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Influence of material models on theoretical forming limit diagram prediction for Ti-6Al-4V alloy under warm condition

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Transactions of Nonferrous Metals Society of China 2016年第3期26卷 736-746页

作者： Nitin KOTKUNDE Sashank SRINIVASAN Geetha KRISHNA Amit Kumar GUPTA Swadesh Kumar SINGH Department of Mechanical Engineering Birla Institute of Technology and Science-PilaniHyderabad CampusHyderabad 500078TelanganaIndia Department of Mechanical Engineering Gokaraju Rangaraju Institute of Engineering and TechnologyHyderabad 500072TelanganaIndia

forming limit diagram (FLD) is an important performance index to describe the maximum limit of principal strains that can be sustained by sheet metals till to the onset of localized necking. It offers a convenient and useful tool to predict the forming limit in the sheet metal forming processes. In the present study, FLD has been determined experimentally for Ti?6Al?4V alloy at 400 °C by conducting a Nakazima test with specimens of different widths. Additionally, for theoretical FLD prediction, various anisotropic yield criteria (Barlat 1989, Barlat 1996, Hill 1993) and different hardening models viz., Hollomon power law (HPL), Johnson?Cook (JC), modified Zerilli–Armstrong (m-ZA), modified Arrhenius (m-Arr) models have been developed. Theoretical FLDs have been determined using Marciniak and Kuczynski (M?K) theory incorporating the developed yield criteria and constitutive models. It has been observed that the effect of yield model is more pronounced than the effect of constitutive model for theoretical FLDs prediction. However, the value of thickness imperfection factor (f0) is solely dependent on hardening model. Hill (1993) yield criterion is best suited for FLD prediction in the right hand side region. Moreover, Barlat (1989) yield criterion is best suited for FLD prediction in left hand side region. Therefore, the proposed hybrid FLD in combination with Barlat (1989) and Hill (1993) yield models with m-Arr hardening model is in the best agreement with experimental FLD.

关键词： Ti-6Al-4V alloy yield criteria hardening model Marciniak and Kuczynski theory forming limit diagram

Experimental Study of the forming limit Stress diagram under Complex Strain Path

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Experimental Study of the Forming Limit Stress Diagram under...

Prediction and Verifcation of forming limit diagrams Based on a Modifed Shear Failure Criterion

2007国际机械工程与力学会议

作者： Hui WANG Lin GAO College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

forming limit diagram（FLD） has been widely used as a failure criterion in sheet metal forming simulation. However many investigations show that FLD can be effect by the loading path. Many experts have pointed out to take place of the FLD with forming limit stress diagram （FLSD） which shows little path dependency. The purpose of this paper is to study the precision of FLSD as a failure criterion in multistage metal forming simulation. forming limit diagram for both proportional and none proportional loading of a mild steel SPCEN with thickness of 0.8mm were determined through experiment. The effect of the strain path on FLD was studied. Then the forming limit stress diagram calculated from different FLD use Hill`s quadratic normal anisotropic plastic potential model. And FLD under different strain path calculated from the FLSD were compared with the experimental ones. All the processes were simulated with a FEM software Pamstamp2g and the precision of FLD and FLSD as a failure criterion in the simulation was tested. Results show that FLD got from different strain path of a same material have much different. The stress based forming limit diagram calculated from different strain path show little dependence on loading path. The forming limit stress diagram shows more precision in complex loading sheet metal forming process simulation.

关键词： strain path forming limit diagram sheet metal forming

来源： cnki会议评论

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Chinese Journal of Mechanical Engineering 2023年第5期36卷 364-373页

作者： Haibo Wang Zipeng Wang Yu Yan Yuanhui Xu School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

The forming limit diagram plays an important role in predicting the forming limit of sheet *** studies have shown that,the method to construct the forming limit diagram based on instability theory of the original shear failure criterion is efective and *** original shear instability criterion can accurately predict the left area of the forming limit diagram but not the right *** this study,in order to improve the accuracy of the original shear failure criterion,a modifed shear failure criterion was proposed based on in-depth analysis of the original shear failure *** detailed improvement strategies of the shear failure criterion and the complete calculation process are *** on the modifed shear failure criterion and diferent constitutive equations,the theoretical forming limit of TRIP780 steel and 5754O aluminum alloy sheet metals are *** comparing the theoretical and experimental results,it is shown that proposed modifed shear failure criterion can predict the right area of forming limit more reasonably than the original shear failure *** efect of the pre-strain and constitutive equation on the forming limits are also analyzed in *** modifed shear failure criterion proposed in this study provides an alternative and reliable method to predict forming limit of sheet metals.

关键词： Modifed shear failure criterion Sheet metal forming forming limit diagram Loading path

Hot Granules Medium Pressure forming Process of AA7075 Conical Parts

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Chinese Journal of Mechanical Engineering 2015年第3期28卷 580-591页

作者： DONG Guojiang ZHAO Changcai PENG Yaxin LI Ying College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University

High strength aluminum alloy plate has a low elongation at room temperature, which leads to the forming of its components need a high temperature. Liquid or gas is used as the pressure-transfer medium in the existing flexible mould forming process, the heat resistance of the medium and pressurizing device makes the application of aluminum alloy plate thermoforming restricted. To solve this problem, the existing medium is replaced by the heat-resisting solid granules and the general pressure equipments are applied. Based on the pressure-transfer performance test of the solid granules medium, the feasibility that the assumption of the extended Drucker-Prager linear model can be used in the finite element analysis is proved. The constitutive equation, the yield function and the theoretical forming limit diagram（FLD） of AA7075 sheet are established. Through the finite element numerical simulation of hot granules medium pressure forming（HGMF） process, not only the influence laws of the process parameters, such as forming temperature, the blank-holder gap and the diameter of the slab, on sheet metal forming performance are discussed, but also the broken area of the forming process is analyzed and predicted, which are coincided with the technological test. The conical part whose half cone angle is 15° and relative height H/d0 is 0.57, is formed in one process at 250℃. The HGMF process solves the problems of loading and seal in the existing flexible mould forming process and provides a novel technology for thermoforming of light alloy plate, such as magnesium alloy, aluminium alloy and titanium alloy.

关键词： granules medium aluminum alloy sheet drawing hot forming forming limit diagram

Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

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Journal of Central South University 2016年第4期23卷 765-777页

作者：董国疆赵长财赵建培押媛媛曹秒艳 College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education (Yanshan University)

Hot granule medium pressure forming （HGMF） process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. Hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram （FLD） of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175-300 ℃ is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 ℃. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

关键词： granule medium aluminum alloy sheet drawing hot forming forming limit diagram

Formability of Fe-Mn-C Twinning Induced Plasticity Steel

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Journal of Iron and Steel Research International 2013年第11期20卷 111-117页

作者： HUANG Yao ZHAO Ai-min MI Zhen-li JING Hai-tao LI Wen-yuan HUI Ya-jun Engineering Research Institute University of Science and Technology Beijing ME Department SAIC Motor Passenger Vehicle Co. Shougang Research Institute of Technology

A comparative analysis of formability was investigated between F^Mn-C twinning induced plasticity steel with different Mn contents and interstitial free steel. Tensile test combing with the morphology of fracture reveals that element Mn is helpful for the forming of inclusion or particles with film or rod shapes inducing the crack initia- tion and propagation. During stamping process, twinning induced plasticity steel without earing shows better anisot- ropy than interstitial-free steel because a typical 〈111〉 fiber texture forms accompanied by a weaker 〈100〉 fiber texture. The difference between the two steels is not evident during Erichsen cone cupping test, but the result of cone cupping test indicates that the twinning induced plasticity steel has superior drawing ability compared with intersti tial-free steel. The different performances can be attributed to the different deformation mechanism during cupping test. FED （forming limit diagram） of tested steels further suggests twinning induced plasticity steel has slightly su- perior deep drawability but low stretchability than that of IF steel, whose FLD0 value can reach 30%.

关键词： TWIP steel earing cone cupping forming limit diagram

Formability of TRIP/TWIP Steel Containing Manganese of 18.8%

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Journal of Iron and Steel Research International 2011年第1期18卷 36-40页

作者： DING Hao DING Hua QIU Chun-lin TANG Zheng you ZENG Jian min YANG Ping School of Materials and Metallurgy Northeastern University Shenyang 110819 I.iaoning China State Key l.aboratory of Rolling and Automation of Northeastern University Shenyang 110819 I.iaoning China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The mechanical property and forming limit experiments were carried out on a higli manganese TRIP/TWIP steels with manganese of 18.8%. And the forming /imit diagram was obtained. This hig：h manganese steel shows outstanding mechanical properties comhining high strength with good formability. Its limit plane strain corresponding to the lowest point in the plain strain condition is about 38%. The effects of conventional mechanical property on the limit plane strain were analyzed. With increasing the content of Mn, the limit plane strain increases, indicating that TWlP effect is advantageous to the increase of formability. Combining with three classical models and volume invaria ble principle, a FLD model was buih, which is suitable for high manganese steels very well.

关键词： high manganese TRIP/TWIP steel mechanical property formability forming limit diagram

Strain limit of Extra Galvannealed Interstitial-Free and Bake Hardened Steel Sheets Under Different Stress Conditions

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Journal of Iron and Steel Research International 2008年第5期15卷 56-60页

作者： R Narayanasamy N L Parthasarathi R Ravindran C Sathiya Narayanan Department of Production Engineering National Institute of TechnologyTiruchirappalli 620015TamilnaduIndia

The formability of bake hardened steel （thickness 0.82 mm）, and the extra galvannealed IF steel （thickness 0.82 mm） have been studied. The suitability of the above steels for forming applications has been critically examined. The microstructure, tensile properties, and formability parameters of the above sheet metals were determined. The manufacturing process of the steels and the significance with reference to its formability were studied.

关键词： bake hardened steel extra galvannealed IF steel microstructure forming limit diagram tensile parameter

Theoretical prediction and experimental investigation on formability of tailor-welded blanks

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Transactions of Nonferrous Metals Society of China 2016年第1期26卷 228-236页

作者：马向东官英平燕山大学先进锻压成形技术与科学教育部重点实验室秦皇岛066004

Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram（FLD） of tailor-welded blanks（TWBs） on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.

关键词： tailor-welded blank forming limit diagram nanoindentation test hemispherical punch bulging test