China Mechanical Engineering

Thickness Measuring Method of High-temperature Power Plant Structures Based on SH Mode Waveguide

XU Hong , GUO Peng, LI Hongyuan, TIAN Zhenhua, DENG Bo

2017, 28(07): 757-763.

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It is significant to put forward a thickness measuring method of high temperature power plant structures based on SH mode, which used a waveguide to isolate the transducers from the high-temperature measurement zones. It was found that a nondispersive SH mode guided wave in rectangular waveguide was employed to transmit the guided wave signals from the transducers to the measurement zones. In addition, experiments were investigated by dry-coupled to attach the waveguides to the components, which shows that clamping the waveguides to the component surfaces may get best results. By using Hanning window modulated sine wave signals with 2MHz center frequency, the thickness difference of the measured values and actual values of wall thickness is 0.016mm at the room temperature(25℃). Performance at high temperatures was tested without signal degradation. The error ranges of wave velocity measurement values and the velocities of the fitting curve are 0.1% to 2.5%.

Research on Relationship between Rotor Profiles and Meshing Lines in Twin-screw Compressors

HE Xueming, JIANG Zhengang, WU Meiping, ZHANG Rong, JI Xiaogang

2017, 28(07): 763-770.

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From the twin-screw compressor rotor meshing line of view, the meshing line method was introduced in detail, the male and female rotor profiles were deduced from the meshing line by meshing and coordinate transformation relationship. The requirements of continuity were given in the meshing line method and the corresponding solving steps which solved the continuity problems in the meshing line method were carried out. Three critical control points on the meshing line were studied and the impacts of its changes of positions on the rotor profiles generated were summarized, including rotor angles, thicknesses and interdental areas. At last, a profile was designed by the meshing line method, and demonstrates the optimization of new profiles by changing the position of critical control points, the design efficiency is increased.

Design and Simulation of Mechanical Decoupling Self-calibration Parallel Six Dimensional Force Sensors

ZHAO Yanzhi, JIAO Leihao, NIU Zhi, LU Chao, ZHAO Tieshi,

2017, 28(07): 771-778.

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To avoide the present situations of the heavy loading calibration of traditional multi-dimensional force sensors, a self-calibration design concept of multi-dimensional force sensors was proposed, the weak coupling full thrust force self-calibration orthogonal parallel six dimensional force sensor structure was design which might realize mechanical decoupling by the rolling of the steel balls. The rolling decoupling principles of the six dimensional force sensors were demonstrated, and then the self-calibration principles of the six dimensional force sensors were demonstrated. An ideal mathematical model of the six dimensional force sensors was established based on the screw theory, and the first order static influence coefficient matrix was obtained. The force analysis and simulation of the six dimensional force sensor were carried out with considering the elastic deformations based on the mechanics solution principles of high-order statically indeterminate structure, and the self-calibration characteristics were proved by combining the numerical examples, which sets the development foundation of the novel six dimensional force sensors.

A Simulation and Optimization Method of Product Degradation Tests

FANG Jun, WEI Xing, ZHAO Sensen

2017, 28(07): 779-784.

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Based on the simulated degradation data, a degradation test optimization method was proposed， which was applicable in the case of known failure mechanism and predicable degradation data. Firstly, the prediction model for confidence interval of the reliable life was built based on the Bootstrap method, and the optimization model for the degradation tests was established, which took the minimum confidence interval of reliable life as the optimization objective, and the experimental costs as the constraints. Then, as an example, the general method of generating simulated degradation data for a certain kind of gun barrel was presented, and the degradation test parameters were designed and optimized. Finally, the verification method of the simulation and optimization results was discussed, and the related examples were analyzed to prove the effectiveness of the method.

Heat Equilibrium Analyses of Shaft-radiator-bearing Systems on Circulating Cooling Water Pumps in Nuclear Power Plants

WU Mingzhe, SUN Dechen, WANG Xiaodong

2017, 28(07): 785-789.

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To ensure the safety work of the bearings, the radiators were generally installed on the shafts between the circulating cooling water pump chambers and the bearings, which might reduce the working temperatures of the bearings. A heat calculation model of the shaft-radiator-bearing system was established using connected heat equilibrium calculation method herein. The heat equilibrium calculation on the shaft-bearing-radiator system was proceeded by home-made calculating program with VC language, and the temperature distribution along the axis was obtained. The influences of the radiator construction on the bearing's operating temperature were analyzed. The calculating results show that, the heat transfer of the shaft-bearing-radiator system is affected greatly as the radiator setting on the shaft, and the reduction of bearing temperatures is only slightly. Other cooling methods should be adopted such as forced-air cooling mode to increase the heat transfer ability of the bearing bracket and further reduce the temperature at the bearing and increase the reliability of the pump.

Design Method of Cam-type Switching Mechanism Contours Based on B-Spline

WANG Wei, YAO Huazhong

2017, 28(07): 789-793.

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In order to investigate the problems of complex contour description and complex quantitative relationship between cam-type switching mechanism contours and force value curves, a design method of cam contour was suggested based on B-spline and energy theory. The descriptive and the differential equations of B-spline were given, the quantitative relationship equation between the internal potential energy and external work of switching mechanism was established, and the iterative design algorithm of mechanism contours was presented. A cam-type wiper switch contour was designed by using MATLAB and the suggested cam contour design method, which involved the energetic relationship equation and the iterative algorithm. The design results indicate that the derived contour may satisfy the expected force value curve requirements, and the derived force value curves by using B-spline are more effective in improving the contour precision and the switch performance than that by using high-order polynomial fitting curves.

Design of Tension Self-stabilization System for Surgical Suture Coating Processes

WEN Jing, HE Yongyi

2017, 28(07): 794-880.

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In the coating processes of surgical sutures, to stabilize the tension, a self-stable system was raised depending on the speed-following principles, and was aimed to solve the limitation of traditional tensions through analyzing the control mode. The tension-controlling system was designed on dynamics and feeds the suture actively. Meanwhile, a spring, served as a tension rod to change the feed speeds through testing the undulation of the tension in the processes, thereby, the undulation ranges might be decreased, in like manner, the stability was improved. With a virtual model, dynamics simulation may draw the spring through ADAMS. This tension rod mechanism may decrease the undulation ranges by 70%. Finally, a waxing machine was used as a test object which was developed with Johnson & Johnson medical(China) Ltd..Comparing with the traditional equipment, this one proves to decrease the undulation ranges by 53%.

Aircraft Hydraulic Booster and Rudder System Modeling and Performance Simulation

CHEN Jian, DENG Zhiqiang, QIAO Jinhong

2017, 28(07): 800-805.

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A simulation model for analyzing a hydraulic booster and rudder system was established based on a typical hydraulic booster of a certain type of aircraft flight control system. The system model that consisted of the dynamics of load, piston, cylinder, and spool of the valve was derived by considering the influences of nonlinear factors such as oil stiffness, structure stiffness, friction and leakage. The influences of key parameters on the system performance and stability were analyzed and elaborated by focusing on the system stability and static dynamic characteristics. The simulation results show that this system has good stability and quick response, as well as good performance in both of static and dynamic.

Fault Diagnosis Method for Rolling Bearings Based on Compression Information Feature Extractions

MENG Zong, LI Jing, LONG Haifeng, PAN Zuozhou

2017, 28(07): 806-812.

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As a new sampling method, compressed sensing samples with the signal sparse features were presented, which was far below the Nyquist sampling theorem. It might reduce generous requirements of data acquisition, transmission and storage hardware. Aiming at the signals from the compression perception within the framework, this paper proposed a new method for rolling bearing fault diagnoses. In this method, part of hadamard matrix was chosen as a measurement matrix, and kurtosis factor, variance and waveform factor as a sensitive parameters. So there was no need to rebuild compression measurement and the gathering informations were utilized to extract sensitive characteristics directly, and then the PSO-SVM algorithm was used for pattern recognition so as to realize fault diagnoses. It is shown that within a certain range compression ratio, the method may use less amount of data of fault characteristics for rolling bearing fault diagnoses.

Computer Automatic Generation of Serial Mechanism Type Synthesis Based on POC Method

SUN Chiyu, SHEN Huiping, ZHU Xiaorong, YANG Tingli

2017, 28(07): 813-822.

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The serial mechanism type synthesis algorithms and the computer automation implementation were studied based on POC set. Firstly, the algorithm for serial mechanism type synthesis was established, and a new expression method for the dimensions and directions of the serial mechanism end-reactor's translations and rotations was proposed. This paper specifically described the processes on algorithm and automation implementation of n-DOF serial mechanism which were based on C language. Secondly, the program interface was completed by MATLAB which optimized the human-computer interactions. Finally, using the 4-DOF serial mechanism type synthesis as an example, the program may automatically generate 10 kinds of 1T3R serial mechanisms, 23 kinds of 2T2R serial mechanisms and 85 kinds of 3T1R serial mechanisms. The users only needed to input the POC set of the mechanisms which they wanted to create, and then the program may automatically generate the results, this operation has good usability and universality.

Fault Diagnosis Method Based on Hypothesis Testing and SVM for Condition Diagnosis of Rotating Machinery

ZHAO Yu, LI Ke, SU Lei, CHEN Peng

2017, 28(07): 823-829.

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A fault diagnosis method was proposed based on adaptive statistic test filter (STF) and SVM for condition diagnosis of rotating machinery to extract weak fault features and identify fault types. STF was based on the statistic of the hypothesis testing in the frequency domain to evaluate similarity among reference signals (noise signal) and original signals, and remove the components of high similarity. The optimal level of significance α was obtained by using particle swarm optimization(PSO). To evaluate the performances of the STF, evaluation factor Ip qwas also defined. Finally, a sequential diagnosis method, using sequential inference and SVM was also proposed, by which the conditions of rolling bearings might be identified sequentially. Practical examples of fault diagnosis for structural faults often occurring in the shafts, such as unbalance, misalignment states were shown to verify that the method is effective.

Calculation of Misjudgment Probabilities Caused by Measurement Uncertainties in Sampling Inspections

WANG Hanbin, CHEN Xiaohuai, LI Hongli, CHENG Yinbao, CHENG Zhenying

2017, 28(07): 829-834.

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To reasonably distribute measurement resources and improve the reliability of the product inspection results, misjudgment risks caused by measurement uncertainties in sampling inspection were evaluated. Different kinds of risks in sampling inspections were analyzed, and the influences of measurement uncertainties were mainly described. Misjudgment probability formulas were given, respectively for the pre-estimations before inspections and calculations after inspections. Taking product size conformity assessment as an example, misjudgment probabilities were calculated and analyzed. Results show that misjudgment probabilities for both acceptance and rejection in sampling inspection increase with the measurement uncertainties, measurement methods should be reasonably chosen before inspections according to acceptable misjudgment probabilities. For the conformity assessment results of specific product batch, corresponding misjudgment probability should also be calculated to ensure the reliability of product inspection results.

Statics Property Analyses of a Novel Spherical Parallel Humanoid Robotic Ankle Mechanism

YANG Long, ZHOU Yulin, MA Qiuming

2017, 28(07): 835-841.

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By the dismantle-bar method, the statics equilibrium equations of the mechanism were set up, considering the elasticity of member and then utilizing the micro-deformation and superposition principle, the deformation equations of compatibility were derived and then the statics analyses of the 2-DOFs parallel humanoid robotic ankle mechanism were fulfilled. As a numerical example, some figures which showed the relationship among each force on each member and the position and posture of the mechanism were drawn under three kinds of external loads, respectively. The results show that, under the external forces only, the forces acting on branched chain 1 are very small, the forces acting on branched chain 2 are approximately zero, and the forces acting on central spherical pair branched chain approximately equal to the external force. Under the external torques only, the force conditions of three branched chains are similar. Under external forces and torques, the force conditions of branched chain 1, 2 are similar to the force conditions that under the external torques only, the forces acting on central spherical pair branched chain are the superposition of the two forces in the above two cases. The force portions of external load are mainly carried by central spherical pair branched chain, the torque portions are jointly carried by three branched chains. The research provides a theoretical basis of statics for structure design and applications of this humanoid robotic ankle mechanisms in engineering．

Optimization of Milling Process Parameters Based on Hybrid Algorithm for Thin-walled Workpieces

ZENG Shasha, PENG Weiping, LEI Jin

2017, 28(07): 842-845,851.

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Combining with advantages of neural network method and genetic algorithm, a method to optimize machining process parameters was proposed for thin-walled workpieces based on back propagation neural network(BPNN). The data gained from Taguchi experiments were applied to train in BPNN so as to generate the S/N ratio predictor and quality predictor. By maximizing the S/N ratio, variation of milling processes was minimized, and the optimal process parameter combinations were found. Through numerical simulation and machining experiments, effectiveness of the proposed method in optimization of milling process parameters of thin-walled workpieces was validated.

Theoretical and Experimental Study on Similar Experimental Prototype of Advanced Support in Fully Mechanized Roadway

XIE Miao, LIU Zhixiang, MAO Jun, LU Jinnan

2017, 28(07): 846-851.

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Under laboratory conditions, in order to carry out roadway advanced support analysis static and dynamic experiments, according to the physics similarity relation, the similarity criterion between the advanced support prototype and experimental prototype was established, the main parameters of the experimental prototype was determined, then, the experimental prototype was established. The modal analysis of the experimental prototype was made by the theory of linear system mode superposition, and the results were compared with the experimental ones. The mechanical characteristics of the roof in the conditions of no support, the single support of advanced support and the support of two groups were analyzed by theoretical method, and the results were compared with the experimental data obtained from the experimental platform.The results show that the maximum error of the theoretical and experimental results of modal analysis is as 12.57%, the maximum error of the theoretical and experimental results of coupling mechanical supports and roof is as 14.80%, lower than 20%, to meet the research requirements verify the reliability of the research results.

Multi-objective Reconfigurable Facility Layout Method Based on Particle Swarm Optimization

DING Xianghai, YAO Wenpeng

2017, 28(07): 852-861.

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A method of multi-objective reconfigurable facilities layout was presented. The space filling curve was used to describe the facilities locations and it was possible to exchange between any two facilities. The flexibility area requirements of facility and the facility's shape constraint coefficient were used to keep the layout solution's feasibility. A multi-objective reconfigurable facilities layout model with costs (material transportation costs and facility reconstruction costs) and works in processes (WIP) as targets was established. An improved particle swarm optimization algorithm was designed for this model. Compared with standard particle swarm optimization the algorithm was improved in the selection of global extremum and individual extremum, and the updating strategy of Pareto solution set. Finally, an example was given to illustrate the effectiveness of this method.

Optimization of Deformation Energy in Single Point Incremental Forming Processes Using Response Surface Methodology

YAO Zimeng, LI Yan, YANG Mingshun, ZHANG Jingchong, ZHANG Chengxing

2017, 28(07): 862-866.

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The deformation energy in single point incremental forming processes had direct impact on the processing costs, also the heats and the wear effects between the tools and formed materials. A box-behnken design(BBD) for cone parts forming processes was performed, which considered the plan of four factors and three levels. The effects of tool diameter, step down, sheet thickness and wall angle on deformation energy were investigated. Meanwhile, the deformation energy was predicted by quadratic equations. Finally, the model was optimized with minimum deformation energy. The results show that, sheet thickness presents the most significant liner effects on deformation energy, while deformation energy increases with the increases of sheet thicknesses, tool diameters and wall angles. At last, tool diameter 4.0mm, step down 0.95mm, sheet thickness 0.57mm and wall angle 45° are combined as the best parameters for the minimum deformation energy.

Theoretical Analyses of Tube Granule Medium Internal High Pressure Forming Processes

YANG Zhuoyun, ZHAO Changcai, DONG Guojiang, ZHANG Xin, CHEN Xiaohua

2017, 28(07): 867-876.

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The discrete granules brough a non-uniform internal pressures and a significant friction between tube and medium to granule medium internal high pressure forming processes. Therefore, a non-uniform pressure transfer model was built for this process to investigate into theoretical analyses of tube bulging. The effects of the non-uniform pressures and the significant friction on tube forming property were studied by the theoretical analyses which were verified by processing tests. The analyses show that the non-uniform pressures and the significant friction may reduce the thickness reductions and forming pressures of tube bulging. The comparison of theoretical analyses and processing tests indicates that the calculated curves of thickness distributions and forming pressures agree well with test results. The non-uniform pressure transfer model for granule medium internal high pressure forming process may be used for the predictions and analyses of tube forming processes.

Effects of Gas Flow on Melt Cross Sections in Polymer Gas-assisted Extrusion

HUANG Yibin, YU Zhong, XIONG Aihua, ZHANG Kai

2017, 28(07): 877-881.

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For the fully gas-assisted extrusion of a polystyrene sheet, a 3D finite element model which described the gas-melt stratified flow was established with the polymer melt and low speed heated air both being considered as incompressible fluid. Numerical computations of the flows in gas-assisted channel were performed by PolyFlow solver with some FEMs such as elastic-viscous-split-stress method (EVSS), streamline-upwind (SU) method etc. The effect laws of gas flow on melt cross sections were analyzed. The results show that in the gas-assisted channels the melt is towed by gas layer. Along the gas-assisted channels, the melt velocity in extrusion direction increases, and the melt sectional area decreases, both with flow distance and gradually reach an extreme value at die exit. On the outlet plane, the melt velocity in extrusion direction increases, and the melt sectional area decreases, both with gas volume inflow rate and in an approximately linear way.

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