Engineering Commons^™

Mechanical Behavior Of Pipeline Steels And An Al0.1cocrfeni High-Entropy Alloy, Bilin Chen

Doctoral Dissertations

This dissertation is composed of two parts. The first part focuses on the mechanical behavior study on pipelines steels. More specifically, the effect of hydrogen on the deformation behavior of the crack tip of an X52 pipeline steel specimen, and the overload effects on the fatigue crack growth of an x70 pipeline weld metal are discussed. For the second part of the dissertation, fatigue behavior of an Al0.1CoCrFeNi high-entropy alloy (HEA) is studied, and the influence of heat treatment is discussed.

The objectives of the first part of this proposed work are to (1) detect the influence of hydrogen on …

On The Fatigue Of Headed Shear Studs In Steel-Concrete Composite Bridge Girders, Brianna Laurene Ovuoba

Graduate Theses and Dissertations

Shear connectors are commonly used in steel bridges to join the concrete deck and steel superstructure, providing a mechanism for shear transfer across the steel-concrete interface. The most common shear connector is the headed shear stud. In the current AASHTO LRFD Bridge Specifications on composite design, shear stud fatigue often governs over static strength, and a large number of shear connectors often result. This dissertation investigates headed shear stud fatigue capacities and demands, and provides insight into conservancies in existing design specifications through examination of existing high-traffic bridge performance.

To investigate stud capacity, a total of six high-cycle fatigue tests …

Automated Pin-Dot Marking Effects On A709-Gr50 Steel Plate Fatigue Capacity, Michael Andrew Noernberg

Graduate Theses and Dissertations

During fabrication of multi-piece steel bridge assemblies, markings are often made on the steel surface to identify/track individual pieces or to provide reference for fabrication layout or later erection. Automated marking methods such as computer numerically controlled (CNC) pin-dot marking offer fabrication efficiencies; however, for marked steel sections subjected to frequent or repeated loading (i.e. bridge girders) many code specifications require experimental testing to verify any marking effects on fatigue capacity. In this study, the effects of automated pin-dot markings on the fatigue capacity of A709-Gr50 bridge steel are experimentally investigated from 13 specimens considering 2 marking frequencies (corresponding to …

Fatigue Impacts On Hdpe Pipe Material Properties, Marjan Shahrokh Esfahani

Civil Engineering Dissertations

During a pipe’s life cycle, failures occur due to numerous factors such as age, loading conditions, environmental conditions, installation quality, manufacturing procedures, operation and maintenance strategies and so on. Frequent pressure surges or fluctuations in a piping system may cause a fatigue failure as fatigue is one of the most important issues in water pipes due to water hammer impacts. Application of buried High Density PolyEthylene (HDPE) water pipelines has significantly increased in recent years, and PE4710 is a new member of HDPE family. So, there is not yet enough information about PE4710 long-term performance. Due to lack of enough …

Development Of Pre-Stressed Retrofit Strategies For Mitigating Fatigue Cracking In Steel Waterway Lock Gate Components, Christine Michelle Lozano

Graduate Theses and Dissertations

Lock gates are an important part of the transportation infrastructure within the United States (US), having many economic, safety, and environmental benefits over rail and highway transportation systems. Unfortunately, many existing lock gates throughout the US have reached or exceeded their initial design life and require frequent repairs to remain in service. Unscheduled repairs often increase as gates age, having a local economic impact on freight transport which can create economic ripples throughout the nation. Fatigue and corrosion are key causes of unscheduled service interruptions, degrading lock gate components over time. Additionally, because lock gates are submerged during operation, crack …

3d Printing Of 316l Stainless Steel And Its Effect On Microstructure And Mechanical Properties, Rawn Penn

Graduate Theses & Non-Theses

Laser powder bed fusion or 3D printing is a potential candidate for net shape forming and manufacturing complex shapes. Understanding of how various parameters affect build quality is necessary. Specimens were made from 316L stainless steel at 0°, 30°, 60°, and 90° angles measured from the build plate. Three tensile and four fatigue specimens at each angle were produced. Fracture morphology investigation was performed to determine the fracture mode of specimens at each build angle. Microstructural analysis was performed on one of each orientation. The average grain size of the samples was marginally influenced by the build angle orientation. Tensile …

Influence Of Fibroblasts On Functional Arteriogenesis In A Murine Chronic Hindlimb Ischemia Model, Ashli A. Santos

Biomedical Engineering

Peripheral arterial occlusive disease (PAOD) occurs when there is a narrowing or blockage – usually a buildup of plaque - within the arteries that reduces blood flow to tissues which can chronic ischemia. As with most diseases, early detection and proactive treatment are important to maximize prognosis. Exercise effectively treats PAOD, but due to ischemic pain in the limbs, or intermittent claudication (IC), exercise can become painful and difficult. Due to the buildup of plaque, occlusions create an ischemic environment that changes the pressure distribution in collateral networks and increases the shear stress in transverse collaterals. Those two responses signal …

Characterization Of Asphalt Healing And Incorporation In A Fatigue Damage Model, Umme A. Mannan

Civil Engineering ETDs

Healing is defined as the restoration of the material property during the rest period after damage. The healing property of the asphalt binder is opposite to fatigue damage, which occurs due to repeated traffic loading. On the other hand, healing occurs in the rest period between loading. Most of the existing methods for characterizing the fatigue damage and healing of asphalt are empirical in nature and do not consider the mechanism of healing. Although the asphalt concrete is a mixture of asphalt binder, fines and aggregates, most of the healing occurs in the asphalt binder. Therefore, it is important to …

Optimum Design Of Composite Wing Spar Subjected To Fatigue Loadings, Juan Reuben Lazarin

Master's Theses

Composites are now being incorporated into aircraft designs because of their high strength to weight ratio compared to traditional metal materials. Due to the complexity of the material, composite parts are presently being over designed to satisfy static and fatigue requirements. A greater understanding of composite fatigue behavior will allow for even greater weight savings leading to increased fuel economy. A critical part of an aircraft that is subjected to fatigue bending loads are its wings. The forces acting on the wings include its lift distribution, powerplant, and fuel which can be carried in the wing body. When in flight …

Studies On Woven Carbon/Vinyl Ester Composites: Environmental Effects, Joining And Hybridization, Ricardo Garcia

Open Access Theses & Dissertations

The incessant demand for fiber reinforced polymer composites, or FRPCs, in industrial applications which desire materials that possess high strength-to-weight ratios, generates a theory-to-practice void which must be filled with scientific research. In this Thesis, woven carbon/vinyl ester composites are studied under a wide spectrum of settings and conditions. The adverse effects of sea water environment and arctic temperatures on such mentioned composites are explored in the form of moisture uptake, impact on flexural modulus, strength and structural damage. It was found that sea water saturation in general degrades the flexural strength up to 19.45%, and arctic exposure and combined …