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Computer simulation technology is based on a variety of disciplines and theories, using computers and their corresponding software as tools, through a virtual test method to analyze and solve a comprehensive technology. Computer simulation (simulation), formerly known as the Monte Carlo method, is a method for solving random problems using random number experiments.
The principle can be traced back to the physical experiment conducted by the French naturalist GLBBuffon in 1773 to estimate the pi value. According to the type of computer used in the simulation process, computer simulation has experienced three major stages: simulator simulation, analog-digital mixer simulation and digital machine simulation. In the 1950s, computer simulation mainly used simulators; after the 1960s, serial processing digital machines were gradually applied to simulation, but it was difficult to meet the simulation time limit requirements of large-scale complex systems such as aerospace and chemical industry; and analog-digital hybrids in the 1970s. The machine was once used in many high-tech research fields such as flight simulation, satellite simulation and nuclear reactor simulation. After the development of parallel processing technology in the 1980s, the digital machine finally became the mainstream of computer simulation. Nowadays, computer simulation technology has been widely used in the fields of machinery manufacturing, aerospace, transportation, ship engineering, economic management, engineering construction, military simulation and medical and health.
First, the realization of computer simulation
For objects that need to be studied, computers are generally not directly recognizable and processed. This requires a mathematical model that reflects the essence of the object being studied and is easily processed by computers.
The mathematical model abstracts the essence of the research object, and the computer processes the abstract mathematical models and displays some of the characteristics of the research object by outputting the relevant data of the models. Of course, the representation can be three-dimensional. As the 3D display is more clear and intuitive, it has been adopted by more and more researchers. By analyzing these outputs, you can more clearly understand the research object. It can also be seen from this relationship that the accuracy of mathematical modeling is the most critical factor in determining the accuracy of computer simulation. From the perspective of the model, the implementation of computer simulation can be divided into three major steps: the establishment of the model, the transformation of the model and the simulation of the model.
1. Model establishment
For the object or problem to be studied, it is first necessary to abstract a certain system according to the purpose of the simulation, and to give the boundary conditions and constraints of the system. After that, it is necessary to use the knowledge of various related disciplines to describe the abstracted system with mathematical expressions. The content of the description is the so-called "mathematical model". This model is the core of computer simulation.
The mathematical model of the system can be divided into static model, continuous time dynamic model, discrete time dynamic model and mixed time dynamic model according to time relationship; it can be divided into continuous variable system model and discrete event system model according to the state description and change mode of the system. For some problems of mathematical modeling, Hu Feng et al. of Xi'an Jiaotong University have a detailed discussion in "Review of Dynamic System Computer Simulation Technology (I) - Simulation Model".
2. Model conversion
The so-called model transformation, that is, the mathematical expression abstracted from the previous step is transformed into a form that the computer can process through various appropriate algorithms and computer language. The content represented by this form is the so-called "simulation model". This model is the key to computer simulation. To achieve this process, you can either develop a new system yourself or use the simulation software already available on the market. For example, the MAGMAsoft software is used for simulation in the casting process.
3. Model simulation experiment
The simulation model obtained in the previous step is loaded into the computer, and the simulation model is run according to the preset experimental scheme to obtain a series of simulation results, which is called "model simulation experiment".
With the above conditions, simulation experiments are an easy task. But how should we evaluate the results of this simulation? This requires analysis of the reliability of the simulation experiment. Hu Feng et al. proposed two methods for verifying the reliability of simulation results in the article "Overview of Dynamic System Computer Simulation Technology (II) - Analysis of Simulation Results": Confidence Channel Method and Reverse Verification Method of Simulation Process, for Reference .
Second, the application of computer simulation in the machinery industry
1. Application of Computer Simulation in Research of Complex Machining Process
The machining process is the basis for the production of the machinery industry. The use of computer simulation helps to discover its mechanism and provide theoretical support for improving machining performance. For example, in the aspect of grinding, Professor Wang Longshan of Jilin University proposed various mathematical models that describe the grinding process depending on time variation. Through computer simulation, the grinding behavior and grinding quality can be predicted and estimated, and the grinding process is optimized and intelligent. Control and virtual grinding create the necessary preconditions. Dr. Li Guofa and others studied the model of the grinding power for the grinding process, and used computer simulation to obtain the optimal grinding solution that can be applied to the actual grinding process. Wang Lin, from the School of Mechanical Engineering of Shandong University, also studied the computer simulation system of grinding temperature field, which realized the prediction and optimization of the grinding temperature field, and provided a theoretical basis for studying the influence of various processing parameters on the grinding temperature field. . In terms of milling, Professor Li Huzeng of the Department of Mechanical Engineering of Tongji University established a dynamic model of multi-tooth end milling process, developed a general software for cutting vibration simulation, and studied the principle of planar end mill cutting vibration by digital simulation method. condition. Professor Ren Fujun of Jiamusi University studied computer graphics simulation technology for multi-axis machining of complex curved surfaces by EDM; Dr. Lou Leming of Shanghai Jiaotong University established a process simulation system for EDM to realize the prediction of processing results and processing parameters. Optimization. In terms of extrusion molding, Dr. Chu Candong of Shanghai Jiaotong University established a computer simulation model of continuous extrusion, and obtained the stress field, strain field and temperature field of the continuous extrusion process through simulation experiments.
2. Application of Computer Simulation in Automotive Manufacturing Research
Automotive manufacturing is an important part of the machinery industry. It has many experimental topics, it is difficult, the cost of the field is high, and the introduction of computer simulation technology has effectively alleviated this problem. For example, in the aspect of the engine, Professor Bi Xiaoping of the Department of Mechanical Engineering of the Armored Force Engineering College established a computer simulation model for the starting process of a multi-cylinder diesel engine. The simulation results are in good agreement with the actual measured values ​​and can be used to simulate the starting performance of a multi-cylinder diesel engine. Cai Yixi of Jiangsu University of Science and Technology realized the dynamic simulation of the gas flow in the intake pipe, visually described the transient process, and provided an effective method for the study of the multi-cylinder engine ventilation process. In terms of automobile flow field, Dr. Lu Mingzhong from the School of Information Science, East China University of Science and Technology successfully simulated the airflow separation and towing vortex phenomenon of the vehicle wake field, established the aerodynamic model of the vehicle external flow field of two models, and simulated it. The experiment achieved satisfactory results. In the collision experiment, Dr. Zhan Yusong from the Institute of Power Machinery and Vehicle Engineering of Zhejiang University established a mathematical model of the occupant dynamic response based on the law between the accident pattern of the car collision and the occupant injury, and developed the corresponding simulation software. The system can partially replace the real vehicle crash test to study the passive safety performance of the car. In other respects, for example, Xiong Jian of the Automotive Engineering Institute conducted a simulation study on the braking process of the automobile. Yao Ge of FAW Volkswagen Automotive Co., Ltd. studied the portability of the steering of the car through simulation.
3. Application of Computer Simulation in Gear Design
Gear is the main basic component of mechanical products, and it is of great significance to carry out simulation research. Many researchers have done relevant research in this aspect. For example, Pang Guibing of Taiyuan University of Technology used Visual Lisp language to discuss the gear modeling and transmission simulation of any face gear from the geometrical point of view. Zhang Guangjun of Shandong Mining Institute used computer simulation to study the dynamics of arc-pin planetary transmission. Zeng Ying of the School of Mechanical and Electrical Engineering of Nanjing University of Aeronautics and Astronautics discussed the influence of the main parameters of the driving gear and the tool, the gear ratio and the modulus on the contact point of the orthogonal gear transmission through computer simulation. Computer simulation also has important applications in the design and manufacture of gears for gear pumps.
The principle can be traced back to the physical experiment conducted by the French naturalist GLBBuffon in 1773 to estimate the pi value. According to the type of computer used in the simulation process, computer simulation has experienced three major stages: simulator simulation, analog-digital mixer simulation and digital machine simulation. In the 1950s, computer simulation mainly used simulators; after the 1960s, serial processing digital machines were gradually applied to simulation, but it was difficult to meet the simulation time limit requirements of large-scale complex systems such as aerospace and chemical industry; and analog-digital hybrids in the 1970s. The machine was once used in many high-tech research fields such as flight simulation, satellite simulation and nuclear reactor simulation. After the development of parallel processing technology in the 1980s, the digital machine finally became the mainstream of computer simulation. Nowadays, computer simulation technology has been widely used in the fields of machinery manufacturing, aerospace, transportation, ship engineering, economic management, engineering construction, military simulation and medical and health.
First, the realization of computer simulation
For objects that need to be studied, computers are generally not directly recognizable and processed. This requires a mathematical model that reflects the essence of the object being studied and is easily processed by computers.
The mathematical model abstracts the essence of the research object, and the computer processes the abstract mathematical models and displays some of the characteristics of the research object by outputting the relevant data of the models. Of course, the representation can be three-dimensional. As the 3D display is more clear and intuitive, it has been adopted by more and more researchers. By analyzing these outputs, you can more clearly understand the research object. It can also be seen from this relationship that the accuracy of mathematical modeling is the most critical factor in determining the accuracy of computer simulation. From the perspective of the model, the implementation of computer simulation can be divided into three major steps: the establishment of the model, the transformation of the model and the simulation of the model.
1. Model establishment
For the object or problem to be studied, it is first necessary to abstract a certain system according to the purpose of the simulation, and to give the boundary conditions and constraints of the system. After that, it is necessary to use the knowledge of various related disciplines to describe the abstracted system with mathematical expressions. The content of the description is the so-called "mathematical model". This model is the core of computer simulation.
The mathematical model of the system can be divided into static model, continuous time dynamic model, discrete time dynamic model and mixed time dynamic model according to time relationship; it can be divided into continuous variable system model and discrete event system model according to the state description and change mode of the system. For some problems of mathematical modeling, Hu Feng et al. of Xi'an Jiaotong University have a detailed discussion in "Review of Dynamic System Computer Simulation Technology (I) - Simulation Model".
2. Model conversion
The so-called model transformation, that is, the mathematical expression abstracted from the previous step is transformed into a form that the computer can process through various appropriate algorithms and computer language. The content represented by this form is the so-called "simulation model". This model is the key to computer simulation. To achieve this process, you can either develop a new system yourself or use the simulation software already available on the market. For example, the MAGMAsoft software is used for simulation in the casting process.
3. Model simulation experiment
The simulation model obtained in the previous step is loaded into the computer, and the simulation model is run according to the preset experimental scheme to obtain a series of simulation results, which is called "model simulation experiment".
With the above conditions, simulation experiments are an easy task. But how should we evaluate the results of this simulation? This requires analysis of the reliability of the simulation experiment. Hu Feng et al. proposed two methods for verifying the reliability of simulation results in the article "Overview of Dynamic System Computer Simulation Technology (II) - Analysis of Simulation Results": Confidence Channel Method and Reverse Verification Method of Simulation Process, for Reference .
Second, the application of computer simulation in the machinery industry
1. Application of Computer Simulation in Research of Complex Machining Process
The machining process is the basis for the production of the machinery industry. The use of computer simulation helps to discover its mechanism and provide theoretical support for improving machining performance. For example, in the aspect of grinding, Professor Wang Longshan of Jilin University proposed various mathematical models that describe the grinding process depending on time variation. Through computer simulation, the grinding behavior and grinding quality can be predicted and estimated, and the grinding process is optimized and intelligent. Control and virtual grinding create the necessary preconditions. Dr. Li Guofa and others studied the model of the grinding power for the grinding process, and used computer simulation to obtain the optimal grinding solution that can be applied to the actual grinding process. Wang Lin, from the School of Mechanical Engineering of Shandong University, also studied the computer simulation system of grinding temperature field, which realized the prediction and optimization of the grinding temperature field, and provided a theoretical basis for studying the influence of various processing parameters on the grinding temperature field. . In terms of milling, Professor Li Huzeng of the Department of Mechanical Engineering of Tongji University established a dynamic model of multi-tooth end milling process, developed a general software for cutting vibration simulation, and studied the principle of planar end mill cutting vibration by digital simulation method. condition. Professor Ren Fujun of Jiamusi University studied computer graphics simulation technology for multi-axis machining of complex curved surfaces by EDM; Dr. Lou Leming of Shanghai Jiaotong University established a process simulation system for EDM to realize the prediction of processing results and processing parameters. Optimization. In terms of extrusion molding, Dr. Chu Candong of Shanghai Jiaotong University established a computer simulation model of continuous extrusion, and obtained the stress field, strain field and temperature field of the continuous extrusion process through simulation experiments.
2. Application of Computer Simulation in Automotive Manufacturing Research
Automotive manufacturing is an important part of the machinery industry. It has many experimental topics, it is difficult, the cost of the field is high, and the introduction of computer simulation technology has effectively alleviated this problem. For example, in the aspect of the engine, Professor Bi Xiaoping of the Department of Mechanical Engineering of the Armored Force Engineering College established a computer simulation model for the starting process of a multi-cylinder diesel engine. The simulation results are in good agreement with the actual measured values ​​and can be used to simulate the starting performance of a multi-cylinder diesel engine. Cai Yixi of Jiangsu University of Science and Technology realized the dynamic simulation of the gas flow in the intake pipe, visually described the transient process, and provided an effective method for the study of the multi-cylinder engine ventilation process. In terms of automobile flow field, Dr. Lu Mingzhong from the School of Information Science, East China University of Science and Technology successfully simulated the airflow separation and towing vortex phenomenon of the vehicle wake field, established the aerodynamic model of the vehicle external flow field of two models, and simulated it. The experiment achieved satisfactory results. In the collision experiment, Dr. Zhan Yusong from the Institute of Power Machinery and Vehicle Engineering of Zhejiang University established a mathematical model of the occupant dynamic response based on the law between the accident pattern of the car collision and the occupant injury, and developed the corresponding simulation software. The system can partially replace the real vehicle crash test to study the passive safety performance of the car. In other respects, for example, Xiong Jian of the Automotive Engineering Institute conducted a simulation study on the braking process of the automobile. Yao Ge of FAW Volkswagen Automotive Co., Ltd. studied the portability of the steering of the car through simulation.
3. Application of Computer Simulation in Gear Design
Gear is the main basic component of mechanical products, and it is of great significance to carry out simulation research. Many researchers have done relevant research in this aspect. For example, Pang Guibing of Taiyuan University of Technology used Visual Lisp language to discuss the gear modeling and transmission simulation of any face gear from the geometrical point of view. Zhang Guangjun of Shandong Mining Institute used computer simulation to study the dynamics of arc-pin planetary transmission. Zeng Ying of the School of Mechanical and Electrical Engineering of Nanjing University of Aeronautics and Astronautics discussed the influence of the main parameters of the driving gear and the tool, the gear ratio and the modulus on the contact point of the orthogonal gear transmission through computer simulation. Computer simulation also has important applications in the design and manufacture of gears for gear pumps.
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