Spatial analysis of draft gear of Railway Wagon by using Six Sigma Approach

A new concept of Six Sigma with its quality control tools have been adopted world-wide in manufacturing sector as well as service sector to improve product quality and reduce variations to make production process robust. The moto of this study is to apply six sigma approaches through its DMAIC (Define-Measure-Analyze-Improve-Control) (Smętkowska & Mrugalska, 2018) methodology on manufacturing of “draft gear’’ a major component of railway wagon freight cars. For measurement system analysis, ‘Minitab19’ software is used to draw the Pareto chart to prioritize the defects, used for cause and effect diagram & also to draw the control chart for attributes. The present work investigates the effect of a crack on the modal frequency of a draft pad. Initially, the first five mode shapes of a healthy draft pad and the first seven mode shapes of healthy draft gear considering compressed draft pads are determined using the finite element approach. A mathematical model of the draft pad is formulated to predict the effect of the crack on its modal frequency. A semi-elliptical shaped crack is modelled in the lateral and longitudinal direction of the draft pad. It is observed that if the crack lies in the zone of minimum modal displacement, then the frequency drop is minimal, and if the crack lies in the zone of maximum modal displacement, then the frequency drop is significant. Various damage scenarios are simulated by varying the width and aspect ratio of the crack in order to identify its effect on the modal frequency. It is seen that if the aspect ratio is varied while the crack’s width is maintained constant, then the frequency drop is linear, whereas if the crack’s width is varied while the aspect ratio is maintained constant, then the frequency drop is parabolic. This study provides a tool for monitoring exciting frequencies of draft gear and shows how each modal frequency is affected by the crack due to parameters like aspect ratio, crack width, and crack location/orientation.