Research On Ultrasonic Assisted Drilling Of SiC Ceramics By Using Step Drill

Nowadays,science and technology is developing at an increasingly rapid pace,which puts forward higher requirements for the properties of materials.Represented by advanced ceramics,functional crystals and their composite materials,hard and brittle materials are widely used in aerospace,electronics industry,optical engineering and many other fields due to their stable physical and chemical properties.A large number of holes are often required for hard and brittle materials in engineering applications to achieve assembly and act as functional structures such as oil circuits.However,because of the characteristics of hard and brittle materials,traditional drilling has various problems,such as high drilling force,poor drilling quality and low processing efficiency,which makes it is difficult to meet the hole quality requirements of hard and brittle materials for traditional drilling.In a certain extent,ultrasonic assisted drilling technology can solve the difficult problems of drilling hard and brittle materials,but damages of hole drilling for hard and brittle materials such as edge chipping still exist,which severely restricts their engineering applications,and the quality of hole drilling needs to be further improved.In order to improve the quality of ultrasonic assisted drilling and drill holes with high efficiency and low damage of hard and brittle materials,this dissertation proposes a method of using step drills in ultrasonic assisted drilling.The hole exit edge chipping and the hole diameter deviation formation processes of drilling as well as the reduction mechanism by using step drill are studied by theoretical method.The research on ultrasonic assisted drilling process for silicon carbide materials is carried out through the self-designed step drill.The main study work of this dissertation includes as follows:(1)According to the composition and principle of the ultrasonic assisted drilling system,the custom ultrasonic horn is designed and simulated.Ultrasonic assisted drilling system is designed,and an amplitude measuring device is built to test the performance the ultrasonic assisted drilling system.(2)The drilling processes of ordinary twist drill and step drill are analyzed,and the kinematics model of ultrasonic assisted drilling with step drill are established.The trajectory of the main cutting edge of the step drill is drawn,and the ultrasonic assisted drilling consumption and drilling duty ratio of step drill are analyzed.The mechanism of using step drill to improve the quality of hole drilling is studied.(3)The finite element simulation model of ultrasonic assisted drilling is established based on finite element simulation technology.The internal stress of the work piece,drilling force and the hole exit damages during the drilling process are analyzed according to the simulations of ultrasonic assisted drilling process using step drill and ordinary twist drill.(4)For drilling holes of silicon carbide material,a comparative test of ultrasonic assisted drilling and traditional drilling is carried out.Two single factor tests of ultrasonic assisted drilling process parameters are carried out with spindle speed and feed speed as parameters.The observed results of the tests can well validate the viability and effectiveness of using step drill to improve the quality of ultrasonic assisted drilling.This dissertation has theoretically analyzed and experimentally researched the quality improvement of ultrasonic assisted drilling based on step drill,some main conclusions have been summarized as follows: Compared with traditional drilling,ultrasonic assisted drilling can improve the drilling quality under the same conditions;Compared with ordinary twist drill,using the step drill with the ratio of the minor diameter to the major diameter is greater than 0.5 can reduce the hole diameter deviation,the size of the hole exit chipping and the surface roughness of hole wall;When the spindle speed and feed rate are large,using step drill with the minor diameter very small,the drilling quality may be worse than that of ordinary twist drill;The hole diameter deviation,the size of the hole exit chipping and the surface roughness of hole wall can be reduced by appropriately increasing the spindle speed or reducing the feed speed.