Failure analysis of strap joint

Abstract

In Exhaust after treatment system strap joint is used for mounting sensor table on which DP, NOx, EGTS, PIN sensors are mounted. While, assembling the sensor table on exhaust system using strap joint multiple issues raised. In which, Strap Bolt Loosening Issue during Vibration Test, Plastic Deformation of Heat shield (outer body) and Bottoming Out of the strap. Under Strap contact area plastic deformation of heat shield is due to increasing contact pressure so that needs to check the recommended value of torque to avoid failures. The basic design assembly of straps consists of T bolt, nut, and trunnion with the strap. In this paper analysis and calculations for torque and parameters affecting the system function have been done to minimize the issues. To reduce plastic deformation internal stand support provided which increase the stiffness of heat shield and observed results showing Bridge strap design concept can be helpful to avoid localized plastic deformation near T-bolt. Calculations at assembly load showing maximum stress and contact pressure near the T bolt. Also effect of inertia load described to check slippage of the strap and after treatment system.