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| 1 | Prediction of the Residual Welding Stress in 2.25Cr-1Mo Steel by Taking into Account the Effect of the Solid-State Phase Transformations显示文摘A computational approach based on the thermal elastic plastic finite element method was developed for predicting welding residual stress in low carbon alloyed steel welds by taking into account the effect of the solid-state phase transformations. The kinetics of phase transformations was described by Johnson Mehl Avrami Kolmogrov (JMAK) equation for bainitic transition and by Koistinen-Marburger (K-M) relationship for martensitic transition. Moreover, an additive rule depending on volumetric phase fraction was adopted to represent the material property changes during heating and cooling. Consequently, the residual welding stresses in a 2.25Cr1Mo steel TIG welded plate were computed. Early calculation results suggest that the bainitic and martensitic transformations took place in the weld the heat-affected zone drastically reduce the residual longitudinal tensile stress in the region. | Dean DENG Yangang TONG Ninshu MA Hidekazu MURAKAWA | 2013 | Acta Metallurgica Sinica(English Letters)2013，26，3： | 7 |
| 2 | Impact of Stack Orientation on Self-Piercing Riveted and Friction Self-Piercing Riveted Aluminum Alloy and Magnesium Alloy Joints显示文摘Self-piercing riveting(SPR)is a mature method to join dissimilar materials in vehicle body assembling.Friction self-piercing riveting(F-SPR)is a newly developed technology for joining low-ductility materials by combining SPR and friction stir spot welding processes.In this paper,the SPR and F-SPR were employed to join AA6061-T6 aluminum alloy and AZ31B magnesium alloy.The two processes were studied in parallel to investigate the effects of stack orientation on riveting force,macro-geomet-rical features,hardness distributions,and mechanical performance of the joints.The results indicate that both processes exhibit a better overall joint quality by riveting from AZ31B to AA6061-T6.Major cracking in the Mg sheet is produced when riveting from AA6061-T6 to AZ31B in the case of SPR,and the cracking is inhibited with the thermal softening effect by friction heat in the case of F-SPR.The F-SPR process requires approximately one-third of the riveting forces of the SPR process but exhibits a maximum of 45.4%and 59.1%higher tensile-shear strength for the stack orientation with AZ31B on top of AA6061-T6 and the opposite direction,respectively,than those of the SPR joints.The stack orientation of riveting from AZ31B to AA6061-T6 renders better cross-section quality and higher tensile-shear strength and is recommended for both processes. | Yunwu Ma Sizhe Niu He Shan Yongbing Li Ninshu Ma | 2020 | Automotive Innovation2020，3，3： | 2 |
| 3 | Additive manufacturing of a high-strength ZrC-SiC and TC4 gradient structure based on a combination of laser deposition technique and brazing显示文摘A ZrC-SiC and TC4 gradient structure(ZTGS)was additively manufactured through the laser deposition technique and brazing process.The research results indicated that SiC-reinforced TC4-based gradient layers could be obtained on the TC4 surface by laser deposition.ZrC-SiC and TC4 coated with gradient layers were brazed using an AgCuTi filler to fabricate the ZTGS.The effects of the gradient structure and brazing parameters on the ZTGS strength were investigated.With an increase in Layer II and Layer III thickness,the ZTGS shear strength increased.The brazing temperature and holding time affected the ZTGS shear strength by controlling the formation and distribution of the Cu4Ti phase in the brazing zone.The strengthening mechanism of the ZTGS was revealed by analyzing the residual stress distribution in the ZTGS.Compressive residual stress was formed in ZrC-SiC adjacent to the TC4 substrate or the deposited gradient layer,which was found to negatively affect the properties of the ZTGS.The increase in gradient layer thickness reduced the maximum residual stress in ZrC-SiC,and the effect of Layer III on the residual stress was more significant than that of Layer II.The calculated residual stress evolution matched the ZTGS property values well,revealing the strengthening mechanism. | Qian Wang Junmiao Shi Lixia Zhang Jiangtao Xiong Jinglong Li Ninshu Ma Jicai Feng | 2021 | Journal of Materiomics2021，7，4： | 2 |
| 4 | Flat friction spot joining of aluminum alloy to carbon fiber reinforced polymer sheets:Experiment and simulation显示文摘The Al alloy and carbon fiber reinforced polymer(CFRP)hybrid structures,incorporating the performance advantages of the two materials,have been attracting more attention in high-end manufacturing fields.In the current investigation,the flat friction spot joining(FSJ)was employed in joining the AA6061-T6 alloy and CFRP sheets.The significance of temperature distribution in influencing joint quality was highlighted through analyzing interface microstructural features,weld defect formation as well as fractography.To understand the role of thermal energy generation and conduction in the process comprehensively,a 3D thermal-mechanical coupling finite element model was established.The interfacial temperature was characterized by an uneven distribution behavior due to the inhomogeneous heat distribution.The peak temperatures on the top surface and Al alloy to CFRP interface at 1500 rpm rotational speed with 0.1 mm/s plunging speed were 498℃and 489°C,respectively.The peak interface temperature was reduced to286℃at 250 rpm,which produced an extremely small melted area.Compared with the plunging speed,rotational speed was found to be the predominant parameter for determining the joint property,which could be optimized to simultaneously realize the avoidance of thermal decomposition of CFRP,the sufficient melting duration time,and the wide enough melted area.Simulated thermal histories and melted area profiles were in agreement with experimental ones.The findings could be utilized to provide some feasible guidance for process optimization of dissimilar FSJ of metals and composites. | Peihao Geng Ninshu Ma Hong Ma Yunwu Ma Kazuki Murakami Huihong Liu Yasuhiro Aoki Hidetoshi Fujii | 2022 | Journal of Materials Science & Technology2022，，12： | 1 |
| 5 | Application of Explicit FEM to Welding Deformation显示文摘 | MA Ninshu UMEZU Y | 2009 | Welding International2009，23，1： | 1 |
| 6 | Simulation 2 of the lecture papers on tube hydroforming显示文摘 | NINSHU Ma | | 0，，09： | 1 |
| 7 | Applications of Inherent Strain and Interface Element to Simulation of Welding Deformation in Thin Plate Structures 显示文摘 | Hidekazu Murakawa Dean Deng Ninshu Ma | 2011 | Computational Materials Science2011，51，1： | 1 |
| 8 | Shear strength of CMT brazed lap joints between aluminum and zinc-coated steel 显示文摘 | Jian Lin Ninshu Ma Yongping Lei | 2013 | Journal of Materials Processing Technology2013，213，8： | 1 |
| 9 | Shear strength of CMT brazed lap joints between aluminum and zinc-coated steel 显示文摘 | Jian Lin Ninshu Ma Yongping Lei | 2013 | Jour- nal of Materials Processing Technology2013，213，8： | 1 |
| 10 | Springback Prediction by Yoshida-Uemori Model and Compensation of Tool Surface Using JSTAMP显示文摘 | Ninshu M Yasuyoshi U Yuko W | | 0，，： | 1 |
| 11 | Dynamic evolution of oxide scale on the surfaces of feed stock particles from cracking and segmenting to peel-off while cold spraying copper powder having a high oxygen content显示文摘The oxide scale present on the feedstock particles is critical for inter-particle bond formation in the cold spray(CS)coating process,therefore,oxide scale break-up is a prerequisite for clean metallic contact which greatly improves the quality of inter-particle bonding within the deposited coating.In general,a spray powder which contains a thicker oxide scale on its surface(i.e.,powders having high oxygen content)requires a higher critical particle velocity for coating formation,which also lowers the deposition efficiency(DE)making the whole process a challenging task.In this work,it is reported for the first time that an artificially oxidized copper(Cu)powder containing a high oxygen content of 0.81 wt.%with a thick surface oxide scale of 0.71μm.,can help achieve an astonishing increment in DE.A transition of surficial oxide scale evolution starting with crack initiations followed by segmenting to peeling-off was observed during the high velocity particle impact of the particles,which helps in achieving an astounding increment in DE.Single-particle deposit observations revealed that the thick oxide scale peels off from most of the sprayed powder surfaces during the high-velocity impact,which leaves a clean metallic surface on the deposited particle.This makes the successive particles to bond easily and thus leads to a higher DE.Further,owning to the peeling-off of the oxide scale from the feedstock particles,very few discontinuous oxide scale segments are retained at inter-particle boundaries ensuring a high electrical conductivity within the resulting deposit.Dependency of the oxide scale threshold thickness for peeling-off during the high velocity particle impact was also investigated. | Xiao-Tao Luo Yi Ge Yingchun Xie Yingkang Wei Renzhong Huang Ninshu Ma Chidambaram Seshadri Ramachandran Chang-Jiu Li | 2021 | Journal of Materials Science & Technology2021，，8： | 1 |
| 12 | Research on welding simulation methods and software development显示文摘 | Hidekazu Murakawa Ninshu Ma | 2014 | China Welding2014，23，1： | 0 |
| 13 | Strength evaluation of ultra-high strength steels and spot weld of automotive bodies显示文摘 | Kenji Takada Kentaro Sato Ninshu Ma | 2014 | China Welding2014，23，1： | 0 |
| 14 | A Comparative Study of Friction Self-Piercing Riveting and Self-Piercing Riveting of Aluminum Alloy AA5182-O显示文摘In this paper,self-piercing riveting(SPR)and friction self-piercing riveting(F-SPR)processes were employed to join aluminum alloy AA5182-O sheets.Parallel studies were carried out to compare the two processes in terms of joint macrogeometry,tooling force,microhardness,quasi-static mechanical performance,and fatigue behavior.The results indicate that the F-SPR process formed both rivet–sheet interlocking and sheet–sheet solid-state bonding,whereas the SPR process only contained rivet–sheet interlocking.For the same rivet flaring,the F-SPR process required 63%less tooling force than the SPR process because of the softening effect of frictional heat and the lower rivet hardness of F-SPR.The decrease in the switch depth of the F-SPR resulted in more hardening of the aluminum alloy surrounding the rivet.The higher hardness of aluminum and formation of solid-state bonding enhanced the F-SPR joint stiffness under lap-shear loading,which contributed to the higher quasi-static lap-shear strength and longer fatigue life compared to those of the SPR joints. | Yunwu Ma He Shan Sizhe Niu Yongbing Li Zhongqin Lin Ninshu Ma | 2021 | Engineering2021，7，12： | 0 |
| 15 | Microstructural evolution in friction self-piercing riveted aluminum alloy AA7075-T6 joints显示文摘Friction self-piercing riveting(F-SPR)is an emerging technique for low ductility materials joining,which creates a mechanical and solid-state hybrid joint with a semi-hollow rivet.The severe plastic deformation of work materials and localized elevated temperatures during the F-SPR process yield complex and heterogeneous microstructures.The cut-off action of the work materials by the rivet further complicates the material flow during joint formation.This study employed the F-SPR process to join AA7075-T6 aluminum alloy sheets and systematically investigated the microstructural evolutions using electron backscatter diffraction(EBSD)techniques.The results suggested that as the base material approached the rivet,grains were deformed and recrystallized,forming two distinct fine grain zones(FGZs)surrounding the rivet and in the rivet cavity,re s pectively.Solid-state bonding of aluminum sheets occurred in the FGZs.The formation of FGZ outside the rivet is due to dynamic recrystallization(DRX)triggered by the sliding-to-sticking transition at the rivet/sheet interface.The FGZ in the rivet cavity was caused by the rotation of the trapped aluminum,which created a sticking affected zone at the trapped aluminum/lower sheet interface and led to DRX.Strain rate gradient in the trapped aluminum drove the further expansion of the sticking affected zone and resulted in grain refinement in a larger span. | Yunwu Ma Sizhe Niu Huihong Liu Yongbing Li Ninshu Ma | 2021 | Journal of Materials Science & Technology2021，，23： | 0 |
| 16 | Characteristic Tensor for Evaluation of Singular Stress Field Under Mixed-Mode Loadings显示文摘A characteristic tensor is defined using stress tensor averaged in a small circular domain at the crack tip and multiplied by the root of domain radius.It possesses the original stress tensor characteristics and has a simple relationship with conventional fracture-mechanics parameters.Therefore,it can be used to estimate stress intensity factors(SIFs)for cracks of arbitrary shape subjected to multiaxial stress loads.A characteristic tensor can also be used to estimate SIFs for kinked cracks.This study examines the relation between a characteristic tensor and SIFs to demonstrate the correlation between the characteristic tensor and fracture-mechanics parameters.Consequently,a single straight crack and a kinked crack of finite length existing in a twodimensional,infinite isotropic elastic body in a plane stress state,were considered to investigate the properties of the characteristic tensor under mixed-mode loadings.To demonstrate the practical utility of the characteristic tensor,the stress distribution obtained through finite element analysis(FEA)was used to estimate mixed-mode SIFs,and the values of estimated SIFs were compared with those obtained using an analytical solution.Results demonstrate that SIFs estimated under mixed-mode loadings exhibit a good agreement with the analytical values.This indicates that the proposed characteristictensor-based approach is effective in extracting features of singular stress fields at crack tips,and can be employed to estimate values of fracture-mechanics parameters,such as SIFs.Owing to its simplicity,the proposed approach can be easily incorporated in commercial FE codes for practical applications to simulate the crack-growth problem under both static and dynamic loading scenarios.The excellent applicability of the characteristic tensor greatly contributes to efficiency of the design process in industries. | Kei Saito Tei Hirashima Ninshu Ma Hidekazu Murakawa | 2020 | Computer Modeling in Engineering & Sciences2020，，2： | 0 |
| 17 | Combined strengthening mechanism of solid-state bonding and mechanical interlocking in friction self-piercing riveted AA7075-T6 aluminum alloy joints显示文摘A recently developed friction self-piercing riveting(F-SPR)technique based on the combination of fric-tion stir processing and riveting has been reported to possess both solid-state bonding and mechanical fastening characteristics.However,there is still a lack of quantitative understanding of the hybrid en-hancement mechanism,hindering its engineering application.To fill in this gap,the current research investigated the microstructure evolution,microhardness distribution,and miniature-tensile performance of the aluminum alloy AA7075-T6 F-SPR joints by experiments.An accurate numerical simulation model was established to quantitatively evaluate the individual contributions of microstructure,local bonding strength,and macro interlocking to the performance of the joint,which could well explain the experi-mental results.It was found that due to the friction stirring of the rivet,solid-state bonding driven by dynamic recrystallization is realized between the trapped aluminum in the rivet cavity and the bottom aluminum sheet.The solid-state bonding zone has 75%yield strength,81%ultimate tensile strength,and 106%elongation compared to the base material.This solid-state bonding enables the internal interlock-ing between the trapped aluminum and the rivet to withstand the additional load,which forms a novel dual-interlock fastening mechanism and increases the peak cross-tension force by 14.3%compared to the single-interlock joint. | Yunwu Ma Bingxin Yang Shanqing Hu He Shan Peihao Geng Yongbing Li Ninshu Ma | 2022 | Journal of Materials Science & Technology2022，，10： | 0 |
| 18 | In Situ DIC Study on LCF Behavior of Retired Weld Joint Subjected to Prolonged Service at Elevated Temperature显示文摘By using digital image correlation(DIC), low-cycle fatigue(LCF) behavior of CrMoV weld joint taken from a retired gas turbine rotor after 15-year service was investigated at 500 ℃ and 540 ℃. The most remarkable plastic strain was observed in the weld metal(WM), which was up to 6 times of the global strain at mid-life cycle. Due to the cyclic accumulation of local deformation, the stress–strain hysteresis loops relative to tensile or compressive strain concentration area in WM displayed the ratchetting shape. The local deformation accumulation of WM was attributed to the effect of the equiaxed grain zone near the WM center. The accumulated plastic strain was considered as the main fatigue failure mechanism. | Anqi Zuo Xia Liu Chendong Shao Mingzhe Fan Ninshu Ma Fenggui Lu | 2022 | Acta Metallurgica Sinica(English Letters)2022，35，8： | 0 |
| 19 | Mechanical Performance Evaluation of Multi‑Point Clinch–Adhesive Joints of Aluminum Alloy A5052‑H34 and High‑Strength Steel JSC780显示文摘The clinch–adhesive process,which combines mechanical clinching and adhesive bonding,is one of the most applied pro-cesses for joining aluminum alloy and steel in the manufacturing of vehicle bodies.In this hybrid process,the clinching joints and adhesive bonds are coupled and influenced by each other,posing challenges to the process design and joining strength evaluation.To understand the influence of the clinching process on the performance of the adhesive layer,this study analyzes the mechanical behavior of clinch–adhesive joints between high-strength steel JSC780 and aluminum alloy A5052-H34 with different stack-up orientations and varying numbers of clinching points.The results reveal that,under the steel-on-top condition,the clinching process causes a discontinuous distribution of the adhesive layer,which significantly decreased the bonding strength.In contrast,under the aluminum-on-top condition,the clinching process has a lesser impact on the distribution of the adhesive layer,resulting in much higher strength than the steel-on-top condition.Simulation mod-els are constructed to quantify the effect of clinching points on the performance of the adhesive layer.The results highlight the need to consider diverse cohesive zone model parameters for the different stack orientations and clinching points in the design of clinch–adhesive aluminum alloy/steel structures. | Yunwu Ma Reika Akita Yohei Abe Peihao Geng Pengjun Luo Seiichiro Tsutsumi Ninshu Ma | 2023 | Automotive Innovation2023，6，3： | 0 |
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