2002 Vol.15(4)
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2002, 16(4).
Abstract:
The experimental study is carried out on high-speed centrifugal pumps with three different impellers. The experimental results and analysis show that high-speed centrifugal pumps with a closed complex impeller can achieve the highest efficiency and the lowest head coefficient followed by those with half-open impeller and open-impeller, and can obtain much easily stable head-capacity characrastic curve, while those with a half-open complex impeller can't. The characteristic curve with a open impeller is almost constant horizontal line before dropping sharply. The results also show that the axial clearance between pump casing and impeller can influence greatly on the performance of centrifugal pumps.
The experimental study is carried out on high-speed centrifugal pumps with three different impellers. The experimental results and analysis show that high-speed centrifugal pumps with a closed complex impeller can achieve the highest efficiency and the lowest head coefficient followed by those with half-open impeller and open-impeller, and can obtain much easily stable head-capacity characrastic curve, while those with a half-open complex impeller can't. The characteristic curve with a open impeller is almost constant horizontal line before dropping sharply. The results also show that the axial clearance between pump casing and impeller can influence greatly on the performance of centrifugal pumps.
2002, 16(4).
Abstract:
A product-oriented process workflow management model is proposed based on the multi-agent technology. The autonomy, inter-operability, scalability and flexibility of agent are used to cooperate the whole process planning and achieve the full share of resource and information. Thus, unnecessary waste of human labor, time and work is reduced and the computer-aided process planning (CAPP) system's adaptability and stability are improved. In the detailed implementation, according to the products'BOM (Bill of materials) in structural design, the task assignment, management control, automatic process making, process examination and process sanction are combined into a unified management to make it convenient for the adjustment, control and management.
A product-oriented process workflow management model is proposed based on the multi-agent technology. The autonomy, inter-operability, scalability and flexibility of agent are used to cooperate the whole process planning and achieve the full share of resource and information. Thus, unnecessary waste of human labor, time and work is reduced and the computer-aided process planning (CAPP) system's adaptability and stability are improved. In the detailed implementation, according to the products'BOM (Bill of materials) in structural design, the task assignment, management control, automatic process making, process examination and process sanction are combined into a unified management to make it convenient for the adjustment, control and management.
2002, 16(4).
Abstract:
A new numerical method to predict the initial blank geometry from the desired objective shape of parts is presented. Based on the conditions that the deformations in material are most evenly distributed and that the volume remains constant, a positive definite functional for blank design is constructed. The functional is minimized by an iterative scheme of finite element, and then the optimal initial configuration is obtained. The method is easy and expedient to use. The results of numerical simulation of forming process and multi-point forming experiments for sheet metal demonstrate that good precision is achieved by the proposed method.
A new numerical method to predict the initial blank geometry from the desired objective shape of parts is presented. Based on the conditions that the deformations in material are most evenly distributed and that the volume remains constant, a positive definite functional for blank design is constructed. The functional is minimized by an iterative scheme of finite element, and then the optimal initial configuration is obtained. The method is easy and expedient to use. The results of numerical simulation of forming process and multi-point forming experiments for sheet metal demonstrate that good precision is achieved by the proposed method.
NOVEL 6-SPS PARALLEL 3-DIMENSIONAL PLATFORM MANIPULATOR AND ITS FORCE / MOTION TRANSMISSION ANALYSIS
2002, 16(4).
Abstract:
The unique design for a novel 6-SPS parallel 3-dimensional platform manipulator with an orthogonal configuration is investigated. The layout feature of the parallel manipulator is described. Its force/motion transmission capability evaluation criteria are presented. At the orthogonal configuration, the criteria and the relationships between the criteria and the link lengths are analyzed, which is important since it can provide designer a piece of valuable information about how to choose the linear actuators. From the analysis of the results it is shown that the force/motion transmission capabilities of the parallel manipulator are characterized by isotropy at the orthogonal configuration. The manipulator is particularly suitable for certain applications in 6-DOF micromanipulators and 6-axis force/moment transducers.
The unique design for a novel 6-SPS parallel 3-dimensional platform manipulator with an orthogonal configuration is investigated. The layout feature of the parallel manipulator is described. Its force/motion transmission capability evaluation criteria are presented. At the orthogonal configuration, the criteria and the relationships between the criteria and the link lengths are analyzed, which is important since it can provide designer a piece of valuable information about how to choose the linear actuators. From the analysis of the results it is shown that the force/motion transmission capabilities of the parallel manipulator are characterized by isotropy at the orthogonal configuration. The manipulator is particularly suitable for certain applications in 6-DOF micromanipulators and 6-axis force/moment transducers.
2002, 16(4).
Abstract:
The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order to compile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of the actual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into new secondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then by the fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the one corresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferred into the fatigue crack growth accelerated load spectrum. Finally, it is verified by tests of two kinds of specimens that the damages of the specimens caused by the accelerated load spectra are near to those by the actual load spectra; namely, the tested life of actual load spectra is similar to that of accelerated load spectra. But the test time of accelerated load spectra is shortened by about three-quarters that of actual load spectra. From these tests, it is also found that the fatigue accelerat-ed test spectrum has an advantage over FALSTAFF spectra.
The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order to compile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of the actual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into new secondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then by the fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the one corresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferred into the fatigue crack growth accelerated load spectrum. Finally, it is verified by tests of two kinds of specimens that the damages of the specimens caused by the accelerated load spectra are near to those by the actual load spectra; namely, the tested life of actual load spectra is similar to that of accelerated load spectra. But the test time of accelerated load spectra is shortened by about three-quarters that of actual load spectra. From these tests, it is also found that the fatigue accelerat-ed test spectrum has an advantage over FALSTAFF spectra.
2002, 16(4).
Abstract:
A high precision method used for on-spot calibration of distributed stereo reference position setting is presented. The high measuring accuracy in stereo reference calibration is derived from using a high precision water level instrument and an accurate height vernier caliper. It settles the problem of reference calibration effectively and accurately, without using large coordinate measuring machines (CMM). It is more adaptable and precise than traditional calibration methods applying theodolites or autocollimators. The error sources of this method are analyzed in detail and several methods are developed to eliminate the calibration error.An optimizing swallowtail-like anchor target is developed. Experiments show that the calibration accuracy can be limited within 0.06 mm in the range of 3～5 m and 0.03 mm with optimizing anchor target. This method can be widely used in on-spot calibration.
A high precision method used for on-spot calibration of distributed stereo reference position setting is presented. The high measuring accuracy in stereo reference calibration is derived from using a high precision water level instrument and an accurate height vernier caliper. It settles the problem of reference calibration effectively and accurately, without using large coordinate measuring machines (CMM). It is more adaptable and precise than traditional calibration methods applying theodolites or autocollimators. The error sources of this method are analyzed in detail and several methods are developed to eliminate the calibration error.An optimizing swallowtail-like anchor target is developed. Experiments show that the calibration accuracy can be limited within 0.06 mm in the range of 3～5 m and 0.03 mm with optimizing anchor target. This method can be widely used in on-spot calibration.
2002, 16(4).
Abstract:
An integrated template of virtual product development alters primarily sequential tradition mode of product life cycle. The template integrates all processes of product development using digital modern. An environment of virtual product development provides product development environment of integration, communion, network, concurrent and collaboration. Combining development of new rapier loom, an innovated design process is researched in virtual product development, which consists three portions：constructing an integration development environment, innovation design and manufacturing simulation. The innovated design process realizes reverse design, mechanism concept design, structural design and analysis, performance analysis and manufacturing process simulation of virtual product, which can enhance greatly product performance and reduce cost and development cycle of new product.
An integrated template of virtual product development alters primarily sequential tradition mode of product life cycle. The template integrates all processes of product development using digital modern. An environment of virtual product development provides product development environment of integration, communion, network, concurrent and collaboration. Combining development of new rapier loom, an innovated design process is researched in virtual product development, which consists three portions：constructing an integration development environment, innovation design and manufacturing simulation. The innovated design process realizes reverse design, mechanism concept design, structural design and analysis, performance analysis and manufacturing process simulation of virtual product, which can enhance greatly product performance and reduce cost and development cycle of new product.
2002, 16(4).
Abstract:
From basic equations of gas-liquid, solid-liquid, solid-gas two-phase flow, the calculating method on flow transients of two-phase flow is developed by means of characteristic method. As one example, a gas-liquid flow transient is calculated and it agrees well with the experimental result. It is shown that the method is satisfactory for engineering demand.
From basic equations of gas-liquid, solid-liquid, solid-gas two-phase flow, the calculating method on flow transients of two-phase flow is developed by means of characteristic method. As one example, a gas-liquid flow transient is calculated and it agrees well with the experimental result. It is shown that the method is satisfactory for engineering demand.
2002, 16(4).
Abstract:
A new method is presented to describe and analyze the spatial compliance of coiled springs using screw theory. After an abbreviated description for the deformation of a beam element using screw theory, the spatial compliance density for a beam element is derived based on the fundamental material theory and reasonable assumptions, and the spatial compliance of the beam with finite length is obtained by integral. The spatial compliance of coiled springs is further analyzed using the spatial compliance density of the beam element. By calculating the eigencompliance and Ball's principle screws for the whole compliance of system, the compliance properties varying with the basic physical parameters of the system are illustrated in detail. The basic ideas can be used for the design and application of the coiled springs and the other compliant mechanisms with spatial compliant beam element.
A new method is presented to describe and analyze the spatial compliance of coiled springs using screw theory. After an abbreviated description for the deformation of a beam element using screw theory, the spatial compliance density for a beam element is derived based on the fundamental material theory and reasonable assumptions, and the spatial compliance of the beam with finite length is obtained by integral. The spatial compliance of coiled springs is further analyzed using the spatial compliance density of the beam element. By calculating the eigencompliance and Ball's principle screws for the whole compliance of system, the compliance properties varying with the basic physical parameters of the system are illustrated in detail. The basic ideas can be used for the design and application of the coiled springs and the other compliant mechanisms with spatial compliant beam element.
2002, 16(4).
Abstract:
The concept of variantional geometric constraints network is presented. Based on ISO's feature, three kinds of variational geometric constraints are defined. The concepts of mate tree (MT) and loop circuit (LC) are presented. The generation method of well-constrained variational geometric constraints network (VGCN) is studied. The network can be applied in generation of well-constrained tolerance types and tolerance chains. A simple example is analyzed to show the scheme to be effective.
The concept of variantional geometric constraints network is presented. Based on ISO's feature, three kinds of variational geometric constraints are defined. The concepts of mate tree (MT) and loop circuit (LC) are presented. The generation method of well-constrained variational geometric constraints network (VGCN) is studied. The network can be applied in generation of well-constrained tolerance types and tolerance chains. A simple example is analyzed to show the scheme to be effective.
2002, 16(4).
Abstract:
A method to solve the elastic conjugate surfaces in multi-teeth meshing is presented. In mechanical manufacturing and design, there exist a lot of problems relating to conjugate surfaces, such as three-dimensional engagement, steel rolling and workpiece machining, which cause great effects on the quality of machining and performances of transmission. This method describes relation between conjugate motion and elastic deformation in the process of mesh-in and mesh-out, and can be used to determine the profile of gear tooth by a certain given load sharing.
A method to solve the elastic conjugate surfaces in multi-teeth meshing is presented. In mechanical manufacturing and design, there exist a lot of problems relating to conjugate surfaces, such as three-dimensional engagement, steel rolling and workpiece machining, which cause great effects on the quality of machining and performances of transmission. This method describes relation between conjugate motion and elastic deformation in the process of mesh-in and mesh-out, and can be used to determine the profile of gear tooth by a certain given load sharing.
2002, 16(4).
Abstract:
By using tilting carbodies, train can negotiate at a higher speed without reducing the passenger's ride quality. This is a good method to allow a significant increase in speed at existing track to improve the railway transportation capability, and to enhance the competition ability of railways with other transportation systems. With the increase of the curve negotiation speed, the wheel-rail lateral forces and wheel-rail wear of the tilting train will increase. The self-steering radial bogie is an effective way to solve the problem. The dynamic model of the tilting passenger car with self-steering bogies is established in detail, and the curving performance of the car is investigated.
By using tilting carbodies, train can negotiate at a higher speed without reducing the passenger's ride quality. This is a good method to allow a significant increase in speed at existing track to improve the railway transportation capability, and to enhance the competition ability of railways with other transportation systems. With the increase of the curve negotiation speed, the wheel-rail lateral forces and wheel-rail wear of the tilting train will increase. The self-steering radial bogie is an effective way to solve the problem. The dynamic model of the tilting passenger car with self-steering bogies is established in detail, and the curving performance of the car is investigated.
2002, 16(4).
Abstract:
An experimental bimorph piezoelectric element (PZT) actuator for small pipe robot is developed. The robot can move in 20 mm pipe, and can carry a CCD camera for detecting cracks or fine holes on inner surface of pipe. The velocity of the robot can reach 17~22 mm/s for vertical pipe up/down, respectively. Moving principle and its performance characteristics are presented.
An experimental bimorph piezoelectric element (PZT) actuator for small pipe robot is developed. The robot can move in 20 mm pipe, and can carry a CCD camera for detecting cracks or fine holes on inner surface of pipe. The velocity of the robot can reach 17~22 mm/s for vertical pipe up/down, respectively. Moving principle and its performance characteristics are presented.
2002, 16(4).
Abstract:
A new idea for designing wheel patterns is presented so as to solve the problems about machining accuracy of workpiece and wear of honing wheel in ultra-precision plane honing. The influence factors on motion principle and pattern structures are analyzed and optimization machining parameters are obtained. By calculating effective cutting length on the surface of workpiece cut by wheel's abrasive and the orbit of one point on the surface of workpiece contacting with wheel, the wear coefficient of different kinds of wheels and accuracy coefficient of workpiece machined by corresponding wheels are obtained. Furthermore, the simulation results show that the optimal pattern structure of wheel turns out to have lower wheel wear and higher machining accuracy.
A new idea for designing wheel patterns is presented so as to solve the problems about machining accuracy of workpiece and wear of honing wheel in ultra-precision plane honing. The influence factors on motion principle and pattern structures are analyzed and optimization machining parameters are obtained. By calculating effective cutting length on the surface of workpiece cut by wheel's abrasive and the orbit of one point on the surface of workpiece contacting with wheel, the wear coefficient of different kinds of wheels and accuracy coefficient of workpiece machined by corresponding wheels are obtained. Furthermore, the simulation results show that the optimal pattern structure of wheel turns out to have lower wheel wear and higher machining accuracy.
2002, 16(4).
Abstract:
Some approaches to measure parallel 6-degree of freedom platforms posture statically and to calibrate the platform's actual structural parameters by measuring a series of the platform's varying postures are studied. In the case where high posture accuracy is required relatively, to obtain the platform's actual structural parameters is very important. Three dimensions measurement with 2 theodolites are used to obtain the platform's postures statically and Newton iterative method is adopted to calibrate structural parameters. Some measures taken in the measurement and the calibration are discussed in detail. And the experiment results of the platform's posture control before and after the calibration are given. The results show that the platform's posture control accuracy after the calibration is improved notably.
Some approaches to measure parallel 6-degree of freedom platforms posture statically and to calibrate the platform's actual structural parameters by measuring a series of the platform's varying postures are studied. In the case where high posture accuracy is required relatively, to obtain the platform's actual structural parameters is very important. Three dimensions measurement with 2 theodolites are used to obtain the platform's postures statically and Newton iterative method is adopted to calibrate structural parameters. Some measures taken in the measurement and the calibration are discussed in detail. And the experiment results of the platform's posture control before and after the calibration are given. The results show that the platform's posture control accuracy after the calibration is improved notably.
2002, 16(4).
Abstract:
Based on the development of the non-contact measurement system of free-form surface, NURBS reconstruction of measurement points of freeform surface is effectively realized by modifying the objective function and recursive procedure and calculating the optimum number of control points. The reconstruction precision is evaluated through Jacobi's transformation method. The feasibility of the measurement system and effectiveness of the reconstruction algorithm above are proved by experiment.
Based on the development of the non-contact measurement system of free-form surface, NURBS reconstruction of measurement points of freeform surface is effectively realized by modifying the objective function and recursive procedure and calculating the optimum number of control points. The reconstruction precision is evaluated through Jacobi's transformation method. The feasibility of the measurement system and effectiveness of the reconstruction algorithm above are proved by experiment.
2002, 16(4).
Abstract:
A multistage warm/hot forming is simulated for the cross grove outer race of constant velocity joint, using a thermo-mechanical coupled rigid viscoplastic finite element method, and specially some problem for process development and die design are analyzed. A forming test shows that computed results have good agreement with experimental results. Above obtained results can be applied to development of multistage warm/hot forming process and die design for outer race.
A multistage warm/hot forming is simulated for the cross grove outer race of constant velocity joint, using a thermo-mechanical coupled rigid viscoplastic finite element method, and specially some problem for process development and die design are analyzed. A forming test shows that computed results have good agreement with experimental results. Above obtained results can be applied to development of multistage warm/hot forming process and die design for outer race.
2002, 16(4).
Abstract:
The wear and destruction appearances of hobs are researched. The reasons of the wear and destruction of hob are analyzed. And the influence of the change of hobbing force and the hobbing temperature on the wear and destruction of hob in gear hobbing is also analyzed. In gear hobbing, the main wear mechanisms are adhension and ploughing when cutting the 20CrMnTi gear using W18Cr4V high-speed steel hob.
The wear and destruction appearances of hobs are researched. The reasons of the wear and destruction of hob are analyzed. And the influence of the change of hobbing force and the hobbing temperature on the wear and destruction of hob in gear hobbing is also analyzed. In gear hobbing, the main wear mechanisms are adhension and ploughing when cutting the 20CrMnTi gear using W18Cr4V high-speed steel hob.
2002, 16(4).
Abstract:
The flow characteristics and cavitation effects of water passing through small sharp-edged cylindrical orifices and valves of different shapes in water hydraulics are investigated. The test results using orifices with different aspect ratios and different diameters show that the flow coefficients in the case of non-cavitating flow are larger than that of flow in the case of cavitation occurrence. The flow coefficients of flow with cavitation initially decrease as Reynolds number increases and ultimately tend to be of constant values close to contraction coefficient. Large aspect ratio has an effect of suppressing cavitation. The experimental results about disc valves illustrate that the valves with sharp edge at large opening are less affected by cavitation than that at small opening. Throttle with triangle notch has better anticavitation ability than that with square notch. The flowrate of the throttle with square notch is significantly affected by the flow direction or the flow passage shape.
The flow characteristics and cavitation effects of water passing through small sharp-edged cylindrical orifices and valves of different shapes in water hydraulics are investigated. The test results using orifices with different aspect ratios and different diameters show that the flow coefficients in the case of non-cavitating flow are larger than that of flow in the case of cavitation occurrence. The flow coefficients of flow with cavitation initially decrease as Reynolds number increases and ultimately tend to be of constant values close to contraction coefficient. Large aspect ratio has an effect of suppressing cavitation. The experimental results about disc valves illustrate that the valves with sharp edge at large opening are less affected by cavitation than that at small opening. Throttle with triangle notch has better anticavitation ability than that with square notch. The flowrate of the throttle with square notch is significantly affected by the flow direction or the flow passage shape.
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