Engineering Commons^™

Assessment Of Bridge Pier Response To Fire, Vehicle Impact, And Air Blast, Chen Fang, Qusai Alomari, Daniel G. Linzell

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Highway bridges exposed to intentional or unintentional fire followed by combined vehicle impact and air blast are at risk of significant damage and, possibly, collapse. Limited studies examining the complex effects of these extreme demands on bridge support elements and parametrizing their response and damage are found in the open literature. Research that is presented is part of an ongoing numerical investigation examining round, multi-column, reinforced concrete (RC), bridge pier behavior subject to multi-hazard scenarios involving fire, vehicle impact, and air blast. Detailed nonlinear finite element analysis models of single columns and multi-column piers supported by a pile foundation system …

Low Velocity Impact Of Hybrid Stacked Steel Plates, H. Hadidi, R. Q. Feng, M. P. Sealy

Department of Mechanical and Materials Engineering: Faculty Publications

Designing and manufacturing high-strength, low-weight parts with enhanced impact resistance is highly sought after in the transportation industry. The most common methods to improve strength-to-weight ratios of impact targets is a composite material composition or a favorable geometric design. An alternative method to improve impact performance is functionally gradient mechanical properties in a single material by hybrid additive stacking. In this study, low-velocity impact tests were conducted on hybrid stacked 1070 steel plates where individual layers were subjected to shot peening (SP) to functionally grade mechanical properties. Hybrid additive stacking refers to secondarily processing preferential layers within a stacked build …

Double-Sided Corrugated Composite Tube And Axle Protective Mechanism For Railway Vehicles, Hozhabr Mozafari

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

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 …

Take Off To Superiority: The Evolution & Impact Of U.S. Aircraft In War, Lane Weidner

Honors Theses

Military aviation has become a staple in the way wars are fought, and ultimately, won. This research paper takes a look at the ways that aviation has evolved and impacted wars across the U.S. history timeline. With a brief introduction of early flight and the modern concept of an aircraft, this article then delves into World Wars I and II, along with the Cold, Korean, Vietnam, and Gulf Wars. The current War on Terrorism is then investigated, and finally, a look toward the future. Topics covered include the newest aircraft of each era, technological advancements, and how strategy and war …

Peridynamic Modeling Of Dynamic Fracture In Bio-Inspired Structures For High Velocity Impacts, Sneha Akula

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Bio-inspired damage resistant models have distinct patterns like brick-mortar, Voronoi, helicoidal etc., which show exceptional damage mitigation against high-velocity impacts. These unique patterns increase damage resistance (in some cases up to 3000 times more than the constituent materials) by effectively dispersing the stress waves produced by the impact. Ability to mimic these structures on a larger scale can be ground-breaking and could be used in numerous applications. Advancements in 3D printing have now made possible fabrication of these patterns with ease and at a low cost. Research on dynamic fracture in bio-inspired structures is very limited but it is …

Evaluation Of The Environmental Impacts Of Bridge Deck Runoff, Shannon L. Bartelt-Hunt, Lauren Swadener, Ekizabeth G. Jones

Nebraska Department of Transportation: Research Reports

Bridges are located in very close proximity to receiving waters, and regulatory agencies often require specific stormwater control measures for bridge deck runoff. While there is some information available on roadway runoff, few studies have focused on bridge deck runoff. Currently, there is no information available regarding the impacts of bridge deck runoff on receiving waters in Nebraska. Due to the cost, maintenance, and design issues associated with implementing structural controls for bridge deck runoff, it is important to develop a better understanding of the relationship between bridge deck runoff and potential impacts to receiving streams. The objectives of this …

Impact Of 0.7 Inch Diameter Strands On Nu I-Grinders, Maher K. Tadros, George Morcous

Nebraska Department of Transportation: Research Reports

No abstract provided.

Numerical And Analytical Verification Of A Multiscale Computational Model For Impact Problems In Heterogeneous Viscoelastic Materials With Evolving Damage, Bruno Bachiega Araujo

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Composites are engineered materials that take advantage of the particular properties of each of its two or more constituents. They are designed to be stronger, lighter and to last longer which can lead to the creation of safer protection gear, more fuel efficient transportation methods and more affordable materials, among other examples.

This thesis proposes a numerical and analytical verification of an in-house developed multiscale model for predicting the mechanical behavior of composite materials with various configurations subjected to impact loading. This verification is done by comparing the results obtained with analytical and numerical solutions with the results found when …

Multiscale Modeling Of The Impact Of Textile Fabrics Based On Hybrid Element Analysis, Gaurav Nilakantan, Michael Keefe, Travis A. Bogetti, John W. Gillespie Jr.

United States Army: Publications

In this work, a multi scale modeling approach has been developed to simulate the impact of woven fabrics using a finite element (FE) analysis. A yarn level of resolution is used in the model. This approach, referred to as the hybrid element analysis (HEA) is based on decreasing the complexity of the finite element model with distance away from the impact zone based on the multiscale nature of the fabric architecture and the physics of the impact event. Solid elements are used to discretize the yarns around the impact region, which transition to shell elements in the surrounding region. A …

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the …

Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru

Department of Engineering Mechanics: Faculty Publications

In this paper a review of impact mechanics and high-energy absorbing materials is presented. We review different theoretical models (rigid-body dynamics, elastic, shock, and plastic wave propagation, and nonclassical or nonlocal models. and computational methods (finite-element, finite-difference, and mesh-free methods. used in impact mechanics. Some recent developments in numerical simulation of impact (e.g., peridynamics) and new design concepts proposed as high energy absorbing materials (lattice and truss structures, hybrid sandwich composites, metal foams, magnetorheological fluids, porous shape memory alloys. are discussed. Recent studies on experimental evaluation and constitutive modeling of strain rate-dependent polymer matrix composites are also presented. Impact damage …

Modeling Of Solid Phase Detonations, C Richter, Hendrik J. Viljoen, N.F.J Van Rensburg

Papers in Reaction Kinetics

In contrast to conventional explosives which constitute rapid decomposition of the molecular structure acconlpanied by the release of large volumes of gaseous products, heterogeneous mixtures in the SHS realm react by progression of a thermal wave at velocities far below the speed of sound in such mixtures. Interestingly, ultrafast solid phase reactions can be initiated under the right conditions. A shock wave compresses the solid mixture to densities well beyond the theoretical mean ambient density (TMD) and compression becomes the major form of preheating. In addition, elastic potential energy is pumped into the lattice structure to induce severe distortion and …