1999 Vol.12(1)
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1999, 13(1).
Abstract:
A new approach is proposed to generate flexible featrure-based models (FFBM), which can be modified dynamically. Brep/CSFG/FRG hybrid scheme is used to describe FFBM, in which Brep explicitly defines the model, CSFG (Constructive solid-feature geomerty) tree records the feature-based modelling procedure and FRG (Feature relation graph reflects different knids of relationship among features. Topological operators with local retrievability are designed to implement feature addition, which is traced ty topogical operation list (TOL) in detail. As a result, FFBM can be modified directly in the system database. Related features' chain reactions and variable topologies are supported in design modification, after which the product information adhering on features will not be lost. Further, a feature can be modified as rapidly as it was added.
A new approach is proposed to generate flexible featrure-based models (FFBM), which can be modified dynamically. Brep/CSFG/FRG hybrid scheme is used to describe FFBM, in which Brep explicitly defines the model, CSFG (Constructive solid-feature geomerty) tree records the feature-based modelling procedure and FRG (Feature relation graph reflects different knids of relationship among features. Topological operators with local retrievability are designed to implement feature addition, which is traced ty topogical operation list (TOL) in detail. As a result, FFBM can be modified directly in the system database. Related features' chain reactions and variable topologies are supported in design modification, after which the product information adhering on features will not be lost. Further, a feature can be modified as rapidly as it was added.
1999, 13(1).
Abstract:
The latest progress on the study of numerical simulation of mold-filling and solidification process of shaped casting is reviewed. In mold-filling process simulation of castings, the SOLA-VOF algorithmis is improved in efficient free surface treatment and turbulence consideration, and parallel computational techniques are implemented to accelerate the fluid flow calculation time as well. Methods for predication of shrinkage defects of steel castings and S.G.iron castings are developed based on the solidification simulation. In order to reduce the residual stree and deformation of castings, a combined FDM/FEM method is implemented for the modelling of stresses. Numerical models for the simulation of microstructure and predication of mechanical properties of S.G.iron are developed. The verifications and applications of the simulation software show that the models and techniques adopted in current research work are efficient and appropriate for numerical simulation of shaped castings.
The latest progress on the study of numerical simulation of mold-filling and solidification process of shaped casting is reviewed. In mold-filling process simulation of castings, the SOLA-VOF algorithmis is improved in efficient free surface treatment and turbulence consideration, and parallel computational techniques are implemented to accelerate the fluid flow calculation time as well. Methods for predication of shrinkage defects of steel castings and S.G.iron castings are developed based on the solidification simulation. In order to reduce the residual stree and deformation of castings, a combined FDM/FEM method is implemented for the modelling of stresses. Numerical models for the simulation of microstructure and predication of mechanical properties of S.G.iron are developed. The verifications and applications of the simulation software show that the models and techniques adopted in current research work are efficient and appropriate for numerical simulation of shaped castings.
1999, 13(1).
Abstract:
The intellient optimizing method of cutting parameters and the cutting stable districts searching method are set up. The cutting parameters of each cutting pass could be optimized automatically, the cutting chatter is predicted through setting up the dynamic cutting force AR(2) model on-line, the spindle rotation speed is adjusted according to the predicting results so as to ensure the cutting system work in stable district.
The intellient optimizing method of cutting parameters and the cutting stable districts searching method are set up. The cutting parameters of each cutting pass could be optimized automatically, the cutting chatter is predicted through setting up the dynamic cutting force AR(2) model on-line, the spindle rotation speed is adjusted according to the predicting results so as to ensure the cutting system work in stable district.
1999, 13(1).
Abstract:
A whole analysis model including forging and flat platens if built, which is used to analyse the process of upsetting a cylinder between flat platens. The influence of surface friction and transient of the whole upsetting process is carried out. From the point of view of numerical calculation, the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified. The concept of plasto-nucleus is presented to explain the forming of double dumps. The efffect of temperature is inspected. The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.
A whole analysis model including forging and flat platens if built, which is used to analyse the process of upsetting a cylinder between flat platens. The influence of surface friction and transient of the whole upsetting process is carried out. From the point of view of numerical calculation, the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified. The concept of plasto-nucleus is presented to explain the forming of double dumps. The efffect of temperature is inspected. The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.
1999, 13(1).
Abstract:
Aiming at the problems existed in the squeeze film damper of the rotation machinery utilizing traditional passive dynamic pressure film bearing, a project of dynamic pressure and static pressure hybrid oil film bearing with piezoelectric crystal electrohydraulic active control supply orifice hole is proposed. For this kind of hybrid film bearing, the π film assumption can not hold true. In order to solve the pressure distribution, a new kind of solving method is proposed.
Aiming at the problems existed in the squeeze film damper of the rotation machinery utilizing traditional passive dynamic pressure film bearing, a project of dynamic pressure and static pressure hybrid oil film bearing with piezoelectric crystal electrohydraulic active control supply orifice hole is proposed. For this kind of hybrid film bearing, the π film assumption can not hold true. In order to solve the pressure distribution, a new kind of solving method is proposed.
1999, 13(1).
Abstract:
A new compressor thermodynamic model is set up. Artificial neural networks(ANN) which have self-adjusting functions are adopted to calculate volumetric efficiency and electrical efficiency of a compressor. The new compressor model composed of the theoretical model and ANN reaches more precise results than traditional ones. Furthermore, thd new compressor model os of better flexibillity in a large scale.
A new compressor thermodynamic model is set up. Artificial neural networks(ANN) which have self-adjusting functions are adopted to calculate volumetric efficiency and electrical efficiency of a compressor. The new compressor model composed of the theoretical model and ANN reaches more precise results than traditional ones. Furthermore, thd new compressor model os of better flexibillity in a large scale.
1999, 13(1).
Abstract:
Taking electrolytic lapping stainless steel for example, the principle of electrolytic lapping with a magnetic field is described, the movement of charged particles in the magnetic field is analyzed in terms of theory. Using a computer, the motion loci of the charged particles in the magnetic field are simulated. The theory and the experiment show that the magnetic field can accelerate the diffusion and mobility of the charged particles, accelerate the electrochemical reaction and reduce the surface roughness of the work more quickly, which improves the lapping efficiency.
Taking electrolytic lapping stainless steel for example, the principle of electrolytic lapping with a magnetic field is described, the movement of charged particles in the magnetic field is analyzed in terms of theory. Using a computer, the motion loci of the charged particles in the magnetic field are simulated. The theory and the experiment show that the magnetic field can accelerate the diffusion and mobility of the charged particles, accelerate the electrochemical reaction and reduce the surface roughness of the work more quickly, which improves the lapping efficiency.
1999, 13(1).
Abstract:
Metal transfer behavior of six kinds of self-shielded flux-cored wire (SSFCW) is studied using the apparatus of SSFCW high-speed photography self-made. Six kinds of metal transfer modes of SSFCW were obtained through observation for high-speed photograph film and analysis. It is believed that the research is of magnificent for improving operative performance and mechanical properties of SSFCW and dynamics characteristic of welding power.
Metal transfer behavior of six kinds of self-shielded flux-cored wire (SSFCW) is studied using the apparatus of SSFCW high-speed photography self-made. Six kinds of metal transfer modes of SSFCW were obtained through observation for high-speed photograph film and analysis. It is believed that the research is of magnificent for improving operative performance and mechanical properties of SSFCW and dynamics characteristic of welding power.
1999, 13(1).
Abstract:
A gear position decision method used in automated methanical transmission is introduced. The algorithm of the method is composed of a driving environment and driver's intention estimator, the shift schedules suit for each typical drving environment and driver's intention situation, and an inference ligic to determine the most proper gear position for the present situation. The estimator identifies the driving environment and driver's intention features thich are diveded into some typical models. Based on the identified results, the algorithm works out the best gear position. It just simulates the course of driver's making gear position decision when driving a automobile with manual transmission. The test results show that the automated mechanical transmission with the method gives less unnecessary shifting and more proper gear position than common shift schedules.
A gear position decision method used in automated methanical transmission is introduced. The algorithm of the method is composed of a driving environment and driver's intention estimator, the shift schedules suit for each typical drving environment and driver's intention situation, and an inference ligic to determine the most proper gear position for the present situation. The estimator identifies the driving environment and driver's intention features thich are diveded into some typical models. Based on the identified results, the algorithm works out the best gear position. It just simulates the course of driver's making gear position decision when driving a automobile with manual transmission. The test results show that the automated mechanical transmission with the method gives less unnecessary shifting and more proper gear position than common shift schedules.
1999, 13(1).
Abstract:
The mechanical properties of the sand of Takelamagan desert in Xinjiang under moving vehicle are studied by soil dynamic triaxial test apparatus. The nonlinear elastic constitutive model of the sand under moving vehicle is established first. These results lay the foundations for studying the interaction between vehicle running gear and the sand of Takelamagan desert in Xinjiang, and developing sand vehicle.
The mechanical properties of the sand of Takelamagan desert in Xinjiang under moving vehicle are studied by soil dynamic triaxial test apparatus. The nonlinear elastic constitutive model of the sand under moving vehicle is established first. These results lay the foundations for studying the interaction between vehicle running gear and the sand of Takelamagan desert in Xinjiang, and developing sand vehicle.
1999, 13(1).
Abstract:
A mechamism of excited arc to be an controlled "ultrasonic emission source" is described. An developed electrical source with an certain frequency bandwidth for the purpose of the arc-excited is connected with an conventional welding power supply through coupling the cables for the experiment. Some resonant frequency hands for the arc-excited ultrasonic are discovered in the welding process, and its frequency, amplitude and phase' shift are recorded. This principle demonstrates that arc can be used not only for a thermal source, but also for an ultrasonic emission source, which may be extent to the industial application in some new way, such as for automatic welding process control and quality inspection.
A mechamism of excited arc to be an controlled "ultrasonic emission source" is described. An developed electrical source with an certain frequency bandwidth for the purpose of the arc-excited is connected with an conventional welding power supply through coupling the cables for the experiment. Some resonant frequency hands for the arc-excited ultrasonic are discovered in the welding process, and its frequency, amplitude and phase' shift are recorded. This principle demonstrates that arc can be used not only for a thermal source, but also for an ultrasonic emission source, which may be extent to the industial application in some new way, such as for automatic welding process control and quality inspection.
1999, 13(1).
Abstract:
Gradual faults and abrupt faults of mechanical systems are differentiated by variation patterns of state varibles. After the reasons of abrupt faults are analyzed by nonlinear dynamics, two methods establishing the mathematical models for abrupt faults are presented. As an example, a cusp catastrophe model of the vibration amplitudes of a Jeffcott rotor with nonlinear stiffness and its parameter condition of the vibration state catastrophe are obtained.
Gradual faults and abrupt faults of mechanical systems are differentiated by variation patterns of state varibles. After the reasons of abrupt faults are analyzed by nonlinear dynamics, two methods establishing the mathematical models for abrupt faults are presented. As an example, a cusp catastrophe model of the vibration amplitudes of a Jeffcott rotor with nonlinear stiffness and its parameter condition of the vibration state catastrophe are obtained.
1999, 13(1).
Abstract:
A new kind of multiobjective simulated annealing algorithm is proposed, in which the concept of non-dominated character is introduced and a new multiobjective acceptance criterion is set up. The optimization example of a typical mathematical problem with two minimum objective functions indicates that all of the solutions contract to the set of the non-dominated points, and the variation trend of the optimal solutions is verified to be identical with that obtained using Genetic Algor thms. The new developed algorithm is then applied to the multiobjective optimization design of turbine cascades, in which it is coupled with the aerodynamics computation of the cascade flow fields and performance and the calculated loss coefficient and work potential of the cascade are considered as the objective functions, thus setting up a technique to the engineering optimization design for the cascades. The optimization results, by the view of a group of optimal solutions, show that the algorithm is superior to the traditional technique of multiobjective optimization design and can be applied to more than two objective optimization cascade design problem or other engineering multiobjective optimization designs.
A new kind of multiobjective simulated annealing algorithm is proposed, in which the concept of non-dominated character is introduced and a new multiobjective acceptance criterion is set up. The optimization example of a typical mathematical problem with two minimum objective functions indicates that all of the solutions contract to the set of the non-dominated points, and the variation trend of the optimal solutions is verified to be identical with that obtained using Genetic Algor thms. The new developed algorithm is then applied to the multiobjective optimization design of turbine cascades, in which it is coupled with the aerodynamics computation of the cascade flow fields and performance and the calculated loss coefficient and work potential of the cascade are considered as the objective functions, thus setting up a technique to the engineering optimization design for the cascades. The optimization results, by the view of a group of optimal solutions, show that the algorithm is superior to the traditional technique of multiobjective optimization design and can be applied to more than two objective optimization cascade design problem or other engineering multiobjective optimization designs.
1999, 13(1).
Abstract:
A nonlinera mathematical model for the shock absorber in TJ7100 is developed. The oil compressibility and the entrapped gas in the oil are considered in the model. As a result, the hysteresis in the force-velocity diagram is included. The results of computer simulation and the experiment are basically identical. The MATLAB/SIMULINK is used for the development of the simulation software. It is found that the pressure inside the cylinder is high if the inputs of velocity or displacement are big by simulation. This is certainly one of the main reasons for which the leak of appeared between the rod and the seal of the shock absorbers for a relatively short time in China.
A nonlinera mathematical model for the shock absorber in TJ7100 is developed. The oil compressibility and the entrapped gas in the oil are considered in the model. As a result, the hysteresis in the force-velocity diagram is included. The results of computer simulation and the experiment are basically identical. The MATLAB/SIMULINK is used for the development of the simulation software. It is found that the pressure inside the cylinder is high if the inputs of velocity or displacement are big by simulation. This is certainly one of the main reasons for which the leak of appeared between the rod and the seal of the shock absorbers for a relatively short time in China.
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