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Heat shock behavior of permanent die during non-solid near-net forming process

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中国有色金属学会会刊：英文版 2009年第S3期19卷 795-801页

作者：张密兰单忠德邢书明姜超许应 State Key Laboratory of Advanced forming Technologyand Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Science and Technology School of Mechanical and Engineering University of Science and Technology Beijing State Key Laboratory of Advanced forming Technology and Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Science and Technology School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University State Key Laboratory of Advanced forming Technology and Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Scienceand Technology

Heat shocks caused by alloy melt and coat spraying are the main reason of die plastic deformation and early fracture. Based on theoretical analysis of heat shock phenomenon, two characteristic parameters of die damage caused by heat shock were proposed, which are heat shock plastic deformation index (HSPI) and heat shock crack index (HSCI). The effect of heat shock on die plastic deformation and fracture behaviors was described quantitatively by these two parameters. HSPI represents approaching of heat shock stress to die yield stress. Plastic deformation will happen on a die if this index reaches 1. HSCI represents approaching of heat shock stress to die tensile strength. Die fracture will happen if this index reaches 1. According to theoretical analysis of heat transfer, theoretical models of HSPI and HSCI were established. It is found that, the smaller the interfacial thermal resistance (ITR) is, the higher the pouring temperature and die temperature are before heat shock, and the greater the HSPI and HSCI are, which can be fitted as exponential curves, linear and cubic curves.

关键词： non-solid near-net forming die heat shock heat shock plastic deformation index heat shock crack index

forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

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Science China(Technological Sciences) 2010年第2期53卷 326-342页

作者： YAN Jing, YANG He, ZHAN Mei & LI Heng College of Materials Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China College of Materials Science and Engineering State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China

With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

关键词： forming limit NC tube bending aluminum alloy thin-walled tubes with large diameters multi-index constraints finite element method

The Effect of Variable Blank-Holder Forces on the Formability of Aluminum Alloy Sheets during Sheet Metal forming

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上海交通大学学报 2004年第Z2期38卷 54-60页

作者： Sun Chengzhi Chen Guanlong Lin Zhongqin School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China

In this paper, the effect of variable Blank-holder forces (VBHF) on the strain path during sheet metal forming has been investigated by numerical simulation and experiments. The formability of select aluminum alloy sheet was evaluated by theory prediction of forming limit curve based on the M-K method. The effect of different VBHF on the formability was presented. In order to verify the predictions of strain path, experiments are being carried out using a recently-built multi-points variable blank-holder forces hydraulic press. The results show that large side BHF with small comer BHF during rectangular box deep drawing can improve the formability of the selected aluminum alloy

关键词： sheet metal forming variable blank-holder force strain path forming limit curve

Influence of deformation path on the forming effect in a multistep flexible rolling process

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International Journal of Minerals,Metallurgy and Materials 2018年第10期25卷 1173-1180页

作者： Ying Li Wen-zhi Fu Ming-zhe Li Xiao-dong Liu Shuo Sun Zhuo Yi Roll Forging Institute Jilin University College of materials science and engineering Jilin University

The flexible rolling process(FRP) is a novel three-dimensional(3 D) forming process that combines the multipoint and traditional rolling forming. The principle of FRP is based on thickness thinning, so the deformation path significantly impacts the forming effect. In this study, the multistep forming process with different deformation paths was introduced to improve the forming effect of FRP. For instance, with the convex surface part, three finite element models of multistep FRP(MSFRP) were established. The corresponding numerical simulations and forming experiments performed among different deformation paths showed the surface part with a longer effective forming region was obtained and the forming regions with more steps in MSFRP were smoother. Thus, the sheet-metal utilization rate was greatly improved. Moreover, the MSFRP can improve the longitudinal bending effect dramatically and thereby endowing the forming part with a better forming effect. Therefore, MSFRP is a prospective method for broad applications.

关键词： 3D surface forming multistep flexible rolling numerical simulation deformation path forming effect

Simulation of jet-flow solid fraction during spray forming

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International Journal of Minerals,Metallurgy and Materials 2017年第6期24卷 657-669页

作者： Zi-qiang Pi Xin Lu Yuan Wu Lu-ning Wang Cheng-chang Jia Xuan-hui Qu Wei Zheng Li-zhi Wu Qing-li Shao Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China Heye Special Steel Co. Ltd. Shijiazhuang 052165 China

A numerical model was developed to simulate the jet-flow solid fraction of W18Cr4 V high-speed steel during spray forming. The whole model comprises two submodels: one is an individual droplet model, which describes the motion and thermal behaviors of individual droplets on the basis of Newton's laws of motion and the convection heat transfer mechanism; the other is a droplet distribution model, which is used to calculate the droplet size distribution. After being verified, the model was used to analyze the effects of parameters, including the initial gas velocity, deposition distance, superheat degree, and the ratio of gas-to-metal mass flow rates, on the jet-flow solid fraction. Finally, an equation to predict the jet-flow solid fraction directly and conveniently according to the parameters was presented. The values predicted by the equation show good agreement with those calculated by the numerical model.

关键词： modeling steel spray forming solid fraction

A Review on Ultrasonic-Assisted forming:Mechanism,Model,and Process

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Chinese Journal of Mechanical Engineering 2021年第5期34卷 147-170页

作者： Guangda Shao Hongwei Li Mei Zhan Shaanxi Key Laboratory of Precision forming Technology and Equipment School of Materials Science and Engineering Northwestern Polytechnical University Xi’an China

Compared with conventional forming processes,ultrasonic-assisted forming technology with a high frequency and small amplitude can significantly improve the forming quality of materials.Owing to the advantages of reduced forming force,improved surface quality,avoidance of forming defects,and strengthened surface structure,ultrasonic-assisted forming technology has been applied to increasingly advanced forming processes,such as incremental forming,spinning,and micro-forming.However,in the ultrasonic-assisted forming process,there are multiple ultrasonic mechanisms,such as the volume effect and surface effect.The explanation of the effect of ultrasonic vibration(UV)on plastic deformation remains controversial,hindering the development of related technologies.Recently,many researchers have proposed many new theories and technologies for ultrasonic-assisted forming.To summarize these developments,systematic discussions on mechanisms,theoretical models,and forming performances are provided in this review.On this basis,the limitations of the current study are discussed.In addition,an outlook for ultrasonic-assisted forming is proposed:efficient and stable UV systems,difficulty forming components with complex geometry,explanation of the in-depth mechanism,a systematic theoretical prediction model,and multi-field-coupling energy-assisted forming are considered to be hot spots in future studies.The present review enhances existing knowledge of ultrasonic-assisted forming,and facilitates a fast reference for related researchers.

关键词： Ultrasonic vibration forming Mechanism Model Processing performance

Role of clove oil in solvent exchange-induced doxycycline hyclate-loaded Eudragit RS in situ forming gel

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Asian Journal of Pharmaceutical Sciences 2018年第2期13卷 131-142页

作者： Thawatchai Phaechamud Sai Myo Thurein Takron Chantadee Department of Pharmaceutical Technology Faculty of Pharmacy Silpakorn University Department Pharmaceutical Engineering Faculty of Pharmacy Silpakorn University Department of Pharmacognosy University of PharmacyMandalay Myanmar

Solvent exchange induced in situ forming gel(ISG) is the promising drug delivery system for periodontitis treatment owing to the prospect of maintaining an effective high drug level in the gingival crevicular fluid. In the present study, the influence of clove oil(CO) on the characteristics of doxycycline hyclate(DH)-loaded ISG comprising Eudragit RS(ERS) was investigated including viscosity/rheology, syringeability, in vitro gel formation/drug release, matrix formation/solvent diffusion and antimicrobial activities. CO could dissolve ERS and increase the viscosity of ISG and its hydrophobicity could also retard the diffusion of solvent and hinder the drug diffusion; thus, the minimization of burst effect and sustained drug release were achieved effectively. All the prepared ISGs comprising CO could expel through the 27-gauge needle for administration by injection and transform into matrix depot after exposure to the simulated gingival crevicular fluid. The antimicrobial activities against Staphylococcus aureus, Escherichia coli, Streptococcus mutans and Porphyromonas gingivalis were increased when the ratio of CO and N-methyl pyrrolidone(NMP) was decreased from 1:1 to 1:10 owing to higher diffusion of DH except that for C. albicans was increased as CO amount was higher.Therefore, CO could minimize the burst while prolonging the drug release of DH-loaded ERS ISG for use as a local drug delivery system for periodontitis treatment.

关键词： In situ forming gel Eudragit RS Clove oil Doxycycline hyclate Periodonditis Burst release

Heat treatment and granule medium internal highpressure forming of AA6061 tube

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Journal of Central South University 2017年第5期24卷 1040-1049页

作者：毕江赵长财毕蒙蒙杜冰陈晓华董国疆 Key Laboratory of Advanced Forging&Stamping Technology and Science of Ministry of Education of China Yanshan UniversityQinhuangdao 066004China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China College of Vehicles and Energy Yanshan UniversityQinhuangdao 066004China

The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the forming requirement, and the granule medium internal high pressure forming method for AA6061 alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. At a solution temperature of 560℃ and time of 120 min, the elongation of the AA6061 extruded tube increases by 300% and the strength and the hardness dramatically decrease too. Therefore, the AA6061 alloy tube meets the requirement of internal high-pressure forming because of the improvement of formability. The experiments shows that the strength and hardness of AA6061 alloy workpiece recover to that of the as-received alloy at an aging temperature of 180℃ and time of 360 min, and the strength of AA6061 alloy workpiece is equal to the base alloy. The typical parts of convex ring tube, stepped shaft tube and hexagonal tube were successfully produced in lab by using the present forming method. The forming tests show that the maximum expansion ratio(MER) of the AA6061 extruded tube increases by 25.5% and the material properties of formed AA6061 alloy tube reached the performance of as-received alloy.

关键词： aluminum alloy tube solution treatment aging treatment granule medium internal high pressure forming

Dislocation evolution with rheological forming of metal

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中国有色金属学会会刊：英文版 1999年第3期9卷 623-628页

作者： Luo Yingshe(罗迎社) Guo Xiaogang(郭小刚) Mei Yafu(梅亚夫) Hu Yungui(胡云贵) Res Inst Fundamental Mech & Mat Engn Xiangtan 411105 Peoples R China

It is known that some internal defects exist in metal materials. Preliminary attempt to relate dislocation evolution with metal rheological forming was done. By the attempt, it is learned that the evolution of dislocation density ρ(x, y, t) is essentially the change of n independent internal variables q α(α=1, 2, …, n) with material. The preliminary research in theory and experiments showed that dislocations piling up could be avoided. One can improve the internal microstructure and mechanical properties of products by rheological forming method.

关键词： dislocation metal rheological forming