Table of Content

25 November 2019, Volume 30 Issue 22

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Contact Stress Analysis of Functionally Graded Elastic Thin Layers with In-plane Variation of Modulus

JIN Mingsheng;KANG Jie;DONG Xiaoxing;WANG Liming;JI Shiming

2019, 30(22):  2647-2654. 

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To attain the requirements for uniform removal of materials, a new processing method was proposed based on functionally graded lapping and polishing plate. Also, the contact stress of functionally graded elastic thin layers with in-plane variation of modulus was studied. Firstly, the frictionless contact stress equation of functionally graded elastic thin layers was derived by semi-inverse method, and the compensation function was introduced to compensate the effects of plane displacement, which simplified the analytical processes. Then, the frictionless contact model of functionally graded lapping and polishing plate was established by ANSYS, the equivalent stress distribution on the specimen surface under displacement loading was obtained. By fitting with the stress equation, the analytical formula of stress prediction equation and the corresponding compensation function were obtained. Finally, a experimental platform was established and the experimental and predicted values were compared. The results show that the errors are within 10%, which verifies the correctness of the analytical formula of contact stress prediction equation.

In-situ Drilling Temperature Measurement of Multilayer PCB Using Thin Film Thermocouple

CUI Yunxian1;MU Yu1;WANG Chengyong2;ZHENG Lijuan2;YIN Junwei1;XUE Shengjun1

2019, 30(22):  2655-2660. 

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Aiming at the technical problems that it were difficult to measure drilling temperature accurately in the processes of the industrial PCB drilling, a method was proposed based on thin film thermocouple sensor to measure the in-situ drilling temperatures of each layer during PCB drilling processes. The drilling processes of PCB were modeled and simulated by method of layered material modeling according to cross-section structures of PCB. The distribution and variations of PCB drilling temperatures during the drilling processes were clarified. The sensor optimum coating positions were the vertical bottoms of the bit feed directions. Thin film thermocouple sensors were deposited on different PCB layers by DC pulsed magnetron sputtering. The static and dynamic performances of the sensors were studied. Results show that the Seebeck coefficient of the temperature sensor is as 37.4 μV/℃ in the range of 30~200 ℃. The non-linear error is less than 0.65%. The dynamic response time is as 0.095 ms.Several groups of drilling temperature measurements were carried out on different PCB layers. Results show that the maximum drilling temperatures of 4 layers, 12 layers and 20 layers during drilling processes are 49.30 ℃, 53.90 ℃ and 63.90 ℃ respectively. The temperature of each group of repeated experiments is stablize, and the errors are less than 0.8 ℃. In summary, the method provides a reference for improving PCB high speed drilling processes.

Universal Model and Applications of Generalized Logarithmic Helix on Surface Grooves

JIANG Jinbo;XU Qichao;CHEN Yuan;ZHAO Wenjing;PENG Xudong

2019, 30(22):  2661-2667. 

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To solve the problems of limitation of classic molded lins shape modification in molded lines design of gas/liquid-lubricated surface grooves, a universal mathematical model of generalized logarithmic helix was derived from equation of typical logarithmic spiral line. The expressions of generalized helix of several typical molded lines such as oblique line, arc line, parabola, and ellipse line were obtained, and evolution rule and geometry commonalities of generalized logarithmic helix at different parameters were studied. Taking gas thrust bearing as an example, the influences of distribution law and variation amplitude of generalized spiral angle on load-carrying capacity of gas thrust bearings at high speed were analyzed. The results show that generalized logarithmic helix has stronger geometrical characterization ability compared to typical molded lines, and the generalized logarithmic helix groove surface has the largest load-carrying capacity.

Hierarchy Growth Method for Optimal Design of Branching Heat Transfer Structures

XIONG Min;DING Xiaohong;JI Yidong;MENG Fanzhen

2019, 30(22):  2668-2674. 

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To design heat transfer structures for high heat flux electronic components with small space, reasonable heat transfer channel layout was the most effective approach. Aiming at the complex geometry boundaries and difficult-to-manufacture for heat transfer structures designed by topology optimization, a hierarchy growth method for optimal design of branching heat transfer structure inspired by hierarchical characteristics of natural vein branching system was suggested. Different growth control criteria were adopted for principal channels and lateral channels, which grew in succession to form heat transfer structures. Specifically, space colonization algorithm with temperature information was applied to the growth of principal channels, and the law of minimal thermal resistance was applied to control the growth of lateral channels. Several typical 2D or 3D design problems were studied by the suggested method, and the design results were compared with those of SIMP method. The results show that the heat transfer structure by hierarchy growth method has simple and clear geometry boundary, no tiny channel and gray element, therefore it is easy to be manufactured, and has good thermal performance.

Modeling Analysis of Load Measurement Errors and Optimal Design of Test Fixtures for High Frequency Resonant Fatigue Machines

GAO Hongli;ZHU Kaiyong;GONG Ao;JIANG Wei

2019, 30(22):  2675-2682. 

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High precision measurement and control of dynamic forces in the electromagnetic resonance fatigue crack growth test processes were important premises to ensure the accuracy of test results and the stability of the system. Fixtures were the important mechanisms for clamping specimen and transferring force, so it is particularly important to optimize the fixture structures. A compact tensile specimen connection stiffness model and a three-degree-of-freedom with damping vibration system dynamical model were established, and the theoretical equation of dynamic force measurement errors was obtained. Influences of fixture stiffness on the dynamic force measurement errors were analyzed. Accordingly, different structure stiffness fixtures were designed, and the stiffness of the fixtures was calculated by the finite element method. The influence results of different structural fixtures on the dynamic force measurement errors were obtained. Rationality of the optimal fixture design was verified by the experiments.

Rock Breaking Characteristics of a Single Cone-PDC Combined Drill Bit in Hard Formation

LI Qin;FU Wentao;HUANG Zhiqiang;MA Yachao;XIE Dou

2019, 30(22):  2683-2690. 

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A new single cone-PDC combined drill bit was put forward, which relied on a single cone broken rock drilling so as to release ground stresses, thus resulting in rock damage, and then help promote the PDC bit cut rock breaking.The nonlinear dynamics models of rock breaking of combined drill bit, two-stage PDC bit and conventional PDC bit were established by finite element method.By describing the D-P criterion of rock constitutive relation and determining the criterion of rock breakage, the rock breaking mechanism of expanding combined drill bit drilling in hard formation was analyzed, and the comparative study of the dynamic rock breaking processes of 3 drill bits was carried out.The results show that the rock stresses of bottom well wall of expanding combined drill bit are obviously released, which greatly improves the drilling ability of rock formation.Rock breaking under tensile stress is the main reason of expanding combined drill bit enhancing the drilling speed greatly in hard formation.The torsional vibration of expanding combined drill bit is greatly reduced during drilling in hard formation, which leads to higher rock-breaking efficiency and longer life of drill bit.As a result of the effects of single cone collar breaking the rock, the rock burst ability of expanding combined drill bit to the bottom of hole is greater, and the drilling is faster in hard formation.The results provide a reference for the research of new types of singlecone-PDC combined drill bit.

Optimization Analysis of O-ring Installation Structures with Installation Processes

CAI Zhiyuan1;WANG Bingqing1;PENG Xudong1,2;MENG Xiangkai1,2

2019, 30(22):  2691-2697. 

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A two-dimensional axisymmetric geometrical model of reciprocating O-ring seals was established by applying the ANSYS software, which was used to predict the statics sealing behavior of O-rings during actual installation. The influences of operating parameters and installation structure parameters of axial end on the maximum von Mises stress and XY shear stress of the seal were analyzed, and the optimal value of the installation structure parameters of axial end for ensuring the reliable installation processes of the sealing ring was given. The results indicate that during the seal installation, when the sealing ring is in contact with the inner rounded corner of the lead angle, the von Mises stress and the XY shear stress of the sealing ring are the largest, and all occurs at the inside of the seal near the air side. Reducing the contact friction coefficient of friction pair, making the angle of the inner end more than 3 mm and choosing the angle reasonably are beneficial to reduce the risk of damage to the sealing ring installation, which is in good agreement with the actual engineering experience.

Robust Switched Control Strategy of Large Erecting Equipment Hydraulic Systems

YANG Jun1;HUANG Shuzhou1;ZENG Le2

2019, 30(22):  2698-2703. 

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Aimed at high energy loss of large erecting equipment due to supply pressure unmatched with load characteristics, the load characteristics were analyzed, which was approximately equivalent to initial-middle-final three-segment broken line load. In initial stage of erection, constant high pressure was used to provide sufficient driving force; in middle stage, pressure decreases linearly and monotonously with the erection angle to reduce energy consumption of the system; in final stage, constant low pressure was used to maintain erection stability. The switching control strategy may match the oil supply pressure with approximate external loads and reduce energy consumption. Aiming at the problems that the switching of supply pressure might lead to vibration and instability in erection processes, a mathematical model of hydraulic system was built, and a robust control strategy was proposed. Experimental and simulation results show that the erecting processes are smooth, stable and not overshoot. The temperature of the oil is reduced about 40℃ compare with the throttle control, which shows the system and robust switched control strategy may save energy effectively.

Vibration Performance on Novel Inertia Cone Crushers

REN Tingzhi;HUANG Kaifeng;CHENG Jiayuan;ZHANG Zilong;JIN Xin

2019, 30(22):  2704-2708. 

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A new type of inertia cone crusher with less vibration and more reduction ratio was designed by using a spatial linkage. When the main exciter and the secondary exciter were simultaneously driven by the motor, a pair of inertial force with opposite phase and same magnitude was generated to achieve the purpose of balancing the unbalanced inertial forces generated during working processes. The inertia force produced by the secondary exciter was fed back to the crushing shaft through the links to gain crushing forces and crushing effects. In order to verify the efficiency of the inertia cone crusher proposed herein, the crushing products and horizontal vibrations were compared with that from the most wildly used inertia cone crushers by experimental and theoretical analysis.

Flank Modification Method of Hypoid Gears with Ease-off Topology Correction

NIE Shaowu1,2;JIANG Chuang2;DENG Xiaozhong2;SU Jianxin2;YANG Jianjun1;WANG Jianhua3

2019, 30(22):  2709-2715,2740. 

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In order to improve meshing performance of drive bridge hypoid gears, a kind of Ease-off topology modification method was proposed for hypoid gears with HFT method. On the basis of establishing conjugate mesh mathematical model, the pinion base tooth flank equation was derived by means of calculating the deviations between the pinion actual tooth flank and pinion base tooth flank, and the Ease-off topology was constructed. The Ease-off topology was decomposed by means of second-order surface approximation, and the tooth flank mismatch factors were calculated, and the modified Ease-off topology was established after correcting mismatch factors. After comparing the current Ease-off topology and the modified Ease-off topology and correcting the deviations between the pinion current flank and the pinion modified flank, the pinion correction processing parameters were obtained. Finally, taking a pair of hypoid gear for example, the flank topology modification and grinding experiments were executed, and the validity of tooth flank topology modification was verified because of the real contact pattern coinciding with the meshing simulation results. The load tooth contact analysis results indicate that the modified tooth flank contact stress distribution is improved and the actual tooth contact ratios under loads are increased, so the validity of modification project is verified.

Control Chart Pattern Recognition Based on Hybrid Model and Improved Multi-classification Mahalanobis-Taguchi System

ZHAN Jun1;CHENG Longsheng1;PENG Zhaiming1;HU Duohai2

2019, 30(22):  2716-2724. 

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In order to improve intelligent monitoring level of product quality during the production, time series hybrid model and improved multi-classification Mahalanobis-Taguchi system were proposed to construct control chart pattern recognition algorithm. Firstly, time series hybrid model was applied to extract features for the control chart real-time data. Secondly, threshold calculation method was improved and multi-classification's discriminant was defined. Improved multi-classification Mahalanobis-Taguchi system was applied to reduce the dimension of features and recognize control chart patterns. Finally, to verify the validity of the algorithm, the public control chart dataset and manufacture cases were tested and the results were compared with other algorithms. Results indicate that an algorithm that is based on time series hybrid model and improved multi-classification Mahalanobis-Taguchi system may yield several successes including higher accuracy and simplify recognition system. Therefore, it is an effective method of control chart pattern recognition.

Key Deviation Source Diagnosis for Aircraft Structural Component Assembly Driven by Small Sample Inspection Data

ZHU Yongguo1;DENG Bin1;HUO Zhengshu1; ZHOU Jiehua2

2019, 30(22):  2725-2733. 

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There were many transitive relationships among aircraft structural component assembly quality and the deviation sources such as nonlinearity, multilevel strong coupling and large uncertainty, which could not be directly built to identify the key deviation sources using the equation of assembly dimension chain. Thus, the measurement information theory was introduced, and a key deviation source diagnosis was presented for aircraft structural component assembly driven by small sample inspection data based on the integrated use of the entropy weight method and the synthetic grey correlation. Firstly, the potential informations were mined from assembly quality inspection data and entropy method was used to measure assembly quality attribute differences. Secondly, the correlation between each deviation source and the assembly quality was quantized by the synthetic grey correlation. Thirdly, the synthetic grey correlation between each deviation sources and assembly quality was modified by the weight of assembly quality attribute. Finally, according to the modified correlation, each deviation source was sorted to determine the key deviation source which affected assembly quality quantitatively. The case of assembly application verifies the accuracy and computational feasibility of the key deviation source diagnosis method based on entropy method and synthetic grey correlation.

Research and Design of AGVs Based on Inertial and Visual Composite Navigation

XIAO Xianqiang1;CHENG Yabing2;WANG Jiaen1

2019, 30(22):  2734-2740. 

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As an important material handling equipment in intelligent manufacturing, AGV’s navigation and positioning accuracy and flexible path configuration performance restricted the applications in intelligent manufacturing. Aiming at this problem, an AGV integrated navigation method was proposed herein based on inertia and vision, which made use of the complementary advantages of the two navigation technologies to achieve high-precision navigation and positioning, and improved the adaptability of AGV to the working environments and navigation reliability. On the basis of this, the AGV working grid map was constructed by a two-dimensional code label, and the grid map was used to realize the flexible configuration of the AGV driving paths. The test results show that the composite navigation method designed may realize the navigation and positioning accuracy of longitudinal 5mm, lateral 10mm, and directional deviation 1°.

Trajectory Tracking Control of Eight-DOF Manipulators

QIN Yanming;ZHAO Jingyi;MA Jinyu;WANG Jianjun

2019, 30(22):  2741-2747,2756. 

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The uncertainty and disturbance of the whole system were observed by the extended state observer for the mechanical electro-hydraulic servo system. Then, a cascade ADRC was designed. The observation matrix and control matrix of the system were obtained based on the linear matrix inequality, and the stability of the closed-loop system was analyzed and proved by Lyapunov stability theory. Based on the actual parameters, the simulation was carried out by MATLAB software. The numerical simulation results show the effectiveness of the proposed method. The comparison with the traditional feed-forward PID algorithm shows the superiority of the designed method. Finally, the feasibility of the proposed controller was verified by experiments.

Research on Overall Accuracy of SPIF Parts

BAI Lang;LI Yan;YANG Mingshun;LIN Yunbo;ZHAO Renfeng;YUAN Qilong

2019, 30(22):  2748-2756. 

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A typical truncated cone was taken as the research object. Based on the deformation mechanism, the causes and main influencing factors of the overall accuracy were analyzed. Then, using the Box-Behnken design (BBD), four-factor three-level response surface experiment was designed for the tool head diameters, layer spacing, sheet thicknesses and forming angles. The second order model of geometric errors in two directions was established. According to the response model, the single and interaction laws of the process parameters on the accuracy in horizontal and vertical directions were obtained. Finally, the response model was used to synchronously minimize the geometric errors of the two directions. The process parameter combination was obtained when the overall accuracy is optimal: the tool head diameter is as 6 mm, the layer spacing is as 0.5 mm, the plate thickness is as 1 mm, and the forming angle is as 45 °. Under these conditions, the geometric errors in two directions are as 1.9146 mm and -0.157 mm respectively. The process optimization and robust control of the overall accuracy of the parts are realized.

ECT Method for Wire Breakage Defects in Wire Ropes

YU Xiaojie1;LI Xudong1;XIE Shejuan1;LI Peng2;WANG Hao2,3;CHEN Zhenmao1

2019, 30(22):  2757-2763. 

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A new type of ECT probe was designed, which mainly induced eddy currents in axial direction of wire ropes. To prove the feasibility, a finite element method code of reduced vector potential formulation (Ar method) was applied to simulate ECT signals due to different defects and probe geometries. Based on the numerical results, an ECT probe was designed and fabricated and the efficiency for inspection of wire ropes was demonstrated through experiments with test-piece of simulated and practical wire ropes. Both the numerical and experimental results reveal that the developed probe can detect the wire breakages in wire ropes efficiently.

Experimental Study on Wear of Middle Plates under Multi Factor Interactions Based on Response Surface Method

LI Bo1,2;XIA Rui1;WANG Xuewen1;YANG Zhaojian1;XI Qingxiang2

2019, 30(22):  2764-2771. 

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In order to confirm the main factors affecting wear of middle plates and interaction relationship, the wear factors were analyzed through wear test based on response surface method with the wear loss as response values. The Plackett-Burman test was used to screen the main factors from the six wear factors. Results show that water content, gangue content and normal load have significant effects on wear loss. According to the results of central composite design (CCD) test, the second-order regression model was established based on the wear loss and significant factors. Response surface analyses show that the water content of bulk materials is the key factor affecting wear. The regression model was optimized to obtain a significant prediction model of wear. The results show that there is no significant difference between the prediction model and the real test (P> 0.05), which indicates that the response surface method is feasible to study the interaction of multiple factors in chute wear.