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RSS2016 Vol. 35, No. 5
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2016, 35(5): 657-661.
doi: 10.13433/j.cnki.1003-8728.2016.0501
PDF 1433KB
Abstract:
The wavelet transform may present the local properties of signal in time-frequency domain,it can zoom up and recognize the mutation signal of structural response under different scales. Numerous studies show both wavelet energy and flexibility curvature are very sensitive to local structural damage. Based on discrete wavelet decomposition, the signal under impact load can be decomposed to different frequency range and reconstructed. This paper presents a new damage index based on discrete wavelet decomposition and modal analysis. Through numerical analysis and experiments of a continuous beam,the results show that the proposed method is effective.
The wavelet transform may present the local properties of signal in time-frequency domain,it can zoom up and recognize the mutation signal of structural response under different scales. Numerous studies show both wavelet energy and flexibility curvature are very sensitive to local structural damage. Based on discrete wavelet decomposition, the signal under impact load can be decomposed to different frequency range and reconstructed. This paper presents a new damage index based on discrete wavelet decomposition and modal analysis. Through numerical analysis and experiments of a continuous beam,the results show that the proposed method is effective.
2016, 35(5): 662-671.
doi: 10.13433/j.cnki.1003-8728.2016.0502
Abstract:
According to the stick slip friction phenomenon existing in the two kinds of mechanical system and the detailed object, the present research results and induced mechanism of the stick slip in the different mechanical system are stated and discussed in this paper from the view of the mechanical modeling, the interesting problem and the research methods. The control and compensation methods for reducing or avoiding stick slip phenomenon are summarized. At last, some problems to be further studied are presented.
According to the stick slip friction phenomenon existing in the two kinds of mechanical system and the detailed object, the present research results and induced mechanism of the stick slip in the different mechanical system are stated and discussed in this paper from the view of the mechanical modeling, the interesting problem and the research methods. The control and compensation methods for reducing or avoiding stick slip phenomenon are summarized. At last, some problems to be further studied are presented.
2016, 35(5): 672-677.
doi: 10.13433/j.cnki.1003-8728.2016.0503
Abstract:
As more and more people have lower limb dyskinesia, lower limb rehabilitation gradually receives greater attention from many scholars and researchers. In order to study the influence of different gait trajectories on the fatigue of the major muscles of a lower human limb, we design three mechanisms that can achieve different trajectories and use SolidWorks to build their three dimensional models. Then, we build the human limb model according to the model in LifeMOD. We use computer simulation to coordinate it with the three-dimensional models and obtain the results of change in stretch tensors of the major muscles. The simulation results show that different gait trajectories have different influences on stretch tensors, namely, fatigue. So it is very important to design mechanisms that have reasonable trajectories to meet the needs of human limb's movement. The analysis results not only provide the evidence for designing some mechanisms for lower human limb rehabilitation exercise, but also provide a new way of rehabilitation evaluation.
As more and more people have lower limb dyskinesia, lower limb rehabilitation gradually receives greater attention from many scholars and researchers. In order to study the influence of different gait trajectories on the fatigue of the major muscles of a lower human limb, we design three mechanisms that can achieve different trajectories and use SolidWorks to build their three dimensional models. Then, we build the human limb model according to the model in LifeMOD. We use computer simulation to coordinate it with the three-dimensional models and obtain the results of change in stretch tensors of the major muscles. The simulation results show that different gait trajectories have different influences on stretch tensors, namely, fatigue. So it is very important to design mechanisms that have reasonable trajectories to meet the needs of human limb's movement. The analysis results not only provide the evidence for designing some mechanisms for lower human limb rehabilitation exercise, but also provide a new way of rehabilitation evaluation.
2016, 35(5): 678-685.
doi: 10.13433/j.cnki.1003-8728.2016.0504
Abstract:
In this paper, a novel simulated-annealing and teaching-learning based optimization (SA-TLBO) algorithm for mobile robots global path planning is presented. Firstly, a new map model for path planning between start-point and goal-point is built by coordinate system transformation. Then, the basic teaching-learning based optimization algorithm is modified in terms of the simulated annealing. Lastly, by utilizing the improved algorithm, the objective function of the path planning is optimized, then getting a global optimal path. The simulation experiment results show that the present method has a faster convergence rate and higher search accuracy with better global search ability, and can effectively solve the global optimization solution for robots global path planning.
In this paper, a novel simulated-annealing and teaching-learning based optimization (SA-TLBO) algorithm for mobile robots global path planning is presented. Firstly, a new map model for path planning between start-point and goal-point is built by coordinate system transformation. Then, the basic teaching-learning based optimization algorithm is modified in terms of the simulated annealing. Lastly, by utilizing the improved algorithm, the objective function of the path planning is optimized, then getting a global optimal path. The simulation experiment results show that the present method has a faster convergence rate and higher search accuracy with better global search ability, and can effectively solve the global optimization solution for robots global path planning.
2016, 35(5): 686-689.
doi: 10.13433/j.cnki.1003-8728.2016.0505
Abstract:
In order to suppress the vibration of the piezoelectric smart structure, the adaptive PD algorithm with perfect reference model tracking performance is usually adopted. But it is lack of stability under rapid disturbance, the problem is particularly prominent caused by random disturbance. Therefore, the direct velocity negative feedback (DVFB) control algorithm is coupled into the adaptive PD algorithm to improve adaptive PD algorithm, and the stability of the new control system is verified by Lyapunov method. The reference model is determined according to the shrinking factor method. Simulation results show that the improved adaptive PD algorithm could have better robustness and stability according to track errors and output displacement effects compared with traditional adaptive PD algorithm under sine signal or random signal excitation.
In order to suppress the vibration of the piezoelectric smart structure, the adaptive PD algorithm with perfect reference model tracking performance is usually adopted. But it is lack of stability under rapid disturbance, the problem is particularly prominent caused by random disturbance. Therefore, the direct velocity negative feedback (DVFB) control algorithm is coupled into the adaptive PD algorithm to improve adaptive PD algorithm, and the stability of the new control system is verified by Lyapunov method. The reference model is determined according to the shrinking factor method. Simulation results show that the improved adaptive PD algorithm could have better robustness and stability according to track errors and output displacement effects compared with traditional adaptive PD algorithm under sine signal or random signal excitation.
2016, 35(5): 690-695.
doi: 10.13433/j.cnki.1003-8728.2016.0506
Abstract:
For the reliability analysis of a type of motorized spindle under the case of extremely-small samples, the virtual augmented method and Boot-strap method were used to virtually extend the original sample, then the degradation model and the reliability function of which the parameters followed random distribution were established. Besides, Through Bayes prior distribution, the reliability function under random coefficients was modified. The reliability function of the motorized spindle under random coefficients after modification was compared with the reliability function deduced under the case of pseudo-life. The results showed that the reliability function obtained by the random coefficient method had a higher precision, and the errors generated by the reliability evaluation using pseudo-life method in which the model parameters were regarded as fixed values were avoided. The method proposed in this paper can be used to obtain the degradation characteristics for the similar products with certain applicability according to the extremely-small sample experimental data.
For the reliability analysis of a type of motorized spindle under the case of extremely-small samples, the virtual augmented method and Boot-strap method were used to virtually extend the original sample, then the degradation model and the reliability function of which the parameters followed random distribution were established. Besides, Through Bayes prior distribution, the reliability function under random coefficients was modified. The reliability function of the motorized spindle under random coefficients after modification was compared with the reliability function deduced under the case of pseudo-life. The results showed that the reliability function obtained by the random coefficient method had a higher precision, and the errors generated by the reliability evaluation using pseudo-life method in which the model parameters were regarded as fixed values were avoided. The method proposed in this paper can be used to obtain the degradation characteristics for the similar products with certain applicability according to the extremely-small sample experimental data.
2016, 35(5): 696-700.
doi: 10.13433/j.cnki.1003-8728.2016.0507
Abstract:
Through the thermal elastic-plastic finite element method, welding residual deformation of excavator boom was successfully predicted by the segmented moving temperature-controlled volume heat source model as welding model and adopting a series measures, which has high precision. Comparing the simulation results with the measured, the which shows that the residual deformation has a contraction in the vertical direction, the front stretch and the rear compression in the horizontal direction, the global existence of the warping phenomenon, which is in an accordance with the measured. The simulation results accurately forecast the evolution of welding residual deformation and serve as a basis for control of welding residual deformation. The characteristic of segmented moving temperature-controlled volume heat source model is easy to adopt, high efficiency and high precision.
Through the thermal elastic-plastic finite element method, welding residual deformation of excavator boom was successfully predicted by the segmented moving temperature-controlled volume heat source model as welding model and adopting a series measures, which has high precision. Comparing the simulation results with the measured, the which shows that the residual deformation has a contraction in the vertical direction, the front stretch and the rear compression in the horizontal direction, the global existence of the warping phenomenon, which is in an accordance with the measured. The simulation results accurately forecast the evolution of welding residual deformation and serve as a basis for control of welding residual deformation. The characteristic of segmented moving temperature-controlled volume heat source model is easy to adopt, high efficiency and high precision.
2016, 35(5): 701-705.
doi: 10.13433/j.cnki.1003-8728.2016.0508
Abstract:
In this paper, the parametric analysis of tetrahedral lattice sandwich cylinder stability under torsional loading is examined by using finite element method. Based on performance-enhancing factor denoted as ratio of sandwich cylinder property to that of solid cylinder with equal mass, the effects of lattice rod cross-section, lattice relative density, lattice number, lattice configuration and cylinder skin thickness on the torsional stability is evaluated. The results show that lattice relative density and cylinder skin thickness have significant influence on the cylinder torsional stability, which is nearly the same for different lattice sandwich cylinder with same lattice rod cross-section area. It shows that sandwich cylinder containing more lattices is conducive to enhancing its torsional stability. When the relative density is small, lattice sandwich cylinder with stubby strut has advantage in the torsional performance. The conclusions are instructive for the design of lattice sandwich cylinder.
In this paper, the parametric analysis of tetrahedral lattice sandwich cylinder stability under torsional loading is examined by using finite element method. Based on performance-enhancing factor denoted as ratio of sandwich cylinder property to that of solid cylinder with equal mass, the effects of lattice rod cross-section, lattice relative density, lattice number, lattice configuration and cylinder skin thickness on the torsional stability is evaluated. The results show that lattice relative density and cylinder skin thickness have significant influence on the cylinder torsional stability, which is nearly the same for different lattice sandwich cylinder with same lattice rod cross-section area. It shows that sandwich cylinder containing more lattices is conducive to enhancing its torsional stability. When the relative density is small, lattice sandwich cylinder with stubby strut has advantage in the torsional performance. The conclusions are instructive for the design of lattice sandwich cylinder.
2016, 35(5): 706-710.
doi: 10.13433/j.cnki.1003-8728.2016.0509
Abstract:
The solution of position is analyzed for the mechanical arm with seven degrees of freedom in this article. Based on the complexity of space configuration and self-motion, seven degrees of freedom will be modular and then divided into two four degrees of freedom modular units. By analyzing the modular units, the complex space configuration will be put into planar configurations, which reduces the computation. The concepts of "anchor point" and "imagine link" which make the posture parameterized are introduced. An analytical method for the inverse kinematics of the redundant robot is proposed with "anchor point" and "imagine link".
The solution of position is analyzed for the mechanical arm with seven degrees of freedom in this article. Based on the complexity of space configuration and self-motion, seven degrees of freedom will be modular and then divided into two four degrees of freedom modular units. By analyzing the modular units, the complex space configuration will be put into planar configurations, which reduces the computation. The concepts of "anchor point" and "imagine link" which make the posture parameterized are introduced. An analytical method for the inverse kinematics of the redundant robot is proposed with "anchor point" and "imagine link".
2016, 35(5): 711-716.
doi: 10.13433/j.cnki.1003-8728.2016.0510
Abstract:
Water-jet cavitation peening uses the shock wave pressure and micro-jet produced by the cavitation bubbles collapsing near the surface of materials to strengthen the material surface, the cavitation bubbles are provided by the submerged cavitating water jet generated by convergent-divergent nozzle. Therefore, the cavitation capability of convergent-divergent nozzle can affect the peening effect directly. With using FLUENT software,the computer simulation is applied to study the submerged cavitating water jets, and the influences of nozzle throat diameter and nozzle divergence angle on the cavitation behavior in the flow field are analyzed. The Fujifilm pressure-sensitive paper is applied to measure the pressure distribution on the section which is perpendicular to the axis of cavitating water jet. The results show that the vapor fraction in flow field rises with the nozzle throat diameter increasing or the nozzle divergence angle decreasing, and the measured pressure in the experiment is up to 300 MPa.
Water-jet cavitation peening uses the shock wave pressure and micro-jet produced by the cavitation bubbles collapsing near the surface of materials to strengthen the material surface, the cavitation bubbles are provided by the submerged cavitating water jet generated by convergent-divergent nozzle. Therefore, the cavitation capability of convergent-divergent nozzle can affect the peening effect directly. With using FLUENT software,the computer simulation is applied to study the submerged cavitating water jets, and the influences of nozzle throat diameter and nozzle divergence angle on the cavitation behavior in the flow field are analyzed. The Fujifilm pressure-sensitive paper is applied to measure the pressure distribution on the section which is perpendicular to the axis of cavitating water jet. The results show that the vapor fraction in flow field rises with the nozzle throat diameter increasing or the nozzle divergence angle decreasing, and the measured pressure in the experiment is up to 300 MPa.
2016, 35(5): 717-721.
doi: 10.13433/j.cnki.1003-8728.2016.0511
Abstract:
The interaction model between the disc cutter and the rock was established by using the finite element method. The forces and the slip displacement of a single disc cutter when breaking rock were obtained via numerical simulation. Based on the relationship between the abrasion loss of volume and the friction energy, an estimation method for predicting the wear content of cutter was proposed. The results show that it is feasible by using the numerical simulation method to obtain the vertical force and slip displacement and then to estimate the cutter's lifespan. The examples show that there is an optimal rate of penetration to leastly decrease the wear for the same geology condition. The increase in the radius of location and rotation speed will increase the wear of the cutter. The increase in the uniaxial compressive strength will also increase the wear of the cutter. The present results may provide a concise method to evaluate the wear, to predict the cutter's lifespan and to determine the period of changing cutters.
The interaction model between the disc cutter and the rock was established by using the finite element method. The forces and the slip displacement of a single disc cutter when breaking rock were obtained via numerical simulation. Based on the relationship between the abrasion loss of volume and the friction energy, an estimation method for predicting the wear content of cutter was proposed. The results show that it is feasible by using the numerical simulation method to obtain the vertical force and slip displacement and then to estimate the cutter's lifespan. The examples show that there is an optimal rate of penetration to leastly decrease the wear for the same geology condition. The increase in the radius of location and rotation speed will increase the wear of the cutter. The increase in the uniaxial compressive strength will also increase the wear of the cutter. The present results may provide a concise method to evaluate the wear, to predict the cutter's lifespan and to determine the period of changing cutters.
2016, 35(5): 722-728.
doi: 10.13433/j.cnki.1003-8728.2016.0512
Abstract:
A failure maintenance decision method based on the meta-action assembly unit was proposed to locate failures quickly and save the maintenance time. Firstly, the meta-action assembly unit was defined and its features and decomposition principles were elaborated. Secondly, the failure risk analysis and the sequencing of the meta-action assembly unit were accomplished by fuzzy sets theory and grey correlation theory. Then critical failures were determined by analyzing the grey correlation of failures through a normalization process and the primary and secondary diagram method. Finally, reasonable maintenance modes for critical failures of the meta-action assembly unit were confirmed by grey clustering approach. The effectiveness of the proposed failure maintenance decision method was demonstrated by an example of the meta-action assembly unit from a certain machining center.
A failure maintenance decision method based on the meta-action assembly unit was proposed to locate failures quickly and save the maintenance time. Firstly, the meta-action assembly unit was defined and its features and decomposition principles were elaborated. Secondly, the failure risk analysis and the sequencing of the meta-action assembly unit were accomplished by fuzzy sets theory and grey correlation theory. Then critical failures were determined by analyzing the grey correlation of failures through a normalization process and the primary and secondary diagram method. Finally, reasonable maintenance modes for critical failures of the meta-action assembly unit were confirmed by grey clustering approach. The effectiveness of the proposed failure maintenance decision method was demonstrated by an example of the meta-action assembly unit from a certain machining center.
2016, 35(5): 729-733.
doi: 10.13433/j.cnki.1003-8728.2016.0513
Abstract:
Machined surface integrity of titanium alloy plays a key role due to its strong correlation with the functional performance and service life. In this paper, several side-milling tests were developed to investigate influence law of different cooling conditions on surface integrity in milling of TC4 alloy. The results showed that the values of surface roughness and microhardness under emulsion condition were lower than that in dry condition with same cutting parameters, machined surface residual stresses were compressive stresses in emulsion and dry conditions. Under emulsion condition, the absolute value of residual compressive stress always increased with the increasing of cutting speed, feed per tooth and milling width, while the reverse redistribution phenomena were found under emulsion condition. Under emulsion and dry conditions, milling depth had less influence on surface integrity than the other milling parameters.
Machined surface integrity of titanium alloy plays a key role due to its strong correlation with the functional performance and service life. In this paper, several side-milling tests were developed to investigate influence law of different cooling conditions on surface integrity in milling of TC4 alloy. The results showed that the values of surface roughness and microhardness under emulsion condition were lower than that in dry condition with same cutting parameters, machined surface residual stresses were compressive stresses in emulsion and dry conditions. Under emulsion condition, the absolute value of residual compressive stress always increased with the increasing of cutting speed, feed per tooth and milling width, while the reverse redistribution phenomena were found under emulsion condition. Under emulsion and dry conditions, milling depth had less influence on surface integrity than the other milling parameters.
2016, 35(5): 734-739.
doi: 10.13433/j.cnki.1003-8728.2016.0514
Abstract:
To explore the work mechanisms of a small-diameter vortex tube, this study establishes the three-dimensional numerical simulation model of its internal flow field and carries out its numerical simulation with the standard k-ε turbulence model. According to the numerical simulation results, the internal flow field is divided into three characteristic regions that combine the flow characteristics of the work medium. The analysis of the distribution of each parameter produces the thermodynamic process of the work medium in the small-diameter vortex tube. The comparison of the simulation results with the experimental data on the inlet and outlet of the small-diameter vortex tube proves that our simulation method is feasible. Therefore it helps us to explain the work medium and temperature separation in the small-diameter vortex tube and optimize the small-diameter vortex tube.
To explore the work mechanisms of a small-diameter vortex tube, this study establishes the three-dimensional numerical simulation model of its internal flow field and carries out its numerical simulation with the standard k-ε turbulence model. According to the numerical simulation results, the internal flow field is divided into three characteristic regions that combine the flow characteristics of the work medium. The analysis of the distribution of each parameter produces the thermodynamic process of the work medium in the small-diameter vortex tube. The comparison of the simulation results with the experimental data on the inlet and outlet of the small-diameter vortex tube proves that our simulation method is feasible. Therefore it helps us to explain the work medium and temperature separation in the small-diameter vortex tube and optimize the small-diameter vortex tube.
2016, 35(5): 740-746.
doi: 10.13433/j.cnki.1003-8728.2016.0515
Abstract:
In order to meet the requirements of speed and accuracy in numerical control system, this paper presents a small line smooth transition algorithm. Firstly, we establish the mathematical model of the small line smooth transition and get the parameters and rotation direction of transition circular arc. Then, with the feed speed limited by mechanical property of processing platform, the numerical track acquired though the semi-hardware simulation system is consistent with the machining graphics with the errors permitted. And the velocity of the algorithm tested by the test platform is improved obviously under the guarantee of machining accuracy and mechanical material properties.
In order to meet the requirements of speed and accuracy in numerical control system, this paper presents a small line smooth transition algorithm. Firstly, we establish the mathematical model of the small line smooth transition and get the parameters and rotation direction of transition circular arc. Then, with the feed speed limited by mechanical property of processing platform, the numerical track acquired though the semi-hardware simulation system is consistent with the machining graphics with the errors permitted. And the velocity of the algorithm tested by the test platform is improved obviously under the guarantee of machining accuracy and mechanical material properties.
2016, 35(5): 747-751.
doi: 10.13433/j.cnki.1003-8728.2016.0516
Abstract:
Aiming at the impact and vibration to CNC(Computer Numerical Control) machine tools due to acceleration discontinuity in the linear and exponential acceleration/deceleration(acc/dec) algorithm, a novel cubic S curve acc/dec is introduced which provides the expression of jerk, acceleration, feedrate and displacement. Feedrate planning method is carried out to deal with various conditions that may occur in acc/dec control based on the optimization theory. The simulation result shows that the present algorithm can guarantee the smooth change in the acceleration and jerk so the intense impact is avoided, and the higher motion stability in the CNC system is obtained, and it can adaptively re-plan the feedrate for the chord length so as to improve the machining efficiency by using the simple and intelligent algorithm.
Aiming at the impact and vibration to CNC(Computer Numerical Control) machine tools due to acceleration discontinuity in the linear and exponential acceleration/deceleration(acc/dec) algorithm, a novel cubic S curve acc/dec is introduced which provides the expression of jerk, acceleration, feedrate and displacement. Feedrate planning method is carried out to deal with various conditions that may occur in acc/dec control based on the optimization theory. The simulation result shows that the present algorithm can guarantee the smooth change in the acceleration and jerk so the intense impact is avoided, and the higher motion stability in the CNC system is obtained, and it can adaptively re-plan the feedrate for the chord length so as to improve the machining efficiency by using the simple and intelligent algorithm.
Research on Nonlinear Error of Micro-accelerometers Considering the Fringe and Parasitic Capacitance
2016, 35(5): 752-757.
doi: 10.13433/j.cnki.1003-8728.2016.0517
Abstract:
In order to make the micro-accelerometers satisfy the specification of linearity, it is very necessary to calculate the nonlinear error of micro-accelerometers accurately. A method for calculating nonlinear error that taking the fringe capacitance and parasitic capacitance into consideration is proposed in this paper. At first, the equivalent circuit model of micro-accelerometers is established on the basis of distribution characteristics of capacitance, and the formula connecting the voltage output with measuring capacitance and parasitic capacitance is derived, where the fringe capacitance is included in the measuring capacitance. Then, based on the finite element method, the methods for calculating the parasitic capacitance and measuring capacitance are proposed respectively. Finally, the relation between the output voltage and the input acceleration of micro-accelerometers is established, and the formula for nonlinear error of micro-accelerometers is derived based on the cubic polynomial fitting. By comparing the theoretical results and the experimental results of nonlinear error, the correctness of the method proposed in this paper is demonstrated.
In order to make the micro-accelerometers satisfy the specification of linearity, it is very necessary to calculate the nonlinear error of micro-accelerometers accurately. A method for calculating nonlinear error that taking the fringe capacitance and parasitic capacitance into consideration is proposed in this paper. At first, the equivalent circuit model of micro-accelerometers is established on the basis of distribution characteristics of capacitance, and the formula connecting the voltage output with measuring capacitance and parasitic capacitance is derived, where the fringe capacitance is included in the measuring capacitance. Then, based on the finite element method, the methods for calculating the parasitic capacitance and measuring capacitance are proposed respectively. Finally, the relation between the output voltage and the input acceleration of micro-accelerometers is established, and the formula for nonlinear error of micro-accelerometers is derived based on the cubic polynomial fitting. By comparing the theoretical results and the experimental results of nonlinear error, the correctness of the method proposed in this paper is demonstrated.
2016, 35(5): 758-761.
doi: 10.13433/j.cnki.1003-8728.2016.0518
Abstract:
The piston gas leakage test of the engine can be used as an effective method to evaluate the matching state of the piston, piston ring and cylinder, which is an important part of the engine performance test. After 100 hours of operation of a certain engine, the piston gas leakage test is carried out to analyze the matching condition of piston ring. By analyszing the experimental data, we obtain the variation law of the gas leakage varying with engine velocity, the average effective cylinder pressure, and the variation law of the fuel consumption rate and the effective thermal efficiency varying the gas leakage. Based on the experimental results, the gas channel of the piston is analyzed, and the cooperation of piston rings, engine speed, the average effective brake pressure and engine displacement are the main factors affecting the gas flow rate.
The piston gas leakage test of the engine can be used as an effective method to evaluate the matching state of the piston, piston ring and cylinder, which is an important part of the engine performance test. After 100 hours of operation of a certain engine, the piston gas leakage test is carried out to analyze the matching condition of piston ring. By analyszing the experimental data, we obtain the variation law of the gas leakage varying with engine velocity, the average effective cylinder pressure, and the variation law of the fuel consumption rate and the effective thermal efficiency varying the gas leakage. Based on the experimental results, the gas channel of the piston is analyzed, and the cooperation of piston rings, engine speed, the average effective brake pressure and engine displacement are the main factors affecting the gas flow rate.
2016, 35(5): 762-767.
doi: 10.13433/j.cnki.1003-8728.2016.0519
Abstract:
The dump truck carriage has a heavy self-weight, and then to improve energy efficiency by reducing itself weight is become an urgent problem for dump truck company. The stiffness and strength performance of static and dynamic working conditions are evaluated by constructing the finite element model for a dump truck carriage. The material and the thickness of parts as design variables are defined, and the optimization design of static and dynamic impact working conditions are conducted by the surrogate-model technique and finite element method without changing the structures of carriage. The result shows that the weight reduces by 23.72% while meets the design requirement.
The dump truck carriage has a heavy self-weight, and then to improve energy efficiency by reducing itself weight is become an urgent problem for dump truck company. The stiffness and strength performance of static and dynamic working conditions are evaluated by constructing the finite element model for a dump truck carriage. The material and the thickness of parts as design variables are defined, and the optimization design of static and dynamic impact working conditions are conducted by the surrogate-model technique and finite element method without changing the structures of carriage. The result shows that the weight reduces by 23.72% while meets the design requirement.
2016, 35(5): 768-773.
doi: 10.13433/j.cnki.1003-8728.2016.0520
Abstract:
The nonlinear finite element analysis method was utilized to analyze the strength of the Roll-over Protective Structure(ROPS) of the safety cab and reliability analysis was also carried out in this paper. The super ellipsoid convex model theory was used to quantify the uncertain parameters of the material such as elastic modulus, poisson's ratio, and density. Due to the complicated or implicit limit state functions in the reliability problems, High Dimensional Model Representation based on Thin Plate Spline Interpolation(TPS-HDMR)was employed to settle the problem. Finally, the iHL-RF method was used to calculate the non-probability parameter reliability. The results show that within the uncertainty scope of the material parameters, the reliability of the cab meets the design requirements.
The nonlinear finite element analysis method was utilized to analyze the strength of the Roll-over Protective Structure(ROPS) of the safety cab and reliability analysis was also carried out in this paper. The super ellipsoid convex model theory was used to quantify the uncertain parameters of the material such as elastic modulus, poisson's ratio, and density. Due to the complicated or implicit limit state functions in the reliability problems, High Dimensional Model Representation based on Thin Plate Spline Interpolation(TPS-HDMR)was employed to settle the problem. Finally, the iHL-RF method was used to calculate the non-probability parameter reliability. The results show that within the uncertainty scope of the material parameters, the reliability of the cab meets the design requirements.
2016, 35(5): 774-777.
doi: 10.13433/j.cnki.1003-8728.2016.0521
Abstract:
Liquefied Natural Gas (LNG) vehicle has been rapidly developed due to its clean and economical characteristics. In this paper, taking a LNG towing vehicle as the target model, the simulation model for LNG truck has established and the power performance and economy performance have been analyzed via AVL CRUISE software. The optimal matching scheme is obtained by orthogonal test for factors of gearbox and final drive speed ratio. The results shows that, comparing with original scheme, despite the climbing and acceleration performance are slightly decreased, the maximum speed of the truck is increased by 10.08%, the fuel consumption is improved by 17.72% and the economy performance is significantly improved, providing reference for the optimization design of powertrain for LNG vehicle.
Liquefied Natural Gas (LNG) vehicle has been rapidly developed due to its clean and economical characteristics. In this paper, taking a LNG towing vehicle as the target model, the simulation model for LNG truck has established and the power performance and economy performance have been analyzed via AVL CRUISE software. The optimal matching scheme is obtained by orthogonal test for factors of gearbox and final drive speed ratio. The results shows that, comparing with original scheme, despite the climbing and acceleration performance are slightly decreased, the maximum speed of the truck is increased by 10.08%, the fuel consumption is improved by 17.72% and the economy performance is significantly improved, providing reference for the optimization design of powertrain for LNG vehicle.
2016, 35(5): 778-783.
doi: 10.13433/j.cnki.1003-8728.2016.0522
Abstract:
A quarter heavy truck dynamic model assembled with the electronically controlled air suspension with stepped adjustable damping is studied, and the ideal and actual controller models of the air suspension are presented based on Matlab/Simulink software, then a method of designing skyhook controller is proposed. In this method, variation laws of the body acceleration denoted as az, the suspension dynamic deflection denoted as fd and the tire dynamic load denoted as tl due to the transfer of suspension damping are analyzed. Moreover, ride comfort (az,fd) and road friendliness (tl) indexes of this suspension control model are weighted to create a new comprehensive index, according to which the best damping coefficient under different control strategies can be obtained. Finally, the simulation results indicate that the ride comfort and road friendliness of the heavy truck can be obviously and efficiently improved by using the optimized skyhook damping controller.
A quarter heavy truck dynamic model assembled with the electronically controlled air suspension with stepped adjustable damping is studied, and the ideal and actual controller models of the air suspension are presented based on Matlab/Simulink software, then a method of designing skyhook controller is proposed. In this method, variation laws of the body acceleration denoted as az, the suspension dynamic deflection denoted as fd and the tire dynamic load denoted as tl due to the transfer of suspension damping are analyzed. Moreover, ride comfort (az,fd) and road friendliness (tl) indexes of this suspension control model are weighted to create a new comprehensive index, according to which the best damping coefficient under different control strategies can be obtained. Finally, the simulation results indicate that the ride comfort and road friendliness of the heavy truck can be obviously and efficiently improved by using the optimized skyhook damping controller.
2016, 35(5): 784-789.
doi: 10.13433/j.cnki.1003-8728.2016.0523
Abstract:
Dynamic characteristics of composite anti-collision fender of bridges under impact load are tested and simulated in the paper. First the fender specimens are tested on the impact testing machine, the dynamic responses under different conditions are obtained. Then the numerical simulation of the fender specimen is carried on through the finite element methods. The comparisons of impact testing data and simulation results show the accuracy of the finite element model, providing the theoretical basis for the selection of actual structural element types and material parameters. Finally the composite anti-collision fender impacted by a ship is simulated by the explicit nonlinear analysis of ANSYS/LS-DYNA, and the energy variation, contact response and damage deformation are analyzed during the collision process. The energy absorption and the deformation history of composite anti-collision fender are obtained and both of them meet the national technical requirements, which provide theoretical basis for optimizing the design of composite anti-collision fender.
Dynamic characteristics of composite anti-collision fender of bridges under impact load are tested and simulated in the paper. First the fender specimens are tested on the impact testing machine, the dynamic responses under different conditions are obtained. Then the numerical simulation of the fender specimen is carried on through the finite element methods. The comparisons of impact testing data and simulation results show the accuracy of the finite element model, providing the theoretical basis for the selection of actual structural element types and material parameters. Finally the composite anti-collision fender impacted by a ship is simulated by the explicit nonlinear analysis of ANSYS/LS-DYNA, and the energy variation, contact response and damage deformation are analyzed during the collision process. The energy absorption and the deformation history of composite anti-collision fender are obtained and both of them meet the national technical requirements, which provide theoretical basis for optimizing the design of composite anti-collision fender.
2016, 35(5): 790-794.
doi: 10.13433/j.cnki.1003-8728.2016.0524
Abstract:
In order to solve the broken dispersion problem of bulk powder, a jet impacting test device with high pressure air has been designed and constructed to develop the test of jet pattern, jet distance and jet impingement. Experiments were conducted to study the broken dispersion effect of jet pressure, jet distance, time, form of nozzle and nozzle number on bulk powder. When the microstructure nozzle diameter is 0.5 mm, the experimental results show that the impact crater volume of nine-hole nozzle is about 5 times of the single-hole nozzle and its penetration depth is about 1.5 times under the same conditions. In the integrated system to consider the impact performance, economic cost and other factors, for single-hole nozzle that diameter is 0.5 mm, its optimal process parameters are that the jet distance is 20 mm, the pressure is 0.5 MPa. Finally, using Fluent software the impact process of single-hole nozzle is simulated, the simulation results were in good agreement with the experimental results.
In order to solve the broken dispersion problem of bulk powder, a jet impacting test device with high pressure air has been designed and constructed to develop the test of jet pattern, jet distance and jet impingement. Experiments were conducted to study the broken dispersion effect of jet pressure, jet distance, time, form of nozzle and nozzle number on bulk powder. When the microstructure nozzle diameter is 0.5 mm, the experimental results show that the impact crater volume of nine-hole nozzle is about 5 times of the single-hole nozzle and its penetration depth is about 1.5 times under the same conditions. In the integrated system to consider the impact performance, economic cost and other factors, for single-hole nozzle that diameter is 0.5 mm, its optimal process parameters are that the jet distance is 20 mm, the pressure is 0.5 MPa. Finally, using Fluent software the impact process of single-hole nozzle is simulated, the simulation results were in good agreement with the experimental results.
2016, 35(5): 795-799.
doi: 10.13433/j.cnki.1003-8728.2016.0525
Abstract:
The surface damage behavior in the cylinder deep drawing of hot-dip galvanized steel(DC53D+Z) and hot-dip galvannealed steel(DC53D+ZF) under the different die radius were investigated. The experimental results indicate that ironing signs and scratching are two kinds of surface damage for hot-dip galvanized steel, coating cracking and scratching are two kinds of surface damage for hot-dip galvannealed steel. The ironing signs of the DC53D+Z and the cracking of the DC53D+ZF coating obviously increases with the decreasing of die radius. The finite element model for cylinder drawing of galvanized sheet with an interface composite was established via ANSYS/LS-DYNA software. The simulation results show that the maximum principal strain along the drawing direction of coating increases with the decreasing of die radius. The maximum principal strain along the drawing direction of coating may be the main reason affecting the level of surface damage.
The surface damage behavior in the cylinder deep drawing of hot-dip galvanized steel(DC53D+Z) and hot-dip galvannealed steel(DC53D+ZF) under the different die radius were investigated. The experimental results indicate that ironing signs and scratching are two kinds of surface damage for hot-dip galvanized steel, coating cracking and scratching are two kinds of surface damage for hot-dip galvannealed steel. The ironing signs of the DC53D+Z and the cracking of the DC53D+ZF coating obviously increases with the decreasing of die radius. The finite element model for cylinder drawing of galvanized sheet with an interface composite was established via ANSYS/LS-DYNA software. The simulation results show that the maximum principal strain along the drawing direction of coating increases with the decreasing of die radius. The maximum principal strain along the drawing direction of coating may be the main reason affecting the level of surface damage.
2016, 35(5): 800-804.
doi: 10.13433/j.cnki.1003-8728.2016.0526
Abstract:
In view of the sound from clamping, punching and shearing of angle steel in machining of iron tower, a method for on-line recognizing the steels of Q235 and Q345 by using the energy ratio of sound signal was put forward in this paper. The experiment system for data acquisition was set up. The sound signals from the two angle steels of Q235 and Q345 were collected. The energy ratio, especially high frequency band and low frequency band, and the mean energy ratio and standard deviation of the sound signal were calculated. The range in the energy ratio for the two kinds of angle steels would be found. In addition, a certain amount of sound signal samples in the sense of processing were collect. According to the statistics principle and the test verification, the accuracy for recognizing the two kinds of steels could be reach up to above 95%.
In view of the sound from clamping, punching and shearing of angle steel in machining of iron tower, a method for on-line recognizing the steels of Q235 and Q345 by using the energy ratio of sound signal was put forward in this paper. The experiment system for data acquisition was set up. The sound signals from the two angle steels of Q235 and Q345 were collected. The energy ratio, especially high frequency band and low frequency band, and the mean energy ratio and standard deviation of the sound signal were calculated. The range in the energy ratio for the two kinds of angle steels would be found. In addition, a certain amount of sound signal samples in the sense of processing were collect. According to the statistics principle and the test verification, the accuracy for recognizing the two kinds of steels could be reach up to above 95%.
2016, 35(5): 805-808.
doi: 10.13433/j.cnki.1003-8728.2016.0527
Abstract:
Minimum Quantity Lubrication (MQL) was an effective method for improving the efficiency of in-situ reparation for the aircraft titanium alloy structural damage. In order to solve the problem that the present MQL system was difficult to adapt the battlefield, a novel MQL integrated box for battlefield reparation was developed. The integrated box was used to generate minimum quantity flow based on pneumatic driven. The flow quantity could be adjusted and displayed. A series of experiment for cutting titanium alloy were conducted to demonstrate the effectiveness of the integrated box. Comparing with the dry cutting method, the tool durability increased 228% by using MQL while the parameters were appropriate. The experiment results indicated the appropriate parameters were at a supply pressure of 0.3 MPa, oil quantity of 80 mL/h, water quantity of 200 mL/h, wetting range of below 40 mm.
Minimum Quantity Lubrication (MQL) was an effective method for improving the efficiency of in-situ reparation for the aircraft titanium alloy structural damage. In order to solve the problem that the present MQL system was difficult to adapt the battlefield, a novel MQL integrated box for battlefield reparation was developed. The integrated box was used to generate minimum quantity flow based on pneumatic driven. The flow quantity could be adjusted and displayed. A series of experiment for cutting titanium alloy were conducted to demonstrate the effectiveness of the integrated box. Comparing with the dry cutting method, the tool durability increased 228% by using MQL while the parameters were appropriate. The experiment results indicated the appropriate parameters were at a supply pressure of 0.3 MPa, oil quantity of 80 mL/h, water quantity of 200 mL/h, wetting range of below 40 mm.
2016, 35(5): 809-814.
doi: 10.13433/j.cnki.1003-8728.2016.0528
Abstract:
As an essential tool for deep space exploration, manned lunar rover is extensive and in-depth studied. The structure of lunar rover wheels and the mechanical properties of tire-terrain interaction have a significant impact on the performance of the rover. Combining with domestic and foreign aircraft wheels, the concept of concave wheel is put forward and the tire-terrain interaction model is established. By setting the sinkage, traction, driving torque as the evaluation indexes, the structure of concave wheels is analyzed by using ABAQUS software, the influence of structural parameters can be obtained, such as concave wheel width and recessed depth on each evaluation index. By making the concave depth and the convex height the same, and contrasting concave wheel and ordinary convex wheel, the advantage of concave wheel in the roll stability and properties of raising lunar dust and three evaluation indexes can be obtained.
As an essential tool for deep space exploration, manned lunar rover is extensive and in-depth studied. The structure of lunar rover wheels and the mechanical properties of tire-terrain interaction have a significant impact on the performance of the rover. Combining with domestic and foreign aircraft wheels, the concept of concave wheel is put forward and the tire-terrain interaction model is established. By setting the sinkage, traction, driving torque as the evaluation indexes, the structure of concave wheels is analyzed by using ABAQUS software, the influence of structural parameters can be obtained, such as concave wheel width and recessed depth on each evaluation index. By making the concave depth and the convex height the same, and contrasting concave wheel and ordinary convex wheel, the advantage of concave wheel in the roll stability and properties of raising lunar dust and three evaluation indexes can be obtained.
2016, 35(5): 815-820.
doi: 10.13433/j.cnki.1003-8728.2016.0529
Abstract:
According to the requirement of accurate oil feeding to each oil nozzle of the test gearbox for a fan drive gear system (FDGS) testing which was used in Geared Turbofan Aircraft Engines, a multi-line variable-pressure oil-separation unit was designed in the oil supply flow of the gear test system, which is closed power and provided by hydraulic load. The inner cavity of oil separation unit contains a number of branches with throttling components. The pressure drop of each throttling component is controllable by adjusting the diameter and length of throttle holes. In this way, multi-line oil with different pressure is supplied to the oil nozzles, which ensure that the oil flow rate and velocity at the oil nozzles can precisely comply with test requirements. In order to study the effects of the throttle hole diameter and length on oil flow rate and velocity at the oil nozzles, a one-dimensional, steady-state simulation of oil supply line in the gear test system was calculated using Flowmaster. The results show that the throttle hole diameter has much significant impact on pressure drop rather than that of throttle hole length. Especially when the throttle hole diameter is adjusted between 1mm to 3mm, the throttling component exhibits an obvious regulating effect on the oil feeding pressure of the gear test system.
According to the requirement of accurate oil feeding to each oil nozzle of the test gearbox for a fan drive gear system (FDGS) testing which was used in Geared Turbofan Aircraft Engines, a multi-line variable-pressure oil-separation unit was designed in the oil supply flow of the gear test system, which is closed power and provided by hydraulic load. The inner cavity of oil separation unit contains a number of branches with throttling components. The pressure drop of each throttling component is controllable by adjusting the diameter and length of throttle holes. In this way, multi-line oil with different pressure is supplied to the oil nozzles, which ensure that the oil flow rate and velocity at the oil nozzles can precisely comply with test requirements. In order to study the effects of the throttle hole diameter and length on oil flow rate and velocity at the oil nozzles, a one-dimensional, steady-state simulation of oil supply line in the gear test system was calculated using Flowmaster. The results show that the throttle hole diameter has much significant impact on pressure drop rather than that of throttle hole length. Especially when the throttle hole diameter is adjusted between 1mm to 3mm, the throttling component exhibits an obvious regulating effect on the oil feeding pressure of the gear test system.
