Research On The Mechanism Of Micro-hole Processing By Ultrasonic Vibration Compounded With Femtosecond Laser

Titanium alloy is widely used in aviation,medical and other fields because of its excellent properties.However,traditional drilling and other methods are difficult to meet the needs of micro-hole machining in high-strength materials such as titanium alloy.In ultra-precision micro-hole processing,laser drilling has high efficiency and good quality,so it is widely used in drilling.The femtosecond laser has the advantages of ultra-short pulse width,very low thermal damage,and high single pulse energy density,and has unique advantages in the preparation of material surface micro-nanostructure,drilling,and so on.In addition,in order to improve the quality of micro-hole machining,composite machining which focuses on the advantages of different processing methods is also the research direction in the field of precision machining,in which ultrasonic vibration-assisted cutting and ultrasonic vibration-assisted laser machining are also being carried out.Therefore,in order to explore the influence law of ultrasonic vibration and femtosecond laser combined machining of micro-holes,Ti-6Al-4V alloy material was selected as the research object,and the composite machining of ultrasonic vibration and femtosecond laser was studied systematically.The main research contents are as follows:(1)Based on the literature at home and abroad,the research progress of traditional,special,and compound machining methods of micro-hole machining is reviewed,and characteristics of common micro-hole composite machining methods are compared.The latest experimental and simulation research on ultrasonic vibration and laser composite micro-hole machining are summarized.(2)The interaction mechanism between femtosecond laser and matter is analyzed,the energy transferred process of femtosecond laser machining titanium alloy micro-holes are studied from the double temperature equation,and the temperature changed process of electron and lattice system is simulated by simulation software during femtosecond laser ablation of titanium alloy materials.The effects of different energy densities,pulse width,and material reflectivity on the temperature of electron and lattice systems are studied.Through simulation analysis,it is found that the coupling equilibrium temperature increases to the increase in energy density or the decrease of the pulse width.The time required to reach the coupling equilibrium temperature also decreases,and the peak temperature of the electron and lattice system increases.When the single pulse energy density is 0.1828J/cm~2and the temperature reaches 0.9Tcr,the material is removed from the form of phase explosion;with the increase of material reflectivity,the electron peak temperature and electron-lattice coupling temperature decrease,but the coupling equilibrium time is almost the same;multi-pulse action shows obvious pulse accumulation effect,and the shorter the pulse interval time,the more obvious the temperature increases,and the faster it reaches the ablation threshold of the material.(3)The principle of ultrasonic vibration and laser composite micro-hole machining and the formation mechanism of micro-hole in the compound mode are analyzed in detail.According to the working requirements of the femtosecond laser machining platform,the ultrasonic vibration device is designed.In this paper,the characteristics of different drilling methods of a femtosecond laser are compared.Taking titanium alloy as the research object,ultrasonic vibration-assisted multi-pulse drilling of the femtosecond laser is studied through the experimental platform of composite machining of titanium alloy.The effects of different energy densities and pulse numbers on the diameter,roundness,and taper of micro-holes are obtained.The results show that with or without ultrasonic vibration assistance,the micropore diameter increases gradually with the increase of pulse energy density,but the growth trend decreases,and the micropore diameter is larger with ultrasonic vibration assistance.The hole roundness deviation decreases with the increase of energy density,and ultrasonic vibration can improve the roundness deviation at the entrance of the micro-hole;with the increase in the number of pulses,the micro-hole machining depth increases linearly.Ultrasonic vibration-assisted drilling can improve the machining depth,reduce the machining taper and improve the morphology of the hole.(4)The ablation threshold of titanium alloy micro-hole machined by femtosecond laser ring cutting was studied by ultrasonic vibration and femtosecond laser machining,and the ablation threshold under different effective pulses was analyzed.The experimental results show that the number of effective pulses increases and the ablation threshold of titanium alloy decreases with the decrease of scanning speed.The effects of laser power,ultrasonic power,scanning speed,and times on the quality characteristics of micro-hole diameter,roundness deviation,and taper are studied by the experimental method of controlling variables.the results show that ultrasonic vibration can effectively improve the depth of micro-hole.Improve the roundness deviation and taper of the micro-hole,but the roundness deviation of the micro-hole will increase under higher ultrasonic power.Finally,a multi-factor orthogonal experiment was carried out to analyze the effects of laser power,scanning speed,scanning times,and ultrasonic power on the entrance diameter,exit roundness deviation,and taper of titanium alloy micro-hole.Scanning speed and laser power have the most significant influence on the observed response value,and the influence of ultrasonic power is greater than that of scanning times.Figure[58]table[11]reference[96]...