The Study Of U-shaped Curved Hole Preparation Based On Casting Core Pulling Method And The Resistance Distribution Characteristics

This research mainly focuses on the U-shaped curved fine-hole base material,U-shaped hole characteristics and core pulling force.This process is based on the poor wettability of carbon fiber and metal matrix aluminum and the high tensile strength of carbon fiber.With the carbon fiber wounded on the stiffness core,the U-shape hole core was made.After the liquid aluminum was solidification the hole cores were pulled out.After the hole making is completed,it is analyzed the quality of the hole wall,the roughness of the hole wall and the resistance of the core pulling.First of all,the experiment was constituted and the core of the straight part and the curved part of the U-shaped hole with large aspect ratio were prepared separately.The metal frame and the core made up the preform.And then using alloys with different silicon contents affecting the shape and characteristics of micropores to choose the metal matrix.Secondly,the aluminum was chosen to be base material and the complete and controllable U-shape was successfully fabricated by using preform.The result shows that: the average diameter and the depth of the U-shape hole is 2mm and 180 mm and the aspect ratio is up to 90.the roughness of hole wall is 30.12?m,which is close to Ra = 25 ~ 50.It reaches the scope of hole wall roughness fabricated by ordinary mechanical processing.The roughness of the hole wall reaches the roughness range achieved by the ordinary machining rough surface.It is analyzed the relationship between roughness and average pore diameter.The results show that the average pore diameter is inversely related to the surface roughness of the hole wall.Thirdly,it is analyzed the pulling force of the U-shape hole.The results show that the minimum pulling force of the straight part is 2564N~2628N,and the minimum pulling force of the curved part is 2921N~2935N.Finally,it is analyzed the influencing factors of the pulling force of U-shape curved hole with large aspect ratio.It can be known that U-shaped curved holes are mainly influenced by factors such as friction factor,contact surface area,curvature radius of U-shaped holes,temperature difference between pouring temperature and core pulling temperature.And when the center angle corresponding to the curved hole is not fixed,the smaller the center angle,the smaller the core pulling force.