一种超声超低温冰层支撑辅助CFRP钻削方法

A method of CFRP drilling assisted by ultrasonic,cryogenic temperature and ice support

提出一种超声振动+超低温液氮+由超低温环境形成的冰冻支撑层(Ultrasonic vibration+Cryogenic liquid nitrogen+Frozen support layer,UCF)来辅助碳纤维增强树脂基复合材料(Carbon fiber reinforced polymer,CFRP)钻削制孔,有效降低钻削缺陷的加工方法。该方法的基本原理为:利用超声作用下的钻头高频振动实现轴向钻削力的弱化,利用超低温液氮以及形成的冰冻支撑层来实现钻削出口侧材料的约束和支撑,并有效降低加工过程的钻削热影响。基于UCF的基本原理,开展了相应的UCF辅助加工实验,通过微观检测表征和缺陷因子计算等手段,与传统钻削模式(Traditional drilling,TD)、低温液氮+冰冻支撑模式(Cryogenic liquid nitrogen+Freezing support,CF)下的CFRP制孔质量进行了对比分析。结果表明,采用UCF模式和CF模式均会引起轴向力增加,但UCF模式下的最大轴向力增幅相对较小;与TD模式相比,采用UCF辅助加工方法最大可使CFRP钻削出口的毛刺因子降低75%,撕裂因子降低8.9%,分层因子降低34.6%,孔壁表面粗糙度Ra降低53.6%。

A method of ultrasonic vibration+cryogenic liquid nitrogen+frozen support layer(UCF)is proposed to assist carbon fiber reinforced polymer(CFRP)drilling and effectively reduce machining defects.The basic principle of this method is as follows:the high frequency vibration of the drill bit under ultrasonic action is used to weaken the axial drilling force;the cryogenic temperature liquid nitrogen and the formation of frozen support layer are used to realize the constraint and support of the material at the drilling exit side,and effectively reduce the whole process of drilling heat effect.Based on the basic principle of UCF,corresponding experiment of UCF assisted drilling were carried out,and the hole quality of CFRP under traditional drilling mode(TD)and cryogenic liquid nitrogen+freezing support mode(CF)was compared and analyzed by means of microscopic inspection and characterization and defect factor calculation.The results show that both UCF and CF can increase the axial force,but the maximum axial force increased little.Compared with TD mode,UCF can reduce burr factor by 75%,tear factor by 8.9%,delamination factor by 34.6%and surface roughness Ra by 53.6%.