Engineering Commons^™

Weibull Model Development For Fatigue Crack Growth, Bobby Day, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

This effort is an attempt to "Weibullize" fatigue crack growth rate data as a function of stress intensity range (ΔΚ). It is not a classical Weibull application in that it does not address a population but rather treats rate of crack growth as a fraction of the highest rate of crack growth rate in the data set (usually the final data point of the set) as the "failed fraction of a population." All da/dN values are converted to a percentage or fraction of the 100% data value, processed into a linear relationship and plotted against the natural log of the …

A Review Of Nanotechnology Applications, Nick Ledbetter, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

A review of current technology research efforts has been conducted in this paper. In nanoscience, objects are measured in nanometers, 1 billionth of a meter. For comparison, a human hair is approximately 100,000 nanometers thick and the smallest feature on current computer chips measures about 200 nanometers. Since nanotechnology has a wide range of applications from computer chip manufacturing, new materials, renewable energy, interconnection technology to mount the nano-chips, and in medical science, this review presents a broad summary of development efforts in the government and private sector laboratories. Therefore this project on the one hand prepares a review of …

Coarsening Dynamics Of Biaxial Nematic Liquid Crystals, Nikolai V. Priezjev, Robert A. Pelcovits

Mechanical and Materials Engineering Faculty Publications

We study the coarsening dynamics of two- and three-dimensional biaxial nematic liquid crystals, using Langevin dynamics. Unlike previous work, we use a model with no a priori relationship among the three elastic constants associated with director deformations. Biaxial nematics possess four topologically distinct classes of defects, three of which have half-integer charge, while the fourth, which plays a minor role in coarsening, is of integer charge. We find a rich variety of coarsening behavior, including the presence of one, two, or three of the half-integer classes at late times, depending on the relative values of the elastic constants and the …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 19, Number 2, November 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Flight Physician - November, 2002, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

Virtual Surfaces, Director Domains And The Freedericksz Transition In Polymer Stabilized Nematic Liquid Crystals, Pavel A. Kossyrev, Jun Qi, Nikolai V. Priezjev, Robert A. Pelcovits, Gregory P. Crawford

Mechanical and Materials Engineering Faculty Publications

The critical field of the Freedericksz transition and switching dynamics are investigated for polymer stabilized nematic liquid crystals as a function of polymer concentration. A simple phenomenological model is proposed to describe the observed critical field and dynamic response time behaviors as a function of concentration. In this model the polymer fibrils form director domains, which are bounded by virtual surfaces with a finite anchoring energy. The Freedericksz transition occurs independently within each of these domains.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 19, Number 1, October 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

A sixteen page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Flight Physician - August, 2002, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

Correlation Between The Xps Peak Shapes Of Y1bu2cu3o7-X And Film Quality, Paul N. Barnes, Sharmila M. Mukhopadhyay, Timothy J. Haugan, Swaminathan Krishnaswami, Justin C. Tolliver, Iman Maartense

Mechanical and Materials Engineering Faculty Publications

X-ray photoelectron spectroscopy (XPS) depth profiling was used to investigate the compositional and chemical profile of a typical YBCO coated conductor architecture. Results of the process revealed that the Y(3d) photoelectronic peak shape in these films is very different from bulk YBCO. To investigate this, several samples of Y i Ba2Cu307_„ thin films were intentionally created of varying quality. The films were deposited on LaA10 3 by pulsed laser deposition with ./c. values ranging from poorly conducting up to several MA/cm2. Initial results indicated a potential correlation between the Y(3d) XPS peak shape (full-width-half-maximum) of the YBCO and the film …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 9, June 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

A twelve page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Flight Physician - June, 2002, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 8, May 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Simulations Of Nematic Liquid Crystals: Confined Geometries, Phase Transitions And Topological Defects, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

The physics of liquid crystals is an exciting field of research with important practical applications. In this dissertation we present the results of simulation studies of nematic liquid crystals using Monte Carlo and molecular dynamic techniques. In our first project we performed Monte Carlo Simulations of the Lebwohl-Lasher (LL) model of nematic liquid crystals confined to cylindrical cavities with perpendicular anchoring. In this particular geometry one has an interesting interplay between bulk and surface energies, which results in different director configurations inside the cylinder. Our work reconciled the apparent contradictions between the results of earlier simulations and approximate analytics theories. …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 7, April 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Topology Tracking For The Visualization Of Time-Dependent Two-Dimensional Flows, Xavier Tricoche, Thomas Wischgoll, Gerik Scheuermann, Hans Hagen

Computer Science and Engineering Faculty Publications

The paper presents a topology-based visualization method for time-dependent two-dimensional vector fields. A time interpolation enables the accurate tracking of critical points and closed orbits as well as the detection and identification of structural changes. This completely characterizes the topology of the unsteady flow. Bifurcation theory provides the theoretical framework. The results are conveyed by surfaces that separate subvolumes of uniform flow behavior in a three-dimensional space–time domain.

Flight Physician - April, 2002, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 6, March 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 5, February 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Flight Physician - February, 2002, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

A Window-Based Software For Fatigue Crack Growth Data Reduction, B. Keeton, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The objective of this research is to develop a Windows-based program to present the fatigue crack growth rate and mode I stress intensity factor range data. Microsoft Visual Basic was used to write the code. The program developed in this study calls out the input data in terms of crack length (α) and the number of cycles (Ν). Secant and seven point polynomial distribution was used to fit the data. The installation procedure for the program was copied onto a disk to install the program. Future work is needed to further modify the a-N data and therefore to present da/dN-ΔΚ …

Dwell Sensitivity Behavior And Modeling, E. Pyburn, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Since engineering materials are exposed to dwell-times in service, it is important to understand the effects of dwell times on the fatigue life. The mechanisms controlling deformation and failure under dwell conditions are in terms of metallographic damage namely; transgranular fracture, intergranular fracture, mixed intergranular transgranular fracture modes, surface striated damage, creep damage and oxidation. These mechanisms are very difficult to include in a quantitative model to predict the dwell sensitivity behavior of high temperature materials. Published creep-fatigue data were compiled from various sources for a number of materials such as copper alloys (NARloy-Z, AMZ1RC), steel alloys (9Cr-lMo), and nickel …

Failure Modes Of Biomedical Implants, Andrew Gratton, Bert Buford, Tarun Goswami, Dana Gaddykurten, Larry Suva

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The metallic biomaterials are very well known among various biomaterials. Stainless steel was used successfully as an implant material in the surgical field, then Vitallium, cobalt based alloys were used as implant materials. Titanium is the newest metallic biomaterial among three main metallic biomaterials, stainless steels, Co-based alloys and titanium alloys. These materials are used for the instrumentation replacing failed hard tissue, for example, artificial hip joints, artificial knee joints, bone plates, dental implants and in similar applications. Biocompatibility characteristics of titanium alloys make it the preferred choice for such applications, additional factors being light weight, excellent mechanical properties, corrosion …

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 18, Number 4, January 2002, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

Closed Streamlines In Flow Visualization, Thomas Wischgoll

Computer Science and Engineering Faculty Publications

Vector Fields occur in many of the problems in science and engineering. In combustion processes for instance, vector fields describe the flow of the gas. This process can be enhanced using vector field visualization techniques. Also wind tunnel experiments can be analyzed. An example is the design of an air wing. The wing can be optimized to crate a smoother flow around it. Vector field visualization methods help the engineer to detect critical features of the flow. Consequently, feature detection methods gained great importance during the last years.

Topological methods are often used to visualize vector fields because they clearly …

Creep-Fatigue Life Prediction Of Low Alloy Steels, James Toland, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The creep-fatigue behavior of Cr-Mo steels has been examined from published data. The published data were compiled in an earlier effort and used in this paper to develop a multivariate best-fit equation to predict the low cycle fatigue life. The fatigue test temperatures were representative of temperatures experienced in nuclear power plants, which varied from room temperature to 600°C. Within this temperature range, depending upon the test parameters used, creep and fatigue processes interact and failure occurs in the lowcycle fatigue regime.

Strongly Screened Vortex Lattice Model With Disorder, C. Giardina', Nikolai V. Priezjev, J. M. Kosterlitz

Mechanical and Materials Engineering Faculty Publications

The three dimensional XY model with quenched random disorder and finite screening is studied. We argue that the system scales to model with λ≃0≃T and the resulting effective model is studied numerically by defect energy scaling. In zero external field we find that there exists a true superconducting phase with a stiffness exponent θ≃+1.0 for weak disorder. For low magnetic field and weak disorder, there is also a superconducting phase with θ≃+1.0 which we conjecture is a Bragg glass. For larger disorder or applied field, there is a non superconducting phase with θ≃−1.0. We estimate the critical external field whose …

Effect Of Exposure Time On The Fatigue Crack Growth Behavior Of Aircraft Skin Material, Kathryn Lemasters, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The objective of this research project is to identify the effects of service exposure on aircraft materials. The senior author participated in the KC-135 Corrosion Prevention Program conducted by the University of Utah, Salt Lake City. Data from this research program was analyzed to compare the fatigue crack growth rates of aged aircraft materials with those of virgin materials. 2024-T3(clad) Middle Tension (M(T)) specimens were machined from the fuselage and upper wing skins of a retired aircraft. Fatigue crack growth rate (da/dN) and mode 1 stress intensity factor range (Δ K) plots were generated for both sets of data. The …

Statistical Modeling Of Fatigue Crack Growth, Ignacio Guerra, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The objective of this research is to fit normal and lognormal distributions to fatigue crack growth rate (da/dN) data and present the data in terms of cumulative frequency distribution (f (x)) and a variant of da/dN and mode I stress intensity factor range (ΔΚ), z. The probability density functions (F(da/dN)) were also plotted for the data. The data was compiled from open literature, conducted on a hot section turbine disk material Inconel 718 under a North Atlantic Treaty Organization (NATO) project, through the Advisory Group on Aerospace Research and Development (AGARD). Incomel 718 was tested at 650°C utilizing various specimen …

Life Prediction Of Stainless Steels Used In Nuclear Reactors, Jonathan Clark, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Effects of dwell times and temperature on creep-fatigue behavior of stainless steels have been examined from published data. The temperatures of these materials varied from 430°C to 816°C. Within this temperature range creep and fatigue processes interact and failure occurs in the low-cycle regime. A least square best fit equation was developed from the compiled data fitting all the data points. The variables were temperature, strain rate, dwell time and strain range and were used with and without transformation functions to derive the equation. Statistical analysis was performed showing a very high coefficient of correlation value for the life prediction …

Defining Benthic Organism Exposure: Bioavailability And Effects Of Non-Polar Organics, Marc Samuel Greenberg

Browse all Theses and Dissertations

Laboratory and field tests were conducted to evaluate the hypothesis that factors such as the total organic carbon (TOC) contents and groundwater-surface water interactions (GSI) in the sediments can affect chemical desorption, bioavailability and benthic organism exposure. Laboratory studies were conducted with the polycyclic aromatic hydrocarbon fluoranthene (FLU) and the herbicide trifluralin (TF). Toxicokinetic parameters were determined for Lumbriculus variegatus and Hyalella azteca in water-only exposures to 0, 5, 20 and 50 µg/L of the compounds and bioaccumulation was measured during exposures to 0, 100 and 200 mg/kg of FLU and TF spiked onto sediments from Lakes Erie and Huron. …