Two Dimensional Machining Test of Hard-Brittle Materials Under High Hydrostatic Pressure

Abstract

This paper reports two dimensional machining tests of a soda glass conducted under high hydrostatic pressure up to 200 MPa. A new device has been developed which enables us two dimensional machining test and in-situ observation by an optical micro scope. The device consists of a pressure vessel, a high pressure pump, a two dimensional machining tester and an optical microscope system. Water is used as pressure medium. The two dimensional machining tester consists of an X stage, a stepping motor that drives the stage, a single point diamond tool, a load cell and a tool holder. The load cell is set on the X stage, and a work piece is mounted on the load cell. The load cell measures both principal force and tangential force simultaneously. All of these mechanisms are installed in the pressure chamber. They work well even under high hydrostatic pressure up to 200MPa. The tool and a work piece are observed by a microscope placed outside of the chamber through a sapphire window. Image of machining process is observed by a CCD camera. Machining tests of soda glasses were conducted using single crystal diamond tools of various rake angles. Three types of chip formation were observed; chipping type and discontinuous type were observed under 0 MPa, and 100 MPa, whereas continuous type was observed under 200 MPa. Measurement of cutting force under 0 MPa and 100 MPa revealed that external hydrostatic pressure is effective to increase both principal force and tangential force. Machining mechanism under hydrostatic pressure is discussed.