The Study Of Regular Controllable Slender Straight-through Hole By Casting

This research was a fundamental study, which mainly focuses on controllable slenderstraight-through hole with casting processes. Based on poor wettability of carbon fiber andmetal and the high tensile strength of carbon fiber, the casting process was realized. Incontrast to conventional pore forming methods such as mechanical or special process, theproposed method did not require any additional sophisticated equipment and acquiredslender straight-through hole with super large aspect ratio by casting. Aiming atdemonstrating the feasibility and making comparative superiority of the proposed poreforming method, pore forming principle, the technical processes were studied.On the one hand, the feasibility of pore forming principle was analyzed and thetheoretical model about the hole diameter under different number of monofilaments wasestablished. The results shown that the pore forming process was feasible in differentmetals and alloys, provided that the wettability of carbon fiber and metal or alloy was poor.In order to demonstrating the universality, controllable slender straight-through hole wereprocessed in Zn, Sn and Al metals respectively. The representative specifications of thecabon fiber is1k. Theoretical hole diameter of185μm was calculated by the theoreticalmodel. On the other hand, the process was optimized for Al. The experimental process,metal model with special purpose and prefabricated bracket were designed. The theoreticalmodel about the hole diameter was amended. The results show that diameter of hole is0.222mm, the average aspect ratio of holes is290. The function of preheating metal moldand prefabricated bracket, and fixing carbon fiber and prefabricated bracket were realizedby designing metal model and prefabricated bracket. The revised model conforms to theactual the size of cast hole. Because of the loose quantity, the actual diameter ofmicro-holes was almost20%larger than that of the theoretical value. Besides, thegeometrical characteristics of casting micro-holes in Al were analyzed. The results showthat micro-holes shape is similar to roundness, shape factor is0.850~0.915, The roughnessof micro-hole (Ra) was within3.2~6.3, straightness of micro-hole is about0.01mm. Andthe influence factors of above parameters are analyzed. To some extent, the analysis results show that parameters of the above mentioned were all influenced by surface glue ofcarbon fiber, the stacking model of monofilaments, reactive condition and reactive degreeof C and Al, surface tension and static pressure of metal. And, at same time, ladderingresistance was influenced by mechanical interlocking. The aspect ratio of cast hole wasdecided by diameter of carbon fiber and height of liquid metal.