cutting with tool vibration show that in the process of chip thickness thinning, the shear angle becomes smaller and the deformation is concentrated, resulting in large deformation. In such a dynamic cutting process, the shear angle changes, which corresponds to the change in the deformation range of chip generation, so the cutting force is not proportional to the cutting thickness of the tool tip. From the shear angle change diagram corresponding to the change of the cutting thickness of the tool tip, it can be seen that even if the cutting thickness of the tool tip is the same, the shear angle when the amplitude increases is larger than that when the amplitude decreases, and the lower part of Lissajou figure is a convex half moon. According to such analytical results, the visualization and understanding of phenomena can be made possible, so as to develop a more practical high-precision approximate analytical method

in addition, physical simulation technology can be used to analyze the cutting of composite metal materials with different material properties, as well as the intermittent cutting of tools such as ultrasonic vibration cutting in the cutting direction. From the analytical example of ferrite and pearlite distributed in layers, it can be seen that the state of chip curl is very different due to the different distribution positions of each layer. If the analytical results of physical simulation can be effectively applied in material design, it is possible to realize chip processing without relying on chip breaking slots. In ultrasonic vibration cutting, the cutting force decreases because the vibration frequency of vibration cutting is much higher than the natural vibration frequency of the material system being machined by the tool. The cutting force obtained from this analysis is the force acting intermittently between the tool and the chip. Assuming that there is no influence of other factors such as friction reduction, this cutting force is the same as the usual cutting

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