20 September 2019, Volume 43 Issue 9
    

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  • Research Status and Application Progress of Thermal-Induced Shape Memory Polymer
    TANG Longhao, WANG Yanling, LI Yongfei, LI Qiang, KANG Yuanbo
    Materials For Mechanical Engineering. 2019, 43(9): 1-7. https://doi.org/10.11973/jxgccl201909001
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    The shape memory effect, shape memory mechanism, types and preparation methods of thermal-induced shape memory polymer are reviewed. The influencing factors of shape memory performance are discussed. The application status of thermal-induced shape memory polymer is introduced. The application prospect of thermal induced shape memory polymer is expected.
  • Precipitation Behavior of α Phase and Its Effect on Fracture Mechanism of Ti-5Al-5Mo-5V-3Cr-1Zr Alloy
    SHAO Hui, ZHAO Minjian, WANG Kaixuan, SHAN Di, ZHANG Saifei, BAI Lijing, ZHANG Guojun, ZHAO Yongqing
    Materials For Mechanical Engineering. 2019, 43(9): 8-12,47. https://doi.org/10.11973/jxgccl201909002
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    Ti-5Al-5Mo-5V-3Cr-1Zr alloy was treated by to aging at 580℃ for different times (0, 5, 15, 60 min), and then α phase precipitation behavior and its effect on the tensile fracture mechanism of the alloy were studied. The results show that α phases with triangle or V shaped, dendritic and cluster morphology successively precipitated in matrix β phase of test alloy with the increase of aging time. The orientation relationship between α phase with different morphology and β phase obeyed the Burgers rule. During the tensile deformation, the dislocations in the structure with triangular morphology α phase were concentrated in the large-sized strip α phase, and the cracks initiated along the preferentially deformed α phase. The dislocations in the structure with dendritic morphology α phase were concentrated in parallel strip α phase; the cracks initiated along the trunk α phase, and then the quasi-cleavage plane was formed. The dislocations in the structure with cluster morphology α phase were activated in β phase between strip α phase; the crack initiated along the high angle β/β phase interface, and then the smooth quasi-cleavage plane was formed.
  • Microstructure and Shear Force of Resistance Spot Welded Titanium/Stainless Steel with NiCr Alloy as Interlayer
    MA Hengbo, QIU Ranfeng, LI Dan, SHI Hongxin, ZHANG Zhanling
    Materials For Mechanical Engineering. 2019, 43(9): 13-17,53. https://doi.org/10.11973/jxgccl201909003
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    TA1 titanium sheet and SUS304 stainless steel sheet were welded by resistance spot welding with 100 μm thick NiCr alloy as the interlayer. The microstructure characteristics of the joint were observed and analyzed. The effects of welding process parameters on the nugget diameter and shear force of the joint were studied. The results show that the reaction layer with 50 μm thickness consisting of α-Ti and Ti2Ni was formed near titanium side at steel/titanium interface outside nugget zone. The reaction layer with 15 μm thickness consisting of α-Ti and TiFe was formed between titanium and nugget; the reaction layer with 7 μm thickness consisting of Fe and TiFe2 between stainless steel and nugget; the center of nugget region was composed of mixtures of TiFe and TiFe2. The nugget diameter of the joint increased with welding current and welding time, and decreased slightly with the increase of electrode force. The shear force of the joint increased and then decreased with the increase of welding current, welding time and electrode force. All joints were torn at the bonding interface after shear tests.
  • Local Mechanical Behavior of 2A12-T4 Aluminum Alloy FSW Joint by Digital Image Correlation and Iso-stress Assumption Method
    HUI Li, WEN Yanze, WANG Lei, ZHAO Xinhua
    Materials For Mechanical Engineering. 2019, 43(9): 18-22,59. https://doi.org/10.11973/jxgccl201909004
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    The inhomogeneous deformation behavior of friction stir welding (FSW) 2A12-T4 aluminum alloy joint during tension was analyzed on the basis of digital image correlation (DIC) method. The local mechanical properties of the joint were then studied by the iso-stress assumption method, and compared with global mechanical properties obtained by the transverse tensile test. The results show that there was a large strain gradient inside the joint during tension by the DIC method. The local true stress-true strain data of base metal obtained by iso-stress assumption method was consistent with the true stress-true strain curve by the test, which verified the accuracy of the iso-stress assumption method. The calculated local true stress-true strain curve of heat affected zone at the distance of 6.5 mm from the weld center on advancing side was closer to the tensile properties of the joint. The yield strength of the junction of thermal-mechanically affected zone and heat affected zone was the smallest, and this position was the weakest area of the joint. The high strength area of the joint had constrains on the low strength area, which led to the better mechanical properties of the joint than the local mechanical properties of the weakest area.
  • Tensile Behavior of LB27 and LB20 Aluminum-Clad Steel Wires
    TIAN Jiazhi, ZHENG Chengming, JIANG Zechao, TIAN Qingchao
    Materials For Mechanical Engineering. 2019, 43(9): 23-27,67. https://doi.org/10.11973/jxgccl201909005
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    LB27 and LB20 aluminum-clad steel wires were prepared by continuous extrusion cladding of aluminum with SWRS72A steel and SWRS82B steel, respectively. Samples before and after cold drawing were prepared and tensile experiments were conducted on them at room temperature. The tensile properties and fracture morphology of the samples were studied. The results show that the yield strength and tensile strength of the SWRS72A steel without aluminum cladding were higher than those with aluminum cladding before cold drawing. Compared with SWRS72A steel without aluminum cladding, the yield strength of the LB27 aluminum-clad steel wire was higher, but the tensile strength decreased slightly. The elongation of the LB27 aluminum-clad steel wire decreased significantly. With the increase of outer diameter, the yield strength of the LB20 aluminum-clad steel wire decreased gradually, but was greater than that of the LB27 aluminum-clad steel wire. The fracture morphology of the LB20 aluminum-clad steel wire was similar to that of the LB27 aluminum-clad steel wire, but shear lip existed at the edge of the steel of the LB20 aluminum-clad steel wire.
  • High Temperature Energy Dissipation Characteristics of Damping Structure Coated with Metal Rubber
    XIAO Kun, BAI Hongbai, XUE Xin, WU Yiwan
    Materials For Mechanical Engineering. 2019, 43(9): 28-32. https://doi.org/10.11973/jxgccl201909006
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    Metal rubber with different densities (2.000, 2.286, 2.571 g·cm-3) was prepared with 304 austenitic stainless steel wires, and then assembled into a damping structure coated with metal rubber. Effects of environmental temperature (25,100,200,300℃) on energy dissipation characteristics and metal rubber density, loading amplitude (0.2, 0.5, 0.8, 1.0 mm) and frequency (1, 2, 3, 4, 5 Hz) on the high temperature (300℃) energy dissipation characteristics of the damping structure were studied. The results show that the energy dissipation, maximum elastic potential energy and loss factor of the metal rubber (with density of 2.286 g·cm-3) coated damping structure at 100-300℃ were slightly lower than those at 25℃, but the difference was relatively small, indicating that the metal rubber had excellent and stable damping properties at high temperatures. At 300℃, with increasing amplitude, the energy dissipation and maximum elastic potential energy of the metal rubber (with density of 2.286 g·cm-3) coated damping structure increased and the loss factor decreased. The frequency had little effect on the high temperature energy dissipation characteristics. With increasing density of metal rubber, the energy dissipation and maximum elastic potential energy at 300℃ increased, and the loss factor showed a fluctuant change.
  • Microstructure and Properties of Aluminum-Silicon Weathering Steel Prepared by Strain Induced Ferrite Transformation Rolling
    LI Wenyuan, LIU Kun, HUI Yajun, LIU Jie, ZHANG Xu, IU Xiaocui
    Materials For Mechanical Engineering. 2019, 43(9): 33-37,72. https://doi.org/10.11973/jxgccl201909007
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    Strain induced ferrite transformation rolling process of a homemade aluminum-silicon weathering steel was determined by measuring its continuous cooling transformation curve and then was applied to the tested steel. The microstructure, mechanical properties and corrosion resistance of the rolled tested steel in 3.5wt% NaCl solution were studied and compared with those of SPA-H steel. The results show that only ferrite and pearlite transformation zones existed in the tested steel at cooling rates of 0.5-25℃·s-1. After rolling, the microstructure consisted of single ferrite, and the grain size of some ferrite was less than 3 μm. Comparing with SPA-H steel, the tested steel had higher elongation and lower yield ratio; also the impact toughness was excellent. After corrosion in NaCl solution, multiple dense Al- and Si-enriched layers existed in the rust layer on surface of the tested steel, and the surface rust layer had better corrosion resistance than the surface rust layer of SPA-H steel had, so the resistance to chloride ion corrosion of the tested steel was better than that of SPA-H steel.
  • High Stress Rolling Contact Fatigue Properties of 32Cr3MoVE Nitrided Bearing Steel
    ZHANG Qiang, SUN Shiqing, YANG Maosheng
    Materials For Mechanical Engineering. 2019, 43(9): 38-42,77. https://doi.org/10.11973/jxgccl201909008
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    Surface nitriding treatment was conducted on 32Cr3MoVE bearing steel prepared by double vacuum melting process. The rolling contact fatigue performance was studied under the high stress of 4.5 GPa by rolling contact fatigue testing machine, and the failure mechanism of rolling contact fatigue was analyzed. The results show that the effective nitriding layer depth of the test steel was 350 μm; the residual compressive stress in the nitriding layer increased and then decreased with the increase of distance from the surface, and had the largest value of 610 MPa at 300 μm distance from surface. The white vein structure distributing along the grain boundaries appeared in the nitriding layer. The rolling contact fatigue characteristic lifetime, rated fatigue lifetime and median fatigue lifetime were 3.040×108, 0.357×108, 2.083×108 cycles, respectively, calculated by two-parameter Weibull distribution. The rolling contact fatigue failure modes of the test steel included surface crack initiation and subsurface crack initiation, and the average diameter and depth of peeling pits in surface crack initiation sample were significantly larger than those of subsurface crack initiation sample. Surface crack initiation sample cracked along pits or scratches on the surface; the subsurface material properties of subsurface crack initiation sample degraded under the action of prolonged cyclic contact stress, resulting in crack initiation.
  • Matching of Crack-Tip Constraint between Pipe Structures and Different Laboratory Specimens
    YANG Jie, LIU Yuman
    Materials For Mechanical Engineering. 2019, 43(9): 43-47. https://doi.org/10.11973/jxgccl201909009
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    Crack-tip constraints of pipe structures and laboratory single edge-notched bend (SENB) specimen, compact tension (CT) specimen, single edge-notched tensile (SENT) specimen and centre-cracked tension (CCT) specimen with different dimensions of initial cracks were characterized by finite element simulation method using the unified constraint parameter Ap, and the matching of crack-tip constraints between pipe structures and laboratory specimens were built. The results show that the matching of crack-tip constraints between pipe structures and SENB specimens, CCT specimens was poor. The crack-tip constraint of pipe structure with a/c=0.2, a/t=0.5 (a representing deep of crack, c representing half length of crack, t representing wall thickness of pipe) was similar to that of the CT specimen with deep cracks (a/W=0.7, W representing width of specimen); the crack-tip constraint of pipe structure with a/c=0.8, a/t=0.5, 0.8 was similar to that of the CT specimen with deep cracks (a/W=0.5,0.6 and 0.7). The crack-tip constraint of pipe structures was similar to that of SENT specimens, their crack-tip constraints matched very well. During the integrity assessment of actual structures, the laboratory specimen with the similar constraint to actual strcutre could be selected to carry out fracture mechanical experiments, and the assessment accuracy could be improved when the actual structure was assessed by the measured fracture mechanical properties.
  • Numerical Simulation of Wrinkling Behavior of Tinplate Based on Yoshida Buckling Test Model
    YUAN Weijie, CHEN Janjun, WU Wenchao, YANG Cheng, LI Wen
    Materials For Mechanical Engineering. 2019, 43(9): 48-53. https://doi.org/10.11973/jxgccl201909010
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    Based on Yoshida buckling test (YBT) model, the wrinkling behavior of tinplate was simulated by ABAQUS software under no application and application of disturbing forces at different positions, and simulated results were verified by experiments. The strain combination of the center point of square sheet under different wrinkling heights was studied by increasing the clamping width gradually, and the wrinkle height evaluation diagram of the tinplate was drawn. The results show that the off-plane displacement distribution perpendicular to the stretching direction of the square sheet was almost the same under application of disturbing forces at different positions, indicating that the position of disturbing force hardly affected the wrinkling behavior. The simulated off-plane displacement distribution perpendicular to the stretching direction of the square sheet center section under application of disturbing force was in agreement with the experimental results, indicating that the simulation method of using disturbing force instead of actual influencing factor was accurate. The compression strain and tension strain of center point of square sheets with different clamping widths both increased with the increase of wrinkling height. Under the same wrinkling height, the compression strain and tension strain of center point of square sheets both increased with the increase of clamping width.
  • High Temperature Low Cycle Fatigue Behavior of 80SH Steel for Thermal Recovery Well Casing Affected by Dynamic Strain Aging
    WEI Wenlan, HAN Lihong, FENG Yaorong, WANG Hang, TIAN Tao
    Materials For Mechanical Engineering. 2019, 43(9): 54-59. https://doi.org/10.11973/jxgccl201909011
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    Low cycle fatigue tests were conducted on 80SH steel for thermal recovery well casing at 20, 120, 250, 350, 450℃ and strain amplitudes of 0.5%, 0.7%, 1.0%, 1.5%, 2.0%. The low cycle fatigue behavior under the influence of dynamic strain aging (DSA) was studied. Based on low cycle fatigue test data, the relation model between low cycle fatigue life and strain amplitude under the influence of DSA was established. The results show that 80SH steel had significant DSA characteristics at 350℃; the significant secondary hardening behavior of 80SH steel during high temperature low cycle fatigue appeared, resulting in dislocation accumulation in grains which prevented crack propagation; then cyclic hardening occurred, resulting in cleavage steps and a large number of secondary cracks appeared in the low cycle fatigue fracture. In the DSA significant temperature range, fatigue life had bilinear relationship with elastic strain in the double logarithmic coordinate system, while had linear relationship with plastic strain. The superposition of Manson-Coffin linear model and Basquin bilinear model could better describe the relation between fatigue life and strain of 80SH steel under the influence of DSA.
  • Finite Element Simulation and High-temperature Creep Property of Hastelloy-X Superalloy Prepared by Selective Laser Melting
    LI Yong, XU Hejun, BA Fahai, HE Beibei, LI Kai
    Materials For Mechanical Engineering. 2019, 43(9): 60-67. https://doi.org/10.11973/jxgccl201909012
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    Based on molding principle of selective laser melting (SLM), the heat source model was simulated by body heat generation method, and the load of moving laser heat source was realized by ANSYS parametric design language (APDL); then the single-layer transient temperature field and molten pool morphology of Hastelloy-X superalloy during SLM process were simulated by finite element model. The simulation results were verified by tests. The high temperature creep property of SLM molding specimens was investigated and compared with Hastelloy-X superalloy hot-rolled rods treated by solution. The results show that the body heat generation method could simulate the single-layer transient temperature field during SLM molding well, and the calculated molten pool size and primary dendrite spacing agreed well with the experimental results. Under the same creep test condition, the steady-state creep rate of SLM molding specimen was much lower than that of Hastelloy-X superalloy hot-rolled rods treated by solution; however, the creep stress index of them were similar, and creep deformation were both dominated by movement and climbing of dislocations.
  • Effects of Compression Deformation in Austenite Zone on Phase Transformation of Bainite in Low-carbon Bainitic Steel
    CAI Xiaowen
    Materials For Mechanical Engineering. 2019, 43(9): 68-72. https://doi.org/10.11973/jxgccl201909013
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    The static supercooled austenite continuous cooling transition curve of Si-Mn-Mo-Cr-V low-carbon bainitic steel was drawn by thermal expanding curve obtained with thermal expansion phase change meter combined with microstructure and hardness test results. The test steel was subjected to compression deformation in austenite zone with different deformation, and then was cooled to different temperatures for 150 s and air cooled to room temperature by thermal simulation testing machine; the effect of compression deformation in austenite zone on bainite phase transformation and microstructure were studied. The results show that the initial temperatures of bainite phase transformation of test steel without compression deformation in austenite zone, with single-pass compression deformation by 40% in austenite zone and with double-pass compression deformation by 58% in austenite zone were 400, 385, 300℃, respectively. The bainite phase transformation of test steel during cooling process was delayed after compression deformation in austenite zone; the initial phase transformation temperature decreased, and the greater the deformation in austenite zone, the lower the initial temperature of the bainite phase transformation. Compared with the test steel without compression deformation in austenite zone, the bainite of the test steel with compression deformation in austenite zone became finer, the grain orientation increased, and the hardness were obviously improved.
  • Numerical Simulation of Delamination Damage during Drilling Carbon Fiber Reinforced Plastic Unidirectional Plate
    ZHANG Minghui, ZHOU Chuwei, LU Hao
    Materials For Mechanical Engineering. 2019, 43(9): 73-77. https://doi.org/10.11973/jxgccl201909014
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    Based on three-dimensional Hashin failure criterion, and quadratic nominal stress criterion and BK failure criterion of the bilinear Cohesive damage model, the delamination damage of carbon fiber reinforced plastic unidirectional plate during drilling was simulated by VUMAT subroutine in ABAQUS/Explicit module, and the simulation results were verified by the ultrasonic C scan results after drilling. The effect of diameter and vertex angle of twist drill on delamination damage was studied. The results show that the tested maximum damage diameter of damage area of unitirectional plate after drilling was 25.6 mm, and the delamination factor was 2.56; the maximum damage diameter was 25 mm, and the delamination factor was 2.50 by finite element simulation. The relative error between experimental results and simulation results was only 2.4%, proving the accuracy of the finite element model. Compared with the top surface layer interface and intermediate interface, the delamination factor of the lower surface layer interface of unidirectional plate was the largest, and the delamination damage was the severest. The delamination factor increased with the increase of diameter and vertex angle of twist drill, and the delamination damage degree also increased.
  • Failure Analysis of GH4033 Nickel Based Alloy Coupling Ring of an Aircraft Engine
    XIONG Yong, CHENG Fasong, LI Yongbin, CHEN Changda, SHEN Jingfang
    Materials For Mechanical Engineering. 2019, 43(9): 78-82. https://doi.org/10.11973/jxgccl201909015
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    During the overhaul decomposition inspection of an aircraft engine, it was found that serious deformation and cracking occurred in the coupling ring of stage Ⅱ turbine guide. The cause of the deformation and cracking was analyzed by macro- and micro-morphology observation, fracture analysis, chemical composition analysis and hardness test. The results show that the cracks in the inner wall of the installation hole of the coupling ring were high cycle fatigue cracks. The fit clearance between axle neck of the guide vane and installation hole of the coupling ring, and the gap between lower edge plates of the guide vane were both small; the linear expansion coefficients of the guide vane and the coupling ring were different and therefore the axle neck could not move freely in the installation hole under high temperature condition. Under the thermal stress, the coupling ring was extruded to the center, resulting in the deformation and fatigue cracking. The periodic change of the clearances caused by temperature variation was the main reason for fatigue crack growth. The similar accidents could be effectively avoided by properly reducing the size of the axial neck of stage Ⅱ turbine guide vane to enlarge fit clearance between the axle neck and the binding ring installation hole as well as the gap between lower edge plates of the guide vane.
  • Reason for Pressure Testing Leakage of Glass Fiber Reinforced Plastic Pipe
    MAO Xueqiang, LI Xunji, CHANG Zeliang, ZHANG Wenle, WANG Peng, QI Guoquan
    Materials For Mechanical Engineering. 2019, 43(9): 83-86. https://doi.org/10.11973/jxgccl201909016
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    The glass fiber reinforced plastic pipe used in ground gathering system of an oil field in China leaked during pressure test on site. The failure reason was analyzed by macroscopic morphology observation, wall thickness measurement, glass transition temperature test, resin content test, hydrostatic pressure test, short-term failure pressure test and microscopic morphology observation. The results show that by the external force dominated by the bending stress, a large number of circumferential cracks appeared in the thickened transition region of the glass fiber reinforced plastic pipe outer wall, resulting in the reduction of overall internal pressure resistance of the pipe, and leading to the leakage of the pipe during pressure test on site. The glass-transition temperature of outer surface of the glass fiber reinforced plastic pipe was low, indicating that the curing degree of the outer surface was low and the performance was poor. The poor performance promoted the appearance of circumferential cracks in the outer wall of the pipe.
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