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RSS2019 Vol. 38, No. 4
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2019, 38(4): 493-498.
doi: 10.13433/j.cnki.1003-8728.20180216
PDF 965KB
Abstract:
In order to solve the problem that it is difficult to directly measure the input load of complex mechanical structures, a method for dynamic load time domain identification of a single DOF vibration system was derived by using Duhamel integration based on the theory of structural dynamics. On this basis, the equation of motion of a multiple DOF vibration system was decoupled by modal coordinate transformation, and then the load identification model and method for the multiple DOF vibration system were established. Taking a multiple DOF spring-damping system as object, the stability and accuracy of the load identification model under three kinds of load modes including sine and cosine combined excitation, random excitation and triangular pulse excitation were verified. The results showed:when the measured response was noiseless, the load identification model had high accuracy for the identification of the three kinds of excitation while the correlation coefficient between the identification results and the original loads reached 0.99; When the measured response contained 30% random noise, the identification results still had high recognition accuracy while the correlation coefficient between the identification results and the original loads reached 0.97.
In order to solve the problem that it is difficult to directly measure the input load of complex mechanical structures, a method for dynamic load time domain identification of a single DOF vibration system was derived by using Duhamel integration based on the theory of structural dynamics. On this basis, the equation of motion of a multiple DOF vibration system was decoupled by modal coordinate transformation, and then the load identification model and method for the multiple DOF vibration system were established. Taking a multiple DOF spring-damping system as object, the stability and accuracy of the load identification model under three kinds of load modes including sine and cosine combined excitation, random excitation and triangular pulse excitation were verified. The results showed:when the measured response was noiseless, the load identification model had high accuracy for the identification of the three kinds of excitation while the correlation coefficient between the identification results and the original loads reached 0.99; When the measured response contained 30% random noise, the identification results still had high recognition accuracy while the correlation coefficient between the identification results and the original loads reached 0.97.
2019, 38(4): 499-506.
doi: 10.13433/j.cnki.1003-8728.20180213
Abstract:
To rationally plan the movement and path of wall-climbing robots from the perspective of reducing the detection zone and saving power consumption of large-scale crude oil storage tanks. The study on the force and power consumption of the wall-climbing robot in the vertical wall movement for the defect detection of large-scale crude oil storage tanks. Firstly, the forces of the uniform linear motion and the steering motion of the robot are respectively analyzed, and the force and power consumption of the robot in the vertical straight motion, horizontal linear motion, large radius steering motion and small radius steering motion are obtained; the power consumption of two uniform linear motions and two kinds of steering motions are analyzed; a prototype experimental platform for climbing wall robots, and verify the power consumption is built; the simulation and experiment show that the power consumption of vertical straight line motion is less than the horizontal straight line motion, and the large radius steering power consumption is less than the small radius steering conclusion.
To rationally plan the movement and path of wall-climbing robots from the perspective of reducing the detection zone and saving power consumption of large-scale crude oil storage tanks. The study on the force and power consumption of the wall-climbing robot in the vertical wall movement for the defect detection of large-scale crude oil storage tanks. Firstly, the forces of the uniform linear motion and the steering motion of the robot are respectively analyzed, and the force and power consumption of the robot in the vertical straight motion, horizontal linear motion, large radius steering motion and small radius steering motion are obtained; the power consumption of two uniform linear motions and two kinds of steering motions are analyzed; a prototype experimental platform for climbing wall robots, and verify the power consumption is built; the simulation and experiment show that the power consumption of vertical straight line motion is less than the horizontal straight line motion, and the large radius steering power consumption is less than the small radius steering conclusion.
2019, 38(4): 507-514.
doi: 10.13433/j.cnki.1003-8728.20180244
Abstract:
Local defects like pitting, spalling and indentation in rolling bearings, manifest themselves as repetitive impulses in collected vibrations. Such impulses along with their repetitive frequency could be considered as bearing fault features. However, it is challenging to identify them due to noise and the interfering vibrations from other components, especially at the early stage of faults. Resonance demodulation (RD) is a known method to extract bearing fault features, but the central frequency and bandwidth of its band-pass filter need to be determined in advance. A new paradigm is proposed in the present study to bring the RD technique into full play. At first, we defined a novel indicator to measure the fitness of a band-pass filter, which is the ratio of the maximum to the root mean square value of the envelop spectrum of the filtered signal, called herein the crest of envelop spectrum (CE). Secondly, complex shifted Morlet wavelet was chosen to construct a band-pass filter considering its wave similarity with the impulses rendered by local defects in bearings. At last, the paradigm makes use of particle swarm optimization (PSO) to find the optimal central frequency and bandwidth of Morlet wavelet using CE as the fitness function. Simulated, experimental and field signals verify the effectiveness and advantages of the proposed RD paradigm.
Local defects like pitting, spalling and indentation in rolling bearings, manifest themselves as repetitive impulses in collected vibrations. Such impulses along with their repetitive frequency could be considered as bearing fault features. However, it is challenging to identify them due to noise and the interfering vibrations from other components, especially at the early stage of faults. Resonance demodulation (RD) is a known method to extract bearing fault features, but the central frequency and bandwidth of its band-pass filter need to be determined in advance. A new paradigm is proposed in the present study to bring the RD technique into full play. At first, we defined a novel indicator to measure the fitness of a band-pass filter, which is the ratio of the maximum to the root mean square value of the envelop spectrum of the filtered signal, called herein the crest of envelop spectrum (CE). Secondly, complex shifted Morlet wavelet was chosen to construct a band-pass filter considering its wave similarity with the impulses rendered by local defects in bearings. At last, the paradigm makes use of particle swarm optimization (PSO) to find the optimal central frequency and bandwidth of Morlet wavelet using CE as the fitness function. Simulated, experimental and field signals verify the effectiveness and advantages of the proposed RD paradigm.
2019, 38(4): 515-521.
doi: 10.13433/j.cnki.1003-8728.20180222
Abstract:
In single-chamber self-oscillation pulse basis nozzle, a double-chamber self-excited oscillation pulse nozzle was established in series, The FLUENT software was used to simulate the external flow field, and the effects of changes in incident pressure, target distance, cavity length ratio and cavity diameter ratio on the external flow field were analyzed. The results show that when the incident pressure varies between 1.1 MPa and 4.4 MPa, the degree of cavitation decreases with the increase of pressure, and the maximum velocity at the target surface increases about 20~76 m/s every time the pressure is doubled; When the target distance varies from 100 mm to 400 mm, the degree of cavitation increases with the increase of the target distance. However, when the target distance reaches 400 mm, the degree of cavitation in the air collapses rapidly due to the target distance. When the cavity length ratio is 0.67 or the cavity diameter ratio is 1.2, the vortex ring structure in the chamber has good symmetry, which is beneficial to the generation of pulse and cavitation. At the same time, it has high kinetic energy. When the cavity length and the cavity diameter are taken its optimal values at the same time, the pulse quality is optimal and has a good cleaning effect.
In single-chamber self-oscillation pulse basis nozzle, a double-chamber self-excited oscillation pulse nozzle was established in series, The FLUENT software was used to simulate the external flow field, and the effects of changes in incident pressure, target distance, cavity length ratio and cavity diameter ratio on the external flow field were analyzed. The results show that when the incident pressure varies between 1.1 MPa and 4.4 MPa, the degree of cavitation decreases with the increase of pressure, and the maximum velocity at the target surface increases about 20~76 m/s every time the pressure is doubled; When the target distance varies from 100 mm to 400 mm, the degree of cavitation increases with the increase of the target distance. However, when the target distance reaches 400 mm, the degree of cavitation in the air collapses rapidly due to the target distance. When the cavity length ratio is 0.67 or the cavity diameter ratio is 1.2, the vortex ring structure in the chamber has good symmetry, which is beneficial to the generation of pulse and cavitation. At the same time, it has high kinetic energy. When the cavity length and the cavity diameter are taken its optimal values at the same time, the pulse quality is optimal and has a good cleaning effect.
2019, 38(4): 522-529.
doi: 10.13433/j.cnki.1003-8728.20180198
Abstract:
As in the process of four corner leveling control in the traditional large hydraulic press leveling control system, the independent control of output force of two diagonal hydraulic cylinders is unable to achieve. Combining with the independent metering control technology, the large hydraulic press leveling control system based on the independent metering control is designed, and the control characteristics and output force characteristics of hydraulic cylinders is analyzed. Using computer simulation software AMESim, the simulation model for the large hydraulic pressure leveling control system was established. The simulation results show that by adjusting the opening degree of four 2/2-way proportional valves by closed loop and the ratio between inlet and outlet valve opening degrees, the automatic leveling control of the movable beam is realized, and also the independent control of the output force of the two diagonal hydraulic cylinders can be realized, as a result that the accuracy and stability of the control system are improved.
As in the process of four corner leveling control in the traditional large hydraulic press leveling control system, the independent control of output force of two diagonal hydraulic cylinders is unable to achieve. Combining with the independent metering control technology, the large hydraulic press leveling control system based on the independent metering control is designed, and the control characteristics and output force characteristics of hydraulic cylinders is analyzed. Using computer simulation software AMESim, the simulation model for the large hydraulic pressure leveling control system was established. The simulation results show that by adjusting the opening degree of four 2/2-way proportional valves by closed loop and the ratio between inlet and outlet valve opening degrees, the automatic leveling control of the movable beam is realized, and also the independent control of the output force of the two diagonal hydraulic cylinders can be realized, as a result that the accuracy and stability of the control system are improved.
2019, 38(4): 530-537.
doi: 10.13433/j.cnki.1003-8728.20180184
Abstract:
Aiming at the problem that the quad-rotor unmanned aerial vehicles (UAV) is vulnerable to be interfered by airflow when flying outside, and it is difficult to achieve accurate control. Firstly, the turbulence of the quad-rotor UAV during outdoor flight is modeled; and the influence of the turbulence is added to the UAV dynamic model. Then, the adaptive extended Kalman filter is designed to improve the filtering accuracy of the UAV attitude data by adjusting the adaptive factor of the noise covariance in real time, and the data is feedback to the PID position controller to control the UAV. The experimental results show that the established model can effectively reflect the motion law of the quadrotor UAV in the wind field environment, and the combination of the PID and AEKF can improve the anti-interference ability of the system and realize the accurate control of the quad-rotor UAV in the turbulence environment.
Aiming at the problem that the quad-rotor unmanned aerial vehicles (UAV) is vulnerable to be interfered by airflow when flying outside, and it is difficult to achieve accurate control. Firstly, the turbulence of the quad-rotor UAV during outdoor flight is modeled; and the influence of the turbulence is added to the UAV dynamic model. Then, the adaptive extended Kalman filter is designed to improve the filtering accuracy of the UAV attitude data by adjusting the adaptive factor of the noise covariance in real time, and the data is feedback to the PID position controller to control the UAV. The experimental results show that the established model can effectively reflect the motion law of the quadrotor UAV in the wind field environment, and the combination of the PID and AEKF can improve the anti-interference ability of the system and realize the accurate control of the quad-rotor UAV in the turbulence environment.
2019, 38(4): 538-543.
doi: 10.13433/j.cnki.1003-8728.20180200
Abstract:
Aiming at the insufficient analysis of the fault mechanism of the check (one-way) valve for the diaphragm pump, a new fault diagnosis method based on multi-time domain feature and SVM was proposed in this paper. The time domain feature of the signal is the earliest application and the most concise and practical feature parameter. Therefore, this paper briefly analyzes the time domain vibration signal of the one-way valve at first, and introduces several signal time domain indicators and characteristics, according to the characteristics of the one-way valve vibration signal. Three types of time domain indicators and features were selected as feature values for fault diagnosis. The training set of feature values was input into the SVM classifier training diagnosis model. The fault diagnosis experiment was performed with the test sample, and the experiment proved that the proposed method was applicable to high pressure diaphragm pumps. The fault diagnostic accuracy of the valve is 98%, and the method has the advantage of a shorter sample signal length.
Aiming at the insufficient analysis of the fault mechanism of the check (one-way) valve for the diaphragm pump, a new fault diagnosis method based on multi-time domain feature and SVM was proposed in this paper. The time domain feature of the signal is the earliest application and the most concise and practical feature parameter. Therefore, this paper briefly analyzes the time domain vibration signal of the one-way valve at first, and introduces several signal time domain indicators and characteristics, according to the characteristics of the one-way valve vibration signal. Three types of time domain indicators and features were selected as feature values for fault diagnosis. The training set of feature values was input into the SVM classifier training diagnosis model. The fault diagnosis experiment was performed with the test sample, and the experiment proved that the proposed method was applicable to high pressure diaphragm pumps. The fault diagnostic accuracy of the valve is 98%, and the method has the advantage of a shorter sample signal length.
2019, 38(4): 544-550.
doi: 10.13433/j.cnki.1003-8728.20180219
Abstract:
An Extended Carbon-Emission Accounting (ECEA) method is proposed by referring Extended Energy Accounting method in this paper. The extended carbon dioxide emissions factors of labor and capital are proposed to calculate based on the basic CDE per capita, total population, annual working hours, intermediate money M2 and the total wage S, etc. The extended carbon dioxide emissions (Ex-CDE) of a manufacturing process can be calculated through these factors. By using the ECEA method, a case of comparatively analyzing on a sheet metal part's cutting process is studied. The result shows ECEA method accounts these production factors in a uniform unit, which is suitable as a basis for judging the sustainability of manufacturing processes and it can help to avoid miscalculation of the best environmental benefits for labor-intensive and capital-intensive manufacturing industries.
An Extended Carbon-Emission Accounting (ECEA) method is proposed by referring Extended Energy Accounting method in this paper. The extended carbon dioxide emissions factors of labor and capital are proposed to calculate based on the basic CDE per capita, total population, annual working hours, intermediate money M2 and the total wage S, etc. The extended carbon dioxide emissions (Ex-CDE) of a manufacturing process can be calculated through these factors. By using the ECEA method, a case of comparatively analyzing on a sheet metal part's cutting process is studied. The result shows ECEA method accounts these production factors in a uniform unit, which is suitable as a basis for judging the sustainability of manufacturing processes and it can help to avoid miscalculation of the best environmental benefits for labor-intensive and capital-intensive manufacturing industries.
2019, 38(4): 551-557.
doi: 10.13433/j.cnki.1003-8728.20180202
Abstract:
The energy conservation problem of a two-machine-one-buffer system is studied, and the energy conservation strategy is proposed for achieving energy conservation and emission-reduction by a manufacturing system. Firstly, a Markov operation model of two-machine-one-buffer manufacturing system is developed, and then the opportunity windows of stoppage for energy conservation of different machines are formulated when machines are blocked or starved in the two-machines-one-buffer manufacturing system. Furthermore, MATLAB is used to simulate the stoppage time for energy conservation with different energy conservation strategies. The simulation results show that the energy conservation rate can reach over 10% by implementing the optimal energy conservation strategy within a certain throughput loss.
The energy conservation problem of a two-machine-one-buffer system is studied, and the energy conservation strategy is proposed for achieving energy conservation and emission-reduction by a manufacturing system. Firstly, a Markov operation model of two-machine-one-buffer manufacturing system is developed, and then the opportunity windows of stoppage for energy conservation of different machines are formulated when machines are blocked or starved in the two-machines-one-buffer manufacturing system. Furthermore, MATLAB is used to simulate the stoppage time for energy conservation with different energy conservation strategies. The simulation results show that the energy conservation rate can reach over 10% by implementing the optimal energy conservation strategy within a certain throughput loss.
2019, 38(4): 558-565.
doi: 10.13433/j.cnki.1003-8728.20180206
Abstract:
In milling a convex surface die, because of its complex surface characteristics, the cutter-worker contact relation changes with the cutting trajectory. The tool edge is subjected to alternating load to increase the degree of tool wear in the milling process, thus reducing the die machining efficiency. In view of the above problems, the influence of curvature radius and lead angle on milling stability should be considered. In this paper, the instantaneous chip thickness model with the curvature of curved surface and the lead angle of the tool considered is established. The Runge-Kutta-based complete discretization method is used to solve the milling stability of the system, and the influence of the surface characteristics on the stability lobe map is studied in depth. The following conclusions are reached:the milling stability decreases with the increase of curvature radius and the stability prediction curve is shifted to the left as the lead angle increases. Finally, time-frequency analysis is used to verify the correctness of the stability prediction curve based on the convex surface milling test.
In milling a convex surface die, because of its complex surface characteristics, the cutter-worker contact relation changes with the cutting trajectory. The tool edge is subjected to alternating load to increase the degree of tool wear in the milling process, thus reducing the die machining efficiency. In view of the above problems, the influence of curvature radius and lead angle on milling stability should be considered. In this paper, the instantaneous chip thickness model with the curvature of curved surface and the lead angle of the tool considered is established. The Runge-Kutta-based complete discretization method is used to solve the milling stability of the system, and the influence of the surface characteristics on the stability lobe map is studied in depth. The following conclusions are reached:the milling stability decreases with the increase of curvature radius and the stability prediction curve is shifted to the left as the lead angle increases. Finally, time-frequency analysis is used to verify the correctness of the stability prediction curve based on the convex surface milling test.
2019, 38(4): 566-570.
doi: 10.13433/j.cnki.1003-8728.20180197
Abstract:
Selective laser melting (SLM) is an attractive manufacturing technique for producing metal parts with complex geometries and high performance. The powder materials used in this study was 316L stainless steel powder. In order to reduce porosity, obtain higher density and better mechanical properties (hardness), a new process was proposed. The powders were pre-melted by using the low laser power, then the powders were melted again by using the high power laser to realize the re-melting process layer by layer. The results show that the porosity decreases from 0.186% to 0.039%, and the hardness value increases from 237.5 HV to 264.3 HV after pre-melting and re-melting. The homogeneity of martensite is improved. It shows the new process had a great prospect for manufacturing the complex metal parts.
Selective laser melting (SLM) is an attractive manufacturing technique for producing metal parts with complex geometries and high performance. The powder materials used in this study was 316L stainless steel powder. In order to reduce porosity, obtain higher density and better mechanical properties (hardness), a new process was proposed. The powders were pre-melted by using the low laser power, then the powders were melted again by using the high power laser to realize the re-melting process layer by layer. The results show that the porosity decreases from 0.186% to 0.039%, and the hardness value increases from 237.5 HV to 264.3 HV after pre-melting and re-melting. The homogeneity of martensite is improved. It shows the new process had a great prospect for manufacturing the complex metal parts.
2019, 38(4): 571-581.
doi: 10.13433/j.cnki.1003-8728.20180217
Abstract:
In order to realize the mass customization of wearable earphones, this paper firstly proposes a conchal mesh surface automatic reconstruction method and reconstructs the mesh surface of 310 samples into NURBS which consists of 795 points. Secondly, an improved hierarchical clustering algorithm for the conchal morphology is proposed, and the advantages of the algorithm are verified. Thirdly, the auricular conchal morphology is divided into 29 groups according to the algorithm, and the database of auricular conchal morphology for earphone design is constructed, and then the reliability of the database is verified. Finally, the earphones are customization-designed, and an objective fit evaluation method for earphone is proposed, which based on finite element simulation analysis.
In order to realize the mass customization of wearable earphones, this paper firstly proposes a conchal mesh surface automatic reconstruction method and reconstructs the mesh surface of 310 samples into NURBS which consists of 795 points. Secondly, an improved hierarchical clustering algorithm for the conchal morphology is proposed, and the advantages of the algorithm are verified. Thirdly, the auricular conchal morphology is divided into 29 groups according to the algorithm, and the database of auricular conchal morphology for earphone design is constructed, and then the reliability of the database is verified. Finally, the earphones are customization-designed, and an objective fit evaluation method for earphone is proposed, which based on finite element simulation analysis.
Analyzing Factors of Influence on Performance of Giant Magnetostrictive Electro-hydrostatic Actuator
2019, 38(4): 582-586.
doi: 10.13433/j.cnki.1003-8728.20180212
Abstract:
First, this paper analyzes the working principle of a giant magnetostrictive actuator, and then establishes its mathematical model. The simulation analysis produces the relationships among the output displacement of the actuator and its driving frequency, its piston diameter, its pump cavity height and output flow rate, its system bias pressure and output flow rate. Finally, the experimental data and simulation results on the actuator are compared to verify the accuracy of the simulation model. Several factors influencing the performance of the electro-hydrostatic actuator are presented and the selection criteria for the influence factors are given.
First, this paper analyzes the working principle of a giant magnetostrictive actuator, and then establishes its mathematical model. The simulation analysis produces the relationships among the output displacement of the actuator and its driving frequency, its piston diameter, its pump cavity height and output flow rate, its system bias pressure and output flow rate. Finally, the experimental data and simulation results on the actuator are compared to verify the accuracy of the simulation model. Several factors influencing the performance of the electro-hydrostatic actuator are presented and the selection criteria for the influence factors are given.
2019, 38(4): 587-593.
doi: 10.13433/j.cnki.1003-8728.20180195
Abstract:
Based on the domestic and foreign research status of biaxial tensile testing machine and the requirement of biaxial tensile test for rubber materials, a biaxial tensile test machine for rubber materials is designed and developed. The overall design of the biaxial tensile testing machine for rubber materials was analyzed. The mainframe and the measurement and control system of the testing machine was designed. Finally, the mainframe and the measurement and control system were integrated and debugged, and the whole biaxial tensile testing machine for rubber materials was completed. The uniaxial tension tests of dumbbell shaped silica filled natural rubber specimens were carried out in X and Y axes of the biaxial tensile machine designed by the authors. The testing results were compared with the results of the universal testing machine, and the consistency, repeatability and accuracy of the two axis stretching performance of the biaxial test machine are verified. The equi-biaxial tension test for the cruciform rubber specimen was carried out and the accuracy in this test is proved by analyzing the results.
Based on the domestic and foreign research status of biaxial tensile testing machine and the requirement of biaxial tensile test for rubber materials, a biaxial tensile test machine for rubber materials is designed and developed. The overall design of the biaxial tensile testing machine for rubber materials was analyzed. The mainframe and the measurement and control system of the testing machine was designed. Finally, the mainframe and the measurement and control system were integrated and debugged, and the whole biaxial tensile testing machine for rubber materials was completed. The uniaxial tension tests of dumbbell shaped silica filled natural rubber specimens were carried out in X and Y axes of the biaxial tensile machine designed by the authors. The testing results were compared with the results of the universal testing machine, and the consistency, repeatability and accuracy of the two axis stretching performance of the biaxial test machine are verified. The equi-biaxial tension test for the cruciform rubber specimen was carried out and the accuracy in this test is proved by analyzing the results.
2019, 38(4): 594-600.
doi: 10.13433/j.cnki.1003-8728.20180207
Abstract:
The six-axis force sensors can detect spatial force information in six directions in real time through the strain gauge and plate girder structure, but the output signal is inevitably polluted by the noise signal. In order to improve this phenomenon, a kind of double-fading factors Kalman filter is designed for the problem of poor performance of the standard Kalman filter due to the inaccuracy of the acoustic noise model. The statistical properties of the additive noise signal are studied in this algorithm. The augmented state equation of the principal mode shape of the rectangular plate is established. The influence of the two acoustic noise model deviations on the filter performance is analyzed. Based on the standard Kalman filter and the theory of orthogonality of innovation, according to the Sage window estimation principle and the least squares criterion, the analytic formula of the double-fading factors are constructed. The working principle of filter is described. The simulation results indicate that the proposed algorithm has better stability comparing with robust Kalman filter; it can effectively reduce the effect of model errors come from noise and improve filtering precision to 38.66 percent.
The six-axis force sensors can detect spatial force information in six directions in real time through the strain gauge and plate girder structure, but the output signal is inevitably polluted by the noise signal. In order to improve this phenomenon, a kind of double-fading factors Kalman filter is designed for the problem of poor performance of the standard Kalman filter due to the inaccuracy of the acoustic noise model. The statistical properties of the additive noise signal are studied in this algorithm. The augmented state equation of the principal mode shape of the rectangular plate is established. The influence of the two acoustic noise model deviations on the filter performance is analyzed. Based on the standard Kalman filter and the theory of orthogonality of innovation, according to the Sage window estimation principle and the least squares criterion, the analytic formula of the double-fading factors are constructed. The working principle of filter is described. The simulation results indicate that the proposed algorithm has better stability comparing with robust Kalman filter; it can effectively reduce the effect of model errors come from noise and improve filtering precision to 38.66 percent.
2019, 38(4): 601-607.
doi: 10.13433/j.cnki.1003-8728.20180201
Abstract:
A new high-temperature oxygen-free fuel reformer and testing system was designed and developed. The fuel reforming under high temperature and oxygen-free condition was realized by means of the engine exhaust gas heating and plasma heating assistance. The structure design of high temperature oxygen-free reformer was made simple and compact without catalyst. The plasma heating was easy to be controlled, small heat transfer area had easy insulation which could reduce energy loss. N-heptane was used as fuel to be reformed and Reformed molecule HCCI (RM-HCCI) combustion was successfully achieved by injecting the reformed fuel into the engine. The comparison between RM-HCCI and Gasoline HCCI (G-HCCI) combustion were carried out. The results showed that the reformed fuel delayed the ignition, resulting in lower heat transfer losses and exhaust losses, leading eventually to higher indicated thermal efficiency.
A new high-temperature oxygen-free fuel reformer and testing system was designed and developed. The fuel reforming under high temperature and oxygen-free condition was realized by means of the engine exhaust gas heating and plasma heating assistance. The structure design of high temperature oxygen-free reformer was made simple and compact without catalyst. The plasma heating was easy to be controlled, small heat transfer area had easy insulation which could reduce energy loss. N-heptane was used as fuel to be reformed and Reformed molecule HCCI (RM-HCCI) combustion was successfully achieved by injecting the reformed fuel into the engine. The comparison between RM-HCCI and Gasoline HCCI (G-HCCI) combustion were carried out. The results showed that the reformed fuel delayed the ignition, resulting in lower heat transfer losses and exhaust losses, leading eventually to higher indicated thermal efficiency.
2019, 38(4): 608-612.
doi: 10.13433/j.cnki.1003-8728.20180215
Abstract:
The distributed driving off-road electric vehicle has the advantages of good dynamic performance, good adaptability of road, but the different wheels' speed results in high complexity of control method. Aiming at this problem, based on different acceleration of four wheels, the maximum driving torque is firstly calculated and the slip ratio observer is built. Then chosing maximum driving torque as the boundary, the motor output torque is controlled to keep slip ratio near the optimal slip ratio. Finally, the simulation work combining with Carsim is done. The results show that the control method can significantly reduce the slip ratio of the car wheels, verify the effectiveness of the control systems.
The distributed driving off-road electric vehicle has the advantages of good dynamic performance, good adaptability of road, but the different wheels' speed results in high complexity of control method. Aiming at this problem, based on different acceleration of four wheels, the maximum driving torque is firstly calculated and the slip ratio observer is built. Then chosing maximum driving torque as the boundary, the motor output torque is controlled to keep slip ratio near the optimal slip ratio. Finally, the simulation work combining with Carsim is done. The results show that the control method can significantly reduce the slip ratio of the car wheels, verify the effectiveness of the control systems.
2019, 38(4): 613-617.
doi: 10.13433/j.cnki.1003-8728.20180218
Abstract:
In this paper, a vehicle with a turbocharged gasoline engine was measured and analyzed because of whistle noise inside the vehicle during a tip-in process. The test results show that the whistle noise inside vehicle is caused by synchronous noise due to unbalance of the rotor system and the synchronous noise disappears by controlling the unbalance of rotor. However, the sub-synchronous noise caused by oil film whirling during bearing clearance is obvious. Then the generating mechanism of sub-synchronous noise is researched so as to resolve the problem fundamentally. A scenario that installing circular oil grooves in the inner bearing wall is proposed to reduce sub-synchronous noise and the test result shows that interior whistle noise had disappeared.
In this paper, a vehicle with a turbocharged gasoline engine was measured and analyzed because of whistle noise inside the vehicle during a tip-in process. The test results show that the whistle noise inside vehicle is caused by synchronous noise due to unbalance of the rotor system and the synchronous noise disappears by controlling the unbalance of rotor. However, the sub-synchronous noise caused by oil film whirling during bearing clearance is obvious. Then the generating mechanism of sub-synchronous noise is researched so as to resolve the problem fundamentally. A scenario that installing circular oil grooves in the inner bearing wall is proposed to reduce sub-synchronous noise and the test result shows that interior whistle noise had disappeared.
2019, 38(4): 618-625.
doi: 10.13433/j.cnki.1003-8728.20180214
Abstract:
In order to analyze the influence of mass ratio on the vertical performance of central-driven electric logistics vehicle, based on the dynamic model of an electric logistics vehicle, taking its power battery and motor mass as variables and using root-mean-squares (RMS) value and frequency domain analysis methods, we study the change trend of the vertical performance index of the vehicle, the favorable area of the quality match, the amplitude-frequency characteristics of the relative dynamic load of the wheel and the vertical vibration of the motor. On the basis of comprehensive analysis of the effects of mass ratios including damping ratio and stiffness ratio on the vertical performance of the vehicle, we present the selection principle of the suspension damping ratio and stiffness ratio of the central-driven electric logistics vehicle. The study results show that increasing the mass ratio can effectively improve the dynamic characteristics of the vehicle but aggravates the vertical vibration of its power motor, thus providing theoretical guidance for the matching design of power battery and motor mass and for the selection of suspension damping ratio and stiffness ratio of the electric logistics vehicle.
In order to analyze the influence of mass ratio on the vertical performance of central-driven electric logistics vehicle, based on the dynamic model of an electric logistics vehicle, taking its power battery and motor mass as variables and using root-mean-squares (RMS) value and frequency domain analysis methods, we study the change trend of the vertical performance index of the vehicle, the favorable area of the quality match, the amplitude-frequency characteristics of the relative dynamic load of the wheel and the vertical vibration of the motor. On the basis of comprehensive analysis of the effects of mass ratios including damping ratio and stiffness ratio on the vertical performance of the vehicle, we present the selection principle of the suspension damping ratio and stiffness ratio of the central-driven electric logistics vehicle. The study results show that increasing the mass ratio can effectively improve the dynamic characteristics of the vehicle but aggravates the vertical vibration of its power motor, thus providing theoretical guidance for the matching design of power battery and motor mass and for the selection of suspension damping ratio and stiffness ratio of the electric logistics vehicle.
2019, 38(4): 626-633.
doi: 10.13433/j.cnki.1003-8728.20180204
Abstract:
Most of the current lightweight studies are usually based on a single design factor, such as size, shape, position, and so on, while ignoring the interactivity between the factors. In addition, design variables inevitably fluctuate in a certain range in the manufacturing process. For the existing door products, combining the variety of design factors, and the effect of the fluctuation of design variables on the performance of the product is considered. The high precision response surface model is constructed by the experimental design method, and the six sigma robust and lightweight design of the door structure is improved by combining the multi-island genetic algorithm and Monte Carlo simulation technology. As a result, the quality of the door is reduced and the robustness of the product is improved.
Most of the current lightweight studies are usually based on a single design factor, such as size, shape, position, and so on, while ignoring the interactivity between the factors. In addition, design variables inevitably fluctuate in a certain range in the manufacturing process. For the existing door products, combining the variety of design factors, and the effect of the fluctuation of design variables on the performance of the product is considered. The high precision response surface model is constructed by the experimental design method, and the six sigma robust and lightweight design of the door structure is improved by combining the multi-island genetic algorithm and Monte Carlo simulation technology. As a result, the quality of the door is reduced and the robustness of the product is improved.
2019, 38(4): 634-638.
doi: 10.13433/j.cnki.1003-8728.20180203
Abstract:
The isothermal fatigue(IF) and thermo-mechanical fatigue(TMF) behaviors of E319 cast aluminum alloy were studied via experiment and scanning electron microscope(SEM). The results showed that by comparing with Nickel-based superalloy and Ti-Al alloy, E319 cast aluminum alloy exhibits unique TMF cyclic stress-strain characteristics and cyclic stress response. Due to the influence of the temperature and stress relaxation, the hysteresis loop has a curved hook shape, and the specimen has a strong cyclic hardening behavior before the fracture. The mean stress is negative. IF and TMF fracture surface is different, in which the two fracture surfaces have different crack growth mechanism and fracture mode, the TMF life is far lower than the IF life.
The isothermal fatigue(IF) and thermo-mechanical fatigue(TMF) behaviors of E319 cast aluminum alloy were studied via experiment and scanning electron microscope(SEM). The results showed that by comparing with Nickel-based superalloy and Ti-Al alloy, E319 cast aluminum alloy exhibits unique TMF cyclic stress-strain characteristics and cyclic stress response. Due to the influence of the temperature and stress relaxation, the hysteresis loop has a curved hook shape, and the specimen has a strong cyclic hardening behavior before the fracture. The mean stress is negative. IF and TMF fracture surface is different, in which the two fracture surfaces have different crack growth mechanism and fracture mode, the TMF life is far lower than the IF life.
2019, 38(4): 639-645.
doi: 10.13433/j.cnki.1003-8728.20180199
Abstract:
The mechanical properties of metals, such as its constitutive relationship can be identified via indentation testing based on the inverse analysis method. However, the identified results are usually not accurate or even not uniqueness. In order to solve this problem, to utilize both loading-displacement curve and residual imprint profile to improve the accuracy of the identified material parameters is proposed. The numerical indentation model is built via ANSYS software, the simulated results are compared to the experimental data for verifying that the numerical indentation model is reliable and available. The identification process is in fact to minimize the difference between the simulated and experimental results via optimization iterations. However, due to the insufficiency of ANSYS in optimization algorithms, MATLAB is performed to compile the corresponding optimization algorithm and combines with ANSYS to carry out the inverse measurement. Finally, a practical illustration is curried out to determine the constitutive relations for some metals. The results clearly show that the imprint profile can significantly improve the identified accuracy of material constitutive relation.
The mechanical properties of metals, such as its constitutive relationship can be identified via indentation testing based on the inverse analysis method. However, the identified results are usually not accurate or even not uniqueness. In order to solve this problem, to utilize both loading-displacement curve and residual imprint profile to improve the accuracy of the identified material parameters is proposed. The numerical indentation model is built via ANSYS software, the simulated results are compared to the experimental data for verifying that the numerical indentation model is reliable and available. The identification process is in fact to minimize the difference between the simulated and experimental results via optimization iterations. However, due to the insufficiency of ANSYS in optimization algorithms, MATLAB is performed to compile the corresponding optimization algorithm and combines with ANSYS to carry out the inverse measurement. Finally, a practical illustration is curried out to determine the constitutive relations for some metals. The results clearly show that the imprint profile can significantly improve the identified accuracy of material constitutive relation.
2019, 38(4): 646-651.
doi: 10.13433/j.cnki.1003-8728.20180211
Abstract:
In order to study the effect of the film thickness on the mechanical properties of Si-based SiO2 films, nanoindentation technology and finite element simulation of ABAQUS were used to test Si-based SiO2 films with different thicknesses. The mechanical properties including the hardness and elastic modulus of films with different thicknesses were analyzed. The effects of the pressure depths and film thickness ratios on the elastic recovery rate of films with different thicknesses are discussed. Based on the experiments, the finite element model was established. The load-displacement relationship of films with different thickness under the same pressure depth was simulated, and the elastic recovery performance of the film was analyzed. The results show that the thicker the SiO2 film is, the smaller the elastic modulus is. When the film is thin, the size effect of the indentation of the film is more obvious, and further analysis by using simulation shows that the thinner the film is, the better the elastic recovery performance is.
In order to study the effect of the film thickness on the mechanical properties of Si-based SiO2 films, nanoindentation technology and finite element simulation of ABAQUS were used to test Si-based SiO2 films with different thicknesses. The mechanical properties including the hardness and elastic modulus of films with different thicknesses were analyzed. The effects of the pressure depths and film thickness ratios on the elastic recovery rate of films with different thicknesses are discussed. Based on the experiments, the finite element model was established. The load-displacement relationship of films with different thickness under the same pressure depth was simulated, and the elastic recovery performance of the film was analyzed. The results show that the thicker the SiO2 film is, the smaller the elastic modulus is. When the film is thin, the size effect of the indentation of the film is more obvious, and further analysis by using simulation shows that the thinner the film is, the better the elastic recovery performance is.
2019, 38(4): 652-656.
doi: 10.13433/j.cnki.1003-8728.20180209
Abstract:
The structural size of the fuel nozzle is an important factor affecting its spray performance. Because of the complex structure, small volume and high dimensional accuracy of fuel nozzle, the conventional measurement methods can not meet. X-ray tomography and hybrid CMM (Coordinate Measuring Machine) and Geometry Qualify which is a three-dimensional modelling software were applied in the three-dimensional size detection of fuel nozzle for aeroengine. Firstly, the inner and outer dimensions of the nozzle-cyclone were measured. And then the state of the assembly of the sub-oil circuit was analyzed. After the measurement, it was found that the size of the inner cone surface of the nozzle-cyclone was seriously out of tolerance, especially the internal dimensions at the inner nozzle were distorted; there was also a gap between the cone surfaces after assembly of the sub-oil circuit. Aiming at the above problems, the process improvement work was carried out. After process centralization and the special tool had been adopted, the problem of over-dimension of the inner cone surface was effectively improved; the problem of surface roughness, lax fit of the inner cone surface was improved by manual grinding.
The structural size of the fuel nozzle is an important factor affecting its spray performance. Because of the complex structure, small volume and high dimensional accuracy of fuel nozzle, the conventional measurement methods can not meet. X-ray tomography and hybrid CMM (Coordinate Measuring Machine) and Geometry Qualify which is a three-dimensional modelling software were applied in the three-dimensional size detection of fuel nozzle for aeroengine. Firstly, the inner and outer dimensions of the nozzle-cyclone were measured. And then the state of the assembly of the sub-oil circuit was analyzed. After the measurement, it was found that the size of the inner cone surface of the nozzle-cyclone was seriously out of tolerance, especially the internal dimensions at the inner nozzle were distorted; there was also a gap between the cone surfaces after assembly of the sub-oil circuit. Aiming at the above problems, the process improvement work was carried out. After process centralization and the special tool had been adopted, the problem of over-dimension of the inner cone surface was effectively improved; the problem of surface roughness, lax fit of the inner cone surface was improved by manual grinding.
