Engineering Commons^™

Fatigue Behavior Of High-Entropy Alloys, Michael Alexander Hemphill

Masters Theses

Research was performed on the Al₉Co_18.2Cr_18.2Cu_18.2Fe_18.2Ni_18.2 [subscripts atomic percent] and Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ high-entropy alloys (HEAs) in an attempt to study their fatigue behavior. The present investigation shows encouraging fatigue-resistance characteristics due to their high fatigue lives of various samples at relatively high stresses. The current results indicate that the fatigue behavior of HEAs compares favorably to many conventional alloys, such as steels, titanium alloys, and advanced bulk metallic glasses with a fatigue-endurance limit of the Al₉Co_18.2Cr_{18.2 …}

Fatigue Life Prediction For Large-Diameter Elastically Constrained Ball Bearings, Jerzy Sawicki, Samuel Johansson, John Rumbarger, Ronald Sharpless

Jerzy T. Sawicki

The application of large-diameter bearing rings and the thereof inherited low stiffness make them susceptible to local distortions caused by their surrounding structures, which are often under heavy loads. The standard accepted design criteria for these bearings are based on the estimation of the internal load distribution of the bearing, under the assumption of rigid circular and flat supporting structures, that keep the bearing inner and outer races in circular, flat, i.e., not deformed shapes. However, in the presence of structural distortions, the element load distribution can be severely altered and cannot be predicted via the standard design criteria. Therefore, …

Neural Network Fatigue Life Prediction In Steel I-Beams Using Mathematically Modeled Acoustic Emission Data, Prathikshen Nambiar Selvadorai

Doctoral Dissertations and Master's Theses

The purpose of this research is to predict fatigue cracking in metal beams using mathematically modeled acoustic emission (AE) data. The AE data was collected from nine samples of steel I-beam that were subjected to three-point bending caused by cyclic loading. The data gathered during these tests were filtered in order to remove long duration hits, multiple hit data, and obvious outliers. Based on the duration, energy, amplitude, and average frequency of the AE hits, the filtered data were classified into the various failure mechanisms of metals using NeuralWorks® Professional II/Plus software based self-organizing map (SOM) neural network. The parameters …

Low-Cycle Fatigue Of Thermally-Cycled Carbon-Epoxy Composite, Ya. B. Unigovski, A. Grinberg, E. M. Gutman, R. Shneck

Journal of Metals, Materials and Minerals

Investigation of low-cycle fatigue of composites is of vital importance for the design of structural components. In this study, the effects of thermal cycling on low-cycle fatigue behavior of carbon-epoxy laminate are investigated in a purely bending mode at strain ratios of -1 and 0.1. It is found that a very small increase in the plastic strain amplitude catastrophically shortens the fatigue life N of the composite determined as a number of cycles corresponding to 0.9 of the initial force. The preliminary thermal cycling of the composite at the temperature varied from 180°C to −195.8°C shortens N values in comparison …

Abnormal Neuromuscular Fatigue And Motor Performance Of The Knee Extensors Post Stroke, Henry Kuhnen

Master's Theses (2009 -)

Stroke causes paresis in leg muscles, such as the knee extensors, that significantly impairs motor control and function during tasks such as walking. Reduced endurance and increased kinematic asymmetries during walking over time indicate paretic musculature may fatigue more quickly than non-paretic musculature. The primary purpose of this study was to identify abnormalities in neuromuscular fatigue (reduction in force over time) of the paretic knee extensors and associate them with motor performance.

We investigated the effects of repeated six second isometric submaximal (30% of maximum voluntary contraction) knee extensor fatiguing contractions on task failure and motor performance in ten chronic …

On The Development Of The Extradosed Bridge Concept, Steven Lynn Stroh

USF Tampa Graduate Theses and Dissertations

The Extradosed Prestressed Bridge represents a relatively new bridge type. The first of this type bridge was constructed in Japan in 1994, and Japan has since built at least 29 examples of this bridge type. Throughout the rest of the world, another 34 of this bridge type have been built, with most countries having only one, or at most a few, examples. A broader application of this bridge type has been hampered by lack of design information and in particular lack design criteria for the stay cables. The purpose of this dissertation is to progress the understanding and application of …

The Significance Of Equi-Biaxial Bubble Inflation In Determining Elastomeric Fatigue Properties, Stephen Jerrams, Niall Murphy, John Hanley

Books/Book Chapters

It is well documented that for the effective modelling of the static and dynamic behaviour of elastomeric components using the finite element (FE) method it is essential to obtain material parameters that are derived from a range of physical tests. For a conventional linear solid, uniaxial testing suffices to fully characterise the material, but for rubber it is necessary to test in at least two deformation modes. Also, the determination of fatigue lives of rubber components is still in its infancy and a reliable, repeatable fatigue test for rubber will have important consequences for component design, functionality, maintenance and cost. …

Development And Validation Of Probabilistic Fatigue Models Containing Out-Life Suspensions, Noel S. Murray

Electronic Theses and Dissertations

Author's abstract: In the area of reliability engineering it is necessary to be confident that a component or system of components will not fail under use for safety and cost reasons. One major mechanism of failure to a mechanical component is fatigue. This is the repetitious motion of loading and unloading of the material, typically below the ultimate tensile strength of the material, which ultimately leads to a catastrophic failure. To ensure this does not happen, engineers design components based on tests to determine the life of these components. These tests are typically conducted on a bench type tester in …