A Research On Safety Of Ultra-high Speed Grinding Wheel

The research objective of this thesis is to investigate the potential mechanisms of abronze bonded CBN, bursted accidentally under ultra-high speed grinding condition. Byusing fracture theory and employing macro and micro topography observationscombined with, spectrum analysis, two fracture modes and reasons of the grinding wheelbursting have been identified.The effects of centrifugal force, grinding force and grinding wheel base and theabrasive layer bonding situation on the safety of grinding wheel were analyzed by usingthe finite element analysis software ANSYS Workbench. The grinding wheel wasoptimized to improve grinding wheel safety.By integrating the analysis of experimental results and finite element calculationresults, the main conclusions were reached as the followings：(1)For grinding wheel fragments of type Ⅰ, fracture mode was brittle fracture.Structure defects and thread in interlayer was the major factor causing crack in itiation.(2)For grinding wheel fragments of type Ⅱ,fracture formation is relevant with thegenerated macroscopic crack before fracturing; fracture mode was brittle fracture.Grinding fore and alternating load, formed by grinding force and centrifugal forc e, werethe reasons for surface and internal cracks formation in abrasive layer.(3)By FEM simulation, centrifugal force made maximum stress in abrasive layerand stress concentration in the thread hole; grinding force had a little impact on thestress in grinding wheel, but would affect the stress of grinding zone in abrasive layer;that bonding surfaces neutralized, leaded maximum stress of abrasive layer to improve,was one cause of fracture of the grinding wheel.(4)Though optimizing abrasive layer material, grinding wheel base and abrasivelayer assembly, grinding wheel material, the maximum stress of abrasive layer could bedecreased to increase the safety of grinding wheel.