Date of Award


Document Type

Open 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

Trisha Sain

Committee Member 2

Stephen Morse


Transformer bushings are a common target for sniper attacks to cause power failure in large areas. Given the size, internal pressure and brittle nature of transformer bushing, pellet impact causes damage to surrounding components due to broken bushing pieces. To mitigate this, a project was initiated by United States Burau of Reclaimation to develop a safety mechanism. Finite Element Analysis is proposed to optimize and reduce cost of the design.

A simplified Finite Element model is created which consists of 0.22 caliber lead pellet impacting Pyrex 7740 borosilicate glass tube. Previous studies on the effect of the mesh pattern, size and cap geometry were carried out. One of the biggest factors which can help in mitigating the transformer component damage is internal pressure of bushing fluid. This study focuses on developing a Finite Element model which captures the fluid-structure interaction between glass tube and internal pressurized air. Arbitrary Lagrangian Eulerian code of LS-DYNA is used to simulate this interaction.

This report describes the modelling techniques used to simulate the pellet impact on pressurized tube. Failure strain calculations are also discussed in the report. The effect of internal pressure and failure strain are addressed. Crack pattern and broken glass fragments size are considered for a comparison between the pellet impact simulation and experiment.