In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion ...In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion bonding effect of the lap interface.Results showed that sound joints,excellently bonded at the lap interface and without hook,were obtained.The lap interfaces on the joints welded using the T-tool and F-tool almost remained intact,thereby indicating that they were formed by diffusion bonding.The material flow behavior was also simulated by FLUENT software and the results showed that the material flow along thickness was significantly enhanced by increasing the pin number.The joint welded by the T-tool showed shear fracture mode.Sound bonding was formed at the lap interface when using the F-tool and thus the joint showed tensile fracture.展开更多
Waterside creatures or aquatic organisms use a fin or web to generate a thrust force. These fins or webs have a non-convex section, referred to as a non-convex shape. We investigate the drag force acting on ...Waterside creatures or aquatic organisms use a fin or web to generate a thrust force. These fins or webs have a non-convex section, referred to as a non-convex shape. We investigate the drag force acting on a non-convex plate during unsteady motion. We perform the experiment in a water tank during free fall. We fabricate the non-convex plate by cutting isosceles triangles from the side of a convex hexagonal plate. The base angle of the triangle is between 0° to 45°. The base angle is 0 indicates the convex hexagonal thin plate. We estimate the drag coefficient with the force balance acting on the model based on the image analysis technique. The results indicate that increasing the base angle by more than 30° increased the drag coefficient. The drag coefficient during unsteady motion changed with the growth of the vortex behind the model. The vortex has small vortices in the shear layer, which is related to the Kelvin-Helmholtz instabilities.展开更多
基金supported by the National Natural Science Foundation of China(No.51874201)。
文摘In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin sheets.Three tools,with several convex-vortex pins were innovatively designed to improve the diffusion bonding effect of the lap interface.Results showed that sound joints,excellently bonded at the lap interface and without hook,were obtained.The lap interfaces on the joints welded using the T-tool and F-tool almost remained intact,thereby indicating that they were formed by diffusion bonding.The material flow behavior was also simulated by FLUENT software and the results showed that the material flow along thickness was significantly enhanced by increasing the pin number.The joint welded by the T-tool showed shear fracture mode.Sound bonding was formed at the lap interface when using the F-tool and thus the joint showed tensile fracture.
文摘Waterside creatures or aquatic organisms use a fin or web to generate a thrust force. These fins or webs have a non-convex section, referred to as a non-convex shape. We investigate the drag force acting on a non-convex plate during unsteady motion. We perform the experiment in a water tank during free fall. We fabricate the non-convex plate by cutting isosceles triangles from the side of a convex hexagonal plate. The base angle of the triangle is between 0° to 45°. The base angle is 0 indicates the convex hexagonal thin plate. We estimate the drag coefficient with the force balance acting on the model based on the image analysis technique. The results indicate that increasing the base angle by more than 30° increased the drag coefficient. The drag coefficient during unsteady motion changed with the growth of the vortex behind the model. The vortex has small vortices in the shear layer, which is related to the Kelvin-Helmholtz instabilities.
文摘以2024-T4铝合金为对象进行了搅拌摩擦扩散焊试验,首次提出并使用涡状搅拌针,且对比分析了涡状搅拌针数量对横截面形貌、材料流动行为与力学性能的影响.结果表明,涡状搅拌针作用下的搭接界面未出现明显的弯曲现象,增加涡状针的数量有利于增加焊核区底部的宽度.当采用4个涡状结构的搅拌针时,发生拉伸断裂模式的搭接接头有效连接宽度与断裂载荷均大于具有6个涡状结构的搅拌针,其值分别为11.74 mm及17 531.83 N.
