Introduction to CAE Technology
1. CAE technology
With the development of science and technology, products will inevitably become more complicated as they become more diversified and intelligent. For complex engineering, people hope to accurately test, analyze and demonstrate the design before the production of the product. These tasks need to be realized by computer, that is, Computer Aided Engineering (CAE). CAE is a comprehensive process including product design, engineering analysis, data management, testing, simulation and manufacturing. The key is based on the 3D solid modeling, starting from the design stage of the product, performing simulation and structural analysis according to actual conditions. Performance requirements are designed and comprehensively evaluated to select the best solution from multiple scenarios or to optimize the design directly.
At present, in order to better carry out the work in various engineering stages, designers have increasingly used computer-aided means, resulting in a series of technical branches, such as Computer Aided Design (CAD), computer-aided test CAT (Computer Aided Test), Computer Aided Process Planning (CAPP), and Computer Aided Manufacturing (CAM) are sometimes referred to as CAX technology.
2. CAE software
The application of CAE technology in engineering requires a carrier, and the carrier of CAE technology is CAE software. CAE software is a comprehensive, knowledge-intensive information product that combines computational mechanics, computational mathematics, related engineering sciences, engineering management, and modern computing technologies.
CAE software can be roughly divided into dedicated and general categories.
Dedicated software, software developed for performance analysis, prediction, and optimization for specific types of objects. Broadly speaking, some small calculation programs at the designer's hand can be considered as dedicated CAE software.
General software, which can analyze, simulate, predict, evaluate and optimize the physical and mechanical properties of various types of objects to realize software for product technology innovation. General CAE software mainly refers to large-scale general commercial software such as NASTRAN, ADAMS, ANSYS, MARC, ADINA, and ABAQUS.
3. CAE connotation
CAE technology mainly includes the following three aspects:
(1) The main object of the finite element method is the part level, including structural stiffness, strength analysis, nonlinear and thermal field calculations;
(2) The main object of simulation technology is sub-system or system, including virtual prototype, flow field calculation and electromagnetic field calculation;
(3) The main object of optimization design is structural design parameters.
From the use of finite element method to the simple check of the performance of the designed product, gradually developed to the accurate prediction of product performance, and then to the accurate simulation of the product work process, finite element method and simulation technology played an important role, won People's universal trust. However, improving product competitiveness requires not only improving the performance and quality of the product, but also reducing the cost of the product and shortening the development cycle. The optimization technology introduced the CAE method, which freed people from the heavy trial and error work, and the CAE technology reached a new height.
When using CAE technology to solve practical engineering problems, you need to pay attention to the following two points.
(1) CAE work is a difficult task. A job won't get results right away because of a 3D solid model and load. In fact, with the 3D solid model, a lot of model conversion and modification work is needed to get the correct analysis model. This work usually accounts for more than 70% of the workload, and it may take longer when the situation is complicated.
(2) The general CAE analysis is based on the assumption that the structural material is defect-free and there is no process problem. If a structure accidentally occurs during use, it may be the cause of the structure itself, or it may be due to material or process. However, if the problem occurs repeatedly, it must be a structural cause, and CAE analysis must be performed. If there are problems with materials and processes, the general CAE analysis conclusions are not applicable unless special CAE analysis of materials and processes is performed.
4. The role of CAE in product development
In the product life cycle, the amount of information (awareness of product performance) and the relationship between risk and development stage are shown in Figure 1.
Figure 1 Relationship between information volume and risk
In the figure, the abscissa is the development stage, and the ordinate is the amount of information and risk. It can be seen that the amount of information and the risk existing are basically axisymmetric. The greater the amount of information, the lower the risk. Traditional technology can't provide users with more product information in the early stage, and high risk is inevitable. With CAE technology, product information can be obtained early, so that the rising and falling sections of the two curves move to the left at the same time (such as arrow diagram Show), you can reduce the risk. The reduction of risk not only reduces development costs, but also shortens the development cycle, improves product quality, and enhances product competitiveness, so that products can be launched earlier than competitors in an increasingly competitive market, increasing market share.
The role of CAE in reducing costs is shown in Figure 2.
Figure 2 The role of CAE in reducing costs
In the process of product development, various factors will inevitably lead to various problems. The most common solution used in the past was to ask the experts or use the appropriate analysis tools to find out the cause and take the corresponding action. Usually, although the proposed modification may be only for a certain component, for a complex system such as a vehicle, it is often a matter of moving around, and while solving a problem, it may bring other problem. In order to avoid a series of changes, designers sometimes have to make some compromises. Although they can solve the problem to a certain extent, they cannot be solved fundamentally, which increases the maintenance cost after the product is put into production.
If CAE technology is adopted in the early stage, although the initial investment is increased, the subsequent product development costs are reduced. The total amount of input is much less than the traditional practice, and after the product is put into production, the investment can be kept at a very low level. Overall, the total cost of product development is reduced, and the time to market of the product is advanced. .
Taking into account the above advantages of CAE technology, in the "National Industrial Technology Policy" formulated by the State Economic and Trade Commission and the relevant departments of the State Council in June 2002, CAE technology was included in the first key industry technology development direction "high-tech and industrialization." "The important content."
Virtual prototype
Virtual prototype technology
Virtual prototyping technology in mechanical engineering, also known as mechanical system dynamic simulation technology, is a CAE technology that emerged with the development of computer technology in the 1980s. It belongs to an important branch of computer-aided engineering. In the virtual prototyping technology, the engineer builds a prototype model on the computer, performs various dynamic performance analysis on the model, and then improves the prototype design scheme, replacing the traditional physical prototype experiment with a digital form.
The main difference between virtual prototyping technology and finite element method is that it analyzes the system from the system level, so the impact of virtual prototyping technology on design methods and processes is greater than that of finite element technology. The use of virtual prototyping technology can greatly simplify the design and development process of mechanical products, greatly shorten the product development cycle, significantly reduce product development costs and costs, significantly improve product quality, improve system-level performance of products, and obtain optimized design products.
At present, virtual prototyping technology has been widely used in various fields, including automobile manufacturing, engineering machinery, aerospace industry, national defense industry and general machinery manufacturing. In all areas, virtual prototyping technology can save users money, time, and provide a satisfactory design for a variety of products.
2. Features of virtual prototyping technology
Before the advent of virtual prototyping technology, the traditional design method was from bottom to top, from component design to complete machine design. The downside of this approach is that designers tend to focus on the details, ignoring overall performance. This kind of thing happens frequently in China. When the performance of the imported prototypes has not been thoroughly seen, the parts are copied. The result is likely to be a detour that has been repeated by people, and even some jokes will appear. The result of this is that the product will always be at least one generation behind others, and the level will never go up. Through virtual technology, we can explore other people's design ideas at a lower cost, improve and innovate in imitation, and improve their own research and development.
In the traditional design process, the target is usually first proposed, then the subsystem and component design, and then assembled into a complete vehicle through production and processing, and the final design of the product can meet the design requirements, only through the physical prototype test To draw a conclusion. If you only find some minor problems during the test, you can solve them with simple changes, but if you find major problems or system problems, you may need to overturn the original design. It can be seen that this model has a lot of blindness and a high risk.
With the help of virtual prototyping technology, after the basic design of the product is completed, the product performance can be roughly understood before the product processing, and the costly system design mistakes are avoided. The simulation results of the early stage virtual prototype can also be used as a reference for part design. For example, the results of dynamics or static analysis can be used to guide the strength design of the part. Compared with the traditional design process, the process of virtual assembly, virtual test, etc. is added, and the product can only enter the processing, assembly and physical test after meeting the product requirements.
The role of the virtual prototype can also be illustrated by comparing traditional design with modern design processes. In the traditional design, from product design to finalization, it is often subjected to multiple cycles of “design-process-testâ€. Each cycle involves the processing and testing of physical prototypes, resulting in a large amount of time, labor and material consumption. In modern design, the virtual prototype test is added between design and processing. There is no need to carry out the “design-process-test†cycle, which saves costs and facilitates early detection of design defects and optimization design. Shorten the research and development cycle.
3. Virtual prototype application effect
As we all know, at different stages of product development, the later the problem is discovered, the higher the cost is required, and the development cycle is extended. It is important to find the problem as early as possible.
The statistics of the Toyota development process are shown in Figure 3.
Figure 3 Toyota Motor Development Statistics
In the development process of the early 1990s, by strengthening communication and coordination between various departments, 40% of problems can be found before the prototype, and 75% of problems can be found before the prototype. After applying 3D CAD to the test design in the mid-1990s, the proportion of problems found in the prototype car and the prototype car reached 50% and 90% respectively (we are at this stage). After the application of the virtual prototype in the late 1990s, the proportion of problems found in the prototype car and the prototype car reached 80% and 95% respectively. Since 95% of the problems before the prototype are found and solved, the importance of the prototype is greatly reduced, so some programs are saved, and the development time and cost are reduced by 30% without affecting the product quality. 40%.
According to the data, after the adoption of virtual prototyping technology, Toyota Camry reduced the development time by 10 months, reduced manpower investment by 20%, reduced research and development costs by 30%, and reduced the number of prototypes by 65%. Another successful example is that Ford used the CAE technology to reduce the number of trials for each new car from 300 to 80.
CAE technology development trend
The development trend of CAE technology can be summarized as the use of the most advanced information technology, the absorption of the latest scientific knowledge and methods, and the expansion of CAE software functions to improve its performance.
This mainly includes the following three aspects.
(1) Functional, performance and software technology aspects: including 3D graphics processing and virtual reality, object-oriented engineering database and its management system, multi-phase polymorphic medium coupling, multi-physics coupling and multi-scale coupling analysis and adaptation to super parallelism High-performance CAE solution technology for computers and fleets.
(2) Multimedia user interface and intelligence: including multimedia user interface, enhanced modeling and data processing functions, and intelligent user interface.
(3) Seamless integration of CAX software: The integration of CAE calculation and analysis software in various professional fields, and the comprehensive calculation analysis and operation simulation of large-scale engineering and complex products will become another important direction of CAE software integration.
CAE technology application examples
In recent years, CAE technology has played an important role in the author's unit, solving or assisting in solving many engineering problems and achieving remarkable results.
Here are a few practical examples from last year.
When designing the engine oil tank, the original design structure is analyzed. The results show that if there is no relative displacement between the installation positions, the structural stress is much smaller than the allowable value, and the structure will not be damaged. Further analysis shows that even if there is a relative displacement of one millimeter between the installation positions, the dangerous parts will generate great stress and cause damage. This requires the selection of appropriate installation and fixing methods, which provides a theoretical basis for improving the design.
In order to solve the torsional resonance problem that occurred in the model car many times, the torsional vibration performance calculation of the transmission system was made, and finally the suitable coupling parameters were found. These parameters were applied in the new design scheme and passed the real The car assessment has not seen similar problems so far.
Dozens of programs for amphibious vehicles and other water propellers have been compared, and the best solution has been selected. Many performance tests have been omitted. The cost of each direct test is only 150,000 yuan. The benefits are also considerable. Does not include the benefits of shortening production time. Part of the analysis results have been verified by relevant experiments, the error of the two is not more than 5%, which fully demonstrates the effectiveness of the analysis.
The overall dynamic performance of a certain type of vehicle is simulated and calculated, and some important parameters of the vehicle and the loads of important parts in the process of passing through the vertical wall, sloping, climbing, etc. are obtained, in order to understand the performance and determination of the vehicle. Component loads have laid the foundation, most of which are difficult to obtain in the past, and even impossible in the design phase, which is important for guiding design.
Suggestions
Finally, the author makes the following suggestions.
(1) Give CAE enough attention. There is always a process of growth for a new technology from the introduction to the application to the production of benefits. Especially in the initial stage, it is especially necessary to pay attention and support from all aspects. Only in this way can we do this work well together.
(2) A large part of the value of CAE is implicit or reflected in the design work. Therefore, it is difficult to see the value of the work from the benefits of the CAE department itself. In addition, it is necessary to straighten out the relationship, clear responsibility, and avoid the phenomenon that “it is the responsibility of the designer, and the responsibility of the analyst is not goodâ€.
(3) The CAE industry is in a period of rapid development and growth, and the mobility of employees is relatively large. Therefore, it is necessary to guide and support this policy, and take effective measures to attract and retain talents to ensure the continuity of work.
(4) The current CAE technology has been basically mature. The availability, reliability and computational efficiency of CAE software have been basically solved. CAE software should be a useful assistant and effective tool for design engineers to achieve engineering innovation and product innovation. Some simple analysis Calculations can be done directly on the CAD software.
(5) Find problems and solve problems in time. It is an important supplement to the design work to be able to perform CAE analysis early in the design and to identify possible problems in time.
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