China Mechanical Engineering

Laser Cleaning of Titanium Alloy and Its Effect on Laser Welding Porosity

CHEN Jiunnhorng1;WEN Peng1,2;CHANG Baohua1,2;SHAN Jiguo1,2;DU Dong1,2;CHENG Hao3

2020, 31(04): 379-383.

Asbtract ( )

HTML

PDF (4946KB) ( )

References | Related Articles | Metrics

Different methods such as sandpaper polishing, pickling, and laser cleaning were used to clean the surface of Ti6Al4V plates before welding. Surface morphology, roughness, and chemical composition were analyzed by scanning electron microscopy, white light interferometer, and energy disperse spectroscopy. The influences of cleaning methods and parameters on the cleaning effectiveness were researched. The influences of cleaning effectiveness on the porosity were investigated under the same laser welding conditions, which pertained to homogenous weld penetration and smooth weld surface. With performing a proper laser cleaning of Ti6Al4V plates before laser welding, the oxide film at the surface was removed efficiently, the surface roughness decreased, and the welded bead achieved a low porosity, which met the requirements of class I weld according to China industry standard of aerospace.

Static Calculation and Load Sharing Characteristics Analysis of Four-wheeled Vehicles with Rigid Suspension

QIN Yanming1;ZHAO Jingyi1;WANG Xiangnan2;MA Jinyu1

2020, 31(04): 384-389.

Asbtract ( )

HTML

PDF (5568KB) ( )

References | Related Articles | Metrics

To research the load sharing characteristics of four-wheeled vehicles with rigid suspension, the statics calculation was done by simultaneous equation solutions of elastic deformation coordination equations and static forces balance equations. The mapping relationships between the suspension force and tire stiffness were obtained. Then, the unbalanced load coefficients of four-wheeled vehicles were defined, the influence rules of load sharing characteristics was produced by tire stiffness changes and the partial loads were analysed and obtained. The stiffness data of tire were obtained by experiments and the statics calculation, and load sharing characteristics analysis were verified.

Surface Microstructure and Load Reduction Mechanism of Broach Tip Prepared by SPDT

LV Junjie;NI Jing;MENG Zhen;REN Xu;FENG Kai;YU Hongfei;WANG Yimeng

2020, 31(04): 390-395,402.

Asbtract ( )

HTML

PDF (6400KB) ( )

References | Related Articles | Metrics

In order to study the load reduction mechanism of broach tip surface microstructures prepared by SPDT, the crater microstructure was prepared in different areas of the same broach by laser etching and SPDT respectively. Contrast broaching experiments of microstructured broach and conventional broach were carried out by the established broaching experiment system. The results show that the microstructure prepared by SPDT may reduce the load more effectively. The reason is that the SPDT may produce compressive stress on the tip surface and make the surface of the broach tip more flat. On one hand, the microstructure fabricated by SPDT may reduce the real contact area of tool-chip. On the other hand, the microstructure may weaken the adhesion among tool tip, workpiece and chip, and reduce the thickness of chip and the load in broaching processes.

Prediction of Pure Torsion Fatigue Strength Considering Effects of Mean Shear Stress

PENG Yan;LI Haoran;LIU Yang

2020, 31(04): 396-402.

Asbtract ( )

HTML

PDF (647KB) ( )

References | Related Articles | Metrics

Aiming at the localization of high-cycle fatigue damage, a pure torsional fatigue strength prediction model, considering the effects of mean shear stress, which was based on continuum damage mechanics was obtained from the hypothesis that the same average intrinsic damage dissipation in critical region meant the same fatigue life. Pure torsional fatigue strength related to material properties and mean shear stress was revealed, and a reasonable explanation for the academic controversy was given. The proposed prediction model was compared with existing prediction model by pure torsional fatigue experimental data of mean shear stress superimposed on three common metal materials. It is shown that the prediction accuracy of the proposed model is much better than that of the existing model.

Electrical Enhanced Photocatalysis Polishing and Removal Mechanism for Single Crystal SiC

HE Yan;YUAN Zewei;DUAN Zhenyun;WANG Xue

2020, 31(04): 403-409.

Asbtract ( )

HTML

PDF (4057KB) ( )

References | Related Articles | Metrics

A new electrical enhanced photocatalysis polishing method for SiC was proposed herein to meet the requirements of ultra-smooth, non-damaging, and highly efficient in the fields of electronic semiconductor. Effects of different type photocatalysts and pH values on the oxygenation, and polishing performance of the slurries were studied. Material removal mechanism was discussed. The results show that the maximum oxidation-reduction potential of p25 type TiO2 slurries is as 633.11 mV, material removal rate is as 1.18 μm/h, and surface roughness Ra is as 0.218 nm. The proportion of oxidized species such as Si-C-O, Si-O, and Si4C4O4 increase noticeably on the polished silicon carbide surfaces, which indicates that the oxidation combined with mechanical action is main material removal mechanism.

Tribological Performance Analysis of Circular Hammerhead-bar Friction Pair in Precision Blanking

ZHANG Lijun;HAN Lin;ZHANG Dexiao;ZHANG Junwei;ZHANG Xuqiang;ZHANG Xin;XIANG Hengfu

2020, 31(04): 410-416,424.

Asbtract ( )

HTML

PDF (2963KB) ( )

References | Related Articles | Metrics

Aiming at the serious problems on friction and wear of circular hammerhead-bar friction pairs existing in precision blanking, friction properties of a friction pair , GCr15 steel block45 steel pillar, were studied with the WTM-2E controllable atmosphere micro-friction and wear tester under the condition of different speeds and nanometer MoS2 additive contents with different mass fractions. The results show that with the increase of upper friction pair(45 steel pillar) speed, the wear stroke becomes longer, while the friction coefficient and the wear amount decrease, and the wear form of surface changes from adhesive wear to abrasive wear. AE technology was used to monitor the wear states of the friction pair surface in real time. The mass fraction of nano-MoS2 additive with a score of 0.5% is further determined, and at the same time the effectiveness of antifriction and antiwear is best.

Propagation Characteristics of SH Wave in Plates with Variable Thickness

SONG Xiaochun;WEN Hui;TU Jun;ZHANG Xu;HUANG Songling

2020, 31(04): 417-424.

Asbtract ( )

HTML

PDF (7440KB) ( )

References | Related Articles | Metrics

In order to study the propagation characteristics of ultrasonic guided waves in variable thickness plates such as tank wall, the propagation models of SH wave were established in free boundary space. The dispersion equation of SH wave in variable thickness plates was derived based on the Navier-Stokes equation of isotropic elastic medium, and the effects of the inclination angle θ on the travel time t of SH wave were analyzed. According to the far-field response of simple harmonic point source, the far-field response equation of SH wave in variable thickness plates was derived by introducing the non-linear relationship of the plate thickness and propagation displacement. Then, the propagation characteristics of SH wave in plates with different inclined angles were verified by finite element simulation and physical experiments. The results show that when SH wave is excited at the thin end of variable thickness plate and propagates along the structure surface, there is no dispersion phenomenon and no wave packet separation phenomenon. However, with the increase of the inclination angles θ of the variable thickness plates, the travel time and the received signal amplitudes of the SH wave decrease non-linearly.

Mathematical Modeling and Experimental Study on Two-step Electrochemical Machining of Thin-wall Long Pipes of Molybdenum

WANG Zhendong1，3;PANG Guibing1;XIN Kaikai2;FAN Shuangjiao1;DING Jinhua1;ZHENG Jianping3

2020, 31(04): 425-431.

Asbtract ( )

HTML

PDF (1804KB) ( )

References | Related Articles | Metrics

Aiming at the difficult problems of processing the high temperature fuel cladding for a reactor, the electrochemical machining technique of molybdenum alloy thin-wall long pipes was studied. The two-step electrochemical machining method with fixed cathodes and movable cathodes was proposed, and the mathematical models of mobile narrow cathode electrochemical machining were established. Experiments were carried out on the implementation methods and process parameters. The experimental results show that the electrochemical processing of the fixed wide cathode may remove a large amount of material, and the electrochemical processing of the mobile narrow cathode may be used for surface finishing. Combining these two processes to machine molybdenum tubes with a diameter of 25.4 mm and a length of 800 mm, the obtained diameter deviation is within 0.05 mm.

Experimental Study of Microstructure and Properties for Laser Phase-change Hardening of H13 Steel

YUN Xiao1;WANG Jing1,2;HE Bing1,2;CHEN Zhikai1,2;ZHU Qinghai1;ZONG Xuemei1,2

2020, 31(04): 432-437,444.

Asbtract ( )

HTML

PDF (8249KB) ( )

References | Related Articles | Metrics

To improve the corrosion resistance and wear resistance of H13 steel, the phase structure, microstructure, microhardness, corrosion resistance, and wear resistance of H13 steel before and after laser phase-change hardening were compared and analyzed by means of XRD diffractometer, optical microscope, scanning electron microscope, microhardness tester, electrochemical workstation, and high temperature friction and wear tester. The microstructures of hardened layers are composed of needle martensite, strip martensite, and carbide. The hardening depth is 0.71 mm. The microhardness of the hardened layer is about 750 HV0.3. In demolder solution, the self-corrosion current density of the hardened layers is one order of magnitude smaller than that of the substrate. The high temperature wear mass of the hardening layers is 7% of as-received H13 steel. The wear mechanism is mainly adhesion wear, while accompanies abrasive wear and oxidation wear.

Influences of Assembly Parameters on Rupture Failure of Accessory Casing Bevel Gears

LUAN Xiaochi1,2;SHA Yundong1;GUO Xiaopeng3;YANG Disi4;MA Ting1,4

2020, 31(04): 438-444.

Asbtract ( )

HTML

PDF (6817KB) ( )

References | Related Articles | Metrics

Aiming at the rupture failures of bevel gears of aero engine accessory cases caused by assembly deviations, traveling wave resonance principle and finite element method were carried out to calculate the mode and static stress of the bevel gears. The influences of gear backlash and vertical installation angle deviations on the root stress of the driving bevel gear were discussed. Simulation and test results show that the driving bevel gear structure includes 1 node-diameter and 2 node-diameter vibration modes. The errors between modal frequency simulation and test are less than 2.5%. The gear backlash has less effect on the root stress. The great influence caused by the installation angle deviations of the driving bevel gears is validated. Thus, the installation angle deviations should be strictly controlled. The analysis of the metallographic structure and fracture characteristics of the driving bevel gears show that the fracture type of the bevel gears is fatigue fracture, and the fracture has the characteristics of nodal-diameter vibration fatigue fracture.
assembly parameter; aeroengine; bevel gear; rupture failure

Spatial Statistical Analysis of Geometric Deviations of Free-form Surfaces

JIN Long;CHEN Yueping;GE Dongyuan

2020, 31(04): 445-450.

Asbtract ( )

HTML

PDF (8118KB) ( )

References | Related Articles | Metrics

To analyze the intrinsic relationship among the geometric deviations of machined free-form surfaces, a spatial statistical analysis method was applied to decompose these deviations into deterministic and random deviations, which would help to determine error sources. The B-spline method was applied to iteratively build a surface that forms deterministic deviations. And the MoranI was used to test the spatial statistical characteristics of the model residuals in every iterative step. If the residuals were spatially independent, then they might present the random deviations. To verify the presented method, the geometric deviations on a CNC machined free-form surface were successfully decomposed into the deterministic and random deviations.

Research on Evaluation and Development of Intelligent Machinery Manufacturing in China

ZHANG Jinlong1;WU Shan1,2;GONG Yeming3

2020, 31(04): 451-458.

Asbtract ( )

HTML

PDF (1313KB) ( )

References | Related Articles | Metrics

Based on the database of industrial enterprises above designated size in China, 15145 intelligent manufacturing enterprises were selected, combined with the field investigation in the main regions of intelligent manufacturing. After peer review, a list of 322 candidates was generated. Then experienced industry experts examined the ability of the candidate enterprises from two aspects of “exploitative innovation” and “exploratory innovation”, and got the top 100 list of Chinas intelligent manufacturing enterprises. Subsequently, according to the industry classification, the list of intelligent machinery manufacturing enterprises was obtained. After summarizing the basic situation of intelligent machinery manufacturing enterprises on the list, the top 20 enterprises were analyzed, and the development path and future development trend of intelligent machinery manufacturing in China were given herein.

Construction and Analysis of Spiral Bevel Gear Ease-off Surfaces Based on Common Tangent Conjugation

ZHANG Bo;WEI Bingyang;LIU Dake

2020, 31(04): 459-464.

Asbtract ( )

HTML

PDF (4689KB) ( )

References | Related Articles | Metrics

A novel conjugate method for spiral bevel gears was proposed, which was more convenient to solve the tooth surface equation of conjugate pinion. Then, the tooth contact analysis was carried out. In the analysis processes, a new ease-off difference surface calculation method was proposed, which used angle errors of the corresponding points instead of straight-line errors to obtain difference surface. Difference curve on ease-off surface was extracted, which might easily determine the contact path and edge contact points. According to the whole difference curve, the distribution of contact marks on the tooth surfaces was obtained.

A Design Method of Complex Nonlinear Systems Based on Ideal Degree and Rough Number Multiple Attribute Decision

GONG Jinliang1;TENG Xuefang2;ZHANG Yanfei3

2020, 31(04): 465-471,481.

Asbtract ( )

HTML

PDF (4696KB) ( )

References | Related Articles | Metrics

Aiming at fuzzy uncertainty of design features and requirements in the conceptual design stage of products, a design method of complex nonlinear systems based on ideal degree and rough number multi-attribute decision was proposed. The set of target technical systems and the set of super systems were determined, and the subsystem was solved at the ideal level. A functional structure model and the product design characteristics hierarchy diagram were established. Based on rough number, the weight factor was calculated. Then the relative evaluation results of design requirements were calculated, and complexity of the target subsystems was analyzed. The system complexity was eliminated by using TRIZ . The feasibility and effectiveness of the proposed method were verified by an example of lower extremity exoskeleton engineering.

Dynamics Analysis of Shift Manipulators Based on Neural Network Load Fluctuation Simulation

ZHOU Nan;CHEN Gang

2020, 31(04): 472-481.

Asbtract ( )

HTML

PDF (8550KB) ( )

References | Related Articles | Metrics

A simulation method of shift load fluctuation was proposed, and the dynamics characteristics of shift manipulators of driving robot under load fluctuation were analyzed. A power transmission model of shift manipulators including the end load fluctuation model of the manipulators was established. In the carrier motion model, the load was decomposed into selecting direction load and shifting direction load. A neural network gear load model was proposed, and the experimental data were compared to verify the effectiveness of the proposed model. The dynamics characteristics of the shift manipulators under load fluctuations were analyzed. The effects of end load changes on the trajectory tracking of the shift manipulators were verified.

Machining Process Planning Based on Immune Genetic Algorithm under Rule Constraints

GUO Xiangyu;WANG Lin;ZHANG Yongjian

2020, 31(04): 482-488.

Asbtract ( )

HTML

PDF (3860KB) ( )

References | Related Articles | Metrics

Since machining features might be adapted to multiple manufacturing methods, the cost difference between manufacturing resources and processing time caused by different processing methods was considered in the calculation formula of machining cost. On the basis of immune genetic algorithm, a precedence graph was used to describe the process step relationship and generate the initial processes. An introduction to adaptive parallel transformation operator was used to guide the dynamic adjustment of processing methods and manufacturing resources, which enabled the algorithm to have adaptive adjustment capabilities that could follow the iterative processes. Finally, the effectiveness of the improved immune genetic algorithm was verified by taking the machining process decision of a rotating part as an example.

Influences of Coolant Channel Outlet Location on Grinding Performance of Pressurized Internal Cooling Grinding Wheels

PENG Ruitao1;WU Yanping1;TANG Xinzi1;LU Xinyan1;HU Yunbo2

2020, 31(04): 489-497.

Asbtract ( )

HTML

PDF (25596KB) ( )

References | Related Articles | Metrics

Considering the influences of channel outlet positions on cooling and lubrication effectiveness of coolant, a pressurized internal-cooling slotted wheel with a rotatable abrasive ring in circumferential direction was designed. The channel outlet location was aligned to abrasive zones or slotted zones. A grinding temperature simulation model was established, it is suggested that better heat transfer effectiveness were obtained when the channel outlet was aligned to slotted zones. Grinding comparison tests of superalloy were carried out under the same grinding parameters, the results indicate that better cooling and lubrication effectineness were achieved when the channel outlet aligned to slotted zones, the grinding temperature and surface roughness are reduced 16% and 15% respectively, surface topography is smoother and more regular, and the surface residual compressive stress is more obvious.

Squeezing Simulation and Experiment of Electric Vehicle Battery Packs

KUANG Songsong;XIONG Fei;LIU Jing;JIA Yinglong;LI Wenyan

2020, 31(04): 498-503.

Asbtract ( )

HTML

PDF (8898KB) ( )

References | Related Articles | Metrics

In order to improve the squeezing simulation accuracy of power battery packs, the ductile damage criterion was introduced in FEM simulation. Ductile damage criterion parameters of 6061-T6 aluminum alloy used in an electric vehicle power battery packs were obtained through uniaxial tensile test, pure shear test, notched tensile test, and FEM simulation. Three-point bending test of section product, squeezing test of a electric vehicle power battery packs and the FEM simulation results of the above tests show that the FEM simulation results with inputing ductile damage criterion parameters have little error with tests, and may accurately describe influences of aluminum alloy damage on the load carrying capacity of structure, while the FEM simulation results without material failure have large error with tests.

Table of Content