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Non‑associated and Non‑quadratic Characteristics in Plastic Anisotropy of Automotive Lightweight Sheet Metals

Automotive Innovation 2023年第3期6卷 364-378页

作者： Yong Hou junying min Myoung‑Gyu Lee Department of Materials Science and Engineering and RIAM Seoul National UniversitySeoul 08826South Korea School of Mechanical Engineering Tongji UniversityShanghai 201804China

Lightweight sheet metals are highly desirable for automotive applications due to their exceptional strength-to-density *** accurate description of the pronounced plastic anisotropy exhibited by these materials in finite element analysis requires advanced plasticity *** recent years,significant efforts have been devoted to developing plasticity models and numeri-cal analysis methods based on the non-associated flow rule(non-AFR).In this work,a newly proposed coupled quadratic and non-quadratic model under non-AFR is utilized to comprehensively investigate the non-associated and non-quadratic characteristics during the yielding of three lightweight sheet metals,i.e.,dual-phase steel DP980,TRIP-assisted steel QP980,and aluminum alloy *** materials are subjected to various proportional loading paths,including uniaxial tensile tests with a 15°increment,uniaxial compressive tests with a 45°increment,in-plane torsion tests,and biaxial tensile tests using laser-deposited arm-strengthened cruciform *** show that the non-AFR approach provides an effective means for accurately modeling the yield behavior,including yield stresses and the direction of plastic strain rates,simultaneously,utilizing two separate functions and a simple calibration *** introduction of the non-quadratic plastic potential reduces the average errors in angle when predicting plastic strain directions by the quadratic plastic potential ***,for DP980,the average error is reduced from 3.1°to 0.9°,for QP980 it is reduced from 6.1°to 3.9°,and for AA5754-O it is reduced from 7.0°to 0.2°.This highlights the importance of considering the non-quadratic characteristic in plasticity modeling,especially for aluminum alloys such as AA5754-O.

关键词： Yield behavior Non-associated flow rule Non-quadratic Lightweight sheet metal

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Investigation on Uniaxial Tensile Instability of USIBOR1500 Steel Sheets at Elevated Temperature

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Chinese Journal of Mechanical Engineering 2010年第1期23卷 94-99页

作者： min junying LIN Jianping TIAN Haobin SUN Guohua XU Zhou College of Mechanical Engineering Tongii University Shanghai 201804 China College of Mechanical and Electrical Engineering Shanghai Second Polytechnic University Shanghai 201209 China

In the sheet forming process with stretch, diffuse instability and localized instability usually occur in the process one after another. The necking rate has a great impact on the instability process and the forming limits of the rate sensitive material, such as USIBOR1500 steel sheets at elevated temperature. The available reports about this steel mainly focus on hot uniaxial tensile, martensitic transformation and forming process, but there are few investigations on instability behavior and forming limits. Based on Inoue Kachiro＇s flow stress constitutive model at elevated temperature, combined with Swift＇s diffuse instability rule and Hill＇s localized instability nile, the relation is theoretically deduced between the diffuse necking rate along with the localized necking rate and the exponent of strain rate sensitivity together with the strain rate in the case of the USIBOR1500 steel sheets at elevated temperature. According to the time-temperature characteristics of the hot stamping process, tensile tests of the steel sheets were carried out on Gleeble3800, and the stress-strain curves were obtained at different temperatures and different strain rates. Then the values of the exponent of strain rate sensitivity and the hardening exponent were obtained through fitting the curves by least squares. The tests also helped to provide the distribution laws of the major strain of the specimens and the uniform strains as well as the necking width. The uniform strains obtained from the tests are matched well with the theoretical calculations.

关键词： USIBOR1500 uniaxial tensile instability uniform strain necking rate

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Necking of Q&P Steel during Uniaxial Tensile Test with the Aid of DIC Technique

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Chinese Journal of Mechanical Engineering 2013年第3期26卷 448-453页

作者： DING Lei LIN Jianping min junying PANG Zheng YE You School of Mechanical Engineering Tongji University Body & Exterior Department Pan Asia Technical Automotive Center

A lot of research has been focused on the necking process during the plastic deformation of sheet metals, but the localized necking is rarely distinguished form diffused necking by experiments, due to the limit of measurement equipment and method. Quenching and Partitioning (Q&P) steel is a 3rd generation advanced high strength steel (AHSS). Its good combination of high strength and ductility ensures potential application in automobile industry. Uniaxial tensile tests of QP980 steel sheet at five strain rates are performed to investigate the necking process and the effect of strain rate on necking behavior of Q&P steel. Digital image correlation (DIC) method is applied during tensile tests, and evolutions of major strain, minor strain and normal strain distributions along gauge section of the tensile specimens are obtained. The diffused and localized necking strains are determined according to SWIFT necking theory and HILL necking theory respectively. The test results indicate that with the increasing of strain rate in the investigated range, the diffused necking strain decreases from 0.152 to 0.120 and localized necking strain decreases from 0.245 to 0.137. Meanwhile, the difference of the two strains decreases form 0.096 to 0.017. Thus it can be concluded that strain rate has an influence on both necking strains during the deformation of QP980 steel sheet. Diffused and localized necking strains are determined by uniaxial tensile tests with the aid of DIC technique and the effect of strain rate on necking strains is evaluated.

关键词： Q&P steel strain rate DIC SWIFT necking theory HILL necking theory

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Special Issue on Automotive Lightweight

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Automotive Innovation 2020年第3期3卷 193-194页

作者： A.Erman Tekkaya junying min Institute of Forming Technology and Lightweight ComponentsTU Dortmund University44227 DortmundGermany School of Mechanical Engineering Tongji UniversityShanghai 201804China

Lightweight is one of the core technologies to realize energy saving,to improve the safety and driving performance of vehicles,and to provide added passenger comfort as *** is of special significance for increasing cruising range of electric or hybrid-powered *** these,lightweight components use less mass and hence reduce the primary energy requirement imbedded in the ***,lightweight has always been a central topic and an important direction in the automotive field whether in the past or in the future.

关键词： weight hence driving

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Constitutive Model of Friction Stir Weld with Consideration of its Inhomogeneous Mechanical Properties

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Chinese Journal of Mechanical Engineering 2016年第2期29卷 357-364页

作者： ZHANG Ling min junying WANG Bin LIN Jianping LI Fangfang LIU Jing School of Mechanical Engineering Tongji University Chair of Production Systems Ruhr-University Bochum

In practical engineering, finite element（FE） modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded（FSW） blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone（HAZ）, thermal-mechanically affected zone（TMAZ） and weld nugget（WN）. Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation（DIC） techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.

关键词： constitutive model inhomogeneous mechanical property friction stir welding tailor welded blanks

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Low‑Carbon‑Emission Hot Stamping:A Review from the Perspectives of Steel Grade,Heating Process,and Part Design

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Automotive Innovation 2023年第3期6卷 324-339页

作者： Zeran Hou Yi Liu Qi He Jianfeng Wang junying min School of Mechanical Engineering Tongji UniversityShanghai 201804China China Science Lab General Motors Global Research and DevelopmentShanghai 201206China

Hot stamping steels have become a crucial strategy for achieving lightweighting and enhancing crash safety in the automo-tive industry over the past two ***,the carbon emissions of the materials and their related stamping processes have been frequently *** is essential to consider these emissions during the design *** materials and technologies in hot stamping pose challenges to the automotive industry's future development in carbon emission *** review discusses the promising materials for future application and their special features,as well as the emerging manufacturing and part design processes that have extended the limit of application for new *** heating processes and corresponding equipment have been proven to improve heating efficiency and control temperature *** material utilization and the overall performance of the components are improved by tailored blanks and an integrated part design *** achieve low-carbon-emission(LCE)hot stamping,it is necessary to systematically consider the steel grade,heating process,and part design,rather than solely focusing on reducing carbon emissions during the manufacturing process *** review aims to present the latest progress in steel grade,heating process,and part design of hot stamping in the automotive industry,providing solutions for LCE from a holistic perspective.

关键词： Low-carbon-emission Hot stamping Steel grade Heating process Part design

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Prediction of Cross-Tension Strength of Self-Piercing Riveted Joints Using Finite Element Simulation and XGBoost Algorithm

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Chinese Journal of Mechanical Engineering 2021年第2期34卷 168-178页

作者： Jianping Lin Chengwei Qi Hailang Wan junying min Jiajie Chen Kai Zhang Li Zhang School of Mechanical Engineering Tongji UniversityShanghai 201804China Pan Asia Technical Automotive Center Shanghai 202106China

Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of *** this work,a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element(FE)simulation and extreme gradient boosting decision tree(XGBoost)*** FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR *** residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints,and cross-tension strengths from FE simulation show a good consistence with the experiment *** on the verified FE model,the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints,which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR *** show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regression model with a respective error less than 7.6%compared to experimental values.

关键词： Self-piercing riveting Joint strength Cross-tension Finite element modeling Machine learning

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Effect of Atmospheric Pressure Plasma Treatment on the Lap-Shear Strength of Adhesive-Bonded Sheet Molding Compound Joints

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Automotive Innovation 2018年第3期1卷 237-246页

作者： Shuang Wang junying min Jianping Lin Chengcheng Sun Shanglu Yang School of Mechanical Engineering Tongji UniversityShanghai 201804China Key Lab of Vehicle Aerodynamics and Vehicle Thermal Management Systems of Shanghai Tongji UniversityShanghai 201804China Shanghai Institute of Optics and Fine Mechanics Shanghai 201800China

Atmospheric pressure plasma treatment(APPT)technology was used herein to treat sheet molding compound(SMC)substrates to increase the lap-shear strength of ***,the mechanisms behind the lap-shear strength improvements in APPT-treated adhesive-bonded SMC joints were explored.A maximum lap-shear strength about three times that of the as-received SMC joints was achieved when the APPT distance was set to 20 *** surface roughness,which exhibited little benefit to the lap-shear strength,was determined to not be the primary reason for the increase in lap-shear ***,X-ray photoelectron spectra revealed that an increased amount of O-containing groups(i.e.,C–O–H,C–O–C,H–O–C=O or R–O–C=O)following APPT contributed to the improved lap-shear *** addition,the surface free energy increased significantly after APPT,which improved the lap-shear strength of the adhesive-bonded SMC *** to the change of surface morphology,the changes in both the surface chemical property and surface free energy played larger roles in increasing the lap-shear strength of APPT-treated SMC joints.

关键词： Plasma treatment Sheet molding compound Lap-shear strength Chemical properties Surface free energies

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Investigation on Yield Behavior of 7075‑T6 Aluminum Alloy at Elevated Temperatures

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Chinese Journal of Mechanical Engineering 2020年第5期33卷 225-236页

作者： Jianping Lin Xingyu Bao Yong Hou junying min Xinlei Qu Zhimin Tao Jiajie Chen School of Mechanical Engineering Tongji UniversityShanghai 201804China Shandong Nanshan Aluminum Co. LtdShandong 265706China Pan Asia Technical Automotive Center Shanghai 202106China

Aluminum alloys have drawn considerable attention in the area of automotive *** strength aluminum alloys are usually deformed at elevated temperatures due to their poor formability at room *** this work,the yield behavior of 7075 aluminum alloy in T6 temper(AA7075-T6)within the temperature ranging from 25°C to 230°C was *** and biaxial tensile tests with the aid of induction heating system were performed to determine the stress *** curves and the yield loci of AA7075-T6 at elevated temperatures,*** Mises,Hill48 and Yld2000-2d yield criteria were applied to predicting yield loci which were compared with experimentally measured yield loci of the *** show that yield stress corresponding to the same equivalent plastic strain decreases with increasing temperature within the investigated temperature range and the shape of yield loci evolves nearly *** experimental yield locus expands with an increase of equivalent plastic strain at the same temperature and the work hardening rate of AA7075-T6 exhibits obvious *** nonquadratic Yld2000-2d yield criterion describes the yield surfaces of AA7075-T6 more accurately than the quadratic von Mises and Hill48 yield criteria,and an exponent of 14 in the Yld2000-2d yield function gives the optimal predictions for the AA7075-T6 at all investigated temperatures.

关键词： Aluminum alloy Yield behavior Biaxial tensile test Warm condition

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Flexural Performance of Steel-FRP Composites for Automotive Applications

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Automotive Innovation 2020年第3期3卷 280-295页

作者： Ye Lin junying min Hao Teng Jianping Lin Jiahao Hu NanjieXu School of Mechanical Engineering Tongji UniversityShanghai 201804China Key Lab of Vehicle Aerodynamics and Vehicle Thermal Management Systems of Shanghai Tongji UniversityShanghai 201804China

The design of hybrid structure offers an attractive solution to enhance strength and structural stiffness as well as to achieve lightweight effect and cost *** applications of steel-FRP(fiber-reinforced polymer)composites in trans-portation and civil engineering have been comprehensively *** order to apply hybrid structures to car body parts such as B-pillar,flexural performance of steel-FRP composites is investigated by means of three-point bending test in this *** analytical model is deduced to calculate the initial stiffness,the bending load and the energy absorption of steel-FRP ***-CFRP(carbon fiber-reinforced polymer)and steel-AFRP(aramid fiber-reinforced polymer)composites are experimentally studied and *** results demonstrate that the steel-FRP composites exhibit significantly higher load-carrying capabilities and initial stiffnesses along with larger energy absorptions in the bending process compared to the single steel sheet.

关键词： Steel-FRPcomposite Hybridstructure Fiber-reinforcedpolymer Flexuralperformance

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