Process Research On Punching Micro-hole Array With Polyurethane Die And Ultrasonic Assist

Polyurethane rubber punching process is a punching method which uses polyurethane elastomer to replace one rigid die in traditional blanking process,and thus interaction between the polyurethane elastomer and the other rigid die will realize the blanking action,thereby obtaining blanked parts.Compared with traditional blanking process,it is easier to realize fabrication and centring of molds by adopting polyurethane rubber punching process.Ultrasonic vibration assisted machining is a technique which applies ultrasonic regular vibration with frequency greater than 15 kHz to traditional processing methods,and the softening effect of ultrasonic vibration on materials can improve the quality of machined parts and optimize the machining process.In this paper,a suite of micro hole array punching equipment using polyurethane rubber was designed and assembled,and ultrasonic vibration with frequency of 40 kHz was applied to the punch.Then,ultrasonic vibration assisted punching experiments were conducted.ABAQUS was adopted to analyze the forming mechanism of metal foil in polyurethane rubber punching process,according to which punching parameters that infect the material blanking fracture process were determined.H62 brass foil was selected as the material in simulation,and parameters of corresponding Johnson-Cook constitutive equation and fracture criterion were referenced to build the material model.Hyperelastic constitutive model,Mooney-Rivlin,was built to define the material characteristics of polyurethane rubber.The simulation results revealed the influence mechanisms of different punching parameters on the punching process.On the basis of the simulation results,punching experiments were carried out using self-designed polyurethane rubber micro hole array.We successfully punched micro holes with diameter of 800 ?m on H62 brass foil and 304 stainless steel under different die depths,which could verify effectiveness of the simulation results.Additionally,single factor experiments of sheet thickness,punch force and punch speed were conducted to explore their influence mechanisms on micro-hole diameter and cross section quality.Proper ultrasonic-frequency power was selected according to experiment requirements,and Langevin transducer was designed considering the influence rules of size factors on transmission of ultrasonic wave.Amplitude transformer was designed based on the sizes of transducer and punch,and further optimized using ANSYS through modal analysis and harmonic response analysis.Ultrasonic vibration assisted micro punching experiments were carried out under different die cavity depths and power voltages.Results revealed that the softening effect of ultrasonic vibration on materials could optimize the punching process and expand the scope of process parameters,which could reduce manufacturing cost of dies.