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Analysis of Collapse in Flattening a Micro-grooved Heat Pipe by Lateral Compression

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Chinese Journal of Mechanical Engineering 2012年第6期25卷 1210-1217页

作者： LI Yong HE Ting ZENG Zhixin School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510640China

The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no other better method to solve this problem. A new method by heating the heat pipe is proposed to eliminate the collapse during the flattening process. The effectiveness of the proposed method is investigated through a theoretical model, a finite element（fe） analysis, and experimental method. Firstly, A theoretical model based on a deformation model of six plastic hinges and the Antoine equation of the working fluid is established to analyze the collapse of thin walls at different temperatures. Then, the fe simulation and experiments of flattening process at different temperatures are carried out and compared with theoretical model. Finally, the fe model is followed to study the loads of the plates at different temperatures and heights of flattened heat pipes. The results of the theoretical model conform to those of the fe simulation and experiments in the flattened zone. The collapse occurs at room temperature. As the temperature increases, the collapse decreases and finally disappears at approximately 130 ℃ for various heights of flattened heat pipes. The loads of the moving plate increase as the temperature increases. Thus, the reasonable temperature for eliminating the collapse and reducing the load is approximately 130℃. The advantage of the proposed method is that the collapse is reduced or eliminated by means of the thermal deformation characteristic of heat pipe itself instead of by external support. As a result, the heat transfer efficiency of heat pipe is raised.

关键词： tube flattening collapse micro-grooved heat pipe heating lateral compression fe simulation

Ballistic tests on hot-rolled Ti-6Al-4V plates:Experiments and numerical approaches

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Defence Technology（防务技术） 2023年第8期26卷 39-53页

作者： Alexander Janda Benjamin James Ralph Yael Demarty Marcel Sorger Stefan Ebenbauer Aude Prestl Ingo Siller Martin Stockinger Helmut Clemens Department of Materials Science Montanuniversitat LeobenFranz Josef-Straße 188700 LeobenAustria Department Product Engineering Montanuniversitat LeobenFranz Josef-Straße 188700 LeobenAustria French-German Research Institute of Saint-Louis 5 Rue du General Cassagnou68300 Saint-LouisFrance voestalpine BOEHLER Bleche GmbH&Co KG Boehler-Gasse 18680MürzzuschlagAustria

Superior ballistic performance and the lightweight character of Ti alloys are considered as main reasons for their use in armour applications against a broad spectrum of ballistic threats,***,fragment or blast *** dynamic loading caused by typical penetrators is characterized by high strain rates,only specific test methods allow a closer investigation of the respective material *** the present study,quasi-static and dynamic compression tests as well as ballistic tests were conducted on a twophase a+βalloy Ti-6Al-4V(in m%)manufactured by ***-deformation heat treatments,influencing microstructure and mechanical properties were applied in order to compare three different microstructural configurations:as-rolled,mill-annealed and ***,on the one hand,ballistic tests were employed for the determination of the ballistic limit velocity v_(50),compression tests,on the other hand,delivered essential input parameters for the application of the Johnson-Cook constitutive model in a finite element simulation of the impact *** comparison of experimental results to simulation results was supplemented by means of microstructural characterization of tested samples with the focus set on the prevalently observed deformation and damage mechanisms,as for example adiabatic shearing.

关键词： Ti-6Al-4V Ballistic performance Split Hopkinson pressure bar fe simulation Adiabatic shear bands Intermetallic phase

An innovative constraining ring rolling process for manufacturing conical rings with thin sterna and high ribs

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Chinese Journal of Aeronautics 2022年第8期35卷 324-339页

作者： Duanyang TIAN Xinghui HAN Lin HUA Xuan HU Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070 China School of Automotive Engineering Wuhan University of TechnologyWuhan 430070China

Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and *** ring rolling is the most preferred method for manufacturing high-performance ring parts,but it can hardly achieve the forming of CRTSHR due to the extreme geometry of *** solve this difficulty,an innovative constraining ring rolling process(CRR)is proposed in this paper to manufacture *** evaluate the proposed CRR and reveal its deformation behaviors,a thermomechanical coupled fe model for CRR of CRTSHR is ***,the experiment for CRR of CRTSHR is performed on a modified ring rolling machine,which proves that CRR of CRTSHR is feasible and the established fe model is *** on the reliable fe model,the metal flow mode in deformed CRTSHR is analyzed,and the deformation characteristics such as the stress state,strain distribution and the evolution of power parameters in CRR of CRTSHR are ***,the influences of key parameters such as the friction factor between ring and molds,the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by fe simulation.

关键词： Conical rings with thin sterna and high ribs Deformation characteristics fe simulation Metal flow Ring rolling

Cross-sectional deformation behavior of double-ridged rectangular tube with fillers in different stages of H-typed bending

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Chinese Journal of Aeronautics 2020年第6期33卷 1799-1811页

作者： Chunmei LIU Yuli LIU Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China

The bent double-ridged rectangular tube(DRRT)with high forming quality is helpful to improve the microwave transmission *** reducing the cross-sectional deformation in the H-typed bending process,in addition to using rigid mandrel to support the inside of tube,ridge groove fillers are also added to restrict the deformation of ridge *** of the change of stress and strain state of bent tube in bending,rigid mandrel retracting and specially twicespringback stages,and the springback of fillers,the cross-sectional deformation of tube in each stage may be ***,based on the ABAQUS platform,the finite element models(feM)for H-typed bending,mandrel retracting and twice-springback stages of H96 DRRT with fillers were established and *** is found that,for the height and width deformation of tube and spacing deformation of ridge grooves,retraction of mandrel can make the distribution of these deformations more uniform along the bending *** first springback can reduce these deformations significantly,which should be *** the second springback only increases them by less amount,which can be *** smaller height deformation of ridge groove and filler can be neglected.

关键词： Cross-sectional deformation fe simulation H96 double-ridged rectangular tube H-typed rotary draw bending Ridge groove fillers Twice-springback stage

Radial envelope forming mechanism and process design method for cylindrical rings with thin wall and high web ribs

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Chinese Journal of Aeronautics 2023年第12期36卷 461-476页

作者： Xinghui HAN Yanlei MIN Wuhao ZHUANG Lin HUA Duanyang TIAN Zushen DENG Ningbo LIU Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070China Hubei Longzhong LaboratoryXiangyang 441000China

Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace ***,it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins,high web ribs and large *** this paper,a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high ***,the principle of radial envelope forming process is ***,an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle,i.e.,CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single ***,a reasonable 3D fe model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively *** the fe simulation and experiments with material of plastic mud,a typical CRTWHWR with diameter of 300 mm,axial height of 192 mm,the maximum rib height of 25 mm,the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed,i.e.,the ratio of the maximum rib height to the minimum rib thickness reaches 8.33,the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches *** above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.

关键词： Radial envelope forming Cylindrical ring with thin wall and high web ribs Forming mechanism fe simulation Tool design

Broadside Compensation Rolling Model for Plan View Pattern Control in Wide and Heavy Plate Rolling Process

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Journal of Iron and Steel Research International 2014年第5期21卷 503-508页

作者： Jin-hua RUAN Li-wen ZHANG Sen-dong GU Jian-lin ZHANG Wen-bin HE Shao-hui CHEN School of Materials Science and Engineering Dalian University of Technology Jiangsu Shagang Group Co. Ltd.

On the basis of a 5 m plate mill, a 3D rigid-plastic finite element （fe） model was developed to investigate changes of plate plan view patterns during hot rolling process. By analyzing the simulation results of conventional rolling processes, it was found that the plate plan view pattern was closely related to broadside rolling ratio. Then, the prediction models for plate plan view patterns were formulated by nonlinear regressive analysis of the simulation results and modified for high accuracy. Based on these models, the broadside compensation rolling method perform- ing at the last pass of broadside rolling phase was designed to decrease plate end crops. Comparing the plate plan view patterns with and without broadside compensation roiling, reduced plate end crops indicate that the broadside compensation roiling model is effective for plate plan view pattern control.

关键词： wide and heavy plate plate plan view pattern broadside compensation roiling method fe simulation

Thermal simulation of flexible LED package enhanced with copper pillars

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Journal of Semiconductors 2015年第6期36卷 85-88页

作者：刘洋梁润园黄洁莹袁长安张国旗孙凤莲 School of Material Science and Engineering Harbin University of Science and Technology Beijing Research Centre Delft University of Technology State Key Laboratory of Solid State Lighting Institute of Semiconductors Chinese Academy of Sciences DIMES Center for SSL Technologies Delft University of Technology

Chip on flexible substrate （COF） is a new packaging technology for light emitting diodes （LED）. This paper investigated the effect of Cu-pillar in the polyimide （PI） layer on the thermal properties of COF LED pack- ages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer sig- nificantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.

关键词： COF LED Cu-pillar thermal performance fe simulation

Ductile Fracture Prediction of 316LN Stainless Steel in Hot Deformation Process

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Journal of Iron and Steel Research International 2014年第10期21卷 923-930页

作者： Jian-li HE Juan LIU Zhen-shan CUI Chao-zhong YANG fei CHEN School of Materials Engineering Shanghai University of Engineering Science National Engineering Research Center for Die and Mold CAD School of Materials Science and EngineeringShanghai Jiao Tong University

A ductile fracture criterion of 316LN stainless steel, combined with the plastic deformation capacity of ma- terial and the stress state dependent damages, was proposed to predict ductile fracture during hot deformation. To the end, tensile tests at high temperatures were first performed to investigate the fracture behavior of 316LN stain- less steel. The experimental results show the variation of the critical fracture strain as a function of temperature and strain rate. Second, the criterion was calibrated by using the upsetting tests and the corresponding numerical simula- tions. Finally, the proposed fracture criterion was validated by the designed tests and the corresponding finite ele- ment （fe） simulation. The results show that the criterion can successfully predict the onset of ductile fracture at ele- vated temperatures.

关键词： ductile fracture criterion fe simulation upsetting test fracture behavior 316LN stainless steel

ExExperimental and numerical studies on the prediction of bendability limit of QSTE340 welded tube in NC bending process

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Science China(Technological Sciences) 2012年第8期55卷 2264-2277页

作者： YANG He REN Ning ZHAN Mei ZHANG ZhiYong QIN YaTao JIANG HaoMin DIAO KeShan CHEN XinPing State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Baosteel Group Corporation Shanghai 200122China

For a low carbon steel tube with small wall factor D/t and bending radius R,the over-thinning induced localized necking is one dominant failure in tube numerical control(NC) bending process,which strongly restricts the bendability limit of the *** addition,the deterioration of bendability of a tube is increased by the existence of the weak weld ***,an important issue is how to determinate and predict the welded tube bendability *** the present study,a finite element(fe) model with weld and subdivided heat affected zones under ABAQUS platform is employed to explore the deformation behaviors of welded tube NC bending.A localized necking criterion based on the critical thickness thinning is used to predict the critical principal strains,critical bending radius and burst location during the forming *** is found that the failures always occur at the rigid supporting point of mandrel flexible balls near the tangent point at the outside of the bend,where the wall thickness of the tube is the *** bending limit curves(BLCs) of the QSTE340 welded tube are obtained by shifting the standard shaped forming limit curve to the critical principal strains along the major strain *** between the numerical and experimental results has shown that the BLC and critical bending radius predictions agree well with the experimental *** addition,the effect of weld positions on BLC is discussed,the weld region shows an almost negligible effect on the forming limit at a non-critical location that is far away from the outside of the ***,when the weld is at the large tensile deformation region on the outside of the bend,a decrease of the forming limit strains is seen.

关键词： bendability limit welded tube NC bending fe simulation critical thickness thinning