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GENERAL SOLUTION FOR U-SHAPED BELLOWS OVERALL-BENDING PROBLEMS 被引量:4
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作者 朱卫平 郭平 黄黔 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2000年第4期371-382,共12页
The formulae for stresses and angular displacements of U-shaped bellows overall bending in a meridian plane under pure bending moments are presented based on the general solution for slender ring shells proposed by Zh... The formulae for stresses and angular displacements of U-shaped bellows overall bending in a meridian plane under pure bending moments are presented based on the general solution for slender ring shells proposed by Zhu Weiping, et al. and the solution for ring plates. The results evaluated in this paper are compared with those on EJMA (standards of the expansion joint manufacturers association) and of the experiment given by Li Tingxilz, et al. 展开更多
关键词 flexible shells shells of revolution circular ring shells BELLOWS u-shaped bellows
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GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅳ)-CALCULATION FOR U-SHAPED BELLOWS
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作者 ZHU Wei-ping(朱卫平) +1 位作者 HUANG Qian(黄黔) 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2002年第10期1164-1169,共6页
This is one of the applications of Part (Ⅰ),in which the angular stiffness, and the corresponding stress distributions of U_shaped bellows were discussed. The bellows was divided into protruding sections, concave sec... This is one of the applications of Part (Ⅰ),in which the angular stiffness, and the corresponding stress distributions of U_shaped bellows were discussed. The bellows was divided into protruding sections, concave sections and ring plates for the calculation that the general solution (Ⅰ) with its reduced form to ring plates were used respectively, but the continuity of the surface stresses and the meridian rotations at each joint of the sections were entirely satisfied. The present results were compared with those of the slender ring shell solution proposed earlier by the authors, the standards of the Expansion Joint Manufacturers Association (EJMA), the experiment and the finite element method. It is shown that the governing equation and the general solution (Ⅰ) are very effective. 展开更多
关键词 theory of flexible shell circular ring shell U_shaped bellows pure bending general solution
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Numerical analysis of dimension precision of U-shaped aluminium profile rotary stretch bending 被引量:5
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作者 于忠奇 林忠钦 《中国有色金属学会会刊:英文版》 EI CSCD 2007年第3期581-585,共5页
In order to enhance the dimension precision of bent part, advanced bending technologies is requested recently. Rotary stretch bending(RSB) is a suitable technology to realize high precision of bent part. The effect of... In order to enhance the dimension precision of bent part, advanced bending technologies is requested recently. Rotary stretch bending(RSB) is a suitable technology to realize high precision of bent part. The effect of processing parameters, namely the side pressure and the stretching force, on the dimension precision of aluminium profile RSB part was studied by finite element method. The numerical simulation of the U-shaped aluminium profile RSB was carried out, and the validity of the simulation was checked. Parametric analysis shows that the section distortion of the U-shaped profile LY12M bent part decreases with the increasing of the side pressure, whereas the springback of curvature increases, and that both of the section distortion and the springback of curvature decrease with the increasing of the stretching force, moreover, the uniformity of curvature of the bent part is clearly enhanced with the increasing of the stretching force. The results above prove that RSB technology can better improve the dimension precision of aluminium profile bent part. 展开更多
关键词 数值分子 旋转拉伸 铝材料 回弹性能
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Experimental,Numerical,and Analytical Studies on the Bending of Mechanically Lined Pipe 被引量:1
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作者 WEI Wen-bin YUAN Lin +1 位作者 ZHOU Jia-sheng LIU Zheng 《China Ocean Engineering》 SCIE EI CSCD 2024年第2期221-232,共12页
Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which cau... Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole line.In this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical methods.Two types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,respectively.The hydraulic expansion and bending experiments of small-scale MLPs are conducted.In addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive side.In contrast,the liner of ALP remains intact without developing any wrinkling and collapse mode.In addition,a dedicated numerical framework and theoretical models were also established.It was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results. 展开更多
关键词 lined pipe bending nonlinear ring theory BUCKLING PLASTICITY
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Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys 被引量:1
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作者 Sumi Jo Gyo Myeong Lee +2 位作者 Jong Un Lee Young Min Kim Sung Hyuk Park 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第2期779-793,共15页
This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The ext... This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air cooling.The extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during extrusion.Due to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser grains.The AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,respectively.However,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and propagation.During bending,a macrocrack initiates on the outer surface of bending specimen in both alloys.The AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 alloy.The bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the specimen.In bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relationship ofε_(f,bending)=–0.1A_(ppt)+5.86. 展开更多
关键词 Mg–Al alloy EXTRUSION bending Precipitation Microstructure
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DAUNet: Detail-Aware U-Shaped Network for 2D Human Pose Estimation
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作者 Xi Li Yuxin Li +2 位作者 Zhenhua Xiao Zhenghua Huang Lianying Zou 《Computers, Materials & Continua》 SCIE EI 2024年第11期3325-3349,共25页
Human pose estimation is a critical research area in the field of computer vision,playing a significant role in applications such as human-computer interaction,behavior analysis,and action recognition.In this paper,we... Human pose estimation is a critical research area in the field of computer vision,playing a significant role in applications such as human-computer interaction,behavior analysis,and action recognition.In this paper,we propose a U-shaped keypoint detection network(DAUNet)based on an improved ResNet subsampling structure and spatial grouping mechanism.This network addresses key challenges in traditional methods,such as information loss,large network redundancy,and insufficient sensitivity to low-resolution features.DAUNet is composed of three main components.First,we introduce an improved BottleNeck block that employs partial convolution and strip pooling to reduce computational load and mitigate feature loss.Second,after upsampling,the network eliminates redundant features,improving the overall efficiency.Finally,a lightweight spatial grouping attention mechanism is applied to enhance low-resolution semantic features within the feature map,allowing for better restoration of the original image size and higher accuracy.Experimental results demonstrate that DAUNet achieves superior accuracy compared to most existing keypoint detection models,with a mean PCKh@0.5 score of 91.6%on the MPII dataset and an AP of 76.1%on the COCO dataset.Moreover,real-world experiments further validate the robustness and generalizability of DAUNet for detecting human bodies in unknown environments,highlighting its potential for broader applications. 展开更多
关键词 Human pose estimation keypoint detection u-shaped network architecture spatial grouping mechanism
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A U-Shaped Network-Based Grid Tagging Model for Chinese Named Entity Recognition
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作者 Yan Xiang Xuedong Zhao +3 位作者 Junjun Guo Zhiliang Shi Enbang Chen Xiaobo Zhang 《Computers, Materials & Continua》 SCIE EI 2024年第6期4149-4167,共19页
Chinese named entity recognition(CNER)has received widespread attention as an important task of Chinese information extraction.Most previous research has focused on individually studying flat CNER,overlapped CNER,or d... Chinese named entity recognition(CNER)has received widespread attention as an important task of Chinese information extraction.Most previous research has focused on individually studying flat CNER,overlapped CNER,or discontinuous CNER.However,a unified CNER is often needed in real-world scenarios.Recent studies have shown that grid tagging-based methods based on character-pair relationship classification hold great potential for achieving unified NER.Nevertheless,how to enrich Chinese character-pair grid representations and capture deeper dependencies between character pairs to improve entity recognition performance remains an unresolved challenge.In this study,we enhance the character-pair grid representation by incorporating both local and global information.Significantly,we introduce a new approach by considering the character-pair grid representation matrix as a specialized image,converting the classification of character-pair relationships into a pixel-level semantic segmentation task.We devise a U-shaped network to extract multi-scale and deeper semantic information from the grid image,allowing for a more comprehensive understanding of associative features between character pairs.This approach leads to improved accuracy in predicting their relationships,ultimately enhancing entity recognition performance.We conducted experiments on two public CNER datasets in the biomedical domain,namely CMeEE-V2 and Diakg.The results demonstrate the effectiveness of our approach,which achieves F1-score improvements of 7.29 percentage points and 1.64 percentage points compared to the current state-of-the-art(SOTA)models,respectively. 展开更多
关键词 Chinese named entity recognition character-pair relation classification grid tagging u-shaped segmentation network
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Fabrication of lightweight 3D interpenetrated NiTi@Mg composite with superior bending properties
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作者 Yu-jing LIU Xiao-chun LIU +4 位作者 Kun-mao LI Xiang WU Sheng-feng ZHOU Wei LI Wen-cai ZHANG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第11期3569-3584,共16页
A NiTi@Mg interpenetrating phase composite with high strength and lightweight was prepared by additive manufacturing(AM)and infiltration technology,and the interface bonding,three-point bending properties and cyclic c... A NiTi@Mg interpenetrating phase composite with high strength and lightweight was prepared by additive manufacturing(AM)and infiltration technology,and the interface bonding,three-point bending properties and cyclic compressive properties of NiTi@Mg composites were investigated.The results show that the metallurgically bonded interface is formed at the NiTi/Mg interfaces.The bending strength and compressive strength of the NiTi@Mg composite are 2.5 and 1.7 times higher than those of the NiTi scaffold,respectively.During the bending deformation process,a large number of dislocations are observed to accumulate in the soft Mg area at the interface.Furthermore,the finite element model showed that the stress accumulation area,where the bending crack is initiated,is located at the interface of NiTi and Mg.The strengthening mechanism of NiTi@Mg composites is attributed to the twinning strengthening of Mg and heterogeneous structure strengthening. 展开更多
关键词 metal composites NiTi@Mg bending properties finite element simulation strengthening mechanism
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Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects
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作者 HOU Fu-heng JIA Lu-sheng +3 位作者 CHEN Yan-fei ZHANG Qi ZHONG Rong-feng WANG Chun-sha 《China Ocean Engineering》 SCIE EI CSCD 2024年第4期636-647,共12页
A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression... A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression strain capacity may be exceeded.Research into the local buckling failure and accurate prediction of the compressive strain capacity are important.A finite element model of a pipeline with a dent is established.Local buckling failure under a bending moment is investigated,and the compressive strain capacity is calculated.The effects of different parameters on pipeline local buckling are analyzed.The results show that the dent depth,external pressure and internal pressure lead to different local buckling failure modes of the pipeline.A higher internal pressure indicates a larger compressive strain capacity,and the opposite is true for external pressure.When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1,the deeper the dent,the greater the compressive strain capacity of the pipeline.And as the ratio is less than 0.1,the opposite is true.On the basis of these results,a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed,which can be referred to during the integrity assessment of a submarine pipeline. 展开更多
关键词 submarine pipeline dent defect bending load local buckling compressive strain capacity
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Cryogenic springback of 2219-W aluminum alloy sheet through V-shaped bending
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作者 Xiao-bo FAN Qi-liang WANG +1 位作者 Fang-xing WU Xu-gang WANG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第10期3185-3193,共9页
A V-shaped bending device was established to evaluate the effects of temperature and bending fillet radius on springback behavior of 2219-W aluminum alloy at cryogenic temperatures.The cryogenic springback mechanism w... A V-shaped bending device was established to evaluate the effects of temperature and bending fillet radius on springback behavior of 2219-W aluminum alloy at cryogenic temperatures.The cryogenic springback mechanism was elucidated through mechanical analyses and numerical simulations.The results indicated that the springback angle at cryogenic temperatures was greater than that at room temperature.The springback angle increased further as the temperature returned to ambient conditions,attributed to the combined effects of the “dual enhancement effect” and thermal expansion.Notably,a critical fillet radius made the springback angle zero for 90° V-shaped bending.The critical fillet radius at cryogenic temperatures was smaller than that at room temperature,owing to the influence of temperature variations on the bending moment ratio between the forward bending section at the fillet and the reverse bending section of the straight arm. 展开更多
关键词 2219-W aluminum alloy cryogenic forming V-shape bending SPRINGBACK critical fillet radius
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Analysis of deformation mechanisms in magnesium single crystals using a dedicated four-point bending tester
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作者 Yutaka Yoshida Rikuto Izawa Kenji Ohkubo 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第5期1911-1917,共7页
In this study,we explored the deformation mechanisms of Mg single crystals using a combination of scanning electron microscopy and electron backscattered diffraction in conjunction with a dedicated four-point bending ... In this study,we explored the deformation mechanisms of Mg single crystals using a combination of scanning electron microscopy and electron backscattered diffraction in conjunction with a dedicated four-point bending tester.We prepared two single-crystal samples,oriented along the<1120>and<1010>directions,to assess the mechanisms of deformation when the initial basal slip was suppressed.In the<1120>sample,the primary{1012}twin(T1)was confirmed along the<1120>direction of the sample on the compression side with an increase in bending stress.In the<1010>sample,T1 and the secondary twin(T2)were confirmed to be along the<1120>direction,with an orientation of±60°with respect to the bending stress direction,and their direction matched with(0001)in T1 and T2.This result implies that crystallographically,the basal slip occurs readily.In addition,the<1010>sample showed the double twin in T1 on the compression side and the tertiary twin along the<1010>direction on the tension side.These results demonstrated that the maximum bending stress and displacement changed significantly under the bend loading because the deformation mechanisms were different for these single crystals.Therefore,the correlation between bending behavior and twin orientation was determined,which would be helpful for optimizing the bending properties of Mg-based materials. 展开更多
关键词 Four-point bending Magnesium single crystal TWINNING Basal slip Scanning electron microscopy Electron backscatter diffraction
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Bending strength degradation of a cantilever plate with surface energy due to partial debonding at the clamped boundary
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作者 Zhenliang HU Xueyang ZHANG Xianfang LI 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第9期1573-1594,共22页
This paper investigates the bending fracture problem of a micro/nanoscale cantilever thin plate with surface energy,where the clamped boundary is partially debonded along the thickness direction.Some fundamental mecha... This paper investigates the bending fracture problem of a micro/nanoscale cantilever thin plate with surface energy,where the clamped boundary is partially debonded along the thickness direction.Some fundamental mechanical equations for the bending problem of micro/nanoscale plates are given by the Kirchhoff theory of thin plates,incorporating the Gurtin-Murdoch surface elasticity theory.For two typical cases of constant bending moment and uniform shear force in the debonded segment,the associated problems are reduced to two mixed boundary value problems.By solving the resulting mixed boundary value problems using the Fourier integral transform,a new type of singular integral equation with two Cauchy kernels is obtained for each case,and the exact solutions in terms of the fundamental functions are determined using the PoincareBertrand formula.Asymptotic elastic fields near the debonded tips including the bending moment,effective shear force,and bulk stress components exhibit the oscillatory singularity.The dependence relations among the singular fields,the material constants,and the plate's thickness are analyzed for partially debonded cantilever micro-plates.If surface energy is neglected,these results reduce the bending fracture of a macroscale partially debonded cantilever plate,which has not been previously reported. 展开更多
关键词 micro/nanoscale cantilever plate partially debonded bending fracture singular integral equation oscillatory singularity
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A Light and Simplified Branch Bending Method for Young Pear Trees
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作者 Jintao XU Longfei LI +3 位作者 Minghui JI Huan LIU Lijuan GAO Baofeng HAO 《Plant Diseases and Pests》 2024年第2期19-21,共3页
Aiming at high cost and low efficiency of conventional branch bending method in the modern intensive planting and labor-saving cultivation mode of young pear trees,this paper provides a new branch bending method with ... Aiming at high cost and low efficiency of conventional branch bending method in the modern intensive planting and labor-saving cultivation mode of young pear trees,this paper provides a new branch bending method with wide source of raw materials,cheap price and simple operation,which is also suitable for the management of low-age branches in the process of high grafting and upgrading of traditional big trees. 展开更多
关键词 Pear tree Light and simplified Branch bending METHOD
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The Effects of the Longitudinal Axis of Loading upon Bending, Shear and Torsion of a Thin-Walled Cantilever Channel Beam
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作者 David W. A. Rees Abdelraouf M. Sami Alsheikh 《World Journal of Mechanics》 2024年第5期73-96,共24页
Three aluminium channel sections of US standard extruded dimension are mounted as cantilevers with x-axis symmetry. The flexural bending and shear that arise with applied axial torsion are each considered theoreticall... Three aluminium channel sections of US standard extruded dimension are mounted as cantilevers with x-axis symmetry. The flexural bending and shear that arise with applied axial torsion are each considered theoretically and numerically in terms of two longitudinal axes of loading not coincident with the shear centre. In particular, the warping displacements, stiffness and stress distributions are calculated for torsion applied to longitudinal axes passing through the section’s centroid and its web centre. The stress conversions derived from each action are superimposed to reveal a net sectional stress distribution. Therein, the influence of the axis position upon the net axial and shear stress distributions is established compared to previous results for each beam when loading is referred to a flexural axis through the shear centre. Within the net stress analysis is, it is shown how the constraint to free warping presented by the end fixing modifies the axial stress. The latter can be identified with the action of a ‘bimoment’ upon each thin-walled section. 展开更多
关键词 Thin-Aluminium Channels Cantilever Beam bending Shear Torsion WARPING BIMOMENT Flexural Axis Centre of Twist CENTROID Shear Centre Torsional Stiffness Constrained Stress
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Prediction of seismic-induced bending moment and lateral displacement in closed and open-ended pipe piles:A genetic programming approach
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作者 Laith Sadik Duaa Al-Jeznawi +2 位作者 Saif Alzabeebee Musab A.Q.Al-Janabi Suraparb Keawsawasvong 《Artificial Intelligence in Geosciences》 2024年第1期82-95,共14页
Ensuring the reliability of pipe pile designs under earthquake loading necessitates an accurate determination of lateral displacement and bending moment,typically achieved through complex numerical modeling to address... Ensuring the reliability of pipe pile designs under earthquake loading necessitates an accurate determination of lateral displacement and bending moment,typically achieved through complex numerical modeling to address the intricacies of soil-pile interaction.Despite recent advancements in machine learning techniques,there is a persistent need to establish data-driven models that can predict these parameters without using numerical simulations due to the difficulties in conducting correct numerical simulations and the need for constitutive modelling parameters that are not readily available.This research presents novel lateral displacement and bending moment predictive models for closed and open-ended pipe piles,employing a Genetic Programming(GP)approach.Utilizing a soil dataset extracted from existing literature,comprising 392 data points for both pile types embedded in cohesionless soil and subjected to earthquake loading,the study intentionally limited input parameters to three features to enhance model simplicity:Standard Penetration Test(SPT)corrected blow count(N60),Peak Ground Acceleration(PGA),and pile slenderness ratio(L/D).Model performance was assessed via coefficient of determination(R^(2)),Root Mean Squared Error(RMSE),and Mean Absolute Error(MAE),with R^(2) values ranging from 0.95 to 0.99 for the training set,and from 0.92 to 0.98 for the testing set,which indicate of high accuracy of prediction.Finally,the study concludes with a sensitivity analysis,evaluating the influence of each input parameter across different pile types. 展开更多
关键词 Genetic programming Pipe piles Lateral response bending moment Earthquake loading Standard penetration test Machine learning
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Three-point bending behavior of aluminum foam sandwich with steel panel 被引量:7
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作者 祖国胤 卢日环 +4 位作者 李小兵 仲照阳 马幸江 韩明博 姚广春 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第9期2491-2495,共5页
Static three-point bending tests of aluminum foam sandwiches with glued steel panel were performed. The deformation and failure of sandwich structure with different thicknesses of panel and foam core were investigated... Static three-point bending tests of aluminum foam sandwiches with glued steel panel were performed. The deformation and failure of sandwich structure with different thicknesses of panel and foam core were investigated. The results indicate that the maximum bending load increases with the thickness of both steel panel and foam core. The failure of sandwich can be ascribed to the crush and shear damage of foam core and the delamination of glued interface at a large bending load, The crack on the foam wall developed in the melting foam procedure is the major factor for the failure of foam core. The sandwich structure with thick foam core and thin steel panel has the optimal specific bending strength. The maximum bending load of that with 8 mm panel and 50 mm foam core is 66.06 kN. 展开更多
关键词 aluminum foam sandwich three-point bending failure mode panel thickness
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Unified Solution Method of Rectangular Plate Elastic Bending 被引量:9
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作者 许琪楼 姬同庚 +2 位作者 姜锐 唐国明 姬鸿恩 《Journal of Southeast University(English Edition)》 EI CAS 2002年第3期241-248,共8页
The bending of rectangular plate is divided into the generalized statically determinate bending and the generalized statically indeterminate bending based on the analysis of the completeness of calculating condition a... The bending of rectangular plate is divided into the generalized statically determinate bending and the generalized statically indeterminate bending based on the analysis of the completeness of calculating condition at the corner point. The former can be solved directly by the equilibrium differential equation and the boundary conditions of four edges of the plate. The latter can be solved by using the superposition principle. Making use of the recommended method, the bending of the plate with all kinds of... 展开更多
关键词 bending of elastic thin plate rectangular plate unified solution method
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A modified Johnson-Cook model for NC warm bending of large diameter thin-walled Ti-6Al-4V tube in wide ranges of strain rates and temperatures 被引量:6
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作者 陶智君 樊晓光 +2 位作者 杨合 马俊 李恒 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2018年第2期298-308,共11页
Numerical control(NC) warm bending is a proven strategy to form the large diameter thin-walled(LDTW) Ti-6 Al-4 V tubes, which are typical light-weight and high-performance structural components urgently required i... Numerical control(NC) warm bending is a proven strategy to form the large diameter thin-walled(LDTW) Ti-6 Al-4 V tubes, which are typical light-weight and high-performance structural components urgently required in many industries. In virtue of unveiling the thermo-mechanical coupled deformation behaviors, uniaxial tensile tests were conducted on Ti-6 Al-4 V tube within wide ranges of temperatures(25-600 ℃) and strain rates(0.00067-0.1 s~(-1)). Moreover, a modified Johnson-Cook(JC) model is proposed with a consideration of nonlinear strain rate hardening and the interaction between strain hardening and thermal softening. Resultantly, the present model gives more accurate predictions for flow stress over the entire deformation ranges and the maximum error decreases by about 90%. By employing proposed model to NC warm bending, preferable precision is obtained in predicting forming defects including fracture, wrinkling and over thinning. The present work lays foundation for the forming limit prediction and process optimization in NC warm bending of LDTW Ti-6 Al-4 V tubes. 展开更多
关键词 NC warm bending Ti-6Al-4V tube Johnson-Cook model
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Theoretical analysis on springback of L-section extrusion in rotary stretch bending process 被引量:13
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作者 于成龙 李小强 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第12期2705-2710,共6页
The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and ... The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy. 展开更多
关键词 SPRINGBACK rotary stretch bending theoretical analysis
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Bending properties and fracture mechanism of C/C composites with high density preform 被引量:9
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作者 张明瑜 苏哲安 +1 位作者 李建立 黄启忠 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第8期1795-1800,共6页
C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration(CVI),with C3H6 as carbon source,N2 as carrier gas,and three-dimensional(3D) 12K PAN-based carbon fabric with high... C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration(CVI),with C3H6 as carbon source,N2 as carrier gas,and three-dimensional(3D) 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment(HTT) at the break of CVI process.According to the load?displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load?displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength. 展开更多
关键词 C/C composites chemical vapor infiltration(CVI) high density preform bending properties fracture mechanism
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