Analysis And Evaluation Of Surface/Subsurface Damage Characterization Of BK7 Glass In Rotary Ultrasonic Machining

Rotary ultrasonic machining is a kind of composite processing method collecting traditional ultrasonic machining and grinding, which can realize the high efficiency machining of BK7 glass microstructure parts. BK7 glass finishing using diamond tool can achieve the required geometric accuracy. However, the great impact load because of the high frequency vibration of tool spindle role to the surface and lead to surface and subsurface damage, which will reduce the load capacity. Therefore, rotary ultrasonic machining mechanism, surface/subsurface damage characteristics and the depth of subsurface crack detection and prediction methods of BK7 glass need to be further studied, so as to realize the high efficiency and low damage machining of BK7 glass parts.In order to study the rotary ultrasonic machining mechanism of material removal and morphology characteristics of surface damage BK7 glass, single scratching and double scratching experiment were conducted, finding that plastic flow and brittle fracture can generate surface damage. The changing cutting depth single scratching experiment in different velocity was carried and found that the increase of scoring speed can lead to increase of brittle/transition critical cutting depth and the critical load. Double scratching experiment in different scratching space and cutting depth were carried, which proved that cutting depth and scratches space also have an effect on the material removal and surface damage.Surface formation mechanism of BK7 glass rotary ultrasonic machining was further analyzed, the subsurface crack formation mechanism of rotary ultrasonic machining was studied by observing morphology of surface/subsurface damage. Finding that residual stress induced the generation of median/radial crack and lateral crack system. Besides, under the action of high frequency vibration, printing press of diamond grits will cause the interaction between adjacent indentations and generate the indentation stress field, which lead to the nucleation and extension of median/radial crack along the score direction, eventually become the largest depth of crack.The end face grains motion curve of end milling machining were analyzed and deduced the milling surface contact arc length and effective grinding grain quantity calculation formula. In addition, the relationship model between surface roughness, cutting force and process parameters was established using design of experiment and regression analysis. The depth of surface damage prediction method of rotary ultrasonic machining was put forward and the end milling process parameters were optimized by the multi-objective optimization method.Based on the brittle material indentation fracture mechanics, the mathematical relationship between radial cutting force and radial indentation load was analyzed. Through the finite element analysis, the edge chipping mechanism was explained and the critical conditions of producing export side damage phenomenon were set up. Besides, the dimension of the side damage on exports was predicted and edge damage suppression strategies of rotary ultrasonic machining was put forward...