China Mechanical Engineering

Design Knowledge Services via Internet——An Analysis on the Functions of China Knowledge Center for Engineering Sciences and Technology（CKCEST）

XIE Youbai1,2

2017, 28(06): 631-641.

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Driving by the slogan “massive innovation”, the websites related to knowledge services appeared as the bamboo shoots after a spring rain. As the innovation could not be successive without a correct design and a correct design could not do without a rich knowledge supplies, most of them had some misunderstandings in the services they were dealt with. What they provided for design could not support the competition of design directly and did not benefit the high efficient utility of knowledges in design. From the basic laws of design knowledges in design science together with the services provided by the CKCEST as examples, the special needs of knowledge services via internet for design were analyzed, the way out from the misunderstandings was discussed and several cases completed by the author and his teams in the past 20 years were given for illustrations herein.

Research on Optimal Dressing Parameters for Wheel Linear Dressing of Double Disc Grinding

ZHOU Zhixiong, XIE Shen, SHU Yang, XU Shixiong, PENG Guanqing, TANG Xiangping

2017, 28(06): 641-647.

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The relevant design parameters of the wheel linear trim was analyzed and determined according to the principles of double disc grinding. Regarding the grinding wheel end surface topography as the research projects, some grinding zone geometry equations were established, calculated and analyzed to get the height curve of upper and lower wheel end surface on the workpiece geometric center trajectory. And then in order to obtain the ideal grinding wheel end surface geometric shape in the grinding zone, optimal dressing parameters of fixed trim and interpolation trim were determined respectively. These may improve the workpiece machining accuracy, accuracy consistency and reduce surface roughness.

Influences of Limbs' Gravity on Force Analyses of Statically Indeterminate Structures

LIU Wenlan, XU Yundou, YAN Wennan, YAO Jiantao, ZHAO Yongsheng,

2017, 28(06): 648-655.

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In view of the facts that the literatures about force analyses of the statically indeterminate structures almost had not considered limb's gravity at present, a method was proposed, which took it into account. Firstly, the constraint force components perpendicular to the axis of each limb which were caused by the corresponding limbs' gravity were solved based on single limb's torque equilibrium equations, and it was regarded as the generalized force imposed on the whole structure. Then, according to the force equilibrium equations and deformation compatibility conditions of the whole structure, the analytical expressions were derived including the limbs' axial constraint force components and the assembly internal forces brought by manufacturing errors. Finally, the influences of limbs' gravity on the force analysis of the statically indeterminate structures were discussed. Taking the planar mechanism 3-RR and the spatial mechanism 7-SS as examples, the constraint forces were analyzed and the rigid-flexible mixed models of the two mechanisms were established. Based on the models the theoretical results were verified.

Modeling and Control of Jetting Dispensing Processes in Microelectronics Packaging

TAN Fang, SHAN Xiuyang

2017, 28(06): 656-660,668.

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To solve the problems of consistency of jetting dispensing systems, a Run by Run PI control method was proposed, which was based on the drop volume estimation model. The rheological behavior of fluid was analyzed. Based on the empirical equation between shear stress and shear rate, the flow rate of jetting dispensing processes was established to derive the volume estimation model. To achieve the consistency control in jetting dispensing systems, the Run by Run PI controller was designed based on the volume estimation model. The simulation and experimental results verify the reliability of the model and demonstrate that the proposed control method may improve the consistency of jetting dispensing systems effectively.

Effects of Spool Structure on Droplet Characteristics of Two-fluid Spray

YANG Chao, CHEN Bo, JIANG Wanlu, GAO Dianrong

2017, 28(06): 661-668.

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In order to study the effects of spool structure on droplet characteristics of two-fluid spray and improve the spray effects, the droplet diameters, droplet axial velocities and droplet numbers of two-fluid spray under different spool structures were measured with phase Doppler particle analyzer(PDPA). According to the test results, the droplet characteristics were analyzed and discussed systematically. The test results indicate that spool structures have a great influence on droplet characteristics. With the axial distance increase, the Sauter mean diameter(SMD) and the arithmetic mean diameter(AMD) of droplet increase first and then remain constant, the droplet axial velocity and turbulent fluctuation velocity decrease, the droplet numbers increase first and then decrease. With the air-water pressure ratio increase, SMD increases first and then decreases, but AMD, droplet axial velocity and droplet numbers decrease. Moreover, the decrease of throat diameter and outlet diameter of spool structure are benefit for improving the spray effectiveness, but it is disadvantage to the stability of speed. It has a good spray effectiveness when the throat diametera is as 1.5mm and the spool outlet diameter is as 2.5mm. Compared with the original spool structure， the droplet numbers and droplet axial velocity increase by 82.43% and 22.31%, the SMD and AMD decrease by 52.18% and 21.47% respectively, the comprehensive spray effectiveness has a great improvement.

Variable Filter Radius Sensitivity Filtering Method Considering Density Compensation

CHEN Chuifu, YANG Xiaoxiang

2017, 28(06): 669-675.

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Constant filter radius sensitivity filtering method could effectively eliminate checkerboard patter and mesh dependence, the optimized results had boundary diffusion, the edges of the graph existed many gray-scale elements.A considering density compensation variable filter radius sensitivity filtering method was proposed as an efficient approach,compensated the elements of relative density in 0.5-1, and reduced element density value in 0-0.5, and gradually reduced the filter radius to 1. Combining the solid isotropic microstructure with penalization model（SIMP）, the classical topology optimization problems were used to prove the superiority of the new method.The experimental results show that the new sensitivity filtering method may eliminate checkerboard patter and mesh independence,then the optimized results have clear boundary, and the optimization efficiency and optimization performance are improved significantly.

Research on Transmission Errors of Closed Loop Gear Transmission Systems

LEI Xianqing, MENG Qi, MA Wensuo, YANG Kelin

2017, 28(06): 675-682.

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A formula among gear transmission errors and time were established by using the theory of equivalent mesh errors. The rules of transmission errors with time were researched. The correctness of the rules of transmission errors with time was verified by using the Monte-Carlo method. According to the angular frequency characteristics of closed loop gear transmission systems, the relation between the gear initial phase errors and transmission errors, and the synchronicity of two branch transmission errors were studied. A coupling model between the synchronous transmission errors and the gear transmission errors was established. The measures for reducing the synchronous transmission error was put forward. Examples show that the measures may improve transmission stability of the closed loop gear transmission systems effectively.

A New Surface Hybrid Mesh Generation Method Based on Subdomain Decomposition

WANG Pan, HAN Lei, JU Chuanming, CHI Baotao, ZHANG Jianming

2017, 28(06): 683-688.

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A new hybrid mesh generation method was proposed based on subdomain decomposition. First, the structured background meshes were generated by mapping method and the locations of small features such as hole and keyway were determined. Then, the meshes which covered by small features were eliminated from background meshes, and unstructured triangular meshes were generated in this region. Finally, the meshes of target domain were obtained by combining the background meshes and the unstructured triangular meshes. It is capable of preserving the advantages of mapping's high efficiency and high quality of the meshes, high computational accuracy of quadrangle meshes and the powerful geometric adaptive capacity of triangle meshes. Numerical experiments show that the proposed method may generate high quality hybrid meshes for complex surfaces automatically, the quality of resulting meshes and the algorithm efficiency are superior to traditional methods such as advancing front method and paving.

Modeling of Multi-dimensional Correlation Function and Its Applications for Low Carbon Case Retrieval

HONG Huanhuan, ZHAO Yanwei, CHEN Weigang

2017, 28(06): 688-694.

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To solve problems of multidimensional case retrieval modeling and its dimensionality reduction calculation for low carbon design, a modeling and application method of multi-dimensional correlation function was proposed. Firstly, an improved side distance method was developed through the principles of variable slope, which provided the basis for developing a multi-dimensional side distance model. Secondly, because side distance formula could not give out the accurate distance values between design parameters and its optimal, a multi-dimensional correlation function which had good dimension reduction effect was established. Then a retrieval method was given based on the multi-dimensional correlation function. Finally, the proposed method and algorithms were verified in the design of a screw air compressor. The evaluation results show that the improved side distance is correct and effective, the dimension reduction method for the multi-dimensional correlation function is fast and viable, and the otherness among these cases is very obvious.

Defect Detection for PCBs Based on Gradient Direction Information Entropy

LI Yunfeng, LI Shengyang,

2017, 28(06): 695-701.

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Aiming at real-time visual inspections of PCB defects, a defect detection algorithm was proposed herein for applying to PCB color image. The typical image features were obtained by analyzing the gradient direction information of the edge pixels in the defect regions. The algorithm consisted of three parts in detail, which were de-noising, target segmentation and feature extraction. Firstly, bilateral filtering in CIE Lab color space was used to reduce the interference of ambient light and ensure the clarity of the edge details; then the uniformity of this color space was used to segment the target areas which needed to be detected; lastly, the neighborhood gradient orientation information entropy was designed as a descriptor for defect feature extraction and feature vector construction, then support vector machine was used to identify defects. Experimental results show that: the new algorithm is able to locate the common defects existing in PCBs rapidly and accurately such as short circuit, open circuit, empty cavity, copper residue, scratch etc. which may meet the real-time detection requirements in production processes.

A Damage Identification Method of a Breathing Cracked Beam by Natural Frequency

LIU Wenguang, GUO Longqing, HE Honglin, YAN Long

2017, 28(06): 702-707,713.

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Firstly, a cracked cantilever beam was simplified into two elastic beams connected by a torsion spring. It was supposed that the vibration response varied as the vibration amplitude of the beam. And the natural frequency equation of a breathing cracked beam was derived. Then, the open and close conditions of the breathing crack during vibrations were considered. A polynomial stiffness model of the breathing cracked beam was built up by the postulation that the stiffness of the cracked beam was one of nonlinear functions of the vibration amplitudes. Thereafter, a damage identification method of a breathing cracked beam by natural frequency was proposed combined with the natural frequency equation and the stiffness model. The feasibility and effectiveness of this method was verified by case studies in the end. Results indicate that the identification precision of this method depends on the testing precision of the experimental natural frequency.

Muscle Degree of Comfort Assessment Rule Based on sEMG

ZHANG Lizhen, SHAO Qi, YANG Jiaqing, YANG Mengmeng, TAO Ningrong, SONG Zheng, DAI Peng

2017, 28(06): 708-713.

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In order to avoid poor posture of long time, the five joints of human were selected for the motion experiments. The sEMG experiments were conducted for muscles that played a main role to motion variations. The sEMG signal differences of different subjects were eliminated by maximum voluntary contraction method, and the EMG percentage values were conducted by normalization and weighted average method. According to the physiological cross-sectional area of muscles involved in action variations, the calculation method of composite motion muscle degree of comfort index was given, and the muscle degree of comfort assessment rules were put forward based on the sEMG. Compared with RULA analysis in DELMIA, the analysis results show that the assessment rules are feasible and suitable for the assessment of staff postures.

Bearing Health Monitoring Based on Ordinal Pattern Dissimilarity Analysis

JIANG Guoqian, XIE Ping, WANG Xiao, HE Qun, LI Jimeng

2017, 28(06): 714-720,727.

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Ordinal pattern analysis might map one-dimensional vibration time series into probability distribution of ordinal patterns in the high-dimensional phase space, and then reveal the internal tiny variations in ordinal pattern structures. It provided a new research view for the weak vibration signal feature extraction. A new monitoring indicator named ordinal information divergence was proposed herein based on ordinal pattern analysis and information divergence, to quantitatively describe the ordinal pattern distribution difference of vibration signals in the high-dimensional phase space between the current status and the reference health status. Two experiments, including the damage degree assessment of bearing inner race and the run-to-failure bearing degradation trend analysis, were used to validate the effectiveness of the proposed new indicator. The comparative studies were performed with the traditional statistics and several existing nonlinear indicators including wavelet entropy, approximate entropy and permutation entropy. Experimental results demonstrate that the proposed new indicator presents better quantitative ability for different damage degrees and is more sensitive to the incipient fault and more stable and efficient in computation, thus easy to implement in engineering applications.

Image Matching Algorithm of Release Valve Bonnet Based on Contours Reconstructed by Oriented Line Segments and Pairwise Geometrical Histogram

ZHAO Daxing, WANG Bo, ZHOU Weiti, SUN Guodong

2017, 28(06): 721-727.

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For the missing faults of release valve bonnets in freight cars, an image matching algorithm was proposed herein based on contour reconstructed by oriented line segment and pairwise geometrical histogram. Firstly, the location of initial sampling point was defined by maximum chord length and polar radius, then the contour was dynamically and hierarchically sampled according to an evaluation mechanism of local curvatures. Then adjacent sample points were lined in counter-clockwise order, oriented relative angles and normalized equivalent distances between pairwise oriented line segment were calculated as the dual descriptors, which were counted into the two dimensional histogram. Finally the similarity between histograms was measured by Bhattacharyya distance. The experimental results show that the algorithm may keep robust under the circumstances of rotations, scales and translations, meanwhile the detection efficiency is also well ensured, which may satisfy the instantaneity of the detection on freight cars.

Structural Design and Dynamic Simulation of a General Profile Electric Scroll Compressor

WANG Licun, DONG Guanghui, WANG Xudong, AO Wengang,

2017, 28(06): 728-733.

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A parametric model of tangential coefficient was built based on characteristics of general scroll profiles. To study the dynamics characteristics of the scroll compressors for electric vehicles, a model of anti-rotation mechanism of cylindrical pin anti-rotation structure was established. On the basis of operational principles of anti-rotation mechanism of cylindrical pin, the forces acted on the cylindrical pins were analyzed with kinematics and the mechanisms. UG was used to design three-dimensional models of the scroll plate and other parts, and a virtual prototype model was established. By the kinematics simulation of the scroll compressor the accurate curves of kinematics parameters were obtained. It may ensure the accuracy and reliability of the cylindrical pin anti-rotation structurs.

Modeling and Control of Rapid Deposition for Functionally Gradient Material Components

JIAO Pande, LI Shujuan, YANG Leipeng, YAN Cunfu

2017, 28(06): 733-738.

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A new additive manufacturing equipment built on engraving machine was developed for the manufacture of FGM components, which extrudes two water-based materials in a certain proportion belowed the temperature of water solidification point. In the deposition processes of three-dimensional parts, the agglomeration and bubbles will inevitably exist in the configuration of the materials. When the release of the bubbles and the decomposition of agglomeration, the extrusion force of deposition processes was changed at any time , the deposition processes were unstable and the quality of deposited parts was hardly guaranteed. Analyzing the various process parameters and disturbances affected on the deposition processes of gradient material components, based on the plentiful experiments, this paper constructed the dynamic model of the deposition processes and the recursive least squares method was used to complete system identification. To test the feasibility of the FGM rapidly deposited and the validity of controller, two different colored Calcium carbonates(CaCO3) were tested.

Deformation Behavior and Numerical Simulation of a Casting AM80 Magnesium Alloy under High Strain Rate Loading

GUO Pengcheng, YE Tuo, CAO Shufen, XU Congchang, LI Luoxing,

2017, 28(06): 739-743.

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The compression deformation behaviors of a solution treated AM80 magnesium alloy were investigated with strain rates of 0.0001s-1, 800s-1, 1050s-1, 1600s-1, 1850s-1 and 2100s-1 respectively using a INSTRON universal compression machine and a split Hopkinson pressure bar(SHPB) apparatus. The results show that the flow stress of the studied AM80 magnesium alloy increase with increasing strain rate as strain rate ε˙≤ 1850s-1, demonstrating a visible positive strain rate sensitivity. However, the flow stress decreases slightly as strain rate reaches to 2100s-1, which is attributed to the effects of local temperature rise promoting the dislocation slip and finally the flow stress decreases slightly. The Johnson-Cook model was employed in characterizing the effects of strain rate on mechanical behaviors of the alloy and the material strain rate hardening parameters were taken as a function of strain rates. The results show that the constitutive equation is in good agreement with the experimental ones. Furthermore, the neglects of local temperature rises under high strain rate loading, lead a good agreement to the experimental results at low and medium strains, and a obviously differences will be appeared at high strains for the numerical simulation flow stresses by using ABAQUS software.

Control Tactics Modeling of Electric Vehicle Permanent Magnet Brushless Wheel Motors

ZHENG Shuqin, LONG Jiangqi

2017, 28(06): 744-749,755.

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According to the independent control problems of wheel motor, the wheel motor basic structures and styles were analyzed, and dynamics model without reduction mechanisms was built and the electromagnetic torque control methods of wheel motor were discussed. The electromagnetic torque control tactics, wheel motor direct torque control model, vehicle simulation model and ground input model were set up based on theoretic analyses. Wheel motor slip rates and wheel speed differences were researched under different loads and objective torque inputs, and a favorable breaking method was chosen by compare motor stator and rotor gap deformations. The simulation and tests indicate that torque control method have high control precision, rapid response characteristics, and electric vehicle has good handling and stability.

Vehicle State Estimation Based on Combined RLS and FAEKF

WANG Yan, WEI Minxiang, ZHAO Wanzhong, ZHANG Fengjiao, YAN Mingyue

2017, 28(06): 750-755.

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For the problems of observation noise time-varying characteristics and model parameter variations in vehicle state estimation, a new algorithm which consisted of RLS method and FAEKF was proposed. The new algorithm was proposed based on 3-DOF nonlinear vehicle dynamics model in order to realize real time update of model parameters and observation noises. Firstly, the total mass of the vehicle was estimated by RLS. Then, a fuzzy controller was established to track the observation noises of extended Kalman filters. Finally, the algorithm was verified using CarSim and MATLAB/Simulink. Results show that the estimation accuracy of the new algorithm is higher than that of the traditional extended Kalman filter. It may provide theoretical support for the development of automobile active control systems.

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