Engineering Commons^™

Analysis Of The Cyclic Behavior And Fatigue Damage Of Low Alloy Steels, Zahra Salemi Najafabadi

Dissertations

Fatigue is the most common type of failure in many structures and components subjected to cyclic loading. Surface effects in fatigued materials are of particular importance, since in most cases the surface is the preferred site of fatigue crack initiation. Microcracks originate at the metal surface due to stress concentration introduced by macro notches and micro defects in the surface layers. The microcrack initiation and propagation are controlled by the localized plastic deformation in the surface layers especially in the initial stage of fatigue failure process. Therefore, the knowledge regarding the cyclically induced changes in deformation resistance at the metal …

Assessing Structural And Functional Brain Alterations And Work-Related Fatigue In Non-Hyposmic And Hyposmic Covid-19 Survivors, Rakibul Hafiz

Dissertations

In the year 2019, life began to change at the advent of a global pandemic caused by the novel coronavirus. Mask mandates and mass vaccinations have mitigated the effects significantly, yet cases keep rising with new variants, especially, in densely populated countries, like India. Recent neuroimaging evidence shows the virus can attack the central nervous system (CNS). However, exactly which brain regions undergo structural and functional changes remain largely unknown. Many patients experience 'loss of/reduced sense of smell' (i.e., hyposmic) and an alarming number of survivors develop persistent symptoms ('long-COVID') for several months after initial infection. Fatigue is the most …

Fatigue Performance Of Rc Beams Strengthened With Near Surface Mounted Cfrp Composites, Tamer Ghaith Mousa Eljufout

Dissertations

Bridges have a fundamental role in improving the effectiveness of highways and providing an expedient and express traffic system. Over time, Reinforced Concrete (RC) bridges degrade due to gradually increased traffic loads and environmental deteriorations. Subsequently, service loads might cause higher stresses in concrete and steel reinforcement than stresses considered in the design stage. This affects the structural performance of RC beams and leads to sudden fatigue failure. As such, there is an essential need for rehabilitation to avoid hazards and tragedies.

Carbon Fiber Reinforced Polymer (CFRP) composites are becoming widely used to strengthen RC bridges. Near Surface Mounted (NSM) …

Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy

Dissertations

The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …

Dynamic Response Of Highway Bridges Under A Moving Truck And Development Of A Rational Serviceability Requirement, Shabnam Darjani

Dissertations

Through the development and usage of high-strength materials, the design of more flexible bridges is unavoidable. It is assumed that limiting a bridge static deflection would control the excessive vibration caused by more flexible design. However, results of prior studies indicate that deflection limits do not necessarily address bridges vibrational issue.

This dissertation addresses the parameters affecting bridge vibration and provides simple equations to compute bridge dynamic acceleration, velocity and displacement in both transient and steady state parts of the vibration. These equations can then be used to control bridges excessive vibration; and provide human comfort and structural performance.

A …