Table of Content

10 June 2019, Volume 30 Issue 11

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Crashworthiness Analysis of Bionic Microcircular Structures for Vehicle Crash Boxes

BAI Zhonghao;TAN Wenxiao;ZHANG Linwei;ZHOU Cunwen

2019, 30(11):  1261-1267. 

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Aiming to improve the crashworthiness of the vehicle crash boxes, a kind of bionic microcircular structure（BMS) was  studied, which was inspired by the microstructures of the beetle's elytra that might be applied to the structure design of the vehicle crash boxes. The finite element models of BMS were established, and the energy absorption characteristics of BMS and traditional rib structure(TRS) were compared and analyzed. Based on the simplified super folding element（SSFE） theory, the theoretical solutions of the average crushing forces for BMS were derived under axial loads. The research results show that compared with TRS, the energy absorption efficiency of TRS is increased more than 32.20%, and the theoretical solutions agree well with the test results.

Dynamic Prediction of Friction Torque Performance Reliability for Satellite Momentum Wheel Bearings

XIA Xintao1,2;CHEN Xiangfeng1;YE Liang3

2019, 30(11):  1268-1275. 

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Based on the gray confidence level, bootstrap-least square method and maximum entropy principle, a dynamic prediction model was established and applied to the dynamic prediction of friction torque performance reliability for the satellite momentum wheel bearings. Firstly, the original data of friction torques were grouped into samples, and the intrinsic sample was selected. Then, a new method was proposed to calculate the variation intensity of each sample by the gray confidence level, and the actual values of the reliability for each sample were obtained. The closest 5 variation intensities were integrated into the bootstrap-least square linear fitting to obtain the fitting coefficients, and then the prediction values and upper and lower intervals of the next sample variation intensity were obtained by the maximum entropy principle. By the closest 5 variation intensities continuously updated, the prediction values and upper and lower intervals of each sample reliability were obtained, and finally the dynamic predictions of friction torque performance reliability for the rolling bearings were realized. The testing results show that the reliability prediction errors are less than 4.1% under constant speed conditions and are at most 9.4% under variable speed conditions, which fully proves the feasibility and correctness of the proposed dynamic prediction model.

Dismantling Equipment Design Method Based on Function to Structure Mapping

YANG Deyu1;XU Zhigang2;SHEN Weidong1;ZHU Zhuoyue1

2019, 30(11):  1276-1286. 

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A dismantling equipment design method was proposed based on function to structure mapping according to the special requirements of dismantling objects and processes. The conceptual design processes of dismantling equipment were defined as the mapping and solution processes among requirement domain, function domain, behavior domain and structure domain. The set of requirement information for dismantling equipment design was established based on the object-oriented technology. The function set and the behavior set were constructed by using functional decomposition and integration rules of function surfaces. The requirement-function mapping model and function-structure mapping model of the dismantling equipment design processes were defined. The basic constraint matrix of structural reconstruction was generated to guide the innovative design of dismantling equipment through the hierarchical extraction, mapping and parameterization of requirement informations. And a case study of dismantling equipment design for keyboard was presented to testify the feasibility and practicability of the proposed method.

Atomization Ablation Forming Technology of Wall Slot Electrodes

SHAO Junke;KONG Linglei;QIU Mingbo;HAN Yunxiao;LIU Zhidong;TIAN Zongjun

2019, 30(11):  1287-1293. 

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In order to solve the problems of large scale of ablation particles, the chip removal difficulty and processing instability in the processes of atomizing discharge ablation forming blind holes, the forming electrodes of hollow copper pipes combined with the square copper billets were made. The simulation analyses and comparisons of the flow field and particle concentration distribution for without wall slot electrodes and with the wall slot electrodes were carried out respectively. The atomizing electrode ablation experiments were carried out based on the flow field simulation results. And the surface topographies of the workpieces machined by two type electrodes were compared and analyzed. The experimental results show that when the slot width is as 1 mm, the slope angle is as 60°, the ablation efficiency is the highest. Under the same atomization ablation processing conditions, compared with the without wall slot electrodes, the removal rate of with wall slot electrodes increases by 15.7%, the relative loss rate of with wall slot electrodes increases by 6.2%. The surface quality of the with wall slot electrodes is better than that of without wall slot electrodes. The experimental results were verified the correctness of the simulation results.

Calculation of Dynamic Stress Intensity Factors Based on XFEM Model

WANG Bisheng1;LI Yibo1,2;LIAO Yashi3;LI Jian1

2019, 30(11):  1294-1301. 

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In order to accurately calculate the stress intensity factors in the crack propagation model based on XFEM, the XFEM model of central crack plate and three-point bending were established in ABAQUS software. The stress intensity factors in the crack propagation processes were realized under mode Ⅰ and Ⅱ fracture modes respectively by using interactive integration method and user subroutine interface. The influences of mesh density and integral radius on the accuracy of stress intensity factor calculation for XFEM were studied. The research results show that when the mesh density factor is as 0.012~0.016 and the relative integral radius is as 3, the stress intensity factors converge to a stable value and the calculation errors are less than 3%. The dynamic stress intensity factors of fatigue crack growth specimens with single side hole were calculated by using the proposed method and programs. The testing results show that the errors between the residual life predicted by Paris theory and the fatigue test results are as 5.3%, which further verifies the correctness of the proposed method and programs.

Research Status of Ultra-precision Machining Technologies for Working Surfaces of Rolling Bearings#br#

WANG Xu;ZHAO Ping;LYU Binghai;YUAN Julong

2019, 30(11):  1301-1309. 

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The quality of working surfaces for rolling bearings, which consist of ring raceway surfaces and roller surfaces, possessed great influences on the accuracy and performance of bearings. The development situations and the latest research advances in ultra-precision machining technologies for the working surfaces of rolling bearings were introduced and analyzed. It provides references for further exploring the key applications on technologies such as electrolytic in-process dressing(ELID), electro-chemical grinding(ECG), dual electrolytic grinding(DEG) and force-induced rheological polishing(FRP) in bearing machining.

Study on Impact Factors of Joint Strength for Serrated Plate Connectors

CAI Junjie1,2;XU Zongzhen1,2;LIU Defeng3;LI Xin3;LIU Mabao1,4

2019, 30(11):  1310-1314,1321. 

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The joint strength and the impact factors in terms of the serrated plate connectors were researched through experiments and FEM analyses. The results indicate that for the less amount of teeth, the joint strength increases almost linearly with the rise of the tooth number. However, for the large amount of teeth, the joint strength augments slowly. Besides, the joint strength raises nearly linearly with the increases of tooth heights as well as the tooth widths. With the increasing pretension forces, the joint strength tends towards augmenting initially and then deteriorates, which implies that the proper pretension force should be selected to improve the joint strength in practical engineering.

Surface Roughness Tests of CFRP Cutting by AWJ

CHEN Zhengwen1;RUAN Xiaofeng2;ZOU Jialin2;REN Qile3;LONG Xinping2;MENG Junkun4

2019, 30(11):  1315-1321. 

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The cutting tests of CFRP were carried out by ultra-high pressure AWJ technology. Three-dimensional views of cutting fronts were reconstructed and surface roughnesses of cutting fronts were measured by μscan laser confocal microscopy. The influences of scan resolution on measurement of surface roughness and the influences of cutting speed and thickness of samples on surface roughness were studied. The testing results show that the scan resolution may have no obvious effects on the measurements of surface roughness. When the cutting depth is shallow (0~0.6 mm), which means at the entrance of cutting fronts, the surface roughness decreases with the increasing of cutting depth. When the cutting depth is deeper(deeper than 0.6 mm), the surface roughness increases with the increasing of cutting depth. Meanwhile, when the thickness of sample is constant, as the cutting speed increases, the overall trend of maximum surface roughness of cutting fronts increases. However, the influences of sample thickness on surface roughness have no obvious rules.

Effects of Channel Shape on Resistances and Flow Characteristics of Working Fluids in Piston Cooling Oil Cavities

ZHANG Liang1;YUAN Yadong1;SUN Zhiqiang1;LI Xujia1;CHEN Hemin2

2019, 30(11):  1322-1328. 

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In order to reveal the effects of channel shape on resistances and flow characteristics of working fluids in piston cooling oil cavities, a straight wall channel was changed into the wave-walled channel, and experimental studies were carried out by pressure difference and visualization methods. The experimental results of pressure difference show that the water in wave-wall channel leads to an earlier transition point of laminar flow to turbulence compared with the flow of water in straight wall channel, and the transition point is brought forward again when non-Newtonian fluid is as the working fluids instead of water. The experimental results of visualization show that the working fluid in the wave-wall channel may observe the unstable flow pattern when the Reynolds number is low. In order to further enhance the process of heat and mass transfer at low Reynolds numbers, the flow characteristics of non-Newtonian fluid in the wave-walled channel were studied under pulsating flow field by experiments and numerical simulation. The results show that the operation parameters of the pulsating flow field have significant influences on instability rate of flow for non-Newtonian in the wave-wall channel, and further impact on the mass transfer.

Redesign Priority Identification of Product Family Modules for Green Performance Optimization

LAI Rongshen1;LIN Wenguang1;WU Yongming2

2019, 30(11):  1329-1335. 

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Aiming at the redesign priority identification of modules in the greening processes of product family, a commonality index of functional modules was proposed to reflect the influences of module types on redesign priority based on the hierarchical structures of product family. A green performance evaluation model for module instances was constructed, and the green performance of module instances was calculated by using fuzzy analytic hierarchy process(FAHP) and gray relational analysis(GRA) respectively. The redesign priority was identified by the ratio of green performance evaluation index to commonality degree. And the feasibility and effectiveness of the proposed method was verified through a case study.

Sub-optimal Energy Management Strategy for Plug-in Hybrid Electric Vehicles

WU Jinjun1;YAN Bingjie2;FANG Jigen1;WANG Xifeng1;XIE Zhipeng3;SHI Yang4;LI Liang2

2019, 30(11):  1336-1342. 

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From the perspectives of practical applications, a sub-optimal energy management strategy was proposed for plug-in hybrid electric vehicles. The optimal gear positions and power distribution were obtained by using SDP. The method which combined internal constraints and external correction was proposed to solve the problems of frequent gearshift in the actual applications. And the instantaneous optimization algorithm was adopted to solve the optimal power distribution in the gear shifting processes. The research results show that compared with the traditional instantaneous optimization control strategy, the fuel economy of theproposed strategy is significantly improved.

Whole Life Cycle Assessment of Automotive Products Considering Recycling Processes

XU Jianquan1;YANG Yanping2

2019, 30(11):  1343-1351. 

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A whole life cycle material, energy consumption and emissions evaluation model of automotive products was established. The model covered the entire closed-loop life cycle stages of automotive products from material acquisition, material processing, part processing and manufacturing, vehicle assembly, operation and use until recycling. The conventional gasoline vehicles manufactured by a company and pure electric vehicles developed on the same platform were selected for comparative analysis by using the evaluation model. The results show that in comparison to the conventional gasoline vehicles, the life cycle energy consumption and the life cycle emissions of CO2, CH4, N2O and NMVOC are all lower, while the life cycle emissions of CO, SOx, NOx and PM are higher for pure electric vehicles. The life cycle impact assessments of two type vehicles were also evaluated by using the CML 2001 model. The results show that the abiotic depletion potential(ADP) of pure electric vehicles is significantly higher than that of conventional gasoline vehicles, due to more use of high scarcity metals copper and lithium on pure electric vehicles. Although pure electric vehicles performed better than conventional gasoline vehicles in terms of the global warming potential(GWP), pure electric vehicles are still inferior to conventional gasoline vehicle as far as the indices of health toxic potential, photochemical ozone creation potential and acid potential are concerned.

Operation Parameter Optimization of Packaging Production Lines under Reliability Constraints

ZHOU Hongming;PENG Jiaojiao;ZHANG Xianglei;WANG Sufen

2019, 30(11):  1352-1358. 

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The selection and optimization of operation parameters for a packaging production line were studied. According to the structural characteristics of the packaging production line, the mapping relationship between reliability and operation parameters of each coupling unit was constructed. The optimization model of operation parameters for the packaging production lines was established under reliability constraints. The effective running speed of the packaging production lines in the order cycle was taken as the optimization goal and the optimal running speed was solved by the adaptive genetic algorithm. The experimental results show that the proposed reliability modeling method is valid and practical for the operation parameter optimization of packaging production lines under reliability constraints.

Research on Laser Beam Wobble Lap Welding Processes of Stainless Steel Sheets

LI Cui 1;ZHOU Dan1;MENG Xiaoming2;YE Bing1;WANG Aihua1,3

2019, 30(11):  1359-1366,1377. 

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The lap welding processes of stainless steel sheets were studied by using fiber laser assembled with D50 wobble laser head, the influences of five laser beam wobble types on weld formations and porosities were analyzed, and the welding process parameters were optimized under the linear beam wobble mode. The research results show that compared with conventional laser welding, the five types of laser beam wobble welding may effectively increase the interface fusion width in the lap joints, and may inhibit the weld porosity. Under the linear beam wobble mode, both of the weld penetration and interface fusion widths increase with increasing welding powers or reducing welding speeds, the weld penetration decreases with increasing wobble frequencies. With the increasing of wobble amplitude, the cross section shapes of lap welding joints change from T-shaped, oval-shape to trapezoid-shape. A good lap welding joint with low porosity and high shear strength may be obtained under the parameters where the laser power, welding speed, defocusing distance, wobble amplitude and wobble frequency are as 3 kW, 2.4 m/min, 5 mm, 1.5 mm and 300 Hz respectively.

Analysis of Forming Performances for AA6061 Extruded Tubes Based on 3D Forming Limit Stress Diagram

ZHU Liangjin;CHEN Mengjie;WANG Wei;DU Fei;DONG Guojiang

2019, 30(11):  1367-1377. 

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To solve the problems of poor forming performances for AA6061 extruded tubes, a new forming process including solution water quenching, granular medium bulging and artificial aging treatment were established for aluminum alloy tubes . The influences of solution water quenching and artificial aging treatment on the properties of the materials were studied. And considering the through thickness normal stresss, a three-dimensional forming limit stress diagram(3D-FLSD) was established. Meanwhile, the finite element simulation model of tube granular medium bulging was established to analyze the deformation trajectories and stress-strain states of the points and predict the rupture points and bulging limits of tubes by theoretical forming limit diagram. The bulging process experimental results of square section tube parts show that the combination of granule medium bulging and reasonable heat treatment may effectively solve the forming problems of the AA6061 extruded tubes. And 3D-FLSD considering the through thickness normal stresses may be used as the criterion for judging the fracture and instability of aluminum alloy tubes when formulating the bulging processes.


Research Advances in Evaluation and Prediction Method of Thermal Fatigue Life for Hot-working Dies

SU Nan;CHEN Minghe

2019, 30(11):  1378-1385. 

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Due to the cyclic changes of temperature and mechanical loading during hot-working processes, the deformations and failure mechanism of hot-working dies were complex, so the thermal fatigue life of hot-working dies was difficult to be evaluated and predicted in the applications of dies. Combined with the existing research results，the methods for evaluating and predicting the thermal fatigue life of hot-working dies were introduced动者in the studies of thermal stress fatigue. The thermal-mechancial fatigue life of hot-working dies was studied from two perspectives of phenomenological life model and damage cumulative model respectively. And the development trends of thermal fatigue life prediction for hot-working dies were prospected.