Toe Sock,Five Toe Sock,Injinji Toe Socks Sellers Union Co., Ltd , http://www.nbshousehold.com
The expert system is a brand new technology. It is still in a period of continuous development. Therefore, the structure of the expert system does not have a fixed pattern. According to the current development situation, it is generally believed that the core of the expert system mainly includes two aspects of knowledge representation and reasoning mechanism, and the specific heat treatment expert system is no exception.
Due to the special nature of materials and heat treatment, heat treatment expert systems have their own characteristics. In terms of knowledge representation, conventional data used for heat treatment, including material grade, part and product name, workpiece type and size, process specification, chemical composition, tensile strength, impact toughness, hardness, hardenability, phase change kinetic data, etc. Generally, it is expressed in numerical form, so the heat treatment expert system usually uses a relational database system to preserve knowledge and use database technology to realize data management and control. On this basis, the knowledge of heat treatment and the knowledge of heat treatment experts are inserted to realize the knowledge representation of the expert system.
In terms of reasoning and decision-making, the calculation of empirical and theoretical formulas is the main clue, supplemented by logical reasoning to achieve decision-making functions. In the decision-making process, it is crucial to get intermediate results based on user input data and known facts, and it is also the "heart" of the entire system. In the heat treatment expert system, this part is called the data export system. Looking at the current heat treatment expert system, its data export mechanism is nothing more than the following two methods, one is based on the phase change dynamics calculation, and the typical ones are STAMP system and PPS system. The other is based on the calculation of the permeability, which is typically AC3 system and SSH system. The data export system is further described below.
It should be pointed out that the expert system based on phase change dynamics calculation and the expert system based on hardenability calculation are not completely different. In many aspects, the technology is mutually infiltrated and the functions are similar.
The expert system with the data export system as its core includes the following aspects:
1) Organization and performance prediction. The microstructure and properties of the workpiece after heat treatment are predicted based on the chemical composition and heat treatment parameters of the steel.
2) Analysis and optimization of process changes. Analyze the influence of process parameter changes on the heat treatment results, and then analyze the heat treatment defects and optimize the process parameters.
3) Heat treatment process assisted design. The computer-aided design of the heat treatment process is carried out using the decision function of the expert system.
4) Online real-time monitoring of the process. The multi-time carbon potential control of the carburizing process optimizes the control of the depth of the layer and the distribution of carbon concentration.
5) Select materials based on part geometry and performance requirements. Select the appropriate grade for the workpiece to be heat treated. The hardness of the grade is sufficient to ensure that the performance at the specified point on the cross section of the workpiece meets the requirements for use when quenching under given conditions.
The following is an example to illustrate the function of the expert system. Assume that the engineering is to select the best steel for the 45mm diameter national axis. For production reasons, quenching oil (flow rate lm/s, quenching intensity H = 0.4 cm-1) was used as a cooling medium. After the workpiece is quenched and tempered, in order to make the workpiece have better fatigue performance, the hardness requirement after tempering at the 3/4 radius of the workpiece section is 35HRC. After inputting the above objectives and constraints, the system first calculates the constraint conditions (the tempering hardness of the workpiece section 3/4 radius is 35HRC), and finally determines that the requirement is equivalent to 11mm from the water-cooled end on the end quenched sample. The hardness is 45.3HRC. Taking this as a constraint condition for decision-making search, the steel grades of GB 40CrNi, GB 4OMnVB and GB 42CrMo were initially obtained. Further comparison of the hardenability zones of the three steel grades, the system determined that GB 42CrMo can well meet the above design requirements.
In addition to the SSH structural steel quenching material selection and process optimization system of Beijing Institute of Mechanical and Electrical Engineering, some universities and factories in China have also carried out many research and development work on heat treatment expert systems. For example, the carburizing process control system developed by Shanghai Jiaotong University uses the mathematical model describing the carburizing process as the knowledge representation method, and uses the computer calculation results as the basis for judgment to realize the prediction of the concentration distribution and hardness distribution of the seepage layer; A new carbon potential control method keeps the entire process in an optimal state. Beijing University of Aeronautics and Astronautics has developed an aeronautical material heat treatment process assisted decision-making system, combining parts CAD and heat treatment theory, using materials, processes and standard databases as knowledge representations, based on which reasoning and decision making, process development and expertise advisory. In addition, some factories are also conducting research and development of computer-aided heat treatment processes, including the generation and management of process cards, and the development of heat treatment processes for special parts.
2. Advantages and disadvantages and scope of use
At present, the expert system has gained practical application in industrial production. For example, some automobile companies have extensively used heat treatment expert systems for process analysis and formulation, existing production cycle optimization, auxiliary material selection, component design, etc., and have achieved good results. The online control system of carburizing process is in China. Many factories are also used. It can be said that the expert system technology has been widely recognized by engineers and technicians. Heat treatment expert systems have played an important role in reducing production costs, shortening production cycles, and improving product quality. A consensus has been reached on this point.
However, it should also be noted that the use of expert systems in the design and industrial sectors is not very high. There are two reasons for this. On the one hand, there is a need to strengthen the use of expert systems; on the other hand, new and better methods need to be developed to enable expert systems to more easily and efficiently assist in tasks such as process design.
Technically, the current heat treatment expert system is based on statistical data and empirical knowledge, and the accuracy and reliability of the results need to be further improved. From the point of view of use, when the expert system is applied to industrial processes and design work, it also contains the components of the traditional trial-and-error method (Tral-and-Egror) to varying degrees. In addition, for the important key parts of industrial production regarding the development of the national economy, as well as the basic parts used in industry, the internal stress and residual deformation generated by the heat treatment process not only affect the performance and quality, but also affect the subsequent assembly precision and processing cost. In the current heat treatment expert system, this factor has not been considered, which cannot be said to be a shortcoming of the current expert system.
At present, the heat treatment expert system is mainly used in the heat treatment process and related design activities of carbon steel and low alloy steel, so it is necessary to broaden the application range of the expert system. In addition, the current expert system decision-making process requires a lot of manual intervention, and further work is needed in the decision-making result processing and human-machine interface to make the expert system more convenient for engineering and technical personnel.
Heat treatment expert system and performance prediction
1. Technical content and technical key