Calculation of Allowance Value for Grinding with Flap Wheels of Shot-Treated Surface to Ensure Required Roughness

Abstract

In the aircraft industry to obtain the necessary form of long panels and sheathing, the technology of shot peen forming and subsequent grinding with flap wheels is successfully implemented. Due to the impact of the shot, a specific microgeometry is formed on the treated surface, a characteristic feature of this microgeometry is the occurrence of numerous shot dimples with various diameters and depths. Since the depth of the shot dimples is much higher than the valleys of the surface microroughness, formed as a result of previous processing, these dimples increase the surface roughness. When grinding with flap wheels, depending on the value of the allowance on the treated surface, a new microrelief is formed in the form of a combination of the traces of the abrasive grains of the flap wheels during grinding and the remaining dimples from shot peen forming. Since the dimples have a shape close to spherical with a much larger radius of curvature than their depth, at each stage of grinding, depending on the allowance, the curvature of the dimples has a significant impact on the formation and the value of roughness of the treated surface. The paper presents a methodology for creating a digital model of roughness during grinding with flap wheels of the surface treated by shot peen forming in dependence to the allowance for grinding, and presents a numerical method for determining the required allowance for obtaining the required values of roughness.