Study Of Acoustical System Of Cellphone Screen Ultrasonic Machining

The acoustical system is an important component of the ultrasound processing equipment, the advantage and disadvantage of its function can show if machining equipment can operate regularly, and affect seriously processing productivity, processing precision and quality of workpiece. Nowadays the material of smartphone screen is sapphire or tempered glass generally, the both are hard and brittle material, and have the nature of high strength and hardness, low fracture toughness, small temperature coefficient, large dielectric constant and so on. Shape of cellphone screen is complex, the dimensional accuracy and surface quality are very high, so ordinary machining technology can not meet processing quality and efficiency. The principle of abrasive impacting machining is studied on ultrasound processing technology, its mathematical model and finite element simulation model are established, acoustic system is analysed in theory, designed, manufactured and measured.In the first chapter, the development status of ultrasound machining technology at home and abroad, the material and processing method of cellphone are summarized, the abrasive impacting machining is proposed on the basis of contents of character of cellphone screen, the main this dissertation are summarized.In the second chapter, the kind, physical performance and choice of abrasive are dissertated, principle of abrasive impacting processing is studied, machining model is established, finite element simulation is operated by ANSYS software, the variations of surface shape and stress are obtained, the effect of technological parameter on removal rate is analysed, and model of material removal volume is presented.In the third chapter, the acoustical system is researched, which is consist of design of solid horn and too, designing method and mathematical model of conventional amplitude transformer is introduced, the vibrating mode of new large dimensional horn and tool with rectangular cross-section is studied, and their model are calculated,3D models are designed and built.In the forth chapter, the finite element analysis method is explained, its theory formula is proposed, model and harmonic response analysis of acoustical system are calculated, the key parameters on resonant frequency, variation of displacement and stress of tip end are obtained, the resonant frequency of acoustical system is19.874kHz, and less126Hz than ideal one20kHz, both of them are pretty close. And the variation of end face displays is obtained.In the fifth chapter, in accordance with of above calculation, design and analysis, the acoustic system are manufactured and tested by automatic impedance analyzer, the error between actual resonance frequency and ideal one is calculated, reason caused errors is studied and analysed deeply, the system is finally satisfied with operational requirement through amending.In the last chapter, the conclusions of the dissertation are summarized and future research of processing method of hard brittle material is proposed.