28 September 2023, Volume 30 Issue 9
    

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  • Simulation results analysis of multi-wedge differential speed rolling for 25CrMo4 solid axle
    HUO Yuan-ming, LIU Ke-ran, HE Tao, CHEN Gang
    Journal of Plasticity Engineering. 2023, 30(9): 1-8. https://doi.org/10.3969/j.issn.1007-2012.2023.09.001
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    Based on the secondary development of DEFORM-3D,the multivariate nonlinear regression hardening model was written,and the parameters of Cockroft-Latham fracture model were determined by high temperature tensile experiments. The forming of 25CrMo4 complex solid axle with different rolling speed ratios of 1.0,1.15,1.25 and 1.5 was simulated by finite element method.The rolling shape,rolling force,flow velocity field,plastic damage and equivalent stress and strain of the complex axle obtained after same and differential speed rolling were analyzed,and the effects of differential speed rolling on axle forming were explored. The results show that the formability of the material can be improved by differential speed rolling,and it is beneficial for the deformation deep into the center. The differential speed rolling force is less than that of same speed rolling. The cross shear rolling effect on the upper and lower symmetrical surfaces of the rolled piece is different,and the side with larger speed has a little more damage. The hindering effect of friction on the rolled piece is reduced by additional shear stress in differential speed rolling,and the equivalent stress is lower than that of the same speed rolling.
  • Research on radial-axial deformation process planning method for large ring rolling with stability and high efficiency
    ZHAO Bo-zhi, DENG Jia-dong, QIAN Dong-sheng, HU Zhi-li
    Journal of Plasticity Engineering. 2023, 30(9): 9-16. https://doi.org/10.3969/j.issn.1007-2012.2023.09.002
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    Aiming at the planning problem of the radial-axial rolling process of large ring,a theoretical model of rolling deformation path planning was proposed according to the size characteristics of formed forgings and ring blanks,and the influence laws and selection methods of key parameters on the linetype and curvature changes of the theoretical model were determined. The mathematical model of the mandrel feed speed was established. Considering the forging penetration and bite conditions of the radial rolling pass of ring and the expanding speed of the outer diameter of ring,the reasonable ranges of the relevant parameters were determined. Combined with the rolling deformation path and the radial feed speed of mandrel,the axial feed speed of the upper cone roll was obtained. The typical section ring rolling deformation process was planned. With the help of ABAQUS software,the three-dimensional thermal mechanical coupling finite element model of radial-axial rolling of large ring was established,and the simulation was carried out according to the planned process. The simulation results show that the planning method can ensure the ring rolling process proceed successfully and stably,which was verified by experiments.
  • Finite element simulation of continuous extrusion of C19210 copper alloy special-shaped strip for lead frame
    LI Han-dong, ZHANG Zhen-feng, LIU Zhi-lin, JIAO Chuan-rong, JIANG Yan-bin, LIN Gao-yong
    Journal of Plasticity Engineering. 2023, 30(9): 17-26. https://doi.org/10.3969/j.issn.1007-2012.2023.09.003
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    The constitutive equation of C19210 copper alloy was established by hot compression experiment,and the metal flow laws of C19210 copper alloy special-shaped strip during continuous extrusion were analyzed by DEFORM-3D finite element simulation software,and the formation mechanisms of defects of special-shaped copper strip in continuous extrusion were revealed by means of equivalent strain,velocity vector and point tracking. It is found that the folding phenomenon of billet in the wheel groove is an important reason for the formation of defects,while the asymmetric distribution of die cavity and die aggravates the formation of defects on the lower side of the extruded copper strip. By optimizing the working belt size of the die,the equivalent stress and flow velocity of the metal in the die cavity become more uniform,and the surface quality of the extruded special-shaped strip is improved obviously.
  • Multi-objective optimization of internal high pressure forming process parameters for aluminum alloy transmission shaft tube with variable cross section
    GUO Xue-qiang, XI Jian-sheng
    Journal of Plasticity Engineering. 2023, 30(9): 27-35. https://doi.org/10.3969/j.issn.1007-2012.2023.09.004
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    To solve the problem of difficult manufacture of aluminum alloy transmission shaft tube with variable cross section,the internal high pressure forming process for aluminum alloy transmission shaft tube was designed,the effect laws of axial feed,forming internal pressure,friction factor and corner radius of die on the forming quality of transmission shaft were discussed. To obtain the transmission shaft tube parts with the best forming quality,the internal high pressure forming process parameters were jointly optimized by finite element numerical simulation and intelligent algorithm. Taking the axial feed,forming internal pressure,friction factor and corner radius of die as optimization independent variables,and the maximum thinning rate and the maximum thickening rate as optimization objectives,the radial basis function (RBF)neural network was trained,and the optimal Pareto′s solution set was obtained by non-dominant sorting genetic algorithm Ⅱ (NSGA-Ⅱ). On this basis,the method of order by similarity to ideal solution(TOPSIS)based on entropy weight method (EWM)was used for comprehensive evaluation and screening. The optimal process parameters were obtained as the axial feed of 110.25 mm,the forming pressure of 13.324 MPa,the friction factor between tube and mold of 0.118,the friction factor between push head and mold of 0.037,and the corner radius of 67 mm. The simulation verification of the optimal process shows that the deviation between the simulation verification results of the maximum thinning rate and the maximum thickening rate and the neural network prediction results are 0.1880% and 0.1637%,respectively,and the prediction results are basically consistent with the simulation results. The feasibility of the method in solving the optimization problem of process parameters is verified.
  • Simulation research on hydraulic bulging process of Venturi tube
    WANG Shu-qiang, ZHANG Yu, JIA Chao, LIU Xi-min
    Journal of Plasticity Engineering. 2023, 30(9): 36-43. https://doi.org/10.3969/j.issn.1007-2012.2023.09.005
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    In view of the problems of multiple production processes and difficult lightweigh of Venturi tube flowmeter at the present stage,the hydraulic bulging process was proposed to produce Venturi tube flowmeter. To explore the influence of various process parameters on the hydraulic bulging of Venturi tube flowmeter,based on the theory of material mechanics,the single factor numerical simulation was conducted based on the finite element software to explore the loading path,friction factor of contact surfaces and loading pressure with better forming effect. Based on the numerical simulation results,the experimental verification was carried out,and the experimental results were compared with the numerical simulation results. The results show that the change trend of the experimental wall thickness is consistent with that of the simulation wall thickness. The maximum thinning position of simulated wall thickness is located at the junction of the transition zone and the forming zone,the thinning rate is 28.9%,the maximum strain is 0.3043,and the overall wall thickness changes continuously.
  • Study on numerical simulation and mechanism of low-temperature superplastic forming of SP700 titanium alloy
    ZHAO Li-na, HAN Yan-bin, ZHANG Qian-wen, LI Xi-feng, WANG Ke-cheng
    Journal of Plasticity Engineering. 2023, 30(9): 44-49. https://doi.org/10.3969/j.issn.1007-2012.2023.09.006
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    According to the demand of engineering application of low-temperature superplastic characteristics of SP700 titanium alloy,the numerical simulation and superplastic forming process parameter optimization were used to guarantee the geometric accuracy of the formed parts. Firstly,the suitable superplastic forming parameters were determined according previous high-temperature tensile tests. The flow stress of SP700 titanium alloy during steady state was depicted based on Backofen model. The determined pressure loading path was used to complete the superplastic gas-bulging forming tests of SP700 titanium alloy box-shaped parts. The thickness distributions of the box-shaped part in different areas were measured by PVX thickness gauge,and compared with the numerical simulation results,the prediction accuracy of numerical simulation of superplastic forming of SP700 titanium alloy was verified. The mechanical properties after low temperature superplastic forming of SP700 titanium alloy were analyzed by room-temperature tension. The results show that SP700 titanium alloy has excellent superplasticity at low temperature and can be used to form box-shaped parts with qualified quality. The numerical simulation results agree well with the test results,and the prediction accuracy can reache more than 90%. The microstructure and properties of SP700 titanium alloy have no obvious change,which still has excellent mechanical properties after superplastic forming.
  • Servo hot stamping process design based on hot working maps and NURBS curves
    SONG Yan-li, CAO Wei-sheng, XIE Guang-ju, LU Jue, LIU Peng
    Journal of Plasticity Engineering. 2023, 30(9): 50-62. https://doi.org/10.3969/j.issn.1007-2012.2023.09.007
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    Considering the complexity of process flow and material deformation behavior in hot stamping process and the time-varying of temperature distribution,a servo hot stamping process design based on hot working maps and NURBS curves was proposed. Taking the common B1500HS hot forming sample as the research object,the true stress-true strain curves of B1500HS boron steel with different hot deformation parameters were measured by high temperature tensile experiments. Based on the DMM principle,the hot working maps of B1500HS boron steel with different strains were constructed,and the optimal speed and temperature range in the forming stage of the material in the servo hot stamping process were calculated. According to the process characteristics of each stage of the typical hot stamping mode and the mathematical model of NURBS curves,the servo hot stamping process curve that meets the constraints was planned and established,and the servo hot stamping process curve was designed. The contrast simulation the experiment of servo hot stamping for automobile middle pillar was carried out by CAE analysis software. The comprehensive analysis shows that,compared with the conventional hot stamping process,the stress and temperature distribution of the middle pillar specimen formed by the proposed servo hot stamping process curve model is more uniform,the maximum thinning rate is reduced by about 7.3%,the maximum wrinkle degree is 4.002×10-3,and the principal strain is reduced by about 12.5%,which indicates that the proposed servo hot stamping process has significant inhibition effect on the fracture trend at dangerous locations.
  • Numerical simulation study on phase separation of metal particle suspension in direct ink writing
    GUO Jun-qing, GUO Heng-rui, CHEN Fu-xiao, XIANG Nan
    Journal of Plasticity Engineering. 2023, 30(9): 63-70. https://doi.org/10.3969/j.issn.1007-2012.2023.09.008
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    To study the flow properties of the suspension in direct ink writing of metal particle,the 316L stainless steel particle suspension with particle diameter of Φ50 μm was prepared. Based on the direct ink writing experiments and Eulerian multiphase flow model,the solid-liquid separation phenomenon in the suspension flow process was numerically simulated. The results show that the phase separation phenomenon during the metal particle suspension flow is related to the changes of the cross-section area of the watershed and the particle diameter. In areas where the cross-section area changes from small to large,particles and solution are prone to dispersion,while in areas where the cross-sectional area changes from large to small,particles are prone to aggregation. The smaller the change in cross-sectional area,the weaker the separation phenomenon. Reducing the particle diameter can also weaken the degree of suspension phase separation. When the particle diameter drops to Φ10 μm,phase separation can be basically eliminated.
  • Core pulling riveting damage and shear property of CFRP components with bushings
    ZHAO Le-tian, HUANG Qi, YANG Tian-zhi, ZUO Yang-jie
    Journal of Plasticity Engineering. 2023, 30(9): 71-77. https://doi.org/10.3969/j.issn.1007-2012.2023.09.009
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    To improve the riveting quality of aircraft carbon fiber reinforced resin matrix composites (CFRP)components,aiming at the CFRP components riveting damage problem with poor openness of aircraft,the single-side core pulling riveting process with bushings was studied,and the tensile shear properties of joints were studied. The results show that the bushings can effectively limit the uneven expansion of the rivet shank in the CFRP hole. The hole wall of CFRP and expanded bushing are interference fit due to the expansion of rivet shank. Moreover,the excessive expansion of rivet shank can cause riveting damage even with the limitation of the bushings. During tensile shear process,the load-displacement response of specimens exhibits the obvious characteristics of linear growth stage,yield stage and transient fracture failure stage. All specimens fail with rivet pulling out,however,the shear damage zone is also observed in CFRP laminate and the joining hole is compressed and deformed,and the final failure mode is the combined failure mode. Specimens are actually loaded by tension-shear coupling loading due to the secondary bending moment action during the tension-shear process. The shear damage occurs first,and then the riveted head extrudes the hole circumference of the CFRP laminates along the length direction of rivet shank that causing the final pulling out failure of rivet. The bushing effectively participates in the tensile and shear load transfer,but reduces the actual contact area between the riveted head and CFRP laminates. The pulling out failure can be prevented by the process parameters optimization.
  • Influence of hot-pressing process parameters on forming quality of glass fiber reinforced polypropylene U-shaped skeleton
    JIANG Bai-long, TANG Hua-ping, SHI Wu-ping, ZHAI Zhan-yu
    Journal of Plasticity Engineering. 2023, 30(9): 78-85. https://doi.org/10.3969/j.issn.1007-2012.2023.09.010
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    The influence of hot-pressing process parameters of surface temperature,forming pressure and die temperature of glass fiber reinforced polypropylene(GF/PP)composites laminates on the forming quality of U-shaped skeleton was studied. The interlaminar shear strength of the U-shaped skeleton was tested,the surface morphologies and dimensional accuracy of section were observed. The results show that when the surface temperature and forming pressure increase,fluidity of resin matrix becomes better,resin matrix redistributes during hot-pressing process,the interlaminar shear strength of U-shaped skeleton increases and the surface roughness is improved. However,excessive surface temperature and forming pressure can extrude the resin,thus reeduce the forming quality. The geometric dimensional accuracy of U-shaped skeleton section is affected by both surface temperature and die temperature. The higher the temperature,the more obvious the elastic forward bending effect. If the forming temperature continues to increase,the forward bending effect tends to be constant. During the forming process of U-shape skeleton,the forming quality of the bottom is better than that of the side area due to the different effects of forming pressure on the bottom and side and the uneven surface temperature of the laminate. The optimal process parameters obtained under the existing conditions are:heating voltage of 70 V,heating time of 60 s,surface temperature of 246.1 ℃,forming pressure of 1.2 MPa,die temperature of 80 ℃.
  • Microstructure evolution and adiabatic shear behavior of SLM 18Ni300 under impact loading
    LIU Xiao, HE Dan-dan, ZHU Bi-wu, XIAO Gang, WEI Chun-hua, WAN Ke-qian
    Journal of Plasticity Engineering. 2023, 30(9): 86-92. https://doi.org/10.3969/j.issn.1007-2012.2023.09.011
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    To study the microstructure evolution and adiabatic shear behavior of 18Ni300 maraging steel produced by selective laser melting (SLM)under high-speed impact load,the impact experiments of SLM 18Ni300 maraging steel with different impact loads at room temperature were carried out by split Hopkinson bar technique. The results show that the microstructure of the cross section for SLM 18Ni300 maraging steel is an ellipsoidal braided structure during impact process. With the increase of impact load,the grain size of the cross section firstly increases and then slowly decreases. The grain structure of longitudinal section gradually changes from the semi-arc molten pool structure to the flat curve structure. The grain size decreases with the increase of impact load,and the change amplitude in grain size is smaller than that of cross section. When the impact load is 0.7 MPa,the adiabatic shear band is formed and bifurcation phenomenon appears. The nucleation,growth,coalescence and propagation of hole in the shear band induce the formation of cracks,eventually causing the failure of adiabatic shear bands.
  • Study on dynamic mechanical behavior of eutectic high entropy alloys based on ultra-high temperature and high strain rate compression experiment method
    WANG Zi-di, WANG Jian-jun, WANG Zhi-hua, WANG Qiang
    Journal of Plasticity Engineering. 2023, 30(9): 93-103. https://doi.org/10.3969/j.issn.1007-2012.2023.09.012
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    A new ultra-high temperature and high strain rate compression experiment method was established based on the split-Hopkinson pressure bar,which can effectively test the dynamic mechanical behaviors of material at 1873 K. The synchronous assembly system of incident rod and transmission rod was driven by the motor,and the start-up time of the launching system of the striker and the synchronous assembly system of incident rod and transmission rod was precisely controlled by the high-precision delay controller. It can realize the precise control of cold contact time (less than 10 ms)and the control of impact force in assembly process on the sample,which can avoid the influence of cold contact time on the test results at ultra-high temperature and the plastic deformation or even destruction of the sample caused by impact force in assembly process. Based on this ultra-high temperature and high strain rate compression experiment method,the mechanical behaviors of eutectic high entropy alloy CoCrFeNiTa0.2Nb0.1 fabricated by powder plasma arc additive were tested in a wide range of temperature (293-1473 K)and strain rate (0.001-5000 s-1). The influence laws of temperature and strain rate on its plastic flow behavior and deformation mechanism were analyzed. The variation laws of the third-type strain aging phenomenon appearing in the curve of flow stress of the material with temperature with strain rate and its physical model were obtained.
  • Study on mechanical behavior of 2024-T351 aluminum alloy at high strain rate and single projectile impact simulation
    ZHOU Li-juan, LUO Guang-xin, CHEN Rui, WEN Lin, WANG Zi-yu, XIE Ling-ling
    Journal of Plasticity Engineering. 2023, 30(9): 104-111. https://doi.org/10.3969/j.issn.1007-2012.2023.09.013
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    In order to study the mechanical properties of 2024-T351 aluminum alloy at high strain rate,the dynamic compression experiments with high strain rates were carried out by the split Hopkinson pressure bar,and the stress-strain curves of the material were obtained. The mechanical behavior of 2024-T351 aluminum alloy under different strain rates was modified based on Johnson-Cook (J-C)constitutive model. The variation law of the internal strain rate of 2024-T351 aluminum alloy during shot peening processs was studied by using the single projectile simulation model,and the differences between the existing constitutive model and the modified constitutive model in strain rate distribution,crater size,equivalent plastic strain and residual stress were compared. The results show that 2424-T351 aluminum alloy exhibits strain rate sensitivity in a wide range of strain rate (3214-11136 s-1),and the average error of fitting results is 3.575%. The internal strain rate of the material during shot peening reaches the order of 105 s-1. The strain rate is the maximum when the projectile just impacts the material,and then shows a decreasing trend. Compared with the existing J-C constitutive model,the crater diameter obtained by the modified J-C constitutive model is basically unchanged,but the crater depth is significantly smaller,the equivalent plastic strain is smaller,and the maximum residual compressive stress value is larger.
  • Static spheroidization kinetics of α lamellar of TC21 titanium alloy
    TAO Cheng, CUI Xia, OUYANG De-lai, LAN Xi-xin, FAN Hao, LI Wei-nan, DING Wei-jie, ZOU Kang-xin
    Journal of Plasticity Engineering. 2023, 30(9): 112-120. https://doi.org/10.3969/j.issn.1007-2012.2023.09.014
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    TC21 titanium alloy was forged for 1-3 forging cycles (corresponding true strains were 1.60,2.71 and 3.82,respectively). The subsequent spheroidization heat treatment experiments were conducted on forged samples at 860-920 ℃ for 0.5-4 h. The effect laws of different process parameters,such as strain,heat treatment temperature and heat treatment time,on the static spheroidization of TC21 titanium alloy α lamellar were studied by quantitative metallographic method,scanning electron microscopy (SEM)and electron back-scattered diffraction (EBSD)techniques,the static spheroidization mechanism was revealed,and the kinetics equation of static spheroidization of TC21 titanium alloy was established. The results show that the static spheroidization volume fraction presents parabolic increase with the increase of heat treatment time. The larger the strain is,the larger the static spheroidization volume fraction is. The static spheroidization with smaller strain is more sensitive to the change of heat treatment temperature. The main static spheroidization mechanism is the combination of β phase wedging α/α interface,Oswald ripening and continuous static recrystallization (CSRX).
  • Grain scale effect and damage modeling of fracture under different stress triaxialities
    WANG Ming-hong, LAN Shu-huai, XU Zhu-tian, PENG Lin-fa, LAI Xin-ming
    Journal of Plasticity Engineering. 2023, 30(9): 121-130. https://doi.org/10.3969/j.issn.1007-2012.2023.09.015
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    Tensile experiments of thin plate with different grain sizes and stress states were carried out,it is found that when the grain is consistent,fracture strain decreases with the increase of stress triaxiality,in view of the shear stress state,the fracture strain increases with the increase of grain size,and grain size overassembly can lead to the change of fracture form. In view of the single and plane strain state,fracture strain decreases with the increase of grain size. To describe the scale effect and the influence of stress state,through finite element simulation,the GTN-Thomason model considering the scale effect was used to simulate the deformation process of specimens,and the experimental and simulated force-displacement curves were compared to verify the accuracy of the model under higher stress triaxiality. The simulation results show that the increase of grain size leads to the acceleration of hole connection,the increase of stress triaxiality is conducive to the growth of holes and leads to rapid fracture. Furthermore,the shear factor is added to the GTN-Thomason model considering the scale effect,which improves the prediction accuracy of the damage model under low stress state.
  • Hot deformation behavior of GH4169 rare earth reinforced Ni-base superalloy
    DING Ben, CAI Jun, ZHANG Bing, CHEN Lin, ZHAO Qian
    Journal of Plasticity Engineering. 2023, 30(9): 131-141. https://doi.org/10.3969/j.issn.1007-2012.2023.09.016
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    The high temperature compression tests of GH4169 rare earth reinforced Ni-base superalloy were carried out by Gleeble-3500 thermo-mechanical simulator,with deformation temperatures of 1223,1273,1323,1373 and 1423 K,strain rates of 0.001,0.01,0.1,1 and 10 s-1,and the reduction of 65%. The flow stress curves of GH4169 rare earth reinforced Ni-base superalloy under different deformation conditions were analyzed,and the effects of true strain,strain rate and deformation temperature on flow stress were obtained by orthogonal test and variance analysis method. The modified nonlinear regression model of GH4169 rare earth reinforced Ni-base superalloy was established,and the correlation coefficient and average absolute relative error were introduced to verify the validity of the established constitutive equation method. The results show that the model can accurately describe the high temperature flow behavior of GH4169 rare earth reinforced Ni-base superalloy.
  • Study on rheological behavior and hot working process window of GH141 superalloy
    JIN Ming, ZHANG Jin-yuan
    Journal of Plasticity Engineering. 2023, 30(9): 142-149. https://doi.org/10.3969/j.issn.1007-2012.2023.09.017
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    To study the high temperature rheological behavior and hot working process window of GH141 superalloy,the isothermal compression experiments of GH141 superalloy were carried out under the conditions of deformation temperature of 1000-1200 ℃ and strain rate of 0.01-10 s-1,and 20 sets of high temperature rheological data were obtained. Hansel-Spittel constitutive model and hot working maps of GH141 superalloy were established based on high temperature rheological data. The microstructure of different hot compression samples was analyzed. The results show that the regression coefficient of Hensel-Spittel constitutive model to the rheological data of the material is 0.99,and its approximation accuracy is high. When the strain is 0.1,the unstable region appears in the temperature range of 1000~1100 ℃,with a logarithmic strain rate of approximately 1. When the strain is greater than 0.1,the unstable region located in the high-temperature and high-strain-rate region. When GH141 alloy is subjected to hot working at temperatures of 1000 and 1050 ℃,the original coarse microstructure undergoes deformation and elongation,accompanied by the formation of small recrystallized grains along grain boundaries. As the deformation temperature rises to 1100 ℃,some of the original coarse grains are replaced by smaller recrystallized grains,while some original grains remain within the material. When the temperature reaches 1150 and 1200 ℃,all the original coarse grains in GH141 alloy are completely replaced by new and fine recrystallized grains. Microscopic analysis validates the utility of the hot working map in quantifying the extent of dynamic recrystallization in GH141 alloy. Combining the hot working map,microstructure and dynamic recrystallization distribution,the optimal hot working process window for GH141 alloy is determined to be within strain rate range of 0.01-0.1 s-1 and temperature range of 1150-1200 ℃.
  • Hot deformation behavior of 34MnSiCrNiAlMo bainitic steel for frog
    SHAO Chao-yu, WANG Hai-xia, YE Neng-yong, ZHOU Zhen-ping
    Journal of Plasticity Engineering. 2023, 30(9): 150-157. https://doi.org/10.3969/j.issn.1007-2012.2023.09.018
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    To realize self-controllable forming technology of complex and variable cross-section core parts of railway frog,the hot deformation behaviors of 34MnSiCrNiAlMo bainite steel for frog under the conditions of deformation temperature of 800-1200 ℃,strain rate of 0.01-10 s-1,compression deformation of 0.2-0.8 were studied on Gleeble-3800 thermal simulator using single pass hot compression experiments based on integral roll-forging process. The true stress-true strain curves were obtained,and the constitutive equation and hot processing maps of 34MnSiCrNiAlMo bainite steel were established,and the appropriate hot working conditions were acquired:true strain is 0.8,temperature is 820-1150 ℃,and strain rate is 0.1-10 s-1. In addition,the microstructure analysis results show that the microstructure is mainly bainite and contains a small amount of residual austenite. The deformation temperature and strain rate have a great impact on the microstructure. The width of bainite ferrite lath is coarser because of the recrystallization process.
  • A new method for fatigue life calculation of notched parts based on stress field intensity theory
    ZENG Yun, HUANG Bo-wen, ZHOU Si-zhu
    Journal of Plasticity Engineering. 2023, 30(9): 158-165. https://doi.org/10.3969/j.issn.1007-2012.2023.09.019
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    To further accurately evaluate the fatigue behavior of notched parts,based on the stress field intensity method,in view of the traditional determination of fatigue damage area is controversial,considering the comprehensive effect of the grain size and stress at each point on the damaged area,a heart-shaped fatigue damage area was proposed,the weight function and damage area definition standards were corrected,a new fatigue life prediction model was established. The fatigue test and example verification of the pump head material 40CrNi2MoV were carried out,the results show that the calculation cost is reduced by the new method,and the fatigue life prediction accuracy of round hole parts and V-shaped notched parts are improved by 20%-50% and 10%-35%,respectively. It is suitable for fatigue life prediction of different notch types.
  • Influence of different control methods on biaxial tensile properties of DP980 steel
    LIANG Xiao, RAN Mao-yu, LI Xiao-tong, XU Xin, LIN Li, LI Chun-lin, SU Hong-ying, LIU Ren-dong
    Journal of Plasticity Engineering. 2023, 30(9): 166-172. https://doi.org/10.3969/j.issn.1007-2012.2023.09.020
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    Taking DP980 steel as the research object,the biaxial tensile test machine was used to carry out biaxial tensile tests with tensile ratios of 4∶1,4∶2,4∶3,4∶4,3∶4,2∶4 and 1∶4 using loading methods of load control,strain control and displacement control. The biaxial tensile stress-strain curves with seven tensile ratios and three control methods were obtained,the offsets change process of the marked point pasted at the center of the specimen was collected with a video extensometer,and the loading history and biaxial tensile curves of the materials under three stability control methods were analyzed. The results show that there are obvious differences between the biaxial tensile curves obtained under three control methods,even if the tensile ratios of the material in two loading directions are same,its stress and strain are not same due to anisotropy. The marked center point has the smallest offset in the strain-controlled test,the change of load and strain during the displacement-controlled test is large.
  • Influence of strain path on residual lamella of TiAl alloy
    LI Dong, ZHU Bin, CHEN Yi, CHENG Liang
    Journal of Plasticity Engineering. 2023, 30(9): 173-179. https://doi.org/10.3969/j.issn.1007-2012.2023.09.021
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    In view the problem of the plasticity of TiAl alloy with full lamella structure affected by a large number of residual lamella after bloom forging,the isothermal compression was carried out in TiAl alloy(α+γ)phase region,the influence of different strain paths on the residual lamella of TiAl alloy was studied. Compression directions and forging direction are 0°,45°and 90°,respectively.The results show that the initial forging structure consists of a large number of residual lamella and recrystallized grains between lamellar clusters. After hot deformation in 0° direction,the microstructure becomes more uniform and the residual lamella decreases significantly. The specimen compressed in 45° direction has uniform microstructure,and the residual lamella are basically decomposed. After compression in 90° direction,part of the residual lamella of sample is decomposed,and the deformed residual lamella interface is 90° to the compression direction. The change of strain path is beneficial to the decomposition of residual lamella. The sample compressed in 45° direction has the lowest rheological softening degree,high grain isometric degree and the best decomposition effect.
  • Bending deformation characteristics of stiffener plate of double-sided laser peen forming of stiffener
    TANG Xin-sen, JIANG Jian-cheng, HU Yong-xiang
    Journal of Plasticity Engineering. 2023, 30(9): 180-187. https://doi.org/10.3969/j.issn.1007-2012.2023.09.022
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    Aiming at the bending deformation problem of stiffener plate of double-sided laser peening of stiffener,the numerical model of stiffener plate of double-sided laser peening of stiffener based on the eigenstrain theory was established. The double-sided laser peening of stiffener simulation and experiment study of stiffener plate were carried out. The numerical model was used to analyze the bending deformation law and deformation characteristics of stiffener plate of laser peening forming of stiffener. The results show that bending deformation of stiffener plate increases with the increase of double-sides laser peening area of stiffener,and the increase amplitude gradually decreases from 71.4% to 6.1%. With the same peening area,the closer the peening area to the skin,the smaller the bending deformation of the stiffener plate. In the case of double-sided laser peening of stiffener,the bending deformation of the stiffener plate is caused by the extension of the stiffener,and the stiffener plate exhibits hyperbolic bending deformation characteristics. The validity of the numerical model was verified by experiments.
  • Study on surface roughness control of metal matrix after slurry blasting based on BP neural network
    QI Hao, ZHOU Cun-long, CHAI Ze-lin, GUO Rui, LI Chun-yang
    Journal of Plasticity Engineering. 2023, 30(9): 188-194. https://doi.org/10.3969/j.issn.1007-2012.2023.09.023
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    Aiming at the problem of the lacking of accurate control model for substrate surface roughness after slurry blasting,the BP neural network prediction model of the slurry blasting process parameters on substrate surface roughness was constructed based on BP neural networks. Taking 304 stainless steel as the research object for the slurry blasting impact tests,the influence degree of each process parameter on the surface roughness was analyzed by analysis of variance test on the sample data,from which the input and output parameters of the network model were determined for the training and validation of the network model. The results show that the maximum relative error between the predicted value of the network model blasting velocity and the total sample is 4.80%;the maximum relative error between the roughness value obtained experimentally for the given blasting velocity by the network model result and the target value is 2.40%. It demonstrates that the neural network model can guide the process parameter setting and realize the accurate control of surface roughness of steel plate after impacting.
  • Impact response characteristics of composite honeycomb structures
    LI Cheng-bing, ZHANG Ji-tao, YE Qiang, LI Rui, LI Ren-fu, YANG Lan-ying
    Journal of Plasticity Engineering. 2023, 30(9): 195-203. https://doi.org/10.3969/j.issn.1007-2012.2023.09.024
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    Based on the traditional hexagonal honeycomb structure,a novel composite honeycomb structure model was designed by replacing part of the cell layers of the original hexagonal honeycomb structure with negative Poisson′s ratio structure. The effects of structural arrangement and relative density of composite honeycomb on deformation mode,dynamic impact stress,impact load efficiency and specific energy absorption with different impact velocities were studied by explicit dynamic finite element method. The results show that the deformation mode of composite honeycomb is more complex than that of hexagonal honeycomb under medium and low velocity impact. In addition to the impact velocity and structure arrangement,the nominal stress of composite honeycomb also depends on the relative density. Composite honeycomb shows negative Poisson′s ratio effect and has better platform stress. Under the same impact velocity,the peak stress of composite honeycomb with weak layer is obviously lower,showing better impact load efficiency. Reasonable selection of arrangement mode for composite honeycomb structure can obviously improve the energy absorption capacity of honeycomb structure.
  • Study on plastic damage assessment technology of X80 pipeline steel based on acoustic emission
    SONG Yu-jia, FAN Li-feng, YANG Xue-ling, GOU Jian-jun, WANG Sen, QIN Shu-qi
    Journal of Plasticity Engineering. 2023, 30(9): 204-210. https://doi.org/10.3969/j.issn.1007-2012.2023.09.025
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    To monitor and evaluate the service status of pipeline steel,taking the most widely used dual-phase structure X80 pipeline steel of bainite and polygonal ferrite (B+PF)as the reaearch object,the acoustic emission (AE)technology was used to monitor and evaluate its damage state during plastic deformation process. The acoustic emission signal denoising and feature extraction were processed using sym4 wavelet,Birge-Massart algorithm and wavelet packet decomposition algorithm,and the extracted features were selected by correlation analysis and LightGBM algorithm. Based on the energy dissipation model and considering the attenuation of elastic modulus during plastic damage process,the damage variables were defined to quantitatively characterize the plastic damage degree. The radial basis function neural network was used to realize the mapping relationship between characteristic parameters and damage variables. The results show that the method can monitor and evaluate pipeline steel in service.
  • Evaluation of uncertainty in steady creep rate measurement of nuclear grade Ag-In-Cd alloy
    FANG Yong-qiang, YU Ze-li, ZHANG Shu-xiang, JIA Meng-lin, LIU Ze-chen, WANG Ke, ZHENG Yi
    Journal of Plasticity Engineering. 2023, 30(9): 211-216. https://doi.org/10.3969/j.issn.1007-2012.2023.09.026
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    The steady creep rate of nuclear grade Ag-In-Cd alloy was measured,the mathematical model of uncertainty was established,the source was analyzed,the uncertainty was evaluated,and the influence of force value and temperature on the compression creep deformation was emphatically studied. The results show that the uncertainty of steady creep rate of Ag-In-Cd alloy mainly comes from the error of force value indication,coaxiality deviation of testing machine and the error and stability of temperature control system in L1 and L2.The uncertainty components of grating ruler in L1 and L2 uncertainty components and the factors in L0 and ti contribute very little to the uncertainty,which can be ignored. Steady state creep rate of Ag-In-Cd alloy is as follow vi=(0.00812± 0.00240)%·h-1,k=2,which is converted into the relative expanded uncertainty of Urel=29.6%,k=2,and the relative expanded uncertainty is very large. When the test result is close to the extreme value required by the product standard,the uncertainty must be fully considered.
  • Study on hole expansion strengthening and response characteristics of aerospace 7050 aluminum alloy
    ZHONG Da-zhi, JIAO Hai-tao, XU Ying-shan, LIU Xiao-peng, ZHANG Qi-liang
    Journal of Plasticity Engineering. 2023, 30(9): 217-225. https://doi.org/10.3969/j.issn.1007-2012.2023.09.027
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    To deeply understand the mechanical response characteristics of the mechanical joint holes expansion strengthening of aerospace 7050 aluminum alloy,several uneven indexes were proposed,and the influence of expasion strengthening parameters on the uneven distribution of residual stress was quantitatively evaluated by numerical simulation. Under alternating loading condition,the influence of expasion-strengthening parameters on the structural stress response was quantitatively analyzed from two dimensions of stress level and stress amplitude.The results show that the residual compressive stress beneficial to fatigue properties is obtained near the hole wall after the mandrel expasion. The stress is distributed in gradient along the thickness direction,and the uneven distribution indexes tend to gentle when the expansion amount exceeds a critical value. The transverse distribution characteristics of the longitudinal residual stress are changing from the high compressive stress with large gradient change and narrow distribution range near the hole wall to the low,gentle tensile stress with wide distribution range on outside,and the extreme values and the distribution range of residual compressive stress increase with the increase of the expansion amount. The longitudinal loading stress of the unextruded specimen decreases monotonically from the hole wall to the outside,and the stress concentration coefficient of the hole wall is reach up to 3.7-4.1,while the loading stress distribution curve of the hole extruded specimen is no longer monotonic due to the effect of compressive residual stress,and the hole wall stress is even less than 50% of the external stress with high expansion amount. The transverse distribution curves of unloading stress almost coincide with those of residual stress under high expansion amount,but the unloading stress near the hole wall is lower than the residual stress when the expansionn amount is less than a critical value. The mandrel hole expansion only reduces the stress near the hole wall,but does not change its amplitude.
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