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RSS2021 Vol. 40, No. 9
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2021, 40(9): 1361-1369.
doi: 10.13433/j.cnki.1003-8728.20200513
PDF 14109KB
Abstract:
The characteristics of engineering equipment bearing fault conditions are often overwhelmed by the external information. In order to effectively extract the fault data, a noise reduction filtering method combining the particle swarm optimization with the sparse reconstruction is proposed. Laplace wavelet base is selected for parameter optimization and dictionary prediction structure, and then the vibration signal of the bearing is sparsely reconstructed. By applying 2 dB Gaussian white noise to the experimental data to simulate the bearing signal in the engineering environment, the optimal sparse reconstruction algorithm is compared with the Butterworth filter and wavelet threshold denoising algorithm. The results show that the present method is more effective in terms of parameters such as peak signal-to-noise ratio and waveform similarity. The fault characteristic frequencies of the inner and outer rings of the reconstructed signal are close to the theoretical characteristic frequencies. After the noise is fully filtered, the original characteristic information provides a good data basis for the later fault diagnosis.
The characteristics of engineering equipment bearing fault conditions are often overwhelmed by the external information. In order to effectively extract the fault data, a noise reduction filtering method combining the particle swarm optimization with the sparse reconstruction is proposed. Laplace wavelet base is selected for parameter optimization and dictionary prediction structure, and then the vibration signal of the bearing is sparsely reconstructed. By applying 2 dB Gaussian white noise to the experimental data to simulate the bearing signal in the engineering environment, the optimal sparse reconstruction algorithm is compared with the Butterworth filter and wavelet threshold denoising algorithm. The results show that the present method is more effective in terms of parameters such as peak signal-to-noise ratio and waveform similarity. The fault characteristic frequencies of the inner and outer rings of the reconstructed signal are close to the theoretical characteristic frequencies. After the noise is fully filtered, the original characteristic information provides a good data basis for the later fault diagnosis.
2021, 40(9): 1313-1319.
doi: 10.13433/j.cnki.1003-8728.20200262
Abstract:
In the natural environment, the main transformer bushing terminal in an ultra high voltage substation is prone to deformation, fracture and other problems caused by the wind. Taking the main transformer bushing terminal as the research object, the Abaqus software is adopted as the platform for building a refined finite element model for the transmission line, down conductor and the main transformer bushing terminal, and the influence of wind direction and wind speed on the mechanical properties of the bushing terminal is analyzed. The results show that the terminal board and bushing terminal have large stresses and displacements, which are the weak links of the structure. The stress and displacement of each part change periodically with the wind direction. The 90° wind direction is the most unfavorable wind direction angle, and there are peaks at 90° and 270° wind direction angles, and these parts will have fatigue damage under the action of alternating stress. When the wind speed is low, the stress and displacement of the bushing terminal and terminal board change little; but when the wind speed exceeds 12.65 m/s, the stress and displacement of the bushing terminal and terminal board show a nonlinear sharp increase with wind speed, and the local stress exceeds the yield limit. The research results provide a reference for the design, improvement and optimization of the same type of the substation and transformer bushing terminal under the same environment.
In the natural environment, the main transformer bushing terminal in an ultra high voltage substation is prone to deformation, fracture and other problems caused by the wind. Taking the main transformer bushing terminal as the research object, the Abaqus software is adopted as the platform for building a refined finite element model for the transmission line, down conductor and the main transformer bushing terminal, and the influence of wind direction and wind speed on the mechanical properties of the bushing terminal is analyzed. The results show that the terminal board and bushing terminal have large stresses and displacements, which are the weak links of the structure. The stress and displacement of each part change periodically with the wind direction. The 90° wind direction is the most unfavorable wind direction angle, and there are peaks at 90° and 270° wind direction angles, and these parts will have fatigue damage under the action of alternating stress. When the wind speed is low, the stress and displacement of the bushing terminal and terminal board change little; but when the wind speed exceeds 12.65 m/s, the stress and displacement of the bushing terminal and terminal board show a nonlinear sharp increase with wind speed, and the local stress exceeds the yield limit. The research results provide a reference for the design, improvement and optimization of the same type of the substation and transformer bushing terminal under the same environment.
2021, 40(9): 1320-1327.
doi: 10.13433/j.cnki.1003-8728.20200213
Abstract:
The supercritical carbon dioxide (SCO2) turbine main shaft cooling device was studied. The mathematical model of pressure distribution in the fluid domain was established with the cylindrical surface expansion method. The functional expressions of pressure distribution and bearing capacity were deduced. The computational fluid dynamics (CFD) method was used to analyse the flow field pressure, bearing capacity and stiffness under different conditions such as inlet pressure, rotation speed and eccentricity. The results show that the low speed of the main shaft has little influence on the film pressure and that the axial pressure is symmetrically distributed along the axial central section of the cooling device. Under the same eccentricity, the bearing capacity increases with the increase of intake pressure; under the condition of constant inlet pressure, the bearing capacity of the film increases with the increase of eccentricity. The stiffness and eccentricity of the cooling device are non-linear. The stiffness of the cooling device increases with the increase of eccentricity and begins to decrease after reaching the limit point, and the extreme point appears at the eccentricity of 0.35.
The supercritical carbon dioxide (SCO2) turbine main shaft cooling device was studied. The mathematical model of pressure distribution in the fluid domain was established with the cylindrical surface expansion method. The functional expressions of pressure distribution and bearing capacity were deduced. The computational fluid dynamics (CFD) method was used to analyse the flow field pressure, bearing capacity and stiffness under different conditions such as inlet pressure, rotation speed and eccentricity. The results show that the low speed of the main shaft has little influence on the film pressure and that the axial pressure is symmetrically distributed along the axial central section of the cooling device. Under the same eccentricity, the bearing capacity increases with the increase of intake pressure; under the condition of constant inlet pressure, the bearing capacity of the film increases with the increase of eccentricity. The stiffness and eccentricity of the cooling device are non-linear. The stiffness of the cooling device increases with the increase of eccentricity and begins to decrease after reaching the limit point, and the extreme point appears at the eccentricity of 0.35.
2021, 40(9): 1328-1337.
doi: 10.13433/j.cnki.1003-8728.20200220
Abstract:
Redundant actuation has the advantages of high stiffness, strong load-carrying capacity and good motion performance. 10-6 and 10-5 configurations with ten links were designed, constructing a semi-analytic algorithm combining numerical method and analytical method, and workspace of the two configurations was analyzed. By adding two virtual links, the two configurations can be further derived into the 12 links topological configuration. Compatibility equations of the 12 links configuration were derived, and the numerical solutions of virtual links were obtained by Newton-Raphson method. Based on the geometric relationship between the characteristic points of the moving platform, the full analytic solution of the forward position solution of the 12 links configuration was derived. Furthermore, the position workspace and orientation workspace of the two configurations were studied by interval analysis method. The results show that the workspace of 10-5 configuration is regular and has good symmetry.
Redundant actuation has the advantages of high stiffness, strong load-carrying capacity and good motion performance. 10-6 and 10-5 configurations with ten links were designed, constructing a semi-analytic algorithm combining numerical method and analytical method, and workspace of the two configurations was analyzed. By adding two virtual links, the two configurations can be further derived into the 12 links topological configuration. Compatibility equations of the 12 links configuration were derived, and the numerical solutions of virtual links were obtained by Newton-Raphson method. Based on the geometric relationship between the characteristic points of the moving platform, the full analytic solution of the forward position solution of the 12 links configuration was derived. Furthermore, the position workspace and orientation workspace of the two configurations were studied by interval analysis method. The results show that the workspace of 10-5 configuration is regular and has good symmetry.
2021, 40(9): 1338-1346.
doi: 10.13433/j.cnki.1003-8728.20200223
Abstract:
According to the forming principle of micro-segment gear profile, the mathematical model of its tooth profile was established. The transmission error of the micro-segment gear was studied by the discrete TCA (tooth contact analysis) and the influence of different deviations on the transmission error and meshing backlash of the involute and micro-segment gear was analyzed comparatively. Through the establishment of micro-segment gear dynamics model, the influence of center distance deviation on dynamic response of involute and micro-segment gear under different loads and speeds was analyzed comparatively, and the result indicates that micro segment gear is more sensitive to center distance deviation than involute gear. Under the condition of low speed and light load, the dynamic characteristics of involute gear are better. But, under the condition of large load, especially under the condition of medium and high speed and heavy load, the micro segment gear has better dynamic characteristics when the center distance deviation is controlled within a certain range.
According to the forming principle of micro-segment gear profile, the mathematical model of its tooth profile was established. The transmission error of the micro-segment gear was studied by the discrete TCA (tooth contact analysis) and the influence of different deviations on the transmission error and meshing backlash of the involute and micro-segment gear was analyzed comparatively. Through the establishment of micro-segment gear dynamics model, the influence of center distance deviation on dynamic response of involute and micro-segment gear under different loads and speeds was analyzed comparatively, and the result indicates that micro segment gear is more sensitive to center distance deviation than involute gear. Under the condition of low speed and light load, the dynamic characteristics of involute gear are better. But, under the condition of large load, especially under the condition of medium and high speed and heavy load, the micro segment gear has better dynamic characteristics when the center distance deviation is controlled within a certain range.
2021, 40(9): 1347-1354.
doi: 10.13433/j.cnki.1003-8728.20200231
Abstract:
In order to improve the separation efficiency of a hydrocyclone for small oil drops, its inlet structure is analyzed. It is found that the inlet of elbow structure has the function of coalescence and reconstruction for different particle-size oil drops. That is to say, different particle-size oil drops enter into different positions of the inlet pipe after passing through the inlet of elbow structure. An oil-water separation hydrocyclone which can realize the reconstruction of particle-size oil drops is designed with the elbow structure of the inlet. The population balance model was used to simulate the breakup and coalescence of oil droplets, and the hydrocyclone with droplet size reconstruction was simulated and analyzed. Particle size distribution, turbulent kinetic energy, velocity, oil concentration and separation efficiency of the hydrocyclone were compared and analyzed, and laboratory tests were carried out. The results show that the oil-water separation hydrocyclone based on particle size reconstruction can improve the separation efficiency of small oil drops and that the hydrocyclone with the 180° bend works best. The efficiency reaches 97.31%, which is 2.85% higher than that of the conventional hydrocyclone, and the particle sizes of oil drops at the inlets of inner and outer layers reach 0.36 mm and 0.33 mm respectively, showing a good coalescence effect. The numerical simulation results are in good agreement with the experimental results, verifying the accuracy of the numerical simulation and the efficiency of the optimization structure.
In order to improve the separation efficiency of a hydrocyclone for small oil drops, its inlet structure is analyzed. It is found that the inlet of elbow structure has the function of coalescence and reconstruction for different particle-size oil drops. That is to say, different particle-size oil drops enter into different positions of the inlet pipe after passing through the inlet of elbow structure. An oil-water separation hydrocyclone which can realize the reconstruction of particle-size oil drops is designed with the elbow structure of the inlet. The population balance model was used to simulate the breakup and coalescence of oil droplets, and the hydrocyclone with droplet size reconstruction was simulated and analyzed. Particle size distribution, turbulent kinetic energy, velocity, oil concentration and separation efficiency of the hydrocyclone were compared and analyzed, and laboratory tests were carried out. The results show that the oil-water separation hydrocyclone based on particle size reconstruction can improve the separation efficiency of small oil drops and that the hydrocyclone with the 180° bend works best. The efficiency reaches 97.31%, which is 2.85% higher than that of the conventional hydrocyclone, and the particle sizes of oil drops at the inlets of inner and outer layers reach 0.36 mm and 0.33 mm respectively, showing a good coalescence effect. The numerical simulation results are in good agreement with the experimental results, verifying the accuracy of the numerical simulation and the efficiency of the optimization structure.
2021, 40(9): 1355-1360.
doi: 10.13433/j.cnki.1003-8728.20200225
Abstract:
In order to analyze the biomechanical characteristics of human lower limbs when the walking speed and load weight are different, a human lower limb musculoskeletal model is established with the biomechanical analysis software OpenSim. Using reverse dynamics, the human gait walking at different speeds and load weights is simulated; the gait walking is driven by ground reaction force and coordination of motion control points. The change curves of the torques of ankle joint, knee joint and hip joint are obtained when the human walks at the same speed but with different load weights and then with the same load weight at different speeds. The relationships of joint torque with the walking speed and load weight are analyzed, and the results show that the walking speed and load weight are positively correlated with joint torque. The muscle activity curves of soleus muscle, gastrocnemius muscle and tibialis anterior are given. The relationships of the muscle activity with the walking speed and load weight are discussed. The analysis results also show that the muscle activity increases with the increase of walking speed and load weight.
In order to analyze the biomechanical characteristics of human lower limbs when the walking speed and load weight are different, a human lower limb musculoskeletal model is established with the biomechanical analysis software OpenSim. Using reverse dynamics, the human gait walking at different speeds and load weights is simulated; the gait walking is driven by ground reaction force and coordination of motion control points. The change curves of the torques of ankle joint, knee joint and hip joint are obtained when the human walks at the same speed but with different load weights and then with the same load weight at different speeds. The relationships of joint torque with the walking speed and load weight are analyzed, and the results show that the walking speed and load weight are positively correlated with joint torque. The muscle activity curves of soleus muscle, gastrocnemius muscle and tibialis anterior are given. The relationships of the muscle activity with the walking speed and load weight are discussed. The analysis results also show that the muscle activity increases with the increase of walking speed and load weight.
2021, 40(9): 1370-1377.
doi: 10.13433/j.cnki.1003-8728.20200219
Abstract:
To improve the vibration performance of active suspension systems subject to actuator faults and disturbances, a terminal sliding mode and super twisting sliding mode-based fault tolerant controller was presented. Firstly, a 7-DOF suspension model and a nonlinear hydraulic actuator model were built for accurate control. The 3-DOF subsystem representing sprung mass motions was considered as the internal dynamics of the suspension system, and the subsystem with 4-DOF including unsprung masses, hydraulic actuators and external disturbances was considered as the external dynamics of the system. Then the proposed controller was implemented in two stages to provide a fault tolerant approach. A nonsingular fast terminal sliding mode based sliding manifold was designed for the internal system to suppress the sprung mass motions arising from road disturbances, and a super twisting algorithm was introduced for the external system to track the desired forces generated by the terminal sliding mode controller. Moreover, the stability of the controller was proved by the strong Lyapunov functions. Simulation results indicate that compared with traditional H∞ approach, the proposed controller can achieve better performance under both faulty and healthy conditions.
To improve the vibration performance of active suspension systems subject to actuator faults and disturbances, a terminal sliding mode and super twisting sliding mode-based fault tolerant controller was presented. Firstly, a 7-DOF suspension model and a nonlinear hydraulic actuator model were built for accurate control. The 3-DOF subsystem representing sprung mass motions was considered as the internal dynamics of the suspension system, and the subsystem with 4-DOF including unsprung masses, hydraulic actuators and external disturbances was considered as the external dynamics of the system. Then the proposed controller was implemented in two stages to provide a fault tolerant approach. A nonsingular fast terminal sliding mode based sliding manifold was designed for the internal system to suppress the sprung mass motions arising from road disturbances, and a super twisting algorithm was introduced for the external system to track the desired forces generated by the terminal sliding mode controller. Moreover, the stability of the controller was proved by the strong Lyapunov functions. Simulation results indicate that compared with traditional H∞ approach, the proposed controller can achieve better performance under both faulty and healthy conditions.
2021, 40(9): 1378-1384.
doi: 10.13433/j.cnki.1003-8728.20200221
Abstract:
In order to improve the peak torque computation accuracy of the rotary high-pressure fuel pump commonly used in a common rail system, a calculation method for whole cycle camshaft torque was proposed. The hydraulic pressure, friction force, spring force and inertia force effected on a plunger were calculated. According to the direction of resultant force on the triangular ring, the location of contact point between the triangular ring and the eccentric wheel was confirmed with the eccentric wheel coordinate system. Through coordinate transformation, the coordinates of contact points in the camshaft coordinate system were obtained, and then the camshaft torque at any rotation angle was worked out. When only the hydraulic pressure acted on the plunger is taken into account, the calculation result is the same as the backward flow induction as is the common case. The results show that the peak torque of the high-pressure fuel pump can be regarded as 1.3 times the flow backward induction. When the theoretical fuel delivery and the fuel pressure are constant, the peak torque increases slightly with the increase of the plunger diameter and decreases with the increase of the number of plungers. But the effect of the increased quantity of peak torque reduction is reduced when the number of plunge pistons exceeds 3.
In order to improve the peak torque computation accuracy of the rotary high-pressure fuel pump commonly used in a common rail system, a calculation method for whole cycle camshaft torque was proposed. The hydraulic pressure, friction force, spring force and inertia force effected on a plunger were calculated. According to the direction of resultant force on the triangular ring, the location of contact point between the triangular ring and the eccentric wheel was confirmed with the eccentric wheel coordinate system. Through coordinate transformation, the coordinates of contact points in the camshaft coordinate system were obtained, and then the camshaft torque at any rotation angle was worked out. When only the hydraulic pressure acted on the plunger is taken into account, the calculation result is the same as the backward flow induction as is the common case. The results show that the peak torque of the high-pressure fuel pump can be regarded as 1.3 times the flow backward induction. When the theoretical fuel delivery and the fuel pressure are constant, the peak torque increases slightly with the increase of the plunger diameter and decreases with the increase of the number of plungers. But the effect of the increased quantity of peak torque reduction is reduced when the number of plunge pistons exceeds 3.
2021, 40(9): 1385-1390.
doi: 10.13433/j.cnki.1003-8728.20200226
Abstract:
In order to test whether the submarine cable tension bending test device can work normally under high tensile load, the finite element analysis method was used to model and simulate the drum and the submarine cable, and finishing the stress, strain and displacement analysis. The results show that under the tensile load of 2×106 N, the maximum stress reaches 1.05×108 Pa, which does not exceed the yield strength of carbon steel. The overlarge deformation does not occur, and the test device can work normally, which means the design scheme of the submarine cable tension bending test device is reasonable.
In order to test whether the submarine cable tension bending test device can work normally under high tensile load, the finite element analysis method was used to model and simulate the drum and the submarine cable, and finishing the stress, strain and displacement analysis. The results show that under the tensile load of 2×106 N, the maximum stress reaches 1.05×108 Pa, which does not exceed the yield strength of carbon steel. The overlarge deformation does not occur, and the test device can work normally, which means the design scheme of the submarine cable tension bending test device is reasonable.
2021, 40(9): 1391-1396.
doi: 10.13433/j.cnki.1003-8728.20200227
Abstract:
In this work, a three-dimensional finite element model of a vehicle disc brake system is established, and the friction-induced vibration and noise characteristics of the brake system are analyzed. Then ABAQUS/Optimization module is used to perform structural topology optimization design for the caliper of brake system, to meet the requirements of lightweight goals and improve the friction-induced vibration and noise problem. Results show that there are four vibration modes generated from the brake system, and the tendency and intensity of vibration noise are the highest at the frequency of 3 632.4 Hz. The reason for the occurrence of this frequency is that the 4th mode of brake caliper is close to the 11th mode frequency of brake disc, and the modal coupling phenomenon is easy to occur during friction process. Through the topological optimization design of the brake caliper body and the removal of materials on both sides of the brake caliper, the 4th mode of the brake caliper is reduced to 2 804 Hz to avoid resonance with the brake disc under the premise of meeting the goal of minimum weight, and the weight of the brake caliper is reduced by 17.1%. The complex eigenvalue analysis is further used to predict the vibration and noise of the braking system after the structural optimization. The results show that only two adjacent modes of the braking system generate modal coupling phenomenon, and the vibration and noise frequency of 3 632.4 Hz is disappeared, indicating that the vibration and noise problem of the brake system has been significantly improved.
In this work, a three-dimensional finite element model of a vehicle disc brake system is established, and the friction-induced vibration and noise characteristics of the brake system are analyzed. Then ABAQUS/Optimization module is used to perform structural topology optimization design for the caliper of brake system, to meet the requirements of lightweight goals and improve the friction-induced vibration and noise problem. Results show that there are four vibration modes generated from the brake system, and the tendency and intensity of vibration noise are the highest at the frequency of 3 632.4 Hz. The reason for the occurrence of this frequency is that the 4th mode of brake caliper is close to the 11th mode frequency of brake disc, and the modal coupling phenomenon is easy to occur during friction process. Through the topological optimization design of the brake caliper body and the removal of materials on both sides of the brake caliper, the 4th mode of the brake caliper is reduced to 2 804 Hz to avoid resonance with the brake disc under the premise of meeting the goal of minimum weight, and the weight of the brake caliper is reduced by 17.1%. The complex eigenvalue analysis is further used to predict the vibration and noise of the braking system after the structural optimization. The results show that only two adjacent modes of the braking system generate modal coupling phenomenon, and the vibration and noise frequency of 3 632.4 Hz is disappeared, indicating that the vibration and noise problem of the brake system has been significantly improved.
2021, 40(9): 1397-1403.
doi: 10.13433/j.cnki.1003-8728.20200230
Abstract:
Aiming at the research methods of extracting bearing fault characteristics, identifying and classifying vibration signals, a new method combining EWT、multi-scale fuzzy entropy and VPMCD algorithms is proposed in the thesis. Firstly, the modal components of the vibration signal are extracted by the empirical wavelet transform (EWT). Secondly, the fuzzy entropy algorithm in information theory is introduced, and multi-scale coarse-grained partitioning method is used to obtain the multi-scale fuzzy entropy feature description. Then, VPMCD algorithm is used to train the model by adaptively selecting prediction model. The experiments show that multi-scale fuzzy entropy of modal components can effectively describe the fault features. VPMCD achieves a minimum classification accuracy of 90% with a small number of training samples, which has better performance than some common classification methods.
Aiming at the research methods of extracting bearing fault characteristics, identifying and classifying vibration signals, a new method combining EWT、multi-scale fuzzy entropy and VPMCD algorithms is proposed in the thesis. Firstly, the modal components of the vibration signal are extracted by the empirical wavelet transform (EWT). Secondly, the fuzzy entropy algorithm in information theory is introduced, and multi-scale coarse-grained partitioning method is used to obtain the multi-scale fuzzy entropy feature description. Then, VPMCD algorithm is used to train the model by adaptively selecting prediction model. The experiments show that multi-scale fuzzy entropy of modal components can effectively describe the fault features. VPMCD achieves a minimum classification accuracy of 90% with a small number of training samples, which has better performance than some common classification methods.
2021, 40(9): 1404-1409.
doi: 10.13433/j.cnki.1003-8728.20200224
Abstract:
According to the frequency spectrum characteristic of the excavator cab noise, it was found that the main noise component is medium-frequency noise. In order to accurately simulate the noise level inside cab, the finite element and statistical energy analysis methods were jointly applied and FE-SEA hybrid simulation model was established. Through theoretical calculation, the modal density, internal loss factor and coupling loss factor were obtained. The sound pressure data of driving outdoor sound field and suspension vibration data were measured by the test method and applied to the corresponding subsystem of the hybrid model as excitation. In the simulation calculation of cabin noise, the simulation error is only 2.38% in the range of 200-1000 Hz, which verifies the accuracy of the hybrid model and the applicability of FE-SEA method to medium-frequency noise. Based on the results, the noise contribution of cab plate was further analyzed, and the acoustic weak part of cab was found, which indicates the direction for optimization and improvement.
According to the frequency spectrum characteristic of the excavator cab noise, it was found that the main noise component is medium-frequency noise. In order to accurately simulate the noise level inside cab, the finite element and statistical energy analysis methods were jointly applied and FE-SEA hybrid simulation model was established. Through theoretical calculation, the modal density, internal loss factor and coupling loss factor were obtained. The sound pressure data of driving outdoor sound field and suspension vibration data were measured by the test method and applied to the corresponding subsystem of the hybrid model as excitation. In the simulation calculation of cabin noise, the simulation error is only 2.38% in the range of 200-1000 Hz, which verifies the accuracy of the hybrid model and the applicability of FE-SEA method to medium-frequency noise. Based on the results, the noise contribution of cab plate was further analyzed, and the acoustic weak part of cab was found, which indicates the direction for optimization and improvement.
2021, 40(9): 1410-1415.
doi: 10.13433/j.cnki.1003-8728.20200215
Abstract:
The calculation of the compression deformation of the bolted connection structure in its clamping region is affected by the shape of the compression body. In order to explore a more suitable equivalent mode of the compression body, the minimum outer diameter of the compression body in the clamped piece contacted with the shaft sleeve was modified based on the four times distribution method of compressive pressure to obtain the modified analytic expression of axial compression deformation. Through the curve fitting and numerical integration calculation for the node stress of finite element simulation, the axial compression deformation of the bolt was obtained. The result shows that the more appropriate equivalent mode of the compression body is the combination of cone, cylinder and double cones. The relative error does not exceed 7.49% after the minimum diameter of the compression body in the clamped piece contacted with the shaft sleeve is modified to be 1.4 times of the average of the outer diameter of the shaft sleeve and the diameter of the bearing surface of the bolt head.
The calculation of the compression deformation of the bolted connection structure in its clamping region is affected by the shape of the compression body. In order to explore a more suitable equivalent mode of the compression body, the minimum outer diameter of the compression body in the clamped piece contacted with the shaft sleeve was modified based on the four times distribution method of compressive pressure to obtain the modified analytic expression of axial compression deformation. Through the curve fitting and numerical integration calculation for the node stress of finite element simulation, the axial compression deformation of the bolt was obtained. The result shows that the more appropriate equivalent mode of the compression body is the combination of cone, cylinder and double cones. The relative error does not exceed 7.49% after the minimum diameter of the compression body in the clamped piece contacted with the shaft sleeve is modified to be 1.4 times of the average of the outer diameter of the shaft sleeve and the diameter of the bearing surface of the bolt head.
2021, 40(9): 1416-1424.
doi: 10.13433/j.cnki.1003-8728.20200229
Abstract:
In order to solve the semi-standard problem of control point insertion in the T-splines surface modeling, a semi-standard local refinement algorithm based on the uniform t-grid splines surface is proposed. Firstly, according to the definition of T-splines surface, B-splines surface is transformed into uniform T-grids splines surface, then control points are inserted on any single grids, and the grids can also be nested and subdivided. In order to meet the refinement requirements of local surface features, the additional coefficients need to be added to some control points to ensure the semi-standard of T-splines surface. The least square method is used to solve the extra coefficients by establishing the overdetermined equation, and the blending function of the initial uniform T-grid is transformed into the blending function of the final T-grids by the transformation matrix. The algorithm is proved to be feasible through examples. Comparing with the local refinement of T-splines surface, when the curved surface reaches the same precision, this method reduces redundant control points.
In order to solve the semi-standard problem of control point insertion in the T-splines surface modeling, a semi-standard local refinement algorithm based on the uniform t-grid splines surface is proposed. Firstly, according to the definition of T-splines surface, B-splines surface is transformed into uniform T-grids splines surface, then control points are inserted on any single grids, and the grids can also be nested and subdivided. In order to meet the refinement requirements of local surface features, the additional coefficients need to be added to some control points to ensure the semi-standard of T-splines surface. The least square method is used to solve the extra coefficients by establishing the overdetermined equation, and the blending function of the initial uniform T-grid is transformed into the blending function of the final T-grids by the transformation matrix. The algorithm is proved to be feasible through examples. Comparing with the local refinement of T-splines surface, when the curved surface reaches the same precision, this method reduces redundant control points.
2021, 40(9): 1425-1431.
doi: 10.13433/j.cnki.1003-8728.20200222
Abstract:
In order to reduce the tool wear and improve the surface quality of titanium alloy, an ultrasonic atomization assisted cutting method with water-based cutting fluid was developed. Firstly, TC4 titanium alloy was used as the cutting material, and the dry cutting experiment of TC4 titanium alloy was carried out. Then, the emulsions formed by mixing nano water-soluble oil-based cutting fluid and deionized water are used as the atomizing media, which were transformed from ultrasonic atomizer into tiny droplets and act on the tool interface. The ultrasonic atomization assisted cutting experiment was carried out. Finally, the surface roughness, tool wear, element diffusion and chip morphology of TC4 workpiece before and after ultrasonic atomization were compared. The experimental results show that the surface roughness of TC4 titanium alloy increased by 47.6%, the wear value of cutting tool on the back face reduced by 36 μm, and the Ti and O contents on the surface of cutting tool reduced from 78.72%, 6.32% to 75.49% and 1.85% , respectively.
In order to reduce the tool wear and improve the surface quality of titanium alloy, an ultrasonic atomization assisted cutting method with water-based cutting fluid was developed. Firstly, TC4 titanium alloy was used as the cutting material, and the dry cutting experiment of TC4 titanium alloy was carried out. Then, the emulsions formed by mixing nano water-soluble oil-based cutting fluid and deionized water are used as the atomizing media, which were transformed from ultrasonic atomizer into tiny droplets and act on the tool interface. The ultrasonic atomization assisted cutting experiment was carried out. Finally, the surface roughness, tool wear, element diffusion and chip morphology of TC4 workpiece before and after ultrasonic atomization were compared. The experimental results show that the surface roughness of TC4 titanium alloy increased by 47.6%, the wear value of cutting tool on the back face reduced by 36 μm, and the Ti and O contents on the surface of cutting tool reduced from 78.72%, 6.32% to 75.49% and 1.85% , respectively.
2021, 40(9): 1432-1438.
doi: 10.13433/j.cnki.1003-8728.20200232
Abstract:
The parameters identification of constitutive model for the sheet warm forming of advanced high strength dual phase steel is the key to improve the simulation accuracy of plastic deformation behavior. By establishing the parameter sensitivity analysis method of constitutive model based on the Latin hypercube sampling method and Spearman rank correlation analysis method, the overall analysis of parameter sensitivity was realized. Then, combining the sensitivity analysis results, the unidirectional tensile test of DP780 steel and the finite element simulation of the tensile process, the response surface model between the distance function and the material parameters in the constitutive model under different temperatures was constructed. The parameter identification problem in the constitutive model was reduced to solving the minimum distance function problem. The optimization algorithm is used for the optimization calculation, and the parameters of the Inoue Sin constitutive model for of DP780 steel under the different temperatures were finally obtained. The results show that the parameter identification method in the constitutive model can meet the requirement of constitutive model accuracy.
The parameters identification of constitutive model for the sheet warm forming of advanced high strength dual phase steel is the key to improve the simulation accuracy of plastic deformation behavior. By establishing the parameter sensitivity analysis method of constitutive model based on the Latin hypercube sampling method and Spearman rank correlation analysis method, the overall analysis of parameter sensitivity was realized. Then, combining the sensitivity analysis results, the unidirectional tensile test of DP780 steel and the finite element simulation of the tensile process, the response surface model between the distance function and the material parameters in the constitutive model under different temperatures was constructed. The parameter identification problem in the constitutive model was reduced to solving the minimum distance function problem. The optimization algorithm is used for the optimization calculation, and the parameters of the Inoue Sin constitutive model for of DP780 steel under the different temperatures were finally obtained. The results show that the parameter identification method in the constitutive model can meet the requirement of constitutive model accuracy.
2021, 40(9): 1439-1443.
doi: 10.13433/j.cnki.1003-8728.20200214
Abstract:
A sliding mode control strategy based on two kinds of Lyapunov function is proposed for the suspension stability of maglev train levitation system under the disturbance of load disturbance and track irregularity excitation. Firstly, according to the dynamic equation and voltage equation, the corresponding mathematical model is established, and the desired suspension gap is designed and set as a virtual input. In the dynamic equation, the sliding mode control algorithm is adopted to realize the tracking control of suspension error. Then, according to the corresponding constraints of vertical suspension gap, Hamilton-Jacobi Inequality (HJI) theory and the Lyapunov function are introduced to design the corresponding controller, which can ensure the suspension stability under various disturbances. In addition, the stability of the closed-loop system is proved using the Lyapunov stability theorem, so that the suspension accuracy of the system can be guaranteed and the error can be adjusted as much as possible when it is disturbed, and the suspension error can be converged to infinity. Finally, the effectiveness and robustness of the proposed control law are verified by comparing the suspension performance of the existing PID control algorithm under the same working condition.
A sliding mode control strategy based on two kinds of Lyapunov function is proposed for the suspension stability of maglev train levitation system under the disturbance of load disturbance and track irregularity excitation. Firstly, according to the dynamic equation and voltage equation, the corresponding mathematical model is established, and the desired suspension gap is designed and set as a virtual input. In the dynamic equation, the sliding mode control algorithm is adopted to realize the tracking control of suspension error. Then, according to the corresponding constraints of vertical suspension gap, Hamilton-Jacobi Inequality (HJI) theory and the Lyapunov function are introduced to design the corresponding controller, which can ensure the suspension stability under various disturbances. In addition, the stability of the closed-loop system is proved using the Lyapunov stability theorem, so that the suspension accuracy of the system can be guaranteed and the error can be adjusted as much as possible when it is disturbed, and the suspension error can be converged to infinity. Finally, the effectiveness and robustness of the proposed control law are verified by comparing the suspension performance of the existing PID control algorithm under the same working condition.
2021, 40(9): 1444-1450.
doi: 10.13433/j.cnki.1003-8728.20200257
Abstract:
Aiming at the optimization of energy management strategy for hybrid electric vehicle with pure power mainly for a single operating condition and lack of adaptive capacity in practical application, an energy management strategy including back propagation neural network operating condition identification control was proposed. Taking lithium battery-supercapacitor composite power pure electric vehicle as the research object, this paper studies the influence of energy management strategies of composite power pure electric vehicle with operating condition recognition on the vehicle economy and battery working state. Modified the vehicle model under MATLAB / Simulink platform and carried out comprehensive test condition simulation. The results show that the energy control strategy including condition identification can accurately identify the driving condition. Compared with the energy management strategy before optimization, the energy consumption of the battery decreases. 2.81%, the total energy consumption decreased by 1341 kJ, the energy distribution between the two energy sources was more reasonable, the battery working condition was further optimized, and the vehicle economy was effectively improved.
Aiming at the optimization of energy management strategy for hybrid electric vehicle with pure power mainly for a single operating condition and lack of adaptive capacity in practical application, an energy management strategy including back propagation neural network operating condition identification control was proposed. Taking lithium battery-supercapacitor composite power pure electric vehicle as the research object, this paper studies the influence of energy management strategies of composite power pure electric vehicle with operating condition recognition on the vehicle economy and battery working state. Modified the vehicle model under MATLAB / Simulink platform and carried out comprehensive test condition simulation. The results show that the energy control strategy including condition identification can accurately identify the driving condition. Compared with the energy management strategy before optimization, the energy consumption of the battery decreases. 2.81%, the total energy consumption decreased by 1341 kJ, the energy distribution between the two energy sources was more reasonable, the battery working condition was further optimized, and the vehicle economy was effectively improved.
2021, 40(9): 1451-1456.
doi: 10.13433/j.cnki.1003-8728.20200212
Abstract:
In order to solve the problem that the gap between HTS Maglev and the track will change under the influence of load or disturbance, a structure model of HTS Maglev with self-adaptive bearing capacity is presented, and the working principle of self-adaptive adjustment of bearing capacity is described. On this basis, the calculation method of bearing capacity and the influencing factors of bearing capacity are studied. The results show that the bearing capacity has obvious hysteresis characteristics, and it increases with the decrease of the gap between the superconductor and the permanent magnet ring. The permanent magnet ring corresponds to an optimal number of superconductors under each structural parameter. The larger the critical current density value of superconductor is, the larger the bearing capacity is. When the diameter value of superconductor is equal to the width value of permanent magnet ring, the bearing capacity reaches the maximum value. The bearing capacity increases with the thickness increase of the permanent magnetic ring in a certain range. When the superconductor deviates from the permanent magnetic ring, the radial restoring force will be produced and the bearing capacity will be reduced.
In order to solve the problem that the gap between HTS Maglev and the track will change under the influence of load or disturbance, a structure model of HTS Maglev with self-adaptive bearing capacity is presented, and the working principle of self-adaptive adjustment of bearing capacity is described. On this basis, the calculation method of bearing capacity and the influencing factors of bearing capacity are studied. The results show that the bearing capacity has obvious hysteresis characteristics, and it increases with the decrease of the gap between the superconductor and the permanent magnet ring. The permanent magnet ring corresponds to an optimal number of superconductors under each structural parameter. The larger the critical current density value of superconductor is, the larger the bearing capacity is. When the diameter value of superconductor is equal to the width value of permanent magnet ring, the bearing capacity reaches the maximum value. The bearing capacity increases with the thickness increase of the permanent magnetic ring in a certain range. When the superconductor deviates from the permanent magnetic ring, the radial restoring force will be produced and the bearing capacity will be reduced.
2021, 40(9): 1457-1463.
doi: 10.13433/j.cnki.1003-8728.20200228
Abstract:
The effect mechanisms of contact load on the tribological properties of aluminum alloy drilling risers were studied on a UTM friction test machine with the physical experiments of 7075 aluminum alloy pin disks and G105 steel pins. Results showed that the friction coefficient decreases significantly and then increases slightly with the increasing of contact load. As the contact load increases, the wear rate declines slowly and then rises sharply. The main wear mechanism was the abrasive wear at the contact load of 10 ~ 30 N and the oxidative wear at a medium load of 50 N. While the contact load increases to 70 N, the main wear mechanism was the adhesive delamination. The critical load is 50 N for the transition of wear mechanisms from wild wear to severe wear. Therefore, for aluminum alloy drilling riser, it is suggested to avoid high-load contact which would cause severe wear and drilling riser failure.
The effect mechanisms of contact load on the tribological properties of aluminum alloy drilling risers were studied on a UTM friction test machine with the physical experiments of 7075 aluminum alloy pin disks and G105 steel pins. Results showed that the friction coefficient decreases significantly and then increases slightly with the increasing of contact load. As the contact load increases, the wear rate declines slowly and then rises sharply. The main wear mechanism was the abrasive wear at the contact load of 10 ~ 30 N and the oxidative wear at a medium load of 50 N. While the contact load increases to 70 N, the main wear mechanism was the adhesive delamination. The critical load is 50 N for the transition of wear mechanisms from wild wear to severe wear. Therefore, for aluminum alloy drilling riser, it is suggested to avoid high-load contact which would cause severe wear and drilling riser failure.
2021, 40(9): 1464-1470.
doi: 10.13433/j.cnki.1003-8728.20200512
Abstract:
In order to clarify the mechanical properties of light cured honeycomb structure photosensitive resin, the mechanical properties of original solid samples and circular honeycomb structure samples with different cell diameters were tested at different strain rates via universal material testing machine and split Hopkinson pressure bar experimental device. The results show that the elastic modulus and yield limit of the photosensitive resin increase with the increasing of strain rate. At low strain rate, the strain softening and strain hardening effect appear when the photosensitive resin reaches the yield limit, which shows the viscoelasticity of the photosensitive resin. At high strain rate, the photosensitive resin has the obvious strain rate effect and strain rate sensitivity. The elastic modulus and yield limit of honeycomb structure decrease with the increasing of cell diameter. Finally, the ZWT nonlinear viscoelastic constitutive model for photosensitive resin with high strain rate is established. The fitting data is in a good agreement with the experimental.
In order to clarify the mechanical properties of light cured honeycomb structure photosensitive resin, the mechanical properties of original solid samples and circular honeycomb structure samples with different cell diameters were tested at different strain rates via universal material testing machine and split Hopkinson pressure bar experimental device. The results show that the elastic modulus and yield limit of the photosensitive resin increase with the increasing of strain rate. At low strain rate, the strain softening and strain hardening effect appear when the photosensitive resin reaches the yield limit, which shows the viscoelasticity of the photosensitive resin. At high strain rate, the photosensitive resin has the obvious strain rate effect and strain rate sensitivity. The elastic modulus and yield limit of honeycomb structure decrease with the increasing of cell diameter. Finally, the ZWT nonlinear viscoelastic constitutive model for photosensitive resin with high strain rate is established. The fitting data is in a good agreement with the experimental.
2021, 40(9): 1471-1476.
doi: 10.13433/j.cnki.1003-8728.20200217
Abstract:
The flexure spring is one of the key technologies of the long life and high reliability of the Micro-miniature cryocooler. In this paper, three kinds of flexure spring for micro-compressors are designed via finite element method. The different thickness of the spring, width of the spiral groove and number of the spiral arms are simulated. The influence of the three geometric parameters on the performance of the flexure spring is analyzed.
The flexure spring is one of the key technologies of the long life and high reliability of the Micro-miniature cryocooler. In this paper, three kinds of flexure spring for micro-compressors are designed via finite element method. The different thickness of the spring, width of the spiral groove and number of the spiral arms are simulated. The influence of the three geometric parameters on the performance of the flexure spring is analyzed.
