Experimental Study On Ultrasonic Vibration Assisted Drilling Of CFRP

Carbon fiber reinforced plastics(CFRP)are more and more widely used for its superior material properties.CFRP has low interlayer strength and poor thermal conductivity,the drilling quality is poor because of large axial force and high drilling temperature in conventional drilling process,therefore it is difficult to achieve high-efficient and high-quality drilling.In this thesis,the mechanism and experimental research in UVAD of CFRP is studied,which mainly includes several aspects as follow:(1)The mechanism in UVAD of CFRP was analyzed.The kinematics characteristics of UVAD were described,including dynamic displacement,velocity,working angles and vibration-impact characteristic.And the influence of drilling parameters on kinematics characteristic was further analyzed.The axial force,drilling heat,exit tear and hole wall surface roughness were analyzed.And then the axial force model and heat transfer model of drilling were established.Meanwhile,the effects of vibration and drilling parameters on axial force,drilling heat,exit tear and hole wall surface roughness were analyzed.(2)The experimental research on the axial force in UVAD of CFRP was studied.The experimental platform was set up to carry out experiment in UVAD of CFRP with carbide bit.And the single factor and orthogonal experiments were designed to analyze the axial force under CD and UVAD.The effects of drilling parameters on the axial force were studied.The optimal drilling parameters were obtained to minimize the axial force,and the prediction model was established and verified.(3)The experimental research on the drilling temperament in UVAD of CFRP was studied.With the help of infrared thermal imager and thermocouple,the temperature was measured in drilling.The measurement method of drilling temperature was designed,and the variation of drilling temperature and temperature transfer along different fiber direction were compared and analyzed.The influence and significance analysis of drilling parameters on drilling temperature were studied.The optimal drilling parameters were obtained to minimize the drilling temperament,the prediction model of drilling temperature was established and verified.(4)The drilling quality of CFRP by UVAD was studied.The hole wall surface roughness and exit tear were measured and used to characterize the drilling quality.The influence and significance analysis of drilling parameters on drilling quality were studied.The optimal parameter combinations were obtained under the objective of minimizing the hole wall surface roughness and exit tear factor.The prediction model of drilling quality was established and verified.Finally,the relationship between axial force,drilling temperature and drilling quality was studied.This paper has reference significance for the research of ultrasonic vibration assisted drilling mechanism of CFRP,and has application value for promoting ultrasonic vibration assisted drilling of CFRP and realizing high-efficiency and high-quality drilling of CFRP.