Experimental Investigation of Subsurface Damages Made by Cup Grinding and Lapping Process of Optical Glass BK7 in Ductile Mode

Subject Areas :

Vahid  Barahimi ¹ (Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran)
Masoud  Farahnakian ² (Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran)

Received: 2016-12-23 Accepted : 2017-03-16 Published : 2017-02-01

Keywords: Optical Glass BK7, Cup Grinding, Subsurface Damages, Ductile Grinding,

Abstract :

Conventional material removal of BK7 optical glass will normally result in brittle fracture at thesurface, generating severe subsurface damage and poor surface finish. Subsurface damages inducedby grinding strongly influence the mechanical strength and optical quality of optical glasses.However, through ductile mode grinding it is possible to reduce the surface and subsurface cracks.It is meaningful to evaluate the depth of subsurface cracking through the measurement of surfaceroughness under different grinding parameters. In this research, the surface and subsurface damagesduring micro cup grinding and lapping process of optical glass BK7 are being investigated. In orderto invest the subsurface damages, cross section polishing method is being used and the crosssections are inspected through SEM microscope. The results indicate that number of subsurfacemedian cracks after lapping process are strongly decreased and surface lateral cracks are extendedall over the sample's ground surface.