Experimental Research On Robotic Rotary Ultrasonic Drilling Of CFRP/aluminum Alloy Laminated Materials

Composite aerospace laminates of carbon fiber composites and aluminum alloys are widely used in aircraft airframes,fuselage skins and other important components of aircraft due to their excellent mechanical and chemical properties.However,the excellent mechanical properties of the material also indicate that it is difficult to process,and the drilling force is large during the drilling process.At present,the most commonly used hole making method in the field of aviation manufacturing is the robotic automatic hole making technology.Due to the low rigidity of the mechanical arm structure,the excessive drilling force will cause the robot to drill the posture and produce the processing tremor,which seriously affects the quality of the hole and drilling accuracy.In this paper,the rotary ultrasonic drilling technology is introduced on the basis of robot hole making,and different tool types,ultrasonic parameters and drilling parameters are selected to carry out basic experimental research,drilling result modeling research and processing parameter optimization research.Firstly,drilling experiments of robotic aerospace laminates are carried out using two different drilling tools,three-point drill and twist drill,to observe and analyze the drilling force and the change of machining quality when drilling different tools.Through the analysis of the cutting edge structure and geometric parameters of different tools,the reasons for the variation of drilling force of different tools are clarified.The mechanism and law of the influence of ultrasonic vibration parameters and drilling process parameters on the drilling force of aviation laminated materials are analyzed.The partial least squares algorithm is used to construct the prediction model of the rotating ultrasonic drilling force of the robot.The average error is 8.02%,which verifies the rationality and accuracy of the model.Secondly,a comparative experimental study on the quality of drilling and the quality of rotary drilling of robots and drilling precision is carried out.The laser microscopy is used to measure the variation of drilling quality and drilling accuracy of aerospace laminates under different process parameters,including hole wall roughness,aperture deviation and aluminum plate hole exit burr height.According to the measured data,the influence curves of ultrasonic parameters and drilling parameters on the quality and precision of drilling are analyzed,and the improvement status and reasons of high-frequency vibration shock on the quality and precision of drilling are clarified.At the same time,the prediction model of hole wall roughness,aperture deviation and aluminum plate hole exit burr height is constructed.The error is controlled at 14.54%,9.35% and 17.65% respectively,which provides a basis for subsequent parameter optimization.Finally,the surface quality and surface damage of laminated materials are observed by laser microscope.The influence of ultrasonic parameters and drilling parameters on machining damage is analyzed.Based on the particle swarm optimization algorithm,combined with the above prediction model,the maximum drilling efficiency is taken as the objective function,and the mathematical model of parameter optimization is constructed with the constraints of drilling force,hole wall roughness,aperture deviation and aluminum plate hole exit burr height.The optimized process parameters of rotary aerodynamic drilling of aerospace laminates are obtained,and the accuracy and rationality of the optimization method are verified by experiments.It provides technical support for the subsequent robotic rotary ultrasonic drilling of aerospace laminate technology.