2005 Vol.18(1)
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2005, 19(1).
Abstract:
The grinding of two parallel sides of a component is accomplished with the accuracy and higher productivity by passing a blank through the truncated cone shape grinders, which are turned angles. The machine is designated by the name of double disc grinding machine (DDGM). Usually, it is used in the mass production. The relationship between these angles, the accuracy, productivity, allowance and parameters of the machine and technology is explained in detail by math, such as vector analysis, transformation of 3D space coordinates, etc. Therefore, in the aspects of qualitative and quantitative analyses, the grinding potential of DDGM is enormous increased and superior to conventional methods. Furthermore, the theoretical foundation of DDGM grinding design and technology is provided to improve, to expand and to create for future. The established machine design and practical experience of grinding technology will get great benefit by them.
The grinding of two parallel sides of a component is accomplished with the accuracy and higher productivity by passing a blank through the truncated cone shape grinders, which are turned angles. The machine is designated by the name of double disc grinding machine (DDGM). Usually, it is used in the mass production. The relationship between these angles, the accuracy, productivity, allowance and parameters of the machine and technology is explained in detail by math, such as vector analysis, transformation of 3D space coordinates, etc. Therefore, in the aspects of qualitative and quantitative analyses, the grinding potential of DDGM is enormous increased and superior to conventional methods. Furthermore, the theoretical foundation of DDGM grinding design and technology is provided to improve, to expand and to create for future. The established machine design and practical experience of grinding technology will get great benefit by them.
2005, 19(1).
Abstract:
The multi-modes feature, the measure of the manipulating flexibility, and self-reconfiguration control method of the underactuated redundant manipulators are investigated based on the optimizing technology. The relationship between the configuration of the joint space and the manipulating flexibility of the underactuated redundant manipulator is analyzed, a new measure of manipulating flexibility ellipsoid for the underactuated redundant manipulator with passive joints in locked mode is proposed, which can be used to get the optimal configuration for the realization of the self-reconfiguration control. Furthermore, a time-varying nonlinear control method based on harmonic inputs is suggested for fulfilling the self-reconfiguration. A simulation example of a three-DOFs underactuated manipulator with one passive joint features some aspects of the investigations.
The multi-modes feature, the measure of the manipulating flexibility, and self-reconfiguration control method of the underactuated redundant manipulators are investigated based on the optimizing technology. The relationship between the configuration of the joint space and the manipulating flexibility of the underactuated redundant manipulator is analyzed, a new measure of manipulating flexibility ellipsoid for the underactuated redundant manipulator with passive joints in locked mode is proposed, which can be used to get the optimal configuration for the realization of the self-reconfiguration control. Furthermore, a time-varying nonlinear control method based on harmonic inputs is suggested for fulfilling the self-reconfiguration. A simulation example of a three-DOFs underactuated manipulator with one passive joint features some aspects of the investigations.
2005, 19(1).
Abstract:
A brand new direct and adaptive slicing approach is proposed, which can apparently improve the part accuracy and reduce the building time. At least two stages are included in this operation: getting the crossing contour of the cutting plane with the solid part and determining the layer thickness. Apart from usual SPI algorithm, slicing of the solid model has its special requirements. Enabling the contour line segments of the cross-section as long as possible is one of them, which is for improving manufacturing efficiency and is reached by adaptively adjusting the step direction and the step size at every crossing point to obtain optimized secant height. The layer thickness determination can be di-vided into two phases: the geometry-based thickness estimation and the material-based thickness verifying. During the former phase, the geometry tolerance is divided into two parts: a variety of curves are approximated by a circular arc, which introduces the first part, and the deviation error between the contour line in LM process and the circular arc generates the second part. The latter phase is mainly verifying the layer thickness estimated in the former stage and determining a new one if necessary. In addition, an example using this slicing algorithm is also illustrated.
A brand new direct and adaptive slicing approach is proposed, which can apparently improve the part accuracy and reduce the building time. At least two stages are included in this operation: getting the crossing contour of the cutting plane with the solid part and determining the layer thickness. Apart from usual SPI algorithm, slicing of the solid model has its special requirements. Enabling the contour line segments of the cross-section as long as possible is one of them, which is for improving manufacturing efficiency and is reached by adaptively adjusting the step direction and the step size at every crossing point to obtain optimized secant height. The layer thickness determination can be di-vided into two phases: the geometry-based thickness estimation and the material-based thickness verifying. During the former phase, the geometry tolerance is divided into two parts: a variety of curves are approximated by a circular arc, which introduces the first part, and the deviation error between the contour line in LM process and the circular arc generates the second part. The latter phase is mainly verifying the layer thickness estimated in the former stage and determining a new one if necessary. In addition, an example using this slicing algorithm is also illustrated.
2005, 19(1).
Abstract:
Homogenous precipitation and subsequent calcination has been used to synthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from the precursor inherit the size and morphology of it. The size and morphology of the precursor are closely related to the preparation process. The morphology, size and distribution of the precursor could be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sized spherical particles is prepared by this method. The powder is used in the chemical-mechanical polishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measured by AFM.
Homogenous precipitation and subsequent calcination has been used to synthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from the precursor inherit the size and morphology of it. The size and morphology of the precursor are closely related to the preparation process. The morphology, size and distribution of the precursor could be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sized spherical particles is prepared by this method. The powder is used in the chemical-mechanical polishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measured by AFM.
2005, 19(1).
Abstract:
The coupling iteration (CI) of the finite element method(FEM) is used to simulate the magnetic and mechanical characteristics for a GMM actuator. The convergent ability under different prestress and different load types is investigated. Then the calculated deformations are compared with the experimental values. The results convince that the CI of FEM is suitable for the simulation of energy coupling and transformation mechanism of the GMM. At last, the output deformation properties are studied under different input currents, showing that there is a good compromise between good linearity and large strain under the prestress 6 Mpa.
The coupling iteration (CI) of the finite element method(FEM) is used to simulate the magnetic and mechanical characteristics for a GMM actuator. The convergent ability under different prestress and different load types is investigated. Then the calculated deformations are compared with the experimental values. The results convince that the CI of FEM is suitable for the simulation of energy coupling and transformation mechanism of the GMM. At last, the output deformation properties are studied under different input currents, showing that there is a good compromise between good linearity and large strain under the prestress 6 Mpa.
2005, 19(1).
Abstract:
Three feedforward (FFD) control techniques for position-servo machine axes are compared. All three FFD controllers are used with two different PID feedback (FBK) controllers. The two different FBK controllers have two different closed-loop bandwidths. They are demonstrated using experimental data from a linear motor test system and from simulations. Laboratory results using the linear motor hardware demonstrate that the velocity & acceleration (V&A) FFD controller improves tracking in all case considered, while the other two FFD controllers actually degrade performance in many cases. Through simulation this degradation is attributed to extreme sensitivity to round off errors. This sensitivity is the result of a complex controller that is implemented outside of the feedback loop.
Three feedforward (FFD) control techniques for position-servo machine axes are compared. All three FFD controllers are used with two different PID feedback (FBK) controllers. The two different FBK controllers have two different closed-loop bandwidths. They are demonstrated using experimental data from a linear motor test system and from simulations. Laboratory results using the linear motor hardware demonstrate that the velocity & acceleration (V&A) FFD controller improves tracking in all case considered, while the other two FFD controllers actually degrade performance in many cases. Through simulation this degradation is attributed to extreme sensitivity to round off errors. This sensitivity is the result of a complex controller that is implemented outside of the feedback loop.
2005, 19(1).
Abstract:
The micro touch sensor which is designed to be used in the blood vessels is proposed. Using this touch sensor, the risk of injuring blood vessels can be reduced. A prototype of micro touch sensor using PZT (lead zirconate titanate) thin film synthesized by hydrothermal method is made. The basic properties of the micro touch sensor are studied. In order to analyse the properties of the micro touch sensor, a mathematical model is set up.
The micro touch sensor which is designed to be used in the blood vessels is proposed. Using this touch sensor, the risk of injuring blood vessels can be reduced. A prototype of micro touch sensor using PZT (lead zirconate titanate) thin film synthesized by hydrothermal method is made. The basic properties of the micro touch sensor are studied. In order to analyse the properties of the micro touch sensor, a mathematical model is set up.
2005, 19(1).
Abstract:
Performance of giant magnetostrictive material (GMM) is introduced. Principle of work, basic structure and key techniques of giant magnetostrictive actuator (GMA) are analyzed. Its dynamic models of magneto-mechanical coupling are established. The structure and principle of the pneumatic servo valve and the micro pipe robot with new homemade GMM are presented. The experiment is carried out under typical working conditions. The experiment results show that the GMM pneumatic servo valve has wide pressure control characteristics, good linearity, and fast response speed. The movement principles of the GMM robot system are reliably feasible and its maximal moving speed is about 8 mm/s. It is preferable to the driving frequency of the robot within 100~300 Hz.
Performance of giant magnetostrictive material (GMM) is introduced. Principle of work, basic structure and key techniques of giant magnetostrictive actuator (GMA) are analyzed. Its dynamic models of magneto-mechanical coupling are established. The structure and principle of the pneumatic servo valve and the micro pipe robot with new homemade GMM are presented. The experiment is carried out under typical working conditions. The experiment results show that the GMM pneumatic servo valve has wide pressure control characteristics, good linearity, and fast response speed. The movement principles of the GMM robot system are reliably feasible and its maximal moving speed is about 8 mm/s. It is preferable to the driving frequency of the robot within 100~300 Hz.
2005, 19(1).
Abstract:
The object of study is about dynamic modeling and control for a 2 degree-of-freedom (DOF) planar parallel mechanism (PM) with flexible links. The kinematic and dynamic equations are established according to the characteristics of mixed rigid and flexible structure. By using the singular perturbation approach (SPA), the model of the mechanism can be separated into slow and fast sub-systems. Based on the feedback linearization theory and input shaping technique, the large scale rigid motion controller and the flexible link vibration controller can be designed separately to achieve fast and accurate positioning of the PM.
The object of study is about dynamic modeling and control for a 2 degree-of-freedom (DOF) planar parallel mechanism (PM) with flexible links. The kinematic and dynamic equations are established according to the characteristics of mixed rigid and flexible structure. By using the singular perturbation approach (SPA), the model of the mechanism can be separated into slow and fast sub-systems. Based on the feedback linearization theory and input shaping technique, the large scale rigid motion controller and the flexible link vibration controller can be designed separately to achieve fast and accurate positioning of the PM.
2005, 19(1).
Abstract:
A high-speed photographic method is mainly used to analyze metal transfer of a cellulose covered electrode in the vertical down welding. The experimental results show that fine droplets spraying transfer and globular transfer are the dominant transfer characteristic. The large droplet spatter, especially the upwards spatter, is a particular phenomenon. It is found that the combination action of gas blow force, surface tension, gravitational force and electromagnetic force lead to globular transfer. Gravitational force and electromagnetic force, which hasten big droplet spatter, should not be neglected.
A high-speed photographic method is mainly used to analyze metal transfer of a cellulose covered electrode in the vertical down welding. The experimental results show that fine droplets spraying transfer and globular transfer are the dominant transfer characteristic. The large droplet spatter, especially the upwards spatter, is a particular phenomenon. It is found that the combination action of gas blow force, surface tension, gravitational force and electromagnetic force lead to globular transfer. Gravitational force and electromagnetic force, which hasten big droplet spatter, should not be neglected.
2005, 19(1).
Abstract:
According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results.
According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results.
2005, 19(1).
Abstract:
Five experimental self-shielded flux cored wires are fabricated with different amount of Fe2O3 in the flux. The effect of Fe2O3 on welding technology and mechanical properties of weld metals deposited by these wires are studied. The results show that with the increase of Fe2O3 in the mix, the melting point of the pretreated mix is increased. LiBaF3 and BaFe12O19, which are very low in inherent moisture, are formed after the pretreatment. The mechanical properties are evaluated to the weld metals. The low temperature notch toughness of the weld metals is increased linearly with the Fe2O3 content in the flux due to the balance between Fe2O3 and residual Al in the weld metal. The optimum Fe2O3 content in flux is 2.5%~3.5 %.
Five experimental self-shielded flux cored wires are fabricated with different amount of Fe2O3 in the flux. The effect of Fe2O3 on welding technology and mechanical properties of weld metals deposited by these wires are studied. The results show that with the increase of Fe2O3 in the mix, the melting point of the pretreated mix is increased. LiBaF3 and BaFe12O19, which are very low in inherent moisture, are formed after the pretreatment. The mechanical properties are evaluated to the weld metals. The low temperature notch toughness of the weld metals is increased linearly with the Fe2O3 content in the flux due to the balance between Fe2O3 and residual Al in the weld metal. The optimum Fe2O3 content in flux is 2.5%~3.5 %.
2005, 19(1).
Abstract:
A new surfacing electrode is developed with cracking resistance and wearability based on high microhardness of TiC and VC, carbides of Ti and V are formed in deposited metal by means of high temperature arc metallurgic reaction. The results show the hardness of surfacing metal increases with the increase of ferrotitanium (Fe-Ti), ferrovanadium (Fe-V) and graphite in the coat. However, when graphite reaches the volume fraction of 11%, the hardness reaches its peak value, and when beyond 11%, the hardness falls off. As Fe-Ti, Fe-V and graphite increase, the cracking resistance of deposited metal and usability of electrode declines. Carbides are dispersedly distributed in the matrix structure. The matrix microstructure of deposited metal is lath martensite. Carbides present irregular block. When using the researched surfacing electrode to continue weld with non-preheated, no seeable crack or only a few micro-cracks can be observed in the surface of deposited metal. The hardness is above 60 HRC. The wear resistance is better than that of EDZCr-C-15.
A new surfacing electrode is developed with cracking resistance and wearability based on high microhardness of TiC and VC, carbides of Ti and V are formed in deposited metal by means of high temperature arc metallurgic reaction. The results show the hardness of surfacing metal increases with the increase of ferrotitanium (Fe-Ti), ferrovanadium (Fe-V) and graphite in the coat. However, when graphite reaches the volume fraction of 11%, the hardness reaches its peak value, and when beyond 11%, the hardness falls off. As Fe-Ti, Fe-V and graphite increase, the cracking resistance of deposited metal and usability of electrode declines. Carbides are dispersedly distributed in the matrix structure. The matrix microstructure of deposited metal is lath martensite. Carbides present irregular block. When using the researched surfacing electrode to continue weld with non-preheated, no seeable crack or only a few micro-cracks can be observed in the surface of deposited metal. The hardness is above 60 HRC. The wear resistance is better than that of EDZCr-C-15.
2005, 19(1).
Abstract:
It is an important precondition for machine fault diagnosis that vibration signal can be extracted effectively. Based on the characteristic of noise interfused during the course of sampling vibration signal, independent component analysis (ICA) method is combined with wavelet to de-noise. Firstly, The sampled signal can be separated with ICA, then the function of frequency band chosen with multi-resolution wavelet transform can be used to judge whether the stochastic disturbance singular signal is interfused. By these ways, the vibration signals can be extracted effectively, which provides favorable condition for subsequent feature detection of vibration signal and fault diagnosis.
It is an important precondition for machine fault diagnosis that vibration signal can be extracted effectively. Based on the characteristic of noise interfused during the course of sampling vibration signal, independent component analysis (ICA) method is combined with wavelet to de-noise. Firstly, The sampled signal can be separated with ICA, then the function of frequency band chosen with multi-resolution wavelet transform can be used to judge whether the stochastic disturbance singular signal is interfused. By these ways, the vibration signals can be extracted effectively, which provides favorable condition for subsequent feature detection of vibration signal and fault diagnosis.
2005, 19(1).
Abstract:
Based on the analysis of collective activities of ant colonies, the typical example of swarm intelligence, a new approach to construct swarm intelligence based multi-agent-system (SMAS) for dynamic real-time scheduling for semiconductor wafer fab is proposed. The relevant algorithm, pheromone-based dynamic real-time scheduling algorithm (PBDR), is given. MIMAC test bed data set mini-fab is used to compare PBDR with FIFO (first in first out), SRPT(shortest remaining proce-ssing time) and CR(critical ratio) under three different release rules, I.e. deterministic rule, Poisson rule and CONWIP (constant WIP). It is shown that PBDR is prior to FIFO, SRPT and CR with better performance of cycle time, throughput, and on-time delivery, especially for on-time delivery perfor-mance.
Based on the analysis of collective activities of ant colonies, the typical example of swarm intelligence, a new approach to construct swarm intelligence based multi-agent-system (SMAS) for dynamic real-time scheduling for semiconductor wafer fab is proposed. The relevant algorithm, pheromone-based dynamic real-time scheduling algorithm (PBDR), is given. MIMAC test bed data set mini-fab is used to compare PBDR with FIFO (first in first out), SRPT(shortest remaining proce-ssing time) and CR(critical ratio) under three different release rules, I.e. deterministic rule, Poisson rule and CONWIP (constant WIP). It is shown that PBDR is prior to FIFO, SRPT and CR with better performance of cycle time, throughput, and on-time delivery, especially for on-time delivery perfor-mance.
2005, 19(1).
Abstract:
A special transparent centrifugal pump is designed. Detailed optical measurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pump impeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow is surveyed at three load conditions qV/qVd = 0.4, qV/qVd = 1.0, qV/qVd = 1.5, respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub and shroud of the impeller are presented. At design load, the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow without separation. The distributions of the relative velocity on different plane along the pump shaft are very different and there is always a low velocity zone near the pressure-side of the blade at both low and design flow rate, but the low-velocity-zone at the low flow rate is much larger than that at the design one. The study demonstrates that the PIV technique is efficient in providing reliable and detailed velocity data over a full impeller passage.
A special transparent centrifugal pump is designed. Detailed optical measurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pump impeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow is surveyed at three load conditions qV/qVd = 0.4, qV/qVd = 1.0, qV/qVd = 1.5, respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub and shroud of the impeller are presented. At design load, the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow without separation. The distributions of the relative velocity on different plane along the pump shaft are very different and there is always a low velocity zone near the pressure-side of the blade at both low and design flow rate, but the low-velocity-zone at the low flow rate is much larger than that at the design one. The study demonstrates that the PIV technique is efficient in providing reliable and detailed velocity data over a full impeller passage.
2005, 19(1).
Abstract:
The microstructure and elements distribution of the deep cryogenic treatment electrodes and non-cryogenic treatment electrodes for spot welding hot dip galvanized steel are observed by a scanning electrical microscope. The grain sizes, the resistivity and the hardness of the electrodes be-fore and after deep cryogenic treatment are measured by X-ray diffraction, the DC double arms bridge and the Brinell hardness testing unit respectively. The spot welding process performance of hot dip galvanized steel plate is tested and the relationship between microstructure and physical properties of deep cryogenic treatment electrodes is analyzed. The experimental results show that deep cryogenic treatment makes Cr, Zr in deep cryogenic treatment electrodes emanate dispersedly and makes the grain of deep cryogenic treatment electrodes smaller than non-cryogenic treatment ones so that the electrical conductivity and the thermal conductivity of deep cryogenic treatment electrodes are im-proved very much, which make spot welding process performance of the hot dip galvanized steel be improved.
The microstructure and elements distribution of the deep cryogenic treatment electrodes and non-cryogenic treatment electrodes for spot welding hot dip galvanized steel are observed by a scanning electrical microscope. The grain sizes, the resistivity and the hardness of the electrodes be-fore and after deep cryogenic treatment are measured by X-ray diffraction, the DC double arms bridge and the Brinell hardness testing unit respectively. The spot welding process performance of hot dip galvanized steel plate is tested and the relationship between microstructure and physical properties of deep cryogenic treatment electrodes is analyzed. The experimental results show that deep cryogenic treatment makes Cr, Zr in deep cryogenic treatment electrodes emanate dispersedly and makes the grain of deep cryogenic treatment electrodes smaller than non-cryogenic treatment ones so that the electrical conductivity and the thermal conductivity of deep cryogenic treatment electrodes are im-proved very much, which make spot welding process performance of the hot dip galvanized steel be improved.
2005, 19(1).
Abstract:
Stainless steel is so different from aluminum alloys in physical and chemical characters. When they are welded directly, there tend to be Al-Fe brittle compounds on the joint. This paper investigates the processing performance, interface microstructures and mechanical properties of aluminum alloys/stainless steel by way of brazing after brush plating a Ni/Cu transitional layer on stainless steel. After the joints are brazed with Al-Si-Cu-Mg-Zn foil brazing filler metal on different brazing parame-ters, both the mechanical properties and the microstructures are satisfactory for application. And the influence of the brazing parameters on bonding quality of the brazed joints is discussed in detail. The results reveal that no brittle Al-Fe intermetallic Compound is found in the interfaces. The Ni/Cu electroplating layer effectively hinders the diffusion of Fe atoms from SUS304 to 5A03. Though a little AlCu3 brittle compound is produced, its quantity is too small to affect the strength of the joint.
Stainless steel is so different from aluminum alloys in physical and chemical characters. When they are welded directly, there tend to be Al-Fe brittle compounds on the joint. This paper investigates the processing performance, interface microstructures and mechanical properties of aluminum alloys/stainless steel by way of brazing after brush plating a Ni/Cu transitional layer on stainless steel. After the joints are brazed with Al-Si-Cu-Mg-Zn foil brazing filler metal on different brazing parame-ters, both the mechanical properties and the microstructures are satisfactory for application. And the influence of the brazing parameters on bonding quality of the brazed joints is discussed in detail. The results reveal that no brittle Al-Fe intermetallic Compound is found in the interfaces. The Ni/Cu electroplating layer effectively hinders the diffusion of Fe atoms from SUS304 to 5A03. Though a little AlCu3 brittle compound is produced, its quantity is too small to affect the strength of the joint.
2005, 19(1).
Abstract:
A test platform is established as per the practical working condition of elevating platform fire truck. The influences of pipes and load on dynamic characteristics of load-sensing system are studied by series of step response experiments. Experimental results show that the feedback pipe makes the most important influence on the dynamic response speed of load-sensing system. Its internal diameter should be opti-mized for given length of pipe. On the other hand, the stability of load-sensing pump is improved as the length of input pipe increases in a certain range. The influence of input pipe on the dynamic response speed is caused mainly by the pressure-wave travel time in the input pipe.
A test platform is established as per the practical working condition of elevating platform fire truck. The influences of pipes and load on dynamic characteristics of load-sensing system are studied by series of step response experiments. Experimental results show that the feedback pipe makes the most important influence on the dynamic response speed of load-sensing system. Its internal diameter should be opti-mized for given length of pipe. On the other hand, the stability of load-sensing pump is improved as the length of input pipe increases in a certain range. The influence of input pipe on the dynamic response speed is caused mainly by the pressure-wave travel time in the input pipe.
2005, 19(1).
Abstract:
The nonlinear dynamic behaviors of flexible rotor system with hydrodynamic bearing supports are analyzed. The shaft is modeled by using the finite element method that takes the effect of inertia and shear into consideration. According to the nonlinearity of the hydrodynamic journal bearing-flexible rotor system, a modified modal synthesis technique with free-interface is represented to reduce degrees-of-freedom of model of the flexible rotor system. According to physical character of oil film, variational constrain approach is introduced to continuously revise the variational form of Reynolds equation at every step of dynamic integration and iteration. Fluid lubrication problem with Reynolds boundary is solved by the isoparametric finite element method without the increasing of computing efforts. Nonlinear oil film forces and their Jacobians are simultaneously calculated and their compatible accuracy is obtained. The periodic motions are obtained by using the Poincaré-Newton-Floquet (PNF) method. A method, combining the predictor-corrector mechanism to the PNF method, is presented to calculate the bifurcation point of periodic motions to be subject to change of system parameters. The local stability and bifurcation behaviors of periodic motions are obtained by Floquet theory. The chaotic motions of the bearing-rotor system are investigated by power spectrum. The numerical examples show that the scheme of this study saves computing efforts but also is of good precision.
The nonlinear dynamic behaviors of flexible rotor system with hydrodynamic bearing supports are analyzed. The shaft is modeled by using the finite element method that takes the effect of inertia and shear into consideration. According to the nonlinearity of the hydrodynamic journal bearing-flexible rotor system, a modified modal synthesis technique with free-interface is represented to reduce degrees-of-freedom of model of the flexible rotor system. According to physical character of oil film, variational constrain approach is introduced to continuously revise the variational form of Reynolds equation at every step of dynamic integration and iteration. Fluid lubrication problem with Reynolds boundary is solved by the isoparametric finite element method without the increasing of computing efforts. Nonlinear oil film forces and their Jacobians are simultaneously calculated and their compatible accuracy is obtained. The periodic motions are obtained by using the Poincaré-Newton-Floquet (PNF) method. A method, combining the predictor-corrector mechanism to the PNF method, is presented to calculate the bifurcation point of periodic motions to be subject to change of system parameters. The local stability and bifurcation behaviors of periodic motions are obtained by Floquet theory. The chaotic motions of the bearing-rotor system are investigated by power spectrum. The numerical examples show that the scheme of this study saves computing efforts but also is of good precision.
2005, 19(1).
Abstract:
Aiming at difficult sorting and retrieving complicated structure assemblies in assembly lib, a method for compartmentalizing assembly design resource by conceptual product structure model is presented. The similar assembly retrieval mechanisms of symbol assembly relation graph matching and symbol assembly relation graph similarity are discussed. The method is validated by taking valve rod assemblies as example.
Aiming at difficult sorting and retrieving complicated structure assemblies in assembly lib, a method for compartmentalizing assembly design resource by conceptual product structure model is presented. The similar assembly retrieval mechanisms of symbol assembly relation graph matching and symbol assembly relation graph similarity are discussed. The method is validated by taking valve rod assemblies as example.
2005, 19(1).
Abstract:
The effect of discrete support of rail on the formation and evolution of rail corrugation is primarily investigated with numerical method in the situation of wheelset curving steadily and repeatedly. In the numerical analysis of corrugation it is considered that a combination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictional work model and a vertical dynamics model of railway vehicle coupled with a curved track. And the uneven support stiffness of rail in the vertical direction due to discrete sleeper support and the different running speed of the wheelset are taken into consideration. The damage on the running surface of rail, concerning rail corrugation formation, is restricted to wear mechanism of rail material. The numerical results obtained indicate that the discrete supports of rail by sleepers have a great influence on the formation of the corrugation under the condition of non-zero and stable creepages of wheelset and track.
The effect of discrete support of rail on the formation and evolution of rail corrugation is primarily investigated with numerical method in the situation of wheelset curving steadily and repeatedly. In the numerical analysis of corrugation it is considered that a combination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictional work model and a vertical dynamics model of railway vehicle coupled with a curved track. And the uneven support stiffness of rail in the vertical direction due to discrete sleeper support and the different running speed of the wheelset are taken into consideration. The damage on the running surface of rail, concerning rail corrugation formation, is restricted to wear mechanism of rail material. The numerical results obtained indicate that the discrete supports of rail by sleepers have a great influence on the formation of the corrugation under the condition of non-zero and stable creepages of wheelset and track.
2005, 19(1).
Abstract:
A method for improving dynamic characteristics of planar linkages by actively varying the speed function of the input link is presented. Design criteria and constraints for the dynamic design of variable speed planar linkages are developed. Both analytical and optimization approaches for deter-mining suitable input speed functions to minimize the driving torque, the shaking moment, or both simultaneously of planar linkages, subject to various design requirements and constraints, are derived. Finally, some examples are given to illustrate the design procedure and to verify its feasibility.
A method for improving dynamic characteristics of planar linkages by actively varying the speed function of the input link is presented. Design criteria and constraints for the dynamic design of variable speed planar linkages are developed. Both analytical and optimization approaches for deter-mining suitable input speed functions to minimize the driving torque, the shaking moment, or both simultaneously of planar linkages, subject to various design requirements and constraints, are derived. Finally, some examples are given to illustrate the design procedure and to verify its feasibility.
2005, 19(1).
Abstract:
Because uncertainty factors inevitably exist under multidisciplinary design environment, a hierarchical multidisciplinary robust optimization design based on response surface is proposed. The method constructs optimization model of subsystem level and system level to coordinate the coupling among subsystems, and also the response surface based on the artificial neural network is introduced to provide information for system level optimization tool to maintain the independence of subsystems, I.e. to realize multidisciplinary parallel design. The application case of electrical packaging demon-strates that reasonable robust optimum solution can be yielded and it is a potential and efficient mul-tidisciplinary robust optimization approach.
Because uncertainty factors inevitably exist under multidisciplinary design environment, a hierarchical multidisciplinary robust optimization design based on response surface is proposed. The method constructs optimization model of subsystem level and system level to coordinate the coupling among subsystems, and also the response surface based on the artificial neural network is introduced to provide information for system level optimization tool to maintain the independence of subsystems, I.e. to realize multidisciplinary parallel design. The application case of electrical packaging demon-strates that reasonable robust optimum solution can be yielded and it is a potential and efficient mul-tidisciplinary robust optimization approach.
2005, 19(1).
Abstract:
Numerical simulations of pilot fuel spray and compressing ignition for pre-mixed natural gas ignited by pilot diesel are described. By means of these modeling, the dual fuel and diesel fuel ignition mechanism of some phenomena investigated on an optional engine by technology of high-speed CCD is analyzed. It is demonstrated that the longer delay of ignition in dual fuel engine is not mainly caused by change of the mixture thermodynamics parameters. The analysis results illustrate that the ignition of pre-mixed natural gas ignited by pilot diesel taking place in dual fuel engine is a process of homogenous charge compression ignition.
Numerical simulations of pilot fuel spray and compressing ignition for pre-mixed natural gas ignited by pilot diesel are described. By means of these modeling, the dual fuel and diesel fuel ignition mechanism of some phenomena investigated on an optional engine by technology of high-speed CCD is analyzed. It is demonstrated that the longer delay of ignition in dual fuel engine is not mainly caused by change of the mixture thermodynamics parameters. The analysis results illustrate that the ignition of pre-mixed natural gas ignited by pilot diesel taking place in dual fuel engine is a process of homogenous charge compression ignition.
2005, 19(1).
Abstract:
Engineering design and geometric modeling often require the ability to modify the shape of parametric curves and surfaces so that their shape satisfy some given geometric constraints, including point, normal vector, curve and surface. Two approaches are presented to directly manipulate the shape of B-spline surface. The former is based on the least-square, whereas the latter is based on minimizing the bending energy of surface. For each method, since unified and explicit formulae are derived to compute new control points of modified surface, these methods are simple, fast and applicable for CAD systems. Algebraic technique is used to simplify the computation of B-spline composition and multiplication. Comparisons and examples are also given.
Engineering design and geometric modeling often require the ability to modify the shape of parametric curves and surfaces so that their shape satisfy some given geometric constraints, including point, normal vector, curve and surface. Two approaches are presented to directly manipulate the shape of B-spline surface. The former is based on the least-square, whereas the latter is based on minimizing the bending energy of surface. For each method, since unified and explicit formulae are derived to compute new control points of modified surface, these methods are simple, fast and applicable for CAD systems. Algebraic technique is used to simplify the computation of B-spline composition and multiplication. Comparisons and examples are also given.
2005, 19(1).
Abstract:
The aim of this study is to suppress a cavitation near the orifice of a relief valve by changing the shape of a poppet. An experimental flow visualization technique and a numerical cavitating flow simulation, using a RNG k-e turbulence model and a cavitation model, are employed to achieve the purpose. In the flow visualization, the cavitation phenomenon near the orifice of a relief valve is observed using a transparent test valve body model and a camera. On the other hand, a three dimensional cavitating flow simulation is conducted to predict the cavitation near the orifice of a relief valve. Six types of poppets are designed by changing the shape of a traditional poppet shape, which is expected to influence the cavitating flow in an orifice. In addition, the cavitation noise of a relief valve is measured and the noise spectrum is analyzed. In conclusion, the cavitation intensity and the cavitation noise are reduced for an optimal poppet geometry obtained in the present study.
The aim of this study is to suppress a cavitation near the orifice of a relief valve by changing the shape of a poppet. An experimental flow visualization technique and a numerical cavitating flow simulation, using a RNG k-e turbulence model and a cavitation model, are employed to achieve the purpose. In the flow visualization, the cavitation phenomenon near the orifice of a relief valve is observed using a transparent test valve body model and a camera. On the other hand, a three dimensional cavitating flow simulation is conducted to predict the cavitation near the orifice of a relief valve. Six types of poppets are designed by changing the shape of a traditional poppet shape, which is expected to influence the cavitating flow in an orifice. In addition, the cavitation noise of a relief valve is measured and the noise spectrum is analyzed. In conclusion, the cavitation intensity and the cavitation noise are reduced for an optimal poppet geometry obtained in the present study.
2005, 19(1).
Abstract:
A hybrid approach is presented to investigate the dynamic behavior of an axially slide-spin flexible rocket with nonlinear clearance. The equations of motion of the flexible rocket are derived based upon Euler-Bernoulli beam theory and Hamilton principle and the finite element method. The characteristics of clearance between the spinning rocket and launcher are considered to be piecewise linear. Numerical solution is developed by direct integration method and demonstrates the validity of the method. The coupled dynamic behavior of axial motion and transverse vibrations of rocket are analyzed, and the influences of axially moving acceleration, spin speed, linking stiffness of elastic “shoes”, and the nonlinearity of clearance on the motion attitude of rocket are studied.
A hybrid approach is presented to investigate the dynamic behavior of an axially slide-spin flexible rocket with nonlinear clearance. The equations of motion of the flexible rocket are derived based upon Euler-Bernoulli beam theory and Hamilton principle and the finite element method. The characteristics of clearance between the spinning rocket and launcher are considered to be piecewise linear. Numerical solution is developed by direct integration method and demonstrates the validity of the method. The coupled dynamic behavior of axial motion and transverse vibrations of rocket are analyzed, and the influences of axially moving acceleration, spin speed, linking stiffness of elastic “shoes”, and the nonlinearity of clearance on the motion attitude of rocket are studied.
2005, 19(1).
Abstract:
The distributions of temperature and residual stresses in thin plates of BT20 titanium alloy are numerically analyzed by three-dimensional finite element software during electron beam welding and electron beam local post-weld heat treatment (EBLPWHT). Combined with numerical calculating results, the effects of different EBLPWHT mode and parameters, including heat treating position, heating width and heating time, on the distribution of welding residual stresses are analyzed. The results show that, the residual tensile stresses in weld center can be largely decreased when the weld is heat treated at back preface of the plate. The numerical results also indicated that the magnitude of the residual longitudinal stresses of the weld and the zone vicinity of the weld is decreased, and the range of the residual longitudinal stresses is increased along with the increase of heating width and heating time.
The distributions of temperature and residual stresses in thin plates of BT20 titanium alloy are numerically analyzed by three-dimensional finite element software during electron beam welding and electron beam local post-weld heat treatment (EBLPWHT). Combined with numerical calculating results, the effects of different EBLPWHT mode and parameters, including heat treating position, heating width and heating time, on the distribution of welding residual stresses are analyzed. The results show that, the residual tensile stresses in weld center can be largely decreased when the weld is heat treated at back preface of the plate. The numerical results also indicated that the magnitude of the residual longitudinal stresses of the weld and the zone vicinity of the weld is decreased, and the range of the residual longitudinal stresses is increased along with the increase of heating width and heating time.
2005, 19(1).
Abstract:
Based on the tests of a build-up welding at plate edge (BWPE) and a multi-layer build-up welding on plate (MBWP), the article studies on the solid-state phase transformations which affect welding distortion process and on the influence rule of transformation starting temperature (TST) of welded metal to the welding residual distortion. The welding distortion can be decreased or controlled by the transformation volume expansion caused by solid-state phase transformation of welded metal during the cooling. The test results of BWPE show that when TST is at about 190 ℃, the bending distortion of welded specimen is the smallest, and its displacements at free end are decreased to 58% and 67% compared with those of conventional welding electrodes A102 and E5015, which TST are less than room temperature and equal to 758 ℃ respectively. The test results of MBWP show that when TST were at 100~250 ℃, the welded specimen would appear reversible bending distortion compared with those of A102 and E5015. The maximum deflection value of reversible bending distortion in 8 mm thick plate is –2.94 mm at about 170 ℃ of TST. The test results provide a valuable method to decrease or to control welding residual distortion.
Based on the tests of a build-up welding at plate edge (BWPE) and a multi-layer build-up welding on plate (MBWP), the article studies on the solid-state phase transformations which affect welding distortion process and on the influence rule of transformation starting temperature (TST) of welded metal to the welding residual distortion. The welding distortion can be decreased or controlled by the transformation volume expansion caused by solid-state phase transformation of welded metal during the cooling. The test results of BWPE show that when TST is at about 190 ℃, the bending distortion of welded specimen is the smallest, and its displacements at free end are decreased to 58% and 67% compared with those of conventional welding electrodes A102 and E5015, which TST are less than room temperature and equal to 758 ℃ respectively. The test results of MBWP show that when TST were at 100~250 ℃, the welded specimen would appear reversible bending distortion compared with those of A102 and E5015. The maximum deflection value of reversible bending distortion in 8 mm thick plate is –2.94 mm at about 170 ℃ of TST. The test results provide a valuable method to decrease or to control welding residual distortion.
2005, 19(1).
Abstract:
The appropriate bireflectance film series are selected to get the beat-frequency of dual-frequency laser using anisotropic bireflectance film (DLABF) from 1.2 MHz to 6 MHz. The maximum measurement velocity of the interferometer utilizing DLABF can be up to1.8 m/s. Generally the outputs of the DLABF in a transverse magnetic field are two orthogonal micro-elliptical polarized components when DLABF can emit dual-frequency laser. When the laser tube is spun in the magnetic field, the ellipticities of these two components are also changed. In some certain relative angles, the outputs the DLABF are two almost ideally orthogonal linear polarized components. The frequency stabilization of DLABF is also discussed. The maximum variation of the beat-frequency of the stabilized DLABF can be 0.15 kHz within 46 h. As no quarter wave plate (QWP) needed, DLABFs have better thermal stability than longitudinal Zeeman lasers.
The appropriate bireflectance film series are selected to get the beat-frequency of dual-frequency laser using anisotropic bireflectance film (DLABF) from 1.2 MHz to 6 MHz. The maximum measurement velocity of the interferometer utilizing DLABF can be up to1.8 m/s. Generally the outputs of the DLABF in a transverse magnetic field are two orthogonal micro-elliptical polarized components when DLABF can emit dual-frequency laser. When the laser tube is spun in the magnetic field, the ellipticities of these two components are also changed. In some certain relative angles, the outputs the DLABF are two almost ideally orthogonal linear polarized components. The frequency stabilization of DLABF is also discussed. The maximum variation of the beat-frequency of the stabilized DLABF can be 0.15 kHz within 46 h. As no quarter wave plate (QWP) needed, DLABFs have better thermal stability than longitudinal Zeeman lasers.
2005, 19(1).
Abstract:
According to bench test results of fuel economy and engine emission for the real powertrain system of EQ7200HEV car, a 3-D performance map oriented quasi-linear model is developed for the configuration of the powertrain components such as internal combustion engine, traction electric motor, transmission, main retarder and energy storage unit. A genetic algorithm based on optimization procedure is proposed and applied for parametric optimization of the key components by considera-tion of requirements of some driving cycles. Through comparison of numerical results obtained by the genetic algorithm with those by traditional optimization methods, it is shown that the present ap-proach is quite effective and efficient in emission reduction and fuel economy for the design of the hybrid electric car powertrain.
According to bench test results of fuel economy and engine emission for the real powertrain system of EQ7200HEV car, a 3-D performance map oriented quasi-linear model is developed for the configuration of the powertrain components such as internal combustion engine, traction electric motor, transmission, main retarder and energy storage unit. A genetic algorithm based on optimization procedure is proposed and applied for parametric optimization of the key components by considera-tion of requirements of some driving cycles. Through comparison of numerical results obtained by the genetic algorithm with those by traditional optimization methods, it is shown that the present ap-proach is quite effective and efficient in emission reduction and fuel economy for the design of the hybrid electric car powertrain.
MODIFIED CLOSED-FORM NUMERICAL ALGORITHM FOR PERIODIC VIBRATION RESPONSE OF MECHANICAL TRANSMISSIONS
2005, 19(1).
Abstract:
A closed-form numerical algorithm (CFNA) is analyzed in detail. CFNA is widely used in mechanical dynamics for periodic solution of second-order original differential equations (SODE) with periodic time-variant coefficients. The principle of the algorithm is to discretize the motion period into many short time intervals, so the coefficient matrices of the equation set are regarded as constant in a time interval. Defects are found in the original algorithm in treating the modal coordinates at the two end-nodes and important modifications to the defects is made for the algorithm. The modified algorithm is finally used to solve the dynamic problem of a three-ring planetary gear transmission.
A closed-form numerical algorithm (CFNA) is analyzed in detail. CFNA is widely used in mechanical dynamics for periodic solution of second-order original differential equations (SODE) with periodic time-variant coefficients. The principle of the algorithm is to discretize the motion period into many short time intervals, so the coefficient matrices of the equation set are regarded as constant in a time interval. Defects are found in the original algorithm in treating the modal coordinates at the two end-nodes and important modifications to the defects is made for the algorithm. The modified algorithm is finally used to solve the dynamic problem of a three-ring planetary gear transmission.
2005, 19(1).
Abstract:
A novel nonlinear control algorithm based on hybrid neural networks is presented to cope with the high-accuracy synchronization control problem for a dual-actuator electrohydraulic drive system which plays an important role for the development of elastomeric launchers. A new objective function for better synchronization performance is introduced and a learning algorithm to adjust the weights of the neural network, based on the gradient descent algorithm, is also derived. The hybrid neural network control algorithm guarantees high-accuracy synchronization performance of two motion cylinders and fast dynamic response as well as good stability of the control system. Prototype test results on the dual-actuator electrohydraulic drive system verifys the effectiveness of the proposed approach.
A novel nonlinear control algorithm based on hybrid neural networks is presented to cope with the high-accuracy synchronization control problem for a dual-actuator electrohydraulic drive system which plays an important role for the development of elastomeric launchers. A new objective function for better synchronization performance is introduced and a learning algorithm to adjust the weights of the neural network, based on the gradient descent algorithm, is also derived. The hybrid neural network control algorithm guarantees high-accuracy synchronization performance of two motion cylinders and fast dynamic response as well as good stability of the control system. Prototype test results on the dual-actuator electrohydraulic drive system verifys the effectiveness of the proposed approach.
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