2002 Vol.15(3)
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2002, 16(3).
Abstract:
A new control scheme, the hybrid fuzzy control method, for active damping suspension system is presented. The scheme is the result of effective combination of the statistical optimal control method based on the statistical property of suspension system, with the bang-bang control method based on the real-time characteristics of suspension system. Computer simulations are performed to compare the effectiveness of hybrid fuzzy control scheme with that of optimal damping control, bang-bang control, and passive suspension. It takes the effects of time-variant factors into full account. The superiority of the proposed hybrid fuzzy control scheme for active damping suspension to the passive suspension is verified in the experiment study.
A new control scheme, the hybrid fuzzy control method, for active damping suspension system is presented. The scheme is the result of effective combination of the statistical optimal control method based on the statistical property of suspension system, with the bang-bang control method based on the real-time characteristics of suspension system. Computer simulations are performed to compare the effectiveness of hybrid fuzzy control scheme with that of optimal damping control, bang-bang control, and passive suspension. It takes the effects of time-variant factors into full account. The superiority of the proposed hybrid fuzzy control scheme for active damping suspension to the passive suspension is verified in the experiment study.
2002, 16(3).
Abstract:
Facing the market economy and global challenge the development of manufacturing industry especially casting industry is critical to the national economy. To reform the traditional casting industry by using computer technology is one of the hottest research frontiers studied by many researchers and engineers. Computer simulation of solidification process of shaped casting can assure the quality of casting, optimize the casting technology, shorten the lead time and therefore decrease the developing and manufacturing cost. Recently, numerical simulation of mold-filling and solidification processes of shaped casting and prediction of microstructure and property as well are extensively studied and put into application in many casting plants with many successful simulation cases.
Facing the market economy and global challenge the development of manufacturing industry especially casting industry is critical to the national economy. To reform the traditional casting industry by using computer technology is one of the hottest research frontiers studied by many researchers and engineers. Computer simulation of solidification process of shaped casting can assure the quality of casting, optimize the casting technology, shorten the lead time and therefore decrease the developing and manufacturing cost. Recently, numerical simulation of mold-filling and solidification processes of shaped casting and prediction of microstructure and property as well are extensively studied and put into application in many casting plants with many successful simulation cases.
2002, 16(3).
Abstract:
A method for determination of tool-chip contact length is theoretically presented in orthogonal metal machining. By using computer simulation and based on the analyses of the elastro-plastic deformation with lagrangian finite element method in the deformation zone, the accumulated representative length of the low layer, the tool-chip contact length of the chip contacting the tool rake are calculated, experimental studies are also carried out with 0.2% carbon steel. It is shown that the tool-chip contact lengths obtained from computer simulation have a good agreement with those of measured values.
A method for determination of tool-chip contact length is theoretically presented in orthogonal metal machining. By using computer simulation and based on the analyses of the elastro-plastic deformation with lagrangian finite element method in the deformation zone, the accumulated representative length of the low layer, the tool-chip contact length of the chip contacting the tool rake are calculated, experimental studies are also carried out with 0.2% carbon steel. It is shown that the tool-chip contact lengths obtained from computer simulation have a good agreement with those of measured values.
2002, 16(3).
Abstract:
Using virtual reality to design a new type of hydraulic support is discussed. That is how to make use of the virtual design to develop coal mining machine in practice. The advantages of virtual design are studied and the simple virtual reality system is built. The 3D parts and elements of hydraulic support are modeled with parametric design in CAD software, then exported to VR environment, in which the virtual hydraulic support is assembled, operated and tested. With the method, the errors and faults of design can be fined easily, many improvements are made and the new hydraulic support is developed successfully.
Using virtual reality to design a new type of hydraulic support is discussed. That is how to make use of the virtual design to develop coal mining machine in practice. The advantages of virtual design are studied and the simple virtual reality system is built. The 3D parts and elements of hydraulic support are modeled with parametric design in CAD software, then exported to VR environment, in which the virtual hydraulic support is assembled, operated and tested. With the method, the errors and faults of design can be fined easily, many improvements are made and the new hydraulic support is developed successfully.
2002, 16(3).
Abstract:
The high failure rate of crane brake results from improper choice of braking torque. The mathematical model of reliability for the crane brake parameters is introduced. Based on large amount of actual data the parameter reliabilities of 5~50 t general overhead travelling cranes are calculated，the probabilities that the braking torque is less than the static torque acting on the axle when the load moves down are obtained. Moreover, the ways to improve the reliability of brake parameters are discussed，the most reasonable values of braking safety coefficient are given.
The high failure rate of crane brake results from improper choice of braking torque. The mathematical model of reliability for the crane brake parameters is introduced. Based on large amount of actual data the parameter reliabilities of 5~50 t general overhead travelling cranes are calculated，the probabilities that the braking torque is less than the static torque acting on the axle when the load moves down are obtained. Moreover, the ways to improve the reliability of brake parameters are discussed，the most reasonable values of braking safety coefficient are given.
2002, 16(3).
Abstract:
The lifetime prediction of ceramics is discussed on the basis of the relationship between stress intensity factor KI and crack velocity v. The effects of water environment, the cyclic loading and microstructure of material on KI-v characteristics are studied by carrying out the crack growth tests by the double torsion (DT) method under the static and cyclic loading in both environments of air and water for alumina and zirconia. KI-v characteristics determined by the double tor-sion method are used to predict time-to-failure under the cyclic loading of alumina and zirconia ceramics. The predictions agree qualitatively with the experimental results.
The lifetime prediction of ceramics is discussed on the basis of the relationship between stress intensity factor KI and crack velocity v. The effects of water environment, the cyclic loading and microstructure of material on KI-v characteristics are studied by carrying out the crack growth tests by the double torsion (DT) method under the static and cyclic loading in both environments of air and water for alumina and zirconia. KI-v characteristics determined by the double tor-sion method are used to predict time-to-failure under the cyclic loading of alumina and zirconia ceramics. The predictions agree qualitatively with the experimental results.
2002, 16(3).
Abstract:
For purpose of simulation of the working characteristics of a new type of fluid coupling shock absorber for vibration protection of sensitive equipment, a physical model is presented by analyzing the internal fluid dynamic phenomenon with respect to the coupling shock absorber and implemented in MATLAB software package. Using the model it is possible to evaluate the importance of different factors for design of the shock absorber. In the meantime, the key-model machine is designed for coupling dynamic test. Comparisons with experimental results confirm the validity of the model. So the CAD/CAE software has been developed in MATLAB for design and experimental test of the new coupling shock absorber.
For purpose of simulation of the working characteristics of a new type of fluid coupling shock absorber for vibration protection of sensitive equipment, a physical model is presented by analyzing the internal fluid dynamic phenomenon with respect to the coupling shock absorber and implemented in MATLAB software package. Using the model it is possible to evaluate the importance of different factors for design of the shock absorber. In the meantime, the key-model machine is designed for coupling dynamic test. Comparisons with experimental results confirm the validity of the model. So the CAD/CAE software has been developed in MATLAB for design and experimental test of the new coupling shock absorber.
2002, 16(3).
Abstract:
The most remarkable characteristic of a metal belt-planetary gear continuously variable transmission is a wider ratio range and a bigger torque capacity than a conventional metal pushing belt continuously variable transmission. A parallel hybrid car with this transmission system not only can reduce fuel consumption and pollutant emission at a ECE city cycle, but also can keep the motor working in the most efficiency area and can be started by a lower power motor by oneself. At the same time, the continuously variable transmission system can realize the smooth switch between the motor and the engine.
The most remarkable characteristic of a metal belt-planetary gear continuously variable transmission is a wider ratio range and a bigger torque capacity than a conventional metal pushing belt continuously variable transmission. A parallel hybrid car with this transmission system not only can reduce fuel consumption and pollutant emission at a ECE city cycle, but also can keep the motor working in the most efficiency area and can be started by a lower power motor by oneself. At the same time, the continuously variable transmission system can realize the smooth switch between the motor and the engine.
2002, 16(3).
Abstract:
Triangulation of scattered points is the first important section during reverse engineering. New concepts of dynamic circle and closed point are put forward based on current basic method. These new concepts can narrow the extent which triangulation process should seek through and optimize the triangles during producing them. Updating the searching edges dynamically controls progress of triangulation. Intersection judgment between new triangle and produced triangles is changed into intersection judgment between new triangle and searching edges. Examples illustrate superiorities of this new algorithm.
Triangulation of scattered points is the first important section during reverse engineering. New concepts of dynamic circle and closed point are put forward based on current basic method. These new concepts can narrow the extent which triangulation process should seek through and optimize the triangles during producing them. Updating the searching edges dynamically controls progress of triangulation. Intersection judgment between new triangle and produced triangles is changed into intersection judgment between new triangle and searching edges. Examples illustrate superiorities of this new algorithm.
2002, 16(3).
Abstract:
Taking AutoCAD2000 as platform, an algorithm for the reconstruction of surface from scattered data points based on VBA is presented. With this core technology customers can be free from traditional AutoCAD as an electronic board and begin to create actual presentation of real-world objects. VBA is not only a very powerful tool of development, but with very simple syntax. Associating with those solids, objects and commands of AutoCAD 2000, VBA notably simplifies previous complex algorithms, graphical presentations and processing, etc. Meanwhile, it can avoid appearance of complex data structure and data format in reverse design with other modeling software. Applying VBA to reverse engineering can greatly improve modeling efficiency and facilitate surface reconstruction.
Taking AutoCAD2000 as platform, an algorithm for the reconstruction of surface from scattered data points based on VBA is presented. With this core technology customers can be free from traditional AutoCAD as an electronic board and begin to create actual presentation of real-world objects. VBA is not only a very powerful tool of development, but with very simple syntax. Associating with those solids, objects and commands of AutoCAD 2000, VBA notably simplifies previous complex algorithms, graphical presentations and processing, etc. Meanwhile, it can avoid appearance of complex data structure and data format in reverse design with other modeling software. Applying VBA to reverse engineering can greatly improve modeling efficiency and facilitate surface reconstruction.
2002, 16(3).
Abstract:
Firstly, constant amplitude P–Sa–Sm–Nc surface family is established. Secondly, four basic assumptions, I.e., monotonically increasing, non-coupling, separability and nonintersecting of fatigue damage accumulation are proposed from the viewpoint of both damage mechanics and fracture mechanics. Then the individual isodamage D–Sa–Sm–N surface under constant amplitude loading is constructed and the two-dimensional individual Miner's rule is derived. Conse-quently, the two-dimensional probabilistic Miner's rule (TPMiner) is established and proved for a population subjected to variable amplitude loading. Finally, with successfully experiment verification, TPMiner proves be to very useful and feasible in fatigue reliability theory.
Firstly, constant amplitude P–Sa–Sm–Nc surface family is established. Secondly, four basic assumptions, I.e., monotonically increasing, non-coupling, separability and nonintersecting of fatigue damage accumulation are proposed from the viewpoint of both damage mechanics and fracture mechanics. Then the individual isodamage D–Sa–Sm–N surface under constant amplitude loading is constructed and the two-dimensional individual Miner's rule is derived. Conse-quently, the two-dimensional probabilistic Miner's rule (TPMiner) is established and proved for a population subjected to variable amplitude loading. Finally, with successfully experiment verification, TPMiner proves be to very useful and feasible in fatigue reliability theory.
2002, 16(3).
Abstract:
An integrated approach to generation of precedence relations and precedence graphs for assembly sequence planning is presented, which contains more assembly flexibility. The approach involves two stages. Based on the assembly model, the components in the assembly can be divided into partially constrained components and completely constrained components in the first stage, and then geometric precedence relation for every component is generated automatically. According to the result of the first stage, the second stage determines and constructs all precedence graphs. The algorithms of these two stages proposed are verified by two assembly examples.
An integrated approach to generation of precedence relations and precedence graphs for assembly sequence planning is presented, which contains more assembly flexibility. The approach involves two stages. Based on the assembly model, the components in the assembly can be divided into partially constrained components and completely constrained components in the first stage, and then geometric precedence relation for every component is generated automatically. According to the result of the first stage, the second stage determines and constructs all precedence graphs. The algorithms of these two stages proposed are verified by two assembly examples.
2002, 16(3).
Abstract:
A dynamic impedance-based structural health monitoring technique is introduced. According to the direct and the converse piezoelectric property of piezoelectric materials, the piezoceramic ( PZT ) can be used as an actuator and a sensor synchronously. If damages like cracks, holes, debonding or loose connections are presented in the structure, the physical variations of the structure will cause the mechanical impedance modified. On the basis of introducing the principle and the theory, the experiment and the analysis on some damages of the structure are studied by means of the dynamic impedance technique. On the view of experiment, kinds of structural damages are evaluated by the information of dynamic impedance in order to validate the feasibility of the method.
A dynamic impedance-based structural health monitoring technique is introduced. According to the direct and the converse piezoelectric property of piezoelectric materials, the piezoceramic ( PZT ) can be used as an actuator and a sensor synchronously. If damages like cracks, holes, debonding or loose connections are presented in the structure, the physical variations of the structure will cause the mechanical impedance modified. On the basis of introducing the principle and the theory, the experiment and the analysis on some damages of the structure are studied by means of the dynamic impedance technique. On the view of experiment, kinds of structural damages are evaluated by the information of dynamic impedance in order to validate the feasibility of the method.
2002, 16(3).
Abstract:
Adopting distributed control architecture is the important development direction for shop floor management and control system, is also the requirement of making it agile, intelligent and concurrent. Some key problems in achieving distributed control architecture are researched. An activity model of shop floor is presented as the requirement definition of the prototype system. The multi-agent based software architecture is constructed. How the core part in shop floor management and control system, production plan and scheduling is achieved. The cooperation of different agents is illustrated. Finally, the implementation of the prototype system is narrated.
Adopting distributed control architecture is the important development direction for shop floor management and control system, is also the requirement of making it agile, intelligent and concurrent. Some key problems in achieving distributed control architecture are researched. An activity model of shop floor is presented as the requirement definition of the prototype system. The multi-agent based software architecture is constructed. How the core part in shop floor management and control system, production plan and scheduling is achieved. The cooperation of different agents is illustrated. Finally, the implementation of the prototype system is narrated.
2002, 16(3).
Abstract:
Based on the analysis of air flow and heat transfer in the dry-cooling tower for Harmon system, a combined iteration method is presented to solve the coupled heat transfer and draft equations derived from theoretical and empirical formulas, with the size of the exchangers and the cooling tower or the systematic parameters being determined. Taking the 686 MW unit as an example, the present calculating results are well agreed with those of the real case, and thus the method presented is practical and feasible for reasonable design of Harmon system.
Based on the analysis of air flow and heat transfer in the dry-cooling tower for Harmon system, a combined iteration method is presented to solve the coupled heat transfer and draft equations derived from theoretical and empirical formulas, with the size of the exchangers and the cooling tower or the systematic parameters being determined. Taking the 686 MW unit as an example, the present calculating results are well agreed with those of the real case, and thus the method presented is practical and feasible for reasonable design of Harmon system.
2002, 16(3).
Abstract:
The viscoelastic properties of the normal PTFE plastic and strengthened PTFE plastic for bearing pad are measured. The mechanical properties of the composite material for bearing pad, which is made of the aforementioned plastics as matrix reinforced by fine bronze elastic springs, are modeled and relaxation modulus of the material are presented. The difference between these two kinds of PTFE is studied. The results show that the complex modulus of PTFE plastics for bearing pad is higher than that of normal PTFE plastics.
The viscoelastic properties of the normal PTFE plastic and strengthened PTFE plastic for bearing pad are measured. The mechanical properties of the composite material for bearing pad, which is made of the aforementioned plastics as matrix reinforced by fine bronze elastic springs, are modeled and relaxation modulus of the material are presented. The difference between these two kinds of PTFE is studied. The results show that the complex modulus of PTFE plastics for bearing pad is higher than that of normal PTFE plastics.
2002, 16(3).
Abstract:
Gears alternately mesh and detach in driving process, and then working conditions of gears are alternately changing, so they are easy to be spalled and worn. But because of the effect of additive gaussian measurement noises, the signal-to-noises ratio is low; their fault features are difficult to extract. This study aims to propose an approach of gear faults classification，using the cumulants and support vector machines. The cumulants can eliminate the additive gaussian noises, boost the signal-to-noises ratio. Generalisation of support vector machines as classifier, which is employed structural risk minimisation principle, is superior to that of conventional neural networks, which is employed traditional empirical risk minimisation principle. Support vector machines as the classifier, and the third and fourth order cumulants as input, gears faults are successfully recognized. The experimental results show that the method of fault classification combining cumulants with support vector machines is very effective.
Gears alternately mesh and detach in driving process, and then working conditions of gears are alternately changing, so they are easy to be spalled and worn. But because of the effect of additive gaussian measurement noises, the signal-to-noises ratio is low; their fault features are difficult to extract. This study aims to propose an approach of gear faults classification，using the cumulants and support vector machines. The cumulants can eliminate the additive gaussian noises, boost the signal-to-noises ratio. Generalisation of support vector machines as classifier, which is employed structural risk minimisation principle, is superior to that of conventional neural networks, which is employed traditional empirical risk minimisation principle. Support vector machines as the classifier, and the third and fourth order cumulants as input, gears faults are successfully recognized. The experimental results show that the method of fault classification combining cumulants with support vector machines is very effective.
2002, 16(3).
Abstract:
In the past half century China has developed and formed her own system of high temperature materials for power, automobile and aero-engine industries in the temperature range from 550 ℃ to 1 100 ℃. These high temperature materials include heat-resisting steels, iron-base, nickel-iron-base and nickel-base superalloys. Some achievements in high temperature strength study, new technologies and new alloy development are also discussed.
In the past half century China has developed and formed her own system of high temperature materials for power, automobile and aero-engine industries in the temperature range from 550 ℃ to 1 100 ℃. These high temperature materials include heat-resisting steels, iron-base, nickel-iron-base and nickel-base superalloys. Some achievements in high temperature strength study, new technologies and new alloy development are also discussed.
2002, 16(3).
Abstract:
The wear forms and reasons of PCBN tools when dry-cutting bearing steel GCr15 are studied systematically. The effect law of the workpiece hardness on PCBN tools is gained and tool wearing with the quickest speed at the workpiece critical hardness is proved. The life equation at two kinds of workpiece hardness demonstrates that the effect of the cutting speed on the PCBN tool life is less than that of carbide tools and ceramic tools.
The wear forms and reasons of PCBN tools when dry-cutting bearing steel GCr15 are studied systematically. The effect law of the workpiece hardness on PCBN tools is gained and tool wearing with the quickest speed at the workpiece critical hardness is proved. The life equation at two kinds of workpiece hardness demonstrates that the effect of the cutting speed on the PCBN tool life is less than that of carbide tools and ceramic tools.
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