Mechanical & Materials Engineering, Department of


First Advisor

Linxia Gu

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor Linxia Gu. Lincoln, Nebraska: December 2019

Copyright 2019 Hozhabr Mozafari


Structural elements in transportation vehicles are exposed to different types of dynamic loadings and impact scenarios. Protecting passengers against injury and providing mechanisms to avoid impact induced damages to the critical components are the two hot topics in crashworthiness engineering. The presented research work includes two parts. The first part is about designing a novel double-sided composite corrugated tube that can be implemented in front chassis rail of ground vehicles to improve their crashworthiness against collision and car accidents. To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the DSC tube in comparison with both SSC and classical straight (S) tubes under axial crushing. Results have shown that the total absorbed energy of the DSC aluminum tube with 14 corrugations was 330% and 32% higher than that of the SSC tube with 14 corrugations and the S-tube, respectively. The second part of this research work is about designing a novel protective mechanism for railway car axle against ballast impact. The ice detached from the train body can fall on the track and form projectiles of ice and gravel (ballast); sharp, heavy, and at high impact energy. The main preventive mechanism in many countries such as Norway is to use protective coating on the axle. But when the coating is damaged by impact, bare steel of the axle can be exposed. The corrosion of these exposed impact zones can cause pits and cavities that become points of stress concentration where fatigue cracks can develop. Due to the current problems with coating technique we suggested a novel protective mechanism and used sandwich panel to protect railway axle against impact. Our results showed that the device can dissipate more than 70 % of impact energy without introducing any damage to the axle surface. Moreover, the rebounding velocity of projectile reduced by 97 % which eliminates the risk of second impact to the other vehicle components. The suggested device can be mounted by using a simple clamping system and unmount easily for potential inspections.