The present research introduces a unique concept of scarf joint technique in friction stir welding(FSW) of aluminum alloy AA 6061-T6 plates and an investigation on weld quality.A new joint configuration with two disti...The present research introduces a unique concept of scarf joint technique in friction stir welding(FSW) of aluminum alloy AA 6061-T6 plates and an investigation on weld quality.A new joint configuration with two distinct scarf angles(75°and 60°) was considered in this study.The various aspects of welding were compared with contemporary simple square butt(SSB) joint configuration.Welding was carried out at a constant tool rotation speed(TRS),tool traverse speed(TTS) and tool tilt angle of 1100 rpm,2 mm/s and2°,respectively.The results are analyzed in terms of force and torque distribution,microstructure,macrostructure,and mechanical property perspective for different joint configurations.The study reveals the minimum amount of force and torque at 60°scarf angle joint configuration compared to that of square butt joint configuration.Macro study shows that all the joints were defect-free,and a prominent onion ring was present in the lower portion of the weld nugget(WN).Fine equiaxed grains with a minimum average grain size diameter of 6.82 μm were obtained in the WN of scarf joint configuration(SJC).The maximum ultimate tensile strength(UTS) and maximum average NZ hardness of 267 MPa and83.82 HV0.1were obtained in SJC3 at a scarf angle of 60°.It has been observed from the investigation that the joint efficiency increases from 72.5%(SSB) to 86%(SJC3) at a 60° scarf angle.This unique characteristic may lay an impetus on probable joint strength enhancement technique without increasing the production cost.展开更多
Some quadruped robots developed recently show better dynamic performance and environmental adaptability than ever, and have been preliminarily applied in the field of emergency disposal, military reconnaissance and in...Some quadruped robots developed recently show better dynamic performance and environmental adaptability than ever, and have been preliminarily applied in the field of emergency disposal, military reconnaissance and infrastructure construction. The development route, mechanisms design, control methods and mobile manipulating approaches of the quadruped robots are surveyed in this article. Firstly, the development route of the quadruped robot is combed, as the references of the forecast of the future work on quadruped robots. Then the bionic structure and the motion control method of the quadruped robot is summarized, the advantages and disadvantages are analyzed in aspects of gait switching, terrain adaption and disturbance resistance. Subsequently, aiming at the mobile manipulation of the quadruped robot, the representative leg-arm collaborative robots and the multi-task-oriented Whole-body Control (WBC) methods are introduced. Finally, the summary and future work of the quadruped robots is given.展开更多
基金the Ministry of Human Resource and Development,Government of India for providing the financial assistantship in the form of fellowship。
文摘The present research introduces a unique concept of scarf joint technique in friction stir welding(FSW) of aluminum alloy AA 6061-T6 plates and an investigation on weld quality.A new joint configuration with two distinct scarf angles(75°and 60°) was considered in this study.The various aspects of welding were compared with contemporary simple square butt(SSB) joint configuration.Welding was carried out at a constant tool rotation speed(TRS),tool traverse speed(TTS) and tool tilt angle of 1100 rpm,2 mm/s and2°,respectively.The results are analyzed in terms of force and torque distribution,microstructure,macrostructure,and mechanical property perspective for different joint configurations.The study reveals the minimum amount of force and torque at 60°scarf angle joint configuration compared to that of square butt joint configuration.Macro study shows that all the joints were defect-free,and a prominent onion ring was present in the lower portion of the weld nugget(WN).Fine equiaxed grains with a minimum average grain size diameter of 6.82 μm were obtained in the WN of scarf joint configuration(SJC).The maximum ultimate tensile strength(UTS) and maximum average NZ hardness of 267 MPa and83.82 HV0.1were obtained in SJC3 at a scarf angle of 60°.It has been observed from the investigation that the joint efficiency increases from 72.5%(SSB) to 86%(SJC3) at a 60° scarf angle.This unique characteristic may lay an impetus on probable joint strength enhancement technique without increasing the production cost.
基金the National Natural Science Founda-tion of China(Grant No.91948201,Grant No.62073191,Grant No.61973135)the Shandong Key R&D Program(No.2019JZZY020317)the Fundamental Research Funds of Shandong University(Grant No.2019GN017).
文摘Some quadruped robots developed recently show better dynamic performance and environmental adaptability than ever, and have been preliminarily applied in the field of emergency disposal, military reconnaissance and infrastructure construction. The development route, mechanisms design, control methods and mobile manipulating approaches of the quadruped robots are surveyed in this article. Firstly, the development route of the quadruped robot is combed, as the references of the forecast of the future work on quadruped robots. Then the bionic structure and the motion control method of the quadruped robot is summarized, the advantages and disadvantages are analyzed in aspects of gait switching, terrain adaption and disturbance resistance. Subsequently, aiming at the mobile manipulation of the quadruped robot, the representative leg-arm collaborative robots and the multi-task-oriented Whole-body Control (WBC) methods are introduced. Finally, the summary and future work of the quadruped robots is given.