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RSS2013 Vol. 32, No. 4
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2013, 32(4): 469-473.
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Abstract:
The poor machinability of titanium alloys has limited good surface integrity which affects the processingand servicing properties.The experimental model for the titanium alloy turning based on the Taguchi method wereproposed to express the correlation between the processing variables and the responses.With material removal rateas objective function and surface roughness, tool life, cutting force as constraint function, the optimization procedure of titanium alloy turning was presented based on the response surface method via Kriging interpolation and genetic algorithm.The results indicate that the optimum parameter levels for different variables have been suggestedas v3 f3a p1 r1 E3.Comparing to the initial experiment, surface roughness, tool life, cutting force and material removalrate of the optimal condition are improved with 75.86%, 65.16%, 36.41% and 557.91%, respectively.
The poor machinability of titanium alloys has limited good surface integrity which affects the processingand servicing properties.The experimental model for the titanium alloy turning based on the Taguchi method wereproposed to express the correlation between the processing variables and the responses.With material removal rateas objective function and surface roughness, tool life, cutting force as constraint function, the optimization procedure of titanium alloy turning was presented based on the response surface method via Kriging interpolation and genetic algorithm.The results indicate that the optimum parameter levels for different variables have been suggestedas v3 f3a p1 r1 E3.Comparing to the initial experiment, surface roughness, tool life, cutting force and material removalrate of the optimal condition are improved with 75.86%, 65.16%, 36.41% and 557.91%, respectively.
2013, 32(4): 474-480.
Abstract:
Twin spool rotor systems are widely used in modern aircraft engines.Between the high pressure (HP)rotor and the low pressure (LP) rotor in a twin spool rotor system, there is normally an inter-bearing supporting oneend of the high pressure (HP) rotor.This structure can reduce the weight of the rotor system but make the couplingbetween the HP rotor and the LP rotor stronger.This paper sets up a simple model for simulating the vibration features of a twin spool rotor.The stiffness and damping of supports in the model are taken into account.The analytical results show that a twin spool rotor can easily exhibit a beat when the speed difference of HP rotor and LP rotoris small, say 10%.The magnitude of the beat can reach very high level at the critical speed.For keeping the vibration of a flexible rotor in an acceptable range, a high accuracy of rotor balancing is required.
Twin spool rotor systems are widely used in modern aircraft engines.Between the high pressure (HP)rotor and the low pressure (LP) rotor in a twin spool rotor system, there is normally an inter-bearing supporting oneend of the high pressure (HP) rotor.This structure can reduce the weight of the rotor system but make the couplingbetween the HP rotor and the LP rotor stronger.This paper sets up a simple model for simulating the vibration features of a twin spool rotor.The stiffness and damping of supports in the model are taken into account.The analytical results show that a twin spool rotor can easily exhibit a beat when the speed difference of HP rotor and LP rotoris small, say 10%.The magnitude of the beat can reach very high level at the critical speed.For keeping the vibration of a flexible rotor in an acceptable range, a high accuracy of rotor balancing is required.
2013, 32(4): 481-487.
Abstract:
Through studying the design ideas of the foreign four-axle vehicle's control system, a preliminary exploration about the hovering algorithm and a brief summary of the system's design were described in this article.AHRSand GPS, which are sensors for measuring key parameters, realize the automatic control of vehicle hovering and laya basis for full self-control flight.
Through studying the design ideas of the foreign four-axle vehicle's control system, a preliminary exploration about the hovering algorithm and a brief summary of the system's design were described in this article.AHRSand GPS, which are sensors for measuring key parameters, realize the automatic control of vehicle hovering and laya basis for full self-control flight.
2013, 32(4): 488-492.
Abstract:
The dynamic response data were obtained with different excitation frequencies at some specific spots ofan ordinary pipeline through harmonic experiments in its steady state.Considering the additional mass caused byaccelerometers, mode characteristics and dynamic response data were calculated and compared with test results respectively.The calculation errors of test results were regarded as error reliability distribution variables, and the error reliability distribution was simulated and combined with calculation results and working frequency range of a jetengine.The equivalent stress and displacement response data were also obtained with the error reliability distribution for a certain complex pipeline, and its safety was evaluated.The paper concludes that the mode test and dynamic response results have great impact on the pipeline constraint.The calculation errors and test results obey theGaussian distribution.
The dynamic response data were obtained with different excitation frequencies at some specific spots ofan ordinary pipeline through harmonic experiments in its steady state.Considering the additional mass caused byaccelerometers, mode characteristics and dynamic response data were calculated and compared with test results respectively.The calculation errors of test results were regarded as error reliability distribution variables, and the error reliability distribution was simulated and combined with calculation results and working frequency range of a jetengine.The equivalent stress and displacement response data were also obtained with the error reliability distribution for a certain complex pipeline, and its safety was evaluated.The paper concludes that the mode test and dynamic response results have great impact on the pipeline constraint.The calculation errors and test results obey theGaussian distribution.
2013, 32(4): 493-498.
Abstract:
A method of tooth grinding for double crowned face gear with helical pinion machined by using grindingdisk was studied in order to manufacture highly precise hardened face gear with helical pinion and obtain parabolictransmission errors and improve meshing performances.The surface of grinding disk with mismatched involute wasdesigned; the generation theory of helical face gear abraded by grinding disk is analyzed, deducing the tooth surfaceequation of double crowned face gear with helical pinion based on the generation theory, the grinding disk with mismatch involute and modification of the grinder movement.A tooth surface calculation and contact analysis exampleof double crowned face gear with helical pinion was represented and the results show that the maximum error of thetheoretical tooth surface of face gear is 5.98×10 -4 μm, the grinding and crowning method is feasible and the parabolic transmission is obtained, avoiding edge contact and approving meshing performances.
A method of tooth grinding for double crowned face gear with helical pinion machined by using grindingdisk was studied in order to manufacture highly precise hardened face gear with helical pinion and obtain parabolictransmission errors and improve meshing performances.The surface of grinding disk with mismatched involute wasdesigned; the generation theory of helical face gear abraded by grinding disk is analyzed, deducing the tooth surfaceequation of double crowned face gear with helical pinion based on the generation theory, the grinding disk with mismatch involute and modification of the grinder movement.A tooth surface calculation and contact analysis exampleof double crowned face gear with helical pinion was represented and the results show that the maximum error of thetheoretical tooth surface of face gear is 5.98×10 -4 μm, the grinding and crowning method is feasible and the parabolic transmission is obtained, avoiding edge contact and approving meshing performances.
2013, 32(4): 499-505.
Abstract:
In order to analyze the nonlinear dynamic response of rotor system, the dynamic model is established forthe rotor supported on the ball bearings with squeeze film dampers (SFD).In the present model, the couplingeffect of rotor, ball bearing and squeeze film damper was considered.For the model of ball bearings, the clearancesof bearings and the nonlinear Hertzian contract force between balls and races were considered, and for the model ofSFD, the nonlinear force of the film was considered.Then the rotor system response was obtained by the numericalintegral method.The influence were analyzed by using bifurcation diagrams, spectrum plot, Poincaré map andwhirl orbit for the nonlinear dynamic response of rotor caused by different rotating speed, stiffness of the supportingand the clearance of the SFD.The results show that the system of rotor will appear quasi-periodic motion more possibly with the higher speed, the bigger support stiffness and clearance of the SFD.
In order to analyze the nonlinear dynamic response of rotor system, the dynamic model is established forthe rotor supported on the ball bearings with squeeze film dampers (SFD).In the present model, the couplingeffect of rotor, ball bearing and squeeze film damper was considered.For the model of ball bearings, the clearancesof bearings and the nonlinear Hertzian contract force between balls and races were considered, and for the model ofSFD, the nonlinear force of the film was considered.Then the rotor system response was obtained by the numericalintegral method.The influence were analyzed by using bifurcation diagrams, spectrum plot, Poincaré map andwhirl orbit for the nonlinear dynamic response of rotor caused by different rotating speed, stiffness of the supportingand the clearance of the SFD.The results show that the system of rotor will appear quasi-periodic motion more possibly with the higher speed, the bigger support stiffness and clearance of the SFD.
2013, 32(4): 506-509.
Abstract:
SUS340 stainless steel is widely used because of high corrosion resistance, wear resistance and combinationproperty.The high toughness and low thermal conductivity make SUS304 stainless steel difficult to be ground or lathed inconventional machining.ELID (Electrolytic in-process dressing) grinding technique is an effective grinding process formirror grinding SUS304 stainless steel.In order to botain optimized grinding parameters for ELID grinding SUS304 stainless steel, orthogonal grinding experiment with seven factors and two levels using #325 grinding wheel and with three factors and two levels using #1200 grinding wheel were conducted.Through changing rotation speed of grinding wheel，speeds of X and Y tables, feed rate and ELID conditions, the influence of grinding parameters on the grinding characteristics were discussed.ELID mirror grinding of SUS304 stainless steel plane was conducted using various grain sizes, andsurface roughness of 3.6 nm in Ra was achieved using #8000 grinding wheel.
SUS340 stainless steel is widely used because of high corrosion resistance, wear resistance and combinationproperty.The high toughness and low thermal conductivity make SUS304 stainless steel difficult to be ground or lathed inconventional machining.ELID (Electrolytic in-process dressing) grinding technique is an effective grinding process formirror grinding SUS304 stainless steel.In order to botain optimized grinding parameters for ELID grinding SUS304 stainless steel, orthogonal grinding experiment with seven factors and two levels using #325 grinding wheel and with three factors and two levels using #1200 grinding wheel were conducted.Through changing rotation speed of grinding wheel，speeds of X and Y tables, feed rate and ELID conditions, the influence of grinding parameters on the grinding characteristics were discussed.ELID mirror grinding of SUS304 stainless steel plane was conducted using various grain sizes, andsurface roughness of 3.6 nm in Ra was achieved using #8000 grinding wheel.
2013, 32(4): 510-513.
Abstract:
Grid motion plays a great role in aeroelasticity analysis.This paper analyzed a dynamic grid based on theradial basis function.Using the compactly supported radial basis function, it deduced the displacement transfer matrix which interpolates the space grid location by surface grid motion.The node-reduction algorithm based on greedalgorithm and parallel technology reduced the computational time and the storage space of the dynamic grid.Considering that the surface had large grid deformation and complex structure, this method can well accomplish the gridmotion.The numerical example demonstrates that this method is suitable for both structural mesh and unstructuredgrid.The grid quality does not change much before and after grid deformation.
Grid motion plays a great role in aeroelasticity analysis.This paper analyzed a dynamic grid based on theradial basis function.Using the compactly supported radial basis function, it deduced the displacement transfer matrix which interpolates the space grid location by surface grid motion.The node-reduction algorithm based on greedalgorithm and parallel technology reduced the computational time and the storage space of the dynamic grid.Considering that the surface had large grid deformation and complex structure, this method can well accomplish the gridmotion.The numerical example demonstrates that this method is suitable for both structural mesh and unstructuredgrid.The grid quality does not change much before and after grid deformation.
2013, 32(4): 514-517.
Abstract:
The device color characteristic description is one of key technologies of color management.Consideringthe fuzzy properties of natural language description of color, this paper transforms RGB color space toCIEL* a* b* color space, for example, builds the device color characterization model by using the fuzzy controltheory and discusses the characterization model by comparing it with the characterization method which is based on3 -dimensional look-up table (3 D-LUT) and the interpolation algorithm.The results show that the characterizationmodel is simple for design and convenient for application.It is suitable for the nonlinear description of device colorcharacteristics.The average number of color errors of test sample points obtained by the characterization model is 2.65 when the number of test sample points is 125.To obtain the same number of average color errors, the 3 D-LUT& interpolation algorithm needs at least 512 test samples points.That is to say, compared with the 3 D-LUT & interpolation algorithm, our color characterization model has better precision even when there are few sample points.
The device color characteristic description is one of key technologies of color management.Consideringthe fuzzy properties of natural language description of color, this paper transforms RGB color space toCIEL* a* b* color space, for example, builds the device color characterization model by using the fuzzy controltheory and discusses the characterization model by comparing it with the characterization method which is based on3 -dimensional look-up table (3 D-LUT) and the interpolation algorithm.The results show that the characterizationmodel is simple for design and convenient for application.It is suitable for the nonlinear description of device colorcharacteristics.The average number of color errors of test sample points obtained by the characterization model is 2.65 when the number of test sample points is 125.To obtain the same number of average color errors, the 3 D-LUT& interpolation algorithm needs at least 512 test samples points.That is to say, compared with the 3 D-LUT & interpolation algorithm, our color characterization model has better precision even when there are few sample points.
2013, 32(4): 518-522.
Abstract:
Aiming at the improper selection of neighborhood diameter and subspace dimension of noise in normal local projective algorithm, an improving method for adaptive parameter selection is proposed.Using the curve diagram of the space vector direction which formed by phase point and its neighbor points within the whole given neighborhood according to the varying diameters, the optimum neighborhood diameter will be appropriately fixed.Andthe dimension of noise subspace is exactly determined by MInka Beyasian Selection(MIBS) criterion.The result ofsimulation experiments on Henon sequence and actual vibration signals of rub-impact rotor indicates that the adaptive filtering algorithm has the better capability of rebuilding chaotic signals and reducing nonlinear noises in theway of more precise reorganization between chaotic data and noise.
Aiming at the improper selection of neighborhood diameter and subspace dimension of noise in normal local projective algorithm, an improving method for adaptive parameter selection is proposed.Using the curve diagram of the space vector direction which formed by phase point and its neighbor points within the whole given neighborhood according to the varying diameters, the optimum neighborhood diameter will be appropriately fixed.Andthe dimension of noise subspace is exactly determined by MInka Beyasian Selection(MIBS) criterion.The result ofsimulation experiments on Henon sequence and actual vibration signals of rub-impact rotor indicates that the adaptive filtering algorithm has the better capability of rebuilding chaotic signals and reducing nonlinear noises in theway of more precise reorganization between chaotic data and noise.
2013, 32(4): 523-527.
Abstract:
The characteristic of joint friction in closed-loop mechanism was analyzed, and a mended exponentialfrictional model which could avoid detecting the point of zero velocity was put forward in this paper.The mathematicmodel of joint friction in closed-loop mechanism was described.The inverse dynamics model of a 5R closed-loopmechanism considering the joint friction was proposed.An iterative arithmetic was presented to solve the model，and joints force, joints friction moment and actuating moments were acquired.Results of simulation indicated thatthe joint friction had obvious influence about drive moments of the mechanism, and the effect deteriorated in the region of relative velocity reversing direction.
The characteristic of joint friction in closed-loop mechanism was analyzed, and a mended exponentialfrictional model which could avoid detecting the point of zero velocity was put forward in this paper.The mathematicmodel of joint friction in closed-loop mechanism was described.The inverse dynamics model of a 5R closed-loopmechanism considering the joint friction was proposed.An iterative arithmetic was presented to solve the model，and joints force, joints friction moment and actuating moments were acquired.Results of simulation indicated thatthe joint friction had obvious influence about drive moments of the mechanism, and the effect deteriorated in the region of relative velocity reversing direction.
2013, 32(4): 528-532.
Abstract:
The structure strength for composite hub-cover of a mega-watt wind turbine is analyzed based on the FEA(finite element analysis) theory using MSC.Patran /Nastran software.Shell element is chosen to build up the FEAmodel of hub-cover by the analysis of various 2D elements.The wind-load distribution coefficients are studied forthe streamlined shape of hub-cover, and each load is calculated according to the property of the third wind region aswell as different curvature radius of the hub-cover.Wind-load, snow-load and ice-load are all concerned to designthe corresponding load-case.To get the maximum stress and displacement, static strength of the composite hub-cover is analyzed and the result shows that the hub-cover won't be destroyed under the ultimate load.
The structure strength for composite hub-cover of a mega-watt wind turbine is analyzed based on the FEA(finite element analysis) theory using MSC.Patran /Nastran software.Shell element is chosen to build up the FEAmodel of hub-cover by the analysis of various 2D elements.The wind-load distribution coefficients are studied forthe streamlined shape of hub-cover, and each load is calculated according to the property of the third wind region aswell as different curvature radius of the hub-cover.Wind-load, snow-load and ice-load are all concerned to designthe corresponding load-case.To get the maximum stress and displacement, static strength of the composite hub-cover is analyzed and the result shows that the hub-cover won't be destroyed under the ultimate load.
2013, 32(4): 533-537.
Abstract:
In a middle-and high-pressure system, viscous heating increases temperature greatly.The spool valve isdistorted by heat inflation.This paper establishes the three-dimensional CFD model and the steady-state FEA thermal model respectively.It uses the FSI method to calculate and analyze the velocity, temperature and distortion ofthe spool valve under different pressures, depths and openings.It finds out the variation trends of the highest temperature and the highest distortion.The analysis method and the simulation results in the paper may be useful forspool valve design.
In a middle-and high-pressure system, viscous heating increases temperature greatly.The spool valve isdistorted by heat inflation.This paper establishes the three-dimensional CFD model and the steady-state FEA thermal model respectively.It uses the FSI method to calculate and analyze the velocity, temperature and distortion ofthe spool valve under different pressures, depths and openings.It finds out the variation trends of the highest temperature and the highest distortion.The analysis method and the simulation results in the paper may be useful forspool valve design.
2013, 32(4): 538-544.
Abstract:
According to the characteristics of hydraulic fault diagnosed of an automobile crane, its hydraulic faultdiagnosis expert system crane was developed.This expert system combines a fault tree with a fuzzy neural network.The construction of knowledge base and the realization of reasoning engine with expert rule representation and fuzzyrepresentation were completed by taking the example of a common fault of the automobile crane.The fault tree model was accordingly established.The difficulty for the expert system to acquire knowledge was solved; self-learningmechanism of the fuzzy neural network was utilized to ensure the completeness and correctness of the knowledgebase.The constant update and expansion of the content of the hydraulic fault diagnosis was achieved and the fault，if it happened, was promptly written in a database which improves the fault-searching accuracy and efficiency, thuspreventing the fault of the hydraulic system of the automobile crane.
According to the characteristics of hydraulic fault diagnosed of an automobile crane, its hydraulic faultdiagnosis expert system crane was developed.This expert system combines a fault tree with a fuzzy neural network.The construction of knowledge base and the realization of reasoning engine with expert rule representation and fuzzyrepresentation were completed by taking the example of a common fault of the automobile crane.The fault tree model was accordingly established.The difficulty for the expert system to acquire knowledge was solved; self-learningmechanism of the fuzzy neural network was utilized to ensure the completeness and correctness of the knowledgebase.The constant update and expansion of the content of the hydraulic fault diagnosis was achieved and the fault，if it happened, was promptly written in a database which improves the fault-searching accuracy and efficiency, thuspreventing the fault of the hydraulic system of the automobile crane.
2013, 32(4): 545-550.
Abstract:
The finite element model of a dump truck frame is established, and the natural frequency of frame is obtained through modal test and modal analysis, and the accuracy and rationality of the model is verified.On thefoundation established, two schemes are carried out.Firstly, choosing the design variables based on the sensitivityanalysis of frame structure and ensuring low grade modal frequency and strength of the frame, the thickness of framecomponent is optimized so as to achieve the goal of light weighting and reduction of the frame weight by 8.0%; secondly, in control of the quality of frame and strength, the lower grade modal frequency and dynamic performance oftruck frame structure are enhanced in order to advance low grade modal frequency of the frame.
The finite element model of a dump truck frame is established, and the natural frequency of frame is obtained through modal test and modal analysis, and the accuracy and rationality of the model is verified.On thefoundation established, two schemes are carried out.Firstly, choosing the design variables based on the sensitivityanalysis of frame structure and ensuring low grade modal frequency and strength of the frame, the thickness of framecomponent is optimized so as to achieve the goal of light weighting and reduction of the frame weight by 8.0%; secondly, in control of the quality of frame and strength, the lower grade modal frequency and dynamic performance oftruck frame structure are enhanced in order to advance low grade modal frequency of the frame.
2013, 32(4): 551-557.
Abstract:
The response surface method (RSM) is used to study the influence of the process parameters on the surface roughness of SiC monocrystal wafer under wire saw with the ultrasonic vibration machining process.The centralcomposite design (CCD) is used to design the experimental scheme.The wire saw's velocity, part feed rate, partspeed and ultrasonic amplitude are the factors that influence the SiC surface roughness.An empirical model hasbeen developed for predicting the surface roughness for machining the SiC monocrystal wafer.The response surfaceregression and variance analysis are used to study the effects of process parameters.The optimum machining condition for minimizing the surface roughness is determined by using the desirability function approach.The influence ofdifferent parameters on machining the SiC monocrystal wafer has been analyzed in detail.The verification experimental results show that this model can well predict the surface roughness for machining monocrystal materials.
The response surface method (RSM) is used to study the influence of the process parameters on the surface roughness of SiC monocrystal wafer under wire saw with the ultrasonic vibration machining process.The centralcomposite design (CCD) is used to design the experimental scheme.The wire saw's velocity, part feed rate, partspeed and ultrasonic amplitude are the factors that influence the SiC surface roughness.An empirical model hasbeen developed for predicting the surface roughness for machining the SiC monocrystal wafer.The response surfaceregression and variance analysis are used to study the effects of process parameters.The optimum machining condition for minimizing the surface roughness is determined by using the desirability function approach.The influence ofdifferent parameters on machining the SiC monocrystal wafer has been analyzed in detail.The verification experimental results show that this model can well predict the surface roughness for machining monocrystal materials.
2013, 32(4): 558-563.
Abstract:
The FE model of coach skeleton was developed.The normal modal parameter, indicators for stiffnessand strength properties under static bending and torsion cases are calculated.Based on the analysis results, thestructure configuration of the skeleton was modified accordingly.Optimization model for lightweight design was formulated.The thicknesses of skeleton components are selected as design variables, and the volume of coach skeletontogether with the indicators for the stiffness of the skeleton are set as responses.A sensitivity analysis is conductedto select the design variables which affect the structural performance most, followed by an updated optimizationmodel with these selected design variables.Finally, a lightweight scheme is proposed to reach a significant weightsaving.The feasibility of the optimization scheme is verified by the comparison with the original model.
The FE model of coach skeleton was developed.The normal modal parameter, indicators for stiffnessand strength properties under static bending and torsion cases are calculated.Based on the analysis results, thestructure configuration of the skeleton was modified accordingly.Optimization model for lightweight design was formulated.The thicknesses of skeleton components are selected as design variables, and the volume of coach skeletontogether with the indicators for the stiffness of the skeleton are set as responses.A sensitivity analysis is conductedto select the design variables which affect the structural performance most, followed by an updated optimizationmodel with these selected design variables.Finally, a lightweight scheme is proposed to reach a significant weightsaving.The feasibility of the optimization scheme is verified by the comparison with the original model.
2013, 32(4): 564-567.
Abstract:
A solution algorithm for irregular part nesting problem was proposed based on shaking bottle mechanism and minimum potential energy principle, and basic physical meaning of the nesting problem was explained from its mechanics.Firstly, inspiring from shaking bottle phenomenon, the shaking bottle algorithm of nesting problem was set up.Then, through the minimum potential energy principle in elastic mechanics, the part always found the lowest center of gravity position through translation and rotation transformation, using the polygon positive and negative gradient projection method to calculate centroid coordinates of the part.Finally, automatic nesting was realized after accessing by use of OBB bounding box intersection test algorithm.The ship parts nesting examples show that the nesting algorithm is feasible and with clear physical meaning, and it can realize irregular part nesting.
A solution algorithm for irregular part nesting problem was proposed based on shaking bottle mechanism and minimum potential energy principle, and basic physical meaning of the nesting problem was explained from its mechanics.Firstly, inspiring from shaking bottle phenomenon, the shaking bottle algorithm of nesting problem was set up.Then, through the minimum potential energy principle in elastic mechanics, the part always found the lowest center of gravity position through translation and rotation transformation, using the polygon positive and negative gradient projection method to calculate centroid coordinates of the part.Finally, automatic nesting was realized after accessing by use of OBB bounding box intersection test algorithm.The ship parts nesting examples show that the nesting algorithm is feasible and with clear physical meaning, and it can realize irregular part nesting.
2013, 32(4): 568-572.
Abstract:
In this paper, the structure of lower extremity skeleton in the human body and CGA (Clinic Gait Analysis) data was introduced.On the basis of the above-mentioned, the models for the mechanical parts and assembliesof the exoskeleton robot were established, and then the model of the final assembly was imported into the system ofMSC.ADAMS, and kinematics and dynamics simulation were carried out.The results suggested that the structuredesign of the exoskeleton robot is reasonable, which assured the flexibility of the mechanism and the comfort to puton, and that the simulation results reflected the changing law of those loads applied on the joints of the exoskeletonrobot.
In this paper, the structure of lower extremity skeleton in the human body and CGA (Clinic Gait Analysis) data was introduced.On the basis of the above-mentioned, the models for the mechanical parts and assembliesof the exoskeleton robot were established, and then the model of the final assembly was imported into the system ofMSC.ADAMS, and kinematics and dynamics simulation were carried out.The results suggested that the structuredesign of the exoskeleton robot is reasonable, which assured the flexibility of the mechanism and the comfort to puton, and that the simulation results reflected the changing law of those loads applied on the joints of the exoskeletonrobot.
The Decision-making Model for the Maintenance Time in Equipment Full Life Cycle Based on Reliability
2013, 32(4): 573-576.
Abstract:
Based on the theory of reliability, a quantitative method of the maintenance time is proposed in this paper, in which can improve the relevance and economy of maintenance activity.Firstly, the impact of predictablemaintenance time on the safety and economy of equipments is described.Secondly, a decision-making model of optimum maintenance time under the principle of minimizing the maintenance cost per unit time in equipment full lifecycle is proposed.Finally, the validity and generalizability verification shows that the model can be effectively applied in the decision of optimized maintenance time.
Based on the theory of reliability, a quantitative method of the maintenance time is proposed in this paper, in which can improve the relevance and economy of maintenance activity.Firstly, the impact of predictablemaintenance time on the safety and economy of equipments is described.Secondly, a decision-making model of optimum maintenance time under the principle of minimizing the maintenance cost per unit time in equipment full lifecycle is proposed.Finally, the validity and generalizability verification shows that the model can be effectively applied in the decision of optimized maintenance time.
2013, 32(4): 577-583.
Abstract:
The existing crane in China has some flaw in controlling its jib.The root cause lies in the fact that themain control valve of the hydraulic system does not match the operation mode of the machine and that it can not adjust promptly to the outside load.Thus the speed is not steady; the reliability and the energy conservation are notgood during the work of the crane jib; there are also some safety problems.To solve these problems, we divide thetraditional proportional and directional valve into two types in terms of its function: the switch direction valve andthe electricity proportion throttle valve.The electricity proportion throttle valve's opening is controlled in a real-timemanner through the hydraulic system parameters' online examination and real-time computation.The hydraulic system parameters can change with the load change and the operation mode requirement so as to accomplish the dynamic optimum control of the crane and the objectives, to enhance the speed, the energy conservation and the reliability of the crane jib and to solve the safety problem.
The existing crane in China has some flaw in controlling its jib.The root cause lies in the fact that themain control valve of the hydraulic system does not match the operation mode of the machine and that it can not adjust promptly to the outside load.Thus the speed is not steady; the reliability and the energy conservation are notgood during the work of the crane jib; there are also some safety problems.To solve these problems, we divide thetraditional proportional and directional valve into two types in terms of its function: the switch direction valve andthe electricity proportion throttle valve.The electricity proportion throttle valve's opening is controlled in a real-timemanner through the hydraulic system parameters' online examination and real-time computation.The hydraulic system parameters can change with the load change and the operation mode requirement so as to accomplish the dynamic optimum control of the crane and the objectives, to enhance the speed, the energy conservation and the reliability of the crane jib and to solve the safety problem.
2013, 32(4): 584-588.
Abstract:
As one of key parts in modem automobiles, the suspension has great influence on the smoothness of automobiles.Based on the ADAMS and MATLAB method, a 1/4 vehicle air-suspension model and an active vehiclePID control model are established with stochastic road excitation together with the PID parameters definition.Andthe effects of passive control and semi-active control are investigated based on the ADAMS-MATLAB co-simulation.The result shows that the present active control can reduce the vibration of automobile and thus improve the smoothness compared to the passive suspension system.This simulation method improves the efficiency of the suspensiondesign and provides a new way for control and simulation of complex mechanical systems while avoiding buildingtheir dynamical and state equations.
As one of key parts in modem automobiles, the suspension has great influence on the smoothness of automobiles.Based on the ADAMS and MATLAB method, a 1/4 vehicle air-suspension model and an active vehiclePID control model are established with stochastic road excitation together with the PID parameters definition.Andthe effects of passive control and semi-active control are investigated based on the ADAMS-MATLAB co-simulation.The result shows that the present active control can reduce the vibration of automobile and thus improve the smoothness compared to the passive suspension system.This simulation method improves the efficiency of the suspensiondesign and provides a new way for control and simulation of complex mechanical systems while avoiding buildingtheir dynamical and state equations.
2013, 32(4): 589-596.
Abstract:
Utilizing the generalized conformation theory, a new layerwise laminated shell element constructionmethod is developed, and the detailed construction process is presented.The construction method can calculate thedisplacement of each layer.The shear strain fields of each layer are determined with the Timoshenko beam theory.When a laminated structure contains thin layers, the thin-layer model degrades into a thin-plate model which is freeof shear locking.During the degradation, the displacement between adjacent elements keeps constant in terms ofintegral due to generalized conformation.Numerical examples show that this laminated shell element can accuratelydescribe the mechanical properties of each layer and calculate the mechanics of a laminated structure with thin andthick layers.
Utilizing the generalized conformation theory, a new layerwise laminated shell element constructionmethod is developed, and the detailed construction process is presented.The construction method can calculate thedisplacement of each layer.The shear strain fields of each layer are determined with the Timoshenko beam theory.When a laminated structure contains thin layers, the thin-layer model degrades into a thin-plate model which is freeof shear locking.During the degradation, the displacement between adjacent elements keeps constant in terms ofintegral due to generalized conformation.Numerical examples show that this laminated shell element can accuratelydescribe the mechanical properties of each layer and calculate the mechanics of a laminated structure with thin andthick layers.
2013, 32(4): 597-600,606.
Abstract:
Swage autofrettage has been widely used in the production of high-pressure vessel and barrel.There areno complete design and process specifications so far.With the help of literature and empirical data, the specimen ofthe thick-walled cylinder and the mandrel was designed.A hydraulic pump drives the experimental device, and thetest system measures strain, mandrel displacement and mandrel push force.Formulas of the push force were summarized according to the experimental data and empirical formulas.The formulas' absolute error is less than �10%in comparison of the calculated values with measured values.Residual strain and external surface strain-mandreldisplacement variation curves were also tested.After low-temperature thermal treatment and machining, changes inthe re-yield pressure of thick-walled cylinders were given.
Swage autofrettage has been widely used in the production of high-pressure vessel and barrel.There areno complete design and process specifications so far.With the help of literature and empirical data, the specimen ofthe thick-walled cylinder and the mandrel was designed.A hydraulic pump drives the experimental device, and thetest system measures strain, mandrel displacement and mandrel push force.Formulas of the push force were summarized according to the experimental data and empirical formulas.The formulas' absolute error is less than �10%in comparison of the calculated values with measured values.Residual strain and external surface strain-mandreldisplacement variation curves were also tested.After low-temperature thermal treatment and machining, changes inthe re-yield pressure of thick-walled cylinders were given.
2013, 32(4): 601-606.
Abstract:
Fast-burning energetic compound (ACP) is one of the most important additives to increase the burningrate of solid propellant, the decomposition effects of ACP to the composite modified double-based (CMDB) propellant were investigated by means of differential scanning calorimeters (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) experiments, the burning rate of CMDB propellant with ACP was determined.The flamestructure and the combustion wave temperature distribution of CMDB propellant with ACP samples were measuredby means of flame photo technique and micro-thermal-couple, respectively.The effect of the major components ofpropellant on the combustion properties was analyzed.The results show that the burning rate of CMDB propellantwith ACP increases with increase in the mass content of ACP, the brightness of combustion structures is luminouswith increase in the content of ACP.
Fast-burning energetic compound (ACP) is one of the most important additives to increase the burningrate of solid propellant, the decomposition effects of ACP to the composite modified double-based (CMDB) propellant were investigated by means of differential scanning calorimeters (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) experiments, the burning rate of CMDB propellant with ACP was determined.The flamestructure and the combustion wave temperature distribution of CMDB propellant with ACP samples were measuredby means of flame photo technique and micro-thermal-couple, respectively.The effect of the major components ofpropellant on the combustion properties was analyzed.The results show that the burning rate of CMDB propellantwith ACP increases with increase in the mass content of ACP, the brightness of combustion structures is luminouswith increase in the content of ACP.
2013, 32(4): 607-611.
Abstract:
Corrugated web girder is a new type of structure.Transverse bending will be induced in the flanges under in-plane load, which makes the bending stresses in the flanges more complex.In accordance with the Abbas'stransverse bending theory, a close form solution for the simply supported girder with sinusoidal corrugated webwhich bears in-plane concentrated load was established.Then an accessible approach to girders with other web profiles which has the same parameters as the sinusoidal profile was given.FEA method was utilized to validate theproposed formula and approach.Furthermore, the total bending stress behavior of the flanges under movable concentrated load was discussed.Finally, the suggestion that transverse bending should be considered in bendingstrength design but can be neglected in fatigue analysis was given.
Corrugated web girder is a new type of structure.Transverse bending will be induced in the flanges under in-plane load, which makes the bending stresses in the flanges more complex.In accordance with the Abbas'stransverse bending theory, a close form solution for the simply supported girder with sinusoidal corrugated webwhich bears in-plane concentrated load was established.Then an accessible approach to girders with other web profiles which has the same parameters as the sinusoidal profile was given.FEA method was utilized to validate theproposed formula and approach.Furthermore, the total bending stress behavior of the flanges under movable concentrated load was discussed.Finally, the suggestion that transverse bending should be considered in bendingstrength design but can be neglected in fatigue analysis was given.
2013, 32(4): 612-615.
Abstract:
In engine compartment, it is difficult to eliminate the effect of interfering signals on vehicle throttle position sensor (TPS) by the traditional signal processing method.In this article, according to the characteristic ofTPS, the wavelet theory was applied to decompose the noise signal for 4 levels by selecting Daubechies (dB5)wavelet in MATLAB.After decomposing, the soft-threshold de-noising method was employed to eliminate noise，then the inverse wavelet transform was used to reconstruct signals for signal de-noising and rebuilding.Finally, thede-noised signal was compared with the un-denoised signal by real vehicle tests.The tests show that the engine runmore stable when using the de-noised TPS signal and the de-noised TPS signal after wavelet transforming can improve the engine control more effectively.
In engine compartment, it is difficult to eliminate the effect of interfering signals on vehicle throttle position sensor (TPS) by the traditional signal processing method.In this article, according to the characteristic ofTPS, the wavelet theory was applied to decompose the noise signal for 4 levels by selecting Daubechies (dB5)wavelet in MATLAB.After decomposing, the soft-threshold de-noising method was employed to eliminate noise，then the inverse wavelet transform was used to reconstruct signals for signal de-noising and rebuilding.Finally, thede-noised signal was compared with the un-denoised signal by real vehicle tests.The tests show that the engine runmore stable when using the de-noised TPS signal and the de-noised TPS signal after wavelet transforming can improve the engine control more effectively.
2013, 32(4): 616-619,624.
Abstract:
In order to eliminate the influence of thermal error on the machining precision, a novel model for thermalerror in machine tools is proposed by using the BP via GA to optimize BP neural network structure and parameters.A versatile interactive thermal error modeling simulation system interface is designed by using Matlab-GUI, the results show that the present model performs better than the traditional BP model.It is good in fitting and precise inprediction for a great number of working conditions.
In order to eliminate the influence of thermal error on the machining precision, a novel model for thermalerror in machine tools is proposed by using the BP via GA to optimize BP neural network structure and parameters.A versatile interactive thermal error modeling simulation system interface is designed by using Matlab-GUI, the results show that the present model performs better than the traditional BP model.It is good in fitting and precise inprediction for a great number of working conditions.
2013, 32(4): 620-624.
Abstract:
Aiming to establish crisscross-coupling relationship in the design evaluation process, an overall evaluation model for complex cavity mold design schemes via the extension methodology is proposed based on the matterelement model, correlation function, weight and membership.A mold for design scheme is discussed, in which isbased on the forming technology, mold structure, mold material and manufacture cost.The result in practice showsthat the method on the extension theory is simple, effective.
Aiming to establish crisscross-coupling relationship in the design evaluation process, an overall evaluation model for complex cavity mold design schemes via the extension methodology is proposed based on the matterelement model, correlation function, weight and membership.A mold for design scheme is discussed, in which isbased on the forming technology, mold structure, mold material and manufacture cost.The result in practice showsthat the method on the extension theory is simple, effective.
