| In the conventional cutting(CC)method,single crystalline diamond(SCD)tool is rarely used to machine the sinteredtungsten carbide(WC)because of its short life and red hardness.Machining surface is prone to brittle crack and it is hard to ensure quality.In the precision machining of WCfor grinding with diamond wheel,multiple superfinishing are required,in order to further improve the precision and reduce the grinding trace,which causes high cost and can’t meet the modern industrial processing efficiency,complexity and accuracy requirements.For improving machinability and achievingefficient ductile machining,a new compound cutting technology of laser assisted and ultrasonic vibration cutting(combined machining)to precision machining of WC is presented.First of all,the nonlocal damage model of laser ultrasonic combined machining WCwas establishedwhich described the relationships of vibration parameters,temperature parameters and internal characteristic parameters in thenonlocal kernel function.Thestrain localization of one-dimensional bar under ultrasonic excitation and specimens with axial tensile under laser ultrasonic combined were simulated by FEA.Secondly,the influence of chute parametersof the amplitude amplifier horn on the resonance frequency and amplitude was analyzed.According to the influence rule,horn was designed,and cutting test was carried.Based on the cutting force and surface quality of workpieces,the applicable horn was elected to complete test platform of laser ultrasonic combined cutting.Then,the model of critical depth of cutfor brittleness-ductility transition of WC in laser ultrasonic combined cutting is established.The influence of processing mode,cutting parameters,temperature,material properties of WC onthe critical cutting depth was analyzed.The influence of material removal mode transformation onsurface quality was researched.Finally,cutting force model ofmachining WCunderlaser ultrasonic combined cutting is established.The cutting force variationcharacteristicswas analyzedand the influence of tool wear on surface qualitywas researched.Results show thatultrasonic excitation and enhancing temperature of material will exacerbate the strain localization phenomenon and local softeningdegree of material is more obvious,the critical cutting depthfor brittleness-ductility transitionof WC in laser assisted and ultrasonic elliptical vibration precision cutting is much higher than that of ultrasonic elliptical vibration cutting(UEVC)and CC.,and cutting force decreased significantly.With larger ultrasonic amplitude and frequency,higher temperature,smaller radius of tool,and higher Co content of WC,critical cutting depth value is greater,cutting force is smaller,tool wear degree is low,surface quality is better,and surface roughness value is smaller.When the resonant frequency,f,of the ultrasonic elliptical vibration is 35 KHz and the longitudinal amplitude is 2.1 um,the critical cutting depth of WC reaches the peak value near the cutting speed v=10m/min.Laser ultrasonic combined cutting can increase ductile cutting and improve machinability of WC.Cutting process is more stable,and the purpose of precision machining of WCshould be realized. |
