Industrial 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 …

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 …

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.

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 …

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 …

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 …

Physical-Statistical Modeling And Optimization Of Cardiovascular Systems, Dongping Du

USF Tampa Graduate Theses and Dissertations

Heart disease remains the No.1 leading cause of death in U.S. and in the world. To improve cardiac care services, there is an urgent need of developing early diagnosis of heart diseases and optimal intervention strategies. As such, it calls upon a better understanding of the pathology of heart diseases.

Computer simulation and modeling have been widely applied to overcome many practical and ethical limitations in in-vivo, ex-vivo, and whole-animal experiments. Computer experiments provide physiologists and cardiologists an indispensable tool to characterize, model and analyze cardiac function both in healthy and in diseased heart. Most importantly, simulation modeling empowers the …

High Temperature Fatigue Crack Growth Behavior Of Ti-6al-4v, N. K. Arakere, Tarun Goswami, J. Krohn, N. Ramachandran

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Experimental evaluation of high temperature, Fatigue Crack Growth Rate (FCGR) data for Ti-6A1-4V, a titanium alloy, is presented. The FCGR data were measured at room temperature, 175, 230, 290 and 345°C using the Direct Current Potential Difference (DCPD) technique. Compact Tension (CT) specimens were used in the program and crack growth rates (da/dN) vs. Mode I stress intensity factor ranges (ΔΚ) were plotted as a function of temperature. A temperature rise from 175 to 345°C did not cause a substantial increase in crack growth rates within the Stage II region where a linear relationship describes the behavior. Fonnation of secondary …

Dwell Fatigue I : Damage Mechanisms, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The mechanisms controlling deformation and failure under high temperature creep-fatigue conditions of materials are examined in this paper. The materials studied are solder alloys, copper alloys, low alloy steels, stainless steels, titanium alloys, and Ni-based alloys. The deformation and failure mechanisms were different (fatigue, creep, oxidation and their interactions) depending upon test and material parameters employed. Deformation mechanisms, such as cavity formation, grain boundary damage, intergranular (IG) and transgranular (TG) damage, oxidation, internal damage, dislocation cell concentration, and oxide mechanisms are very important in order to gain more knowledge of fatigue behavior of materials. The observed mechanisms can be categorized …

Transition Criteria - From A Pit To A Crack, Tarun Goswami, David W. Hoeppner

Biomedical, Industrial & Human Factors Engineering Faculty Publications

A brief review of pitting, which is a localized corrosion process resulting from pitting and fatigue interaction has been conducted in this paper. The transition of a pit to a crack is a very important phenomenon occurring under PCF conditions. Various theories for transition of a pit to a crack were examined within the limits of present understanding and limitations of the models. The transition of a pit to a crack was also discussed for a variety of pit shapes utilizing the pit aspect ratios, defect size and linear elastic fracture mechanics, crack tip characterizing parameters such as Mode I …

Flange Bolt Failure Analysis, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Failure cause investigation of flange bolts from the bi-axial shaft fatigue test rig was carried out and crack growth rates in combined bending and torsion conditions were determined. Flange bolts are used in gas turbine engines that are pre-torqued exerting bending and torsion fatigue situation arising from high centrifugal stresses. The fracture surface features were characteristic of bending fatigue (BF), where striations were observed, a distinct area within which conjoint bending and torsion fatigue (CBTF) features were documented, and a region between the BF and CBTF, a region of overloading (OL), where ductile dimples were observed. Striations dominated within BF …

A New Model Of High Temperature Low Cycle Fatigue Life Prediction - Applicability With Low Alloy Steels, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Creep-fatigue data on low alloy steels were collected from National Research Institute for Metals (NRIM) Tokyo, Japan. These data were generated for lCr-Mo-V, 2.25Cr-Mo, and 9Cr-lMo steels under a wide range of test conditions. A new creep-fatigue life prediction method was developed and data compiled were assessed to examine the applicability of the new method. A brief review of the empirically based, phenomenological life prediction methods was presented where no method was found to be applicable universally to all the creep-fatigue data. The new model was developed within the viscosity concepts, in which the damage parameter was accounted for in …

Dwell Sensitivity Fatigue Behaviour Of High Temperature Materials, Tarun Goswami, G. R. Halford, D. W. Hoeppner

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The dwell sensitivity fatigue behavior of six high temperature materials is examined in this paper: two stainless steels, 304L and 304, two tantalum alloys, Τ- Ι 11 and ASTAR 811C, pure nickel Ni 201 and a single crystal nickel-base superalloy, PWA 1480. The stainless steel alloys were found to be tensile dwell sensitive; however, a saturation in dwell sensitivity was found with the increase in strain range for all materials examined. At lower strain ranges the dwell cycles were producing lower lives than at higher strains, as found in the case of AISI SS 304 and two tantalum based alloys, …

Review Of Pit Nucleation, Growth And Pitting Corrosion Fatigue Mechanisms, Tarun Goswami, D. W. Hoeppner

Biomedical, Industrial & Human Factors Engineering Faculty Publications

This paper presents a review of the state of the art developments in the pitting corrosion fatigue of aircraft structural materials. Mechanisms that govern the nucleation and growth of pitting and corrosion fatigue (CF) are briefly addressed. Some of the developments made in the author's laboratories in proposing the fretting induced pit nucleation and growth mechanisms, analysis of the hidden corrosion constituents in fuselage joints and pitting corrosion fatigue crack growth (PCFCG) model are elucidated. An epistemology of the topic is presented which will be of assistance to the community working in this area.

Corrosion Fatigue Crack Growth Behavior Of Aircraft Materials, Tarun Goswami, D. W. Hoeppner

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The effects of test parameters on the corrosion fatigue crack growth behavior of structural materials have been examined in this paper. Test parameters such as stress ratio, frequency, hold time, temperature, pH level of the media, and other parameters are known to alter the corrosion fatigue crack growth rates in structural materials. Numerous laboratory test variables that affect the crack growth and/or corrosion growth rates, which in an operating environment of an aircraft are not characterized, are reviewed. A summary of such information may help determine the inspection intervals of the new and aged airplanes, perform the inspections, and develop …

A New Creep-Fatigue Life Prediction Model, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

A published creep-fatigue life prediction model is modified in this paper and assessed with data on Inconel 718 under different test conditions. It has been shown that the method developed within the viscosity concepts correlates the low-cycle fatigue data well. This paper reports the modification over the previous model.

Creep Fatigue, Part Iii: Diercks Equation: Modification And Applicability, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Creep-fatigue data of low allow steels were compiled from international sources, and trends in creep-fatigue behavior were identified in Paper I. Methods of life prediction and their trends were examined in Paper II with respect to compiled data. Diercks equation, a multivariate creep-fatigue life extrapolation equation, for SS, 304, in terms of strain range, temperature, hold time and strain rate parameters is modified and extended to the life prediction of low alloy steels in this paper.

Applicability Of Modified Diercks Equation With Nrim Data, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

The applicability of the modified Diercks equation (MDE) was assessed with elevated temperature low cycle fatigue (ETLCF) data generated by the National Research Institute for Metals (NRIM) for lCr-Mo-V, 1.25Cr-Mo, 2.25Cr-Mo and 9Cr-lMo steels respectively. The modified Diercks equation was assessed with data generated with symmetrical, slow-fast and hold-time waveforms for low alloy steels. The following characteristics were observed: Symmetrical waveforms: Five strain rates were used with these waveforms where predicted life was by a factor of ± x2 for 77%, 87%, 82% and 92% of data points for lCr-Mo-V, 1.25Cr-Mo, 2.25Cr-Mo and 9CrlMo steels respectively. Slow-fast waveforms: Diercks equation …

Creep Fatigue, Part Ii: Creep Fatigue Life Prediction: Methods And Trends, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Creep-fatigue data of low allow steels were compiled from international sources, and trends in creep-fatigue behavior were identified in Paper I. This paper reviews the methods of creep-fatigue life prediction that were assessed from the compiled data. The methods reviewed in this paper are phenomenological in nature. However, an empirical method has also been discussed which offers very high reliability of the prediction capability. Various test requirements, from which material parameters are determined for each method, have been tabulated. No single method has been generalized as a best method of life prediction for all types of creep-fatigue test conditions.

Creep Fatigue, Part I: Compilation Of Data And Trends In The Creep-Fatigue Behavior Of Low Alloy Steels, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

This paper describes an attempt to compile the creep-fatigue data of low alloy steels. In part I, international data have been collected to compare the variability that exists in a particular low alloy steel when characterized in different laboratories. From this work of compilation, trends in the creep-fatigue behavior of low alloy steels have been identified in Part II of this paper and a review of life prediction methods and assessments will be discussed in subsequent papers. The creep-fatigue behavior, in general, improved with the increase in chromium content; however, when additional alloying elements were added to a standard alloy …

Creep-Fatigue Life Prediction - A Ductility Model, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

Creep-fatigue life prediction methods are briefly reviewed. Phenomenological methods of life prediction are very popular, since they use several test and metallographic parameters in model formulation. They also require numerous test parameters determined from specialized tests. Requirements of phenomenological methods have been summarized. Ductility measurement and modeling aspects have been reviewed. A new model has been developed with the assumption that with increasing fatigue cycles the ductility gradually decreases and the specimen fails as a result of exhaustion of ductility. This has been achieved in terms of dynamic viscosity (product of stress and cycle time), equated with material toughness, which …