Engineering Commons^™

Experiments And Modeling Of The Chemo-Mechanically Coupled Behavior Of Polymeric Gels, Nikola Bosnjak

Dissertations

Polymeric materials consist of mutually entangled or chemically crosslinked long njitmolecular chains which form a polymer network. Due to their molecular structure, the njitpolymeric materials are known to undergo large deformation in response to various njitenvironmental stimuli, such as temperature, chemical potential and light.

When a polymer network is exposed to a suitable chemical solvent, the solvent molecules are able to diffuse inside the network, causing it to undergo a large volumetric deformation, known as swelling. In addition to volumetric deformation, this process involves the chemical mixing of the polymer network and solvent molecules, and is typically environmentally responsive. A …

Blast Shock-Wave Characterization In Experimental Shock Tubes, Sudeepto Kahali

Dissertations

Blast-induced traumatic brain injuries have affected U.S. soldiers deployed for extended periods in the gulf and Afghanistan wars. To identify the biomechanical and biochemical mechanisms of injury, critical in the identification of diagnostic and therapeutic tools, compressed gas-driven shock tubes are used by investigators to study shockwave-animal specimen interactions and its biological consequences. However, shock tubes are designed and operated in a variety of geometry with a range of process parameters, and the quality of shock wave characteristics relevant to field conditions and therefore the study of blast-induced traumatic brain injuries suffered by soldiers is affected by those conditions. Lab-to-lab …

Parametric Study Of Residual Stresses In Wire And Arc Additive Manufactured Parts, Hisham Khaled Jamil Abusalma

Mechanical & Aerospace Engineering Theses & Dissertations

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective additive manufacturing process due to its capability to fabricate large metal parts with high deposition rate and low equipment cost. Although this method is gaining popularity in manufacturing industry, more research is needed to understand process parameters’ effects on residual stress (RS) distribution and part distortion. As such, a 3D thermo-elastic-plastic transient model was established in ABAQUS and employed to investigate the effect of process parameters such as the torch speed, the deposition power and the interlayer dwell time on RS distribution and distortion in WAAM part. The numerical model utilized …

Friction Predication On Pin-To-Plate Interface Of Ptfe Material And Steel, Zhuming Bi, Donald W. Mueller

Friction

In this paper, the friction behavior at a pin-to-plate interface is investigated. The pin and plate are made of Polytetrafluoroethylene (PTFE) and steel, respectively, and there is a reciprocating motion at the interface. Governing mathematical models for the relations of design variables and frictions are investigated, and a general procedure is proposed to solve the developed models and predict the friction forces at the interface subjected to given test conditions. Novel models have been developed to represent intrigued friction behaviors affected by various factors such as pin geometrics and finishes, lubrication conditions, and reciprocating speed. The test data from experiments …

Finite Element Analysis Investigation Of Hybrid Thin-Ply Composites For Improved Performance Of Aerospace Structures, Alana M. Zahn

Mechanical & Aerospace Engineering Theses & Dissertations

Commercial and private aircraft have a need for strong yet light materials in order to have the most ideal performance possible. This study looks at the use of thin-ply composite materials to improve the performance of aircraft structures by means of weight savings and/or strength increase when compared to laminates that are composed of exclusively standard-ply materials. In order to perform an investigation based solely on finite element analysis, validation efforts were performed using test data from open hole tension, open hole compression, notched tension, and notched compression specimens. Once the models were validated sufficiently, the same modeling practices were …

Energy Harvesting Using Flextensional Piezoelectric Energy Harvesters In Resonance And Off-Resonance Modes, Mohamed A. Shabara

Mechanical & Aerospace Engineering Theses & Dissertations

Energy harvesting technologies are integrated into various modern devices and systems. These systems include Artificial Intelligence (AI) systems, Internet of Things (IoT), various types of energy harvesters are integrated in many engineering applications such as automotive, aerospace and ocean engineering. In order to develop a fully functioning stand-alone system, it is essential to integrate it with a built in power source such as a battery or a power generator. Also, in many situations, city power sources might not be available. Therefore, reliable, renewable and sustainable local power generators are desired. Piezoelectric energy harvesting (PEH) technologies, which are piezoelectric material-based devices, …

A Computational Investigation Into Acromial Fractures After Reverse Total Shoulder Arthroplasty, Jason Lockhart

Electronic Thesis and Dissertation Repository

Acromial fractures are a debilitating complication following reverse total shoulder arthroplasty (RTSA). The purpose of this work is to (1) improve the current state of FE bone stress estimates after RTSA and to investigate the effects of (2) plane of elevation, (3) hand loads, and (4) baseplate screw position on scapular spine stress. The FE method used was validated against an in-vitro strain gauge based experiment and found to be accurate in the prediction of stress increases and decreases after RTSA. The coronal plane of elevation was found to increase scapular spine stress compared to more central planes of elevation. …

Influence Of Dynamic Multiaxial Transverse Loading On Ultrahigh Molecular Weight Polyethylene Single Fiber Failure, Frank David Thomas

Theses and Dissertations

High performance fibers such as ultrahigh molecular weight polyethylene (UHMWPE) are often used for ballistic impact applications in the form of textile fabrics and composite laminates. In order to predict the ballistic performance of such materials, single-fiber experiments are performed to quantify the material behavior at smaller length scales, which can be applied to larger length scales as a result. Failure of UHMWPE is well understood as a function of simple tension at low and high strain rates, as well as under various multiaxial loading states. However, experimental characterization of single UHMWPE fibers under transverse loading at high strain rates …

Compaction And Residual Stress Modeling In Composite Manufactured With Automated Fiber Placement, Von Clyde Jamora

Mechanical & Aerospace Engineering Theses & Dissertations

Automated fiber placement is a state-of-the-art manufacturing process that allows for complex layup patterns and can quickly place, cut, and restart composite tows. However, with this type of manufacturing process layup defects are inevitable, and manufacturing defects propagate after curing. Process modeling is the considered approach for exploring the defect prediction. Two different but related works were conducted, which are the thermochemical and hyperelastic model and the residual deformation model. For the model before cooling, a hyperelastic model and a thermo-chemical were made to simulate the compaction and heat transfer. Temperature dependent properties that are a function of degree of …