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Date of Award

2016

Document Type

Campus Access Master's Report

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Gregory Odegard

Committee Member 1

Adam Loukus

Committee Member 2

Jeremy Worm

Abstract

This study is part of a major project to design and develop a non-cylindrical CNG tank for automotive application. There are two phases of this project. Phase I consists of design and development of rectangular shaped CNG tanks having inner structure inspired by ‘P Schwarz’ structure whereas Phase II consists of development of conformable CNG tanks. The purpose of this study is to perform finite element analysis of Phase I CNG tank and supporting brackets. It also focuses on the study of dynamic behavior of chassis when the newly designed CNG tanks and brackets were mounted on it. Following analyses were conducted in this study- Static analysis of CNG tank and brackets, Modal analysis of Chassis with the tanks and brackets attached to it. For this study, Finite analysis software package ‘Hyperworks’ was used. The static and modal analysis was done using ‘Optistruct’ solver.

The static analysis of brackets supporting the tank was carried out to check its structural integrity. Based on the analysis, the factor of safety for side bracket and back bracket was determined to be 5.4 and 4.45, respectively. Hence it can be concluded that the bracket design satisfies the design criterion.

Linear static analysis of tank was conducted to find out the maximum stress due to the CNG pressure loads inside it. From the analysis results, it was observed that the maximum strain in the tank was 0.003 and maximum stress in the tank was 31000 psi. The Factor of safety was observed to be 1.61; hence, we can conclude that the tank structure sustains the CNG pressure loads.

Modal analysis of the chassis was conducted to find the natural frequency of the chassis structure after the newly designed brackets are mounted on it. As per the analysis, the first mode natural frequency was found to be 15.36 Hz. Modal testing and strain gauge measurements can be performed to validate the analysis results in future.

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