The Experts below are selected from a list of 13104 Experts worldwide ranked by ideXlab platform
Chuan Song Wu - One of the best experts on this subject based on the ideXlab platform.
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modified constitutive equation for use in modeling the ultrasonic vibration enhanced Friction Stir Welding process
Scripta Materialia, 2016Co-Authors: Chuan Song Wu, G K PadhyAbstract:Abstract A modified material constitutive equation characterizing the acoustic softening effect on aluminum alloys is proposed and validated for modeling the ultrasonic vibration enhanced Friction Stir Welding process. The dependence of the acoustic softening effect on temperature and strain rate is quantitatively analyzed. The numerical investigation based on the constitutive equation shows that it can describe the effect of ultrasonic vibration on Friction Stir Welding of aluminum alloy plates reasonably.
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elimination of tunnel defect in ultrasonic vibration enhanced Friction Stir Welding
Materials & Design, 2016Co-Authors: Chuan Song WuAbstract:Abstract Through observing the marker material (MM) distribution and the exit holes left by the “tool sudden stop action” technique, the formation mechanism of tunnel defect in Friction Stir Welding (FSW) is elucidated. Based on the MM distribution on the transverse cross-sections, the weld nugget zone is divided into three subzones, i.e., shoulder affected zone (SAZ), pin affected zone (PAZ), and weld bottom zone (WBZ). There is a time-delay feature of material flow which is considered as the inducement of tunnel defect formation. When a tunnel defect occurs in FSW joints, three subzones connect with each other and there exists a converging point. The insufficient material flow from retreating side to advancing side in the PAZ and the shortage of downward material transfer in the SAZ are the primary and secondary reasons for tunnel defect occurrence, respectively. Under the same Welding conditions, ultrasonic vibration enhanced Friction Stir Welding (UVeFSW) can eliminate the tunnel defect in the weld nugget zone where the SAZ and WBZ are separated by the PAZ, because the exerted ultrasonic vibration improves the material flow in the PAZ and reduces or even suppresses the time-delay of material flow in the PAZ.
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Modeling the effects of ultrasonic vibration on Friction Stir Welding
Journal of Materials Processing Technology, 2015Co-Authors: L. Shi, Chuan Song Wu, X. C. LiuAbstract:A mathematical model is developed to analyze the effects of superimposed ultrasonic vibration on heat generation, temperature distribution and material flow in Friction Stir Welding process. Ultrasonic softening plays a dominant role in ultrasonic vibration enhanced Friction Stir Welding process, while the thermal effect of ultrasonic vibration is insignificant. Superimposing ultrasonic vibration in Friction Stir Welding process can produce an enhanced plastic material flow, increase the Welding speed and Welding efficiency, and also improve the weld quality by enhancing the plastic material flow near the tool. The model is validated by a comparison of the calculated thermal cycles and thermo-mechanically affected zone boundaries with the experimentally measured ones.
G K Padhy - One of the best experts on this subject based on the ideXlab platform.
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effect of ultrasonic vibration on Welding load temperature and material flow in Friction Stir Welding
Journal of Materials Processing Technology, 2017Co-Authors: Y B Zhong, G K PadhyAbstract:Abstract The main process variables were measured, characterized and compared in Friction Stir Welding with/without ultrasonic vibration. The exerted ultrasonic vibration causes reduction in traverse force, tool torque and axial force of Welding. Based on the measurement of thermal cycles in Friction Stir Welding process, the thermal effect of ultrasonic vibration is negligible, and the mechanical coupling between ultrasonic vibration and tool action plays a more important role in affecting both the Welding process effectiveness and the joint quality. Ultrasonic vibrations improved weld formation by either reducing or eliminating the weld defects, and the suitable process-parameter window is expanded. Dissimilar Welding of AA6061-T6 to AA2024-T3 with ultrasonic vibration was used to characterize the enhanced material flow which results in the better weld formation.
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modified constitutive equation for use in modeling the ultrasonic vibration enhanced Friction Stir Welding process
Scripta Materialia, 2016Co-Authors: Chuan Song Wu, G K PadhyAbstract:Abstract A modified material constitutive equation characterizing the acoustic softening effect on aluminum alloys is proposed and validated for modeling the ultrasonic vibration enhanced Friction Stir Welding process. The dependence of the acoustic softening effect on temperature and strain rate is quantitatively analyzed. The numerical investigation based on the constitutive equation shows that it can describe the effect of ultrasonic vibration on Friction Stir Welding of aluminum alloy plates reasonably.
Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.
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dissimilar Friction Stir Welding of pure ti and carbon fibre reinforced plastic
Science and Technology of Welding and Joining, 2020Co-Authors: Jeongwon Choi, Hidetoshi Fujii, Yoshiaki Morisada, Huihong Liu, Kohsaku Ushioda, Kimiaki Nagatsuka, Kazuhiro NakataAbstract:Dissimilar Friction Stir Welding was conducted on the combination of pure Ti and carbon fibre reinforced plastic. The weld interface microstructure and mechanical properties of the obtained joints ...
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investigation of temperature dependent microstructure evolution of pure iron during Friction Stir Welding using liquid co2 rapid cooling
Materials Characterization, 2018Co-Authors: X. C. Liu, Yufeng Sun, Tomoya Nagira, Hidetoshi FujiiAbstract:Abstract The microstructure evolution of pure iron during Friction Stir Welding was reconstructed by an ingenious experimental design, in which the rapid cooling Friction Stir Welding combined with the tool “stop action” technique and the subsequent short-time annealing were adopted to “freeze” the transient microstructure during the Stirring and reproduce the normal cooling during conventional Friction Stir Welding, respectively. The microstructure evolution during the Stirring and normal cooling was investigated along the material flow path and in the annealed “frozen” weld zone by high-resolution electron-backscatter-diffraction technique. The results show that the continuous and discontinuous dynamic recrystallizations occur simultaneously at the severe deformation stage in front of the tool both under low and high heat input conditions. However, during the material flow, the microstructure evolution involves the plastic deformation, recrystallization, high angle boundaries migration and dynamic recovery under the low heat input condition, while in a dynamic balance of deformation, recrystallization and grain growth under the high heat input conditions. At the cooling stage, normal grain growth occurs both for the low and high heat input Welding conditions, while it is very limited for the low heat input condition.
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Friction Stir Welding of f82h steel for fusion applications
Journal of Nuclear Materials, 2016Co-Authors: Sanghoon Noh, Hidetoshi Fujii, Masami Ando, Hiroyasu Tanigawa, Akihiko KimuraAbstract:Abstract In the present study, Friction Stir Welding was employed to join F82H steels and develop a potential joining technique for a reduced activation ferritic/martensitic steel. The microstructures and mechanical properties on the joint region were investigated to evaluate the applicability of Friction Stir Welding. F82H steel sheets were successfully butt-joined with various Welding parameters. In Welding conditions, 100 rpm and 100 mm/min, the Stirred zone represented a comparable hardness distribution with a base metal. Stirred zone induced by 100 rpm reserved uniformly distributed precipitates and very fine ferritic grains, whereas the base metal showed a typical tempered martensite with precipitates on the prior austenite grain boundary and lath boundary. Although the tensile strength was decreased at 550 °C, the Stirred zone treated at 100 rpm showed comparable tensile behavior with base metal up to 500 °C. Therefore, Friction Stir Welding is considered a potential Welding method to preserve the precipitates of F82H steel.
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new technique of self refilling Friction Stir Welding to repair keyhole
Science and Technology of Welding and Joining, 2012Co-Authors: Li Zhou, Hidetoshi Fujii, Kazuhiro Nakata, Duo Liu, Takuya Tsumura, Kenji Ikeuchi, Yukio Michishita, Yasuyuki Fujiya, M MorimotoAbstract:AbstractA new technique of self-refilling Friction Stir Welding (SRFSW) relying on non-consumable joining tool has been developed to repair the keyhole left at the end of 316L stainless steel Friction Stir Welding/Friction Stir processing (FSW/FSP) seam. The conventional FSW process was transformed by adopting a series of non-consumable tools with gradual change in geometry to create a solid state refilled joint step by step. Using the combined plastic deformation and flow of the material around the keyhole, the SRFSW process is able to repair the keyhole with both metallurgical and mechanical bonding characteristics, and the FSW/FSP seam can be achieved without keyhole or other obvious macro defects. Microstructural observation results showed that the grains in the refilled zone were significantly refined by the tool. Tensile test results showed the refilled joint fractured at the base metal side, and the relative tensile strength and elongation are 112 and 82% of the base metal respectively. Moreover, n...
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three dimensional visualization of material flow during Friction Stir Welding by two pairs of x ray transmission systems
Scripta Materialia, 2011Co-Authors: Yoshiaki Morisada, Hidetoshi Fujii, Kazuhiro Nakata, Yousuke Kawahito, Manabu TanakaAbstract:Material flow during Friction Stir Welding is crucial to obtaining sound joints. However, this phenomenon is still not fully understood despite many investigations and numerous models. In this study, the material flow is three-dimensionally visualized by X-ray radiography using a tiny spherical tungsten tracer. The movement of the tracer during the Friction Stir Welding is observed by two pairs of X-ray transmission real-time imaging systems. The three-dimensional material flow is obtained by following the locus of the tracer.
X. C. Liu - One of the best experts on this subject based on the ideXlab platform.
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investigation of temperature dependent microstructure evolution of pure iron during Friction Stir Welding using liquid co2 rapid cooling
Materials Characterization, 2018Co-Authors: X. C. Liu, Yufeng Sun, Tomoya Nagira, Hidetoshi FujiiAbstract:Abstract The microstructure evolution of pure iron during Friction Stir Welding was reconstructed by an ingenious experimental design, in which the rapid cooling Friction Stir Welding combined with the tool “stop action” technique and the subsequent short-time annealing were adopted to “freeze” the transient microstructure during the Stirring and reproduce the normal cooling during conventional Friction Stir Welding, respectively. The microstructure evolution during the Stirring and normal cooling was investigated along the material flow path and in the annealed “frozen” weld zone by high-resolution electron-backscatter-diffraction technique. The results show that the continuous and discontinuous dynamic recrystallizations occur simultaneously at the severe deformation stage in front of the tool both under low and high heat input conditions. However, during the material flow, the microstructure evolution involves the plastic deformation, recrystallization, high angle boundaries migration and dynamic recovery under the low heat input condition, while in a dynamic balance of deformation, recrystallization and grain growth under the high heat input conditions. At the cooling stage, normal grain growth occurs both for the low and high heat input Welding conditions, while it is very limited for the low heat input condition.
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Modeling the effects of ultrasonic vibration on Friction Stir Welding
Journal of Materials Processing Technology, 2015Co-Authors: L. Shi, Chuan Song Wu, X. C. LiuAbstract:A mathematical model is developed to analyze the effects of superimposed ultrasonic vibration on heat generation, temperature distribution and material flow in Friction Stir Welding process. Ultrasonic softening plays a dominant role in ultrasonic vibration enhanced Friction Stir Welding process, while the thermal effect of ultrasonic vibration is insignificant. Superimposing ultrasonic vibration in Friction Stir Welding process can produce an enhanced plastic material flow, increase the Welding speed and Welding efficiency, and also improve the weld quality by enhancing the plastic material flow near the tool. The model is validated by a comparison of the calculated thermal cycles and thermo-mechanically affected zone boundaries with the experimentally measured ones.
Kiyoshi Nogi - One of the best experts on this subject based on the ideXlab platform.
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Friction Stir Welding of a high carbon steel
Scripta Materialia, 2007Co-Authors: Hidetoshi Fujii, Nobuhiro Tsuji, Kiyoshi NogiAbstract:A high carbon steel joint, S70C (0.72 wt.% C), was successfully Friction Stir welded without any pre- or post-heat treatment. There are two methods for obtaining proper joint properties. The first method is to decrease the peak temperature to below A 1 and the other is to decrease the cooling rate to less than the lower critical cooling rate. It was proved that Friction Stir Welding enables us to properly control the cooling rate and peak temperature, which was impossible using traditional Welding.
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Friction Stir Welding of carbon steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Hidetoshi Fujii, Nobuhiro Tsuji, Kazuhiro Nakata, Ling Cui, Masakatsu Maeda, Kiyoshi NogiAbstract:Abstract In order to determine the effect of the carbon content and the transformation on the mechanical properties and microstructures of the FSW carbon steel joints, three types of carbon steels with different carbon contents (IF steel, S12C, S35C) were Friction Stir welded under various Welding conditions. Compared with IF steel, the microstructures and mechanical properties of the carbon steel joints are significantly affected by the Welding conditions. The strength of the S12C steel joints increases with the increasing Welding speed (decreasing the heat input), while the strength of the S35C steel joints shows a peak near 200 mm/min. This can be explained by the relationship between the peak temperature and the A 1 and A 3 points. When Friction Stir Welding is performed in the ferrite–austenite two-phase region, the microstructure is refined and the highest strength is then achieved.
