Dissertations / Theses: 'Fatigue life prediction'

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Wertz, John Nicholas. "Isothermal Fatigue Life Prediction Techniques." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363195868.

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Conner, Brett P. (Brett Page) 1975. "Contact fatigue : life prediction and palliatives." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16866.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.
Includes bibliographical references (p. 125-135).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Fretting fatigue is defined as damage resulting from small magnitude (0.5-50 microns) displacement between contacting bodies where at least one of the bodies has an applied bulk stress. The applicability and limits of a fracture mechanics based life prediction is explored. Comparisons are made against highly controlled experiments and less controlled but more realistic experiments using a novel dovetail attachment fixture. Surface engineering approaches are examined from a mechanics perspective. Using a new tool, depth sensing indentation, the mechanical properties of an aluminum bronze coating are determined. Fretting fatigue experiments are performed on specimens coated with aluminum bronze and on specimens treated with low plasticity burnishing. Low plasticity burnishing is a new method of introducing beneficial compressive residual stresses without significant cold work at the surface. A mechanics based approach to the selection of palliatives is addressed.
by Brett P. Conner.
Ph.D.

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Ding, Fei. "A general approach for fatigue life prediction /." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3250682.

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Thesis (Ph. D.)--University of Nevada, Reno, 2006.
"December, 2006." Includes bibliographical references (leaves 77-94). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.

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Beheshti, Milad. "Fatigue life prediction of threaded pipe connection." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15588.

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In the oil and gas industry, threaded pipe connection is frequently used to connect the casing string, drill pipe strings or production and transportation risers and pipelines. The connection is normally preloaded in order to maintain a sealed and secure connection while in service and avoid leakage. Tapered thread are a common connection and in order to introduce preload to the threaded connection when they are assembled a certain make-up torque is going to be applied. The make-up torque plus external loads result in a multiaxial stress distribution over the connection, where the threaded connections act as stress risers. Environment such as waves and currents cause dynamic loads acting on the pipe line and offshore structures. The weakest point in offshore structure is the pipe connection because of fatigue crack initiated in the connection's threads. Researchers and engineers developed a variety of patented threaded pipe connection which all claiming to improve a connection's fatigue life. The experimental data for patented designs, available in literature, is limited. Most published studies usually comprise experiments on a single connection type. For detailed fatigue analysis those published studies cannot be used since there is no uniformity in testing setup, loading conditions and damage detection technique exist. Moreover, current design curves in codes and standards lead to overly conservative or inaccurate results. The aim of this work is to provide a better understanding of the fatigue mechanisms of threaded pipe connections and to study the effect of different design features on a connection's fatigue life. The final goal is to formulate guidelines for new fatigue resistant connection designs. API connection is used as a reference in this study. Several modifications and design features are applied to the connection type. To simulate the effect of these modifications, a parametric 2D axisymmetric finite element model, ABAQUS is used. 2D finite element result are compared with a 3D model to prove its validity for both make-up. In addition, the results of the 2D axisymmetric simulation are validated by static strain gauge measurements during a make-up test and an axial tension test. The validated model is then used to evaluated the influence of the connection properties and design features on the threaded connection's behaviour. Test rigs were designed to perform axial fatigue experiment on two scales: the small-scale experiments on 1" (33.4 mm outer diameter) connections are performed in axial fatigue testing, the medium scale tests on 4.5" (114.3 mm) connections are carried out under axial tension for which a setup is developed. The majority of the performed fatigue tests are small scale experiments. Several modified configurations are tested. The S-N curve is constructed, so that the effect of certain configuration on the connection's fatigue life can be quantified. The local modification of the threaded connection's geometry as well as the connection's contact condition's contact conditions can have an important influence on the fatigue life of the connection. A beach marking technique is used to visualized the crack fronts at different moments during the tests so that exact crack shape can be seen during post-mortem analysis. The result shown that a crack initiates at the root of the last engaged thread of the male part of the connection, and propagates slowly over a large segment of the circumference, forming a long shallow crack. When the crack penetrates the pipe wall, it rapidly increases in size along two crack fronts. The shape of crack observed in beach mark analysis do not have a semi-elliptical shape as commonly used in fracture mechanics. A fatigue crack growth analysis that considers the crack as an annular flaw, is effective in describing the crack growth behaviour. The experimentally obtained S-N curves and the result from the finite element simulations are combined in multiaxial damage evolution law. The observed trend in fatigue lives of the configuration are explained by using the fatigue analysis. Using a connection's thread load distribution as a measure for its fatigue life is proven to be inaccurate. The main reason for this is that the load distribution is related to axial stresses over the connection. The fatigue life of a threaded connection is determined by the local multiaxial stress distribution and strain range around the root of the last engaged thread. These local conditions are not only the result of the load distribution, but they are also affected by the hoop stress introduced during make-up, which can additionally be affected by a changed connection stiffness. The multiaxial damage evolution law is used to analyse the influence of several features on a connection's fatigue life. It is not for all patented modifications that an increased fatigue life is predicted when applied to the API connection. The final conclusion reached is that, in order to optimize a fatigue resistant connection, several design features must be combined together. The thread shape can be optimized to obtained a low stress concentration factor and reduce the local strains at the thread root. The connection's global geometry and make-up conditions can be optimized to improve the load distribution over the threads and reduce local stresses and strains at the threads.

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Critz, David Karl. "Computer aided fatigue life prediction for polymers." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10489.

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Miller, Mark. "Fatigue life prediction of nickel base superalloys." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/68693/.

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Neural networks have been used extensively in material science with varying success. It has been demonstrated that they can be very effective at predicting mechanical properties such as yield strength and ultimate tensile strength. These networks require large amounts of input data in order to learn the correct data trends. A neural network modelling process has been developed which includes data collection methodology and subsequent filtering techniques in conjunction with training of a neural network model. It has been shown that by using certain techniques to ‘improve’ the input data a network will not only fit seen and unseen Ultimate Tensile Strength (UTS) and Yield Strength (YS) data but correctly predict trends consistent with metallurgical understanding. Using the methods developed with the UTS and YS models, a Low Cycle Fatigue (LCF) life model has been developed with promising initial results. Crack initiation at high temperatures has been studied in CMSX4 in both air and vacuum environments, to elucidate the effect of oxidation on the notch fatigue initiation process. In air, crack initiation occurred at sub-surface interdendritic pores in all cases. The sub-surface crack grows initially under vacuum conditions, before breaking out to the top surface. Lifetime is then dependent on initiating pore size and distance from the notch root surface. In vacuum conditions, crack initiation has been observed more consistently from surface or close-to-surface pores - indicating that surface oxidation is in-filling/”healing” surface pores or providing significant local stress transfer to shift initiation to sub-surface pores. Complementary work has been carried out using PWA 1484 and Rene N5. Extensive data has been collected on initiating pores for all 3 alloys. A model has been developed to predict fatigue life based upon geometrical information from the initiating pores. A Paris law approach is used in conjunction with long crack propagation data. The model shows a good fit with experimental data and further improvements have been recommended in order to increase the capability of the model.

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Leander, John. "Improving a bridge fatigue life prediction by monitoring." Licentiate thesis, KTH, Bro- och stålbyggnad, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28618.

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For steel railway bridges, fatigue is the main reason for a limited service life. An initial prediction of the fatigue life is usually performed using loads and conservative assumptions stated in the governing standards. The result is used for decisions of further actions. Even if the result is an insufficient residual life, some bridges are not easy to strengthen or replace without causing large traffic disturbance. In this licentiate thesis, the real load effect is studied by monitoring a bridge during service. The aim is to improve the fatigue life prediction by reducing the uncertainties in the traffic load and finally attain a longer theoretical service life of the bridge. A case study of the Söderström Bridge in central Stockholm, one of Sweden’s most important railway bridges, is incorporated in the studies. Previously performed theoretical assessments have shown alarming results regarding the remaining fatigue life for some of the structural members in the bridge. To verify the result and hopefully receive more favorable stress ranges, the bridge was instrumented with a monitoring system in 2008. The bridge and the monitoring campaign are thoroughly presented. Owing to the large data volume produced by the monitoring system, robust routines and procedures for quality assurance have been required. A deterministic fatigue assessment is presented based on 43 days of continuous measurements comprising more than 17 thousand train passages. Unfortunately, also this fatigue assessment indicates high fatigue damages. A large monitoring system with many gauges enables a statistical evaluation of the quality of the measurements. By the principle of Analysis of Variance, a comparison of the stress range spectra can be performed with the aim of finding deviant spectra and corrupt gauges. An additional aspect is the length of the monitoring period, meaning the required duration for obtaining a stable result. A model for the convergence progress is proposed which could be incorporated in a monitoring system for use during service. The extensive monitoring program of the Söderström Bridge has resulted in reliable stress range spectra. By curve fitting and goodness-of-fit tests measured spectra have been compared with known statistical distributions. These distributions can be used for future fatigue reliability assessments.
QC 20110120

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ZARRIN, GHALAMI TOUHID. "Fatigue Life Prediction and Modeling of Elastomeric Components." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1367411090.

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Che, Yunxiang, and S3145469@student rmit edu au. "Aging structure life prediction and reliability assessment." RMIT University. SAMME, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091113.114541.

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Confront with the serious aging problem in aircraft structure field, the profession was tasked to unveil the mysterious in the mechanism of aging. In decades, many endeavours were put into different subjects such as, fatigue and crack calculation, corrosion analysis, reliability evaluation, life prediction, structure monitor and protection, structure repair, etc. In an effort of developing a reasonable model for life prediction and reliability evaluation, a wide range of topics in the field of aging structure reliability are reviewed. Many existing methods and tools are carefully studied to distinguish the advantages, disadvantages and the special application. With consideration of corrosion fatigue life, and based on the data obtained through investigating service status of the aging aircraft, a fuzzy reliability approach is proposed and presented. Initially, the thesis presents the literature review in the field, introducing the well-established theories and analysis tools of reliability and points out how such these methods can be used to assess the life and reliability of aging structure. Meanwhile, some characteristic parameters and distributions, as well as some crucial calculation formulations, procedures for aging aircraft reliability/risk analysis are given. Secondly, mathematical models are established to evaluate the initial crack size and to assess both randomness and fuzziness of the variables, which also successfully work out the probability of survival of existing structures over a time period and predict the operation time under specific reliability requirement. As a practical approach to the reliability of aging aircraft structure, example is presented and evaluated. While conduct the calculation, a few programs based on FORTRAN code are developed to solve the none-linear equation, to work out the multi dimension integration and to simulate the survival probability. The crack life prediction software AFGROW is selected for comparison of the calculation results, which also shows the appropriate accuracy of the established model. As conclusion, the effects of some variables including fuzzy factors on reliability and life of aging aircraft structure are finally discussed. It is apparent that the confines of the model are existing as fact because of the huge assumption of the parameters input and model uncertainties. Suggestions on further prospective research are proposed respectively.

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Karl, Justin. "Thermomechanical Fatigue Life Prediction of Notched 304 Stainless Steel." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5796.

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The behavior of materials as they are subjected to combined thermal and mechanical fatigue loads is an area of research that carries great significance in a number of engineering applications. Power generation, petrochemical, and aerospace industries operate machinery with expensive components that undergo repeated applications of force while simultaneously being exposed to variable temperature working fluids. A case of considerable importance is found in steam turbines, which subject blades to cyclic loads from rotation as well as the passing of heated gases. The complex strain and temperature histories from this type of operation, combined with the geometric profile of the blades, make accurate prediction of service life for such components challenging. Development of a deterministic life prediction model backed by physical data would allow design and operation of turbines with higher efficiency and greater regard for reliability. The majority of thermomechanical fatigue (TMF) life prediction modeling research attempts to correlate basic material property data with simplistic strain and thermal histories. With the exception of very limited cases, these types of efforts have been insufficient and imprecise in their capabilities. Early researchers did not account for the multiple damage mechanisms that operate and interact within a material during TMF loads, and did not adequately address the extent of the relationship between smooth and notched parts. More recent research that adequately recognizes the multivariate nature of TMF develops models that handle life reduction through summation of constitutive damage terms. It is feasible that a modification to the damage-based approach can sufficiently include cases that involve complex geometry. The focus of this research is to construct an experimentally-backed extension of the damage-based approach that improves handling of geometric discontinuities. Smooth and notched specimens of Type 304 stainless steel were subjected to several types of idealized fatigue conditions to assemble a clear picture of the types of damage occurring in a steam turbine and similarly-loaded mechanical systems. These results were compared with a number of idealized TMF experiments, and supplemented by numerical simulation and microscopic observation. A non-uniform damage-summation constitutive model was developed primarily based on physical observations. An additional simplistic model was developed based on phenomenological effect. Findings from this study will be applicable to life prediction efforts in other similar material and load cases.
Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering

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Heffern, Thomas V. "Probabilistic modeling and simulation of metal fatigue life prediction." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FHeffern.pdf.

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2002.
Thesis advisor(s): Ramesh Kolar, E. Roberts Wood. Includes bibliographical references (p. 113). Also available online.

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Dittenber, David Brian. "Fatigue of polymer composites life prediction and environmental effects /." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10888.

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Thesis (M.S.)--West Virginia University, 2010.
Title from document title page. Document formatted into pages; contains xii, 138 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-120).

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Erasmus, Daniel Jacobus. "The fatigue life cycle prediction of a light aircraft undercarriage." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1527.

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The reliability of systems relies heavily on accurate fatigue life prediction of related components. Fatigue life prediction is a complicated process requiring the correct methodology to determine accurate and reliable predictions. The Palmgren – Miner damage accumulation hypothesis is widely used in determining the fatigue life of components exposed to variable loading conditions. Modifications have been made to this hypothesis trying to achieve a greater degree of accuracy, of these the Liu – Zenner modification has been the most successful. In this report the systematic process of fatigue life prediction using the Liu – Zenner modification to achieve reliable results is calculated. A representative stress time history measured in service on the component forms the basis for defining a flight cycle which is the chosen unit in which to express the fatigue life. Rainflow cycle counting performed on the stress time history allowed the formulation of a load spectrum to which the component is exposed in one cycle. Combining the load spectrum with the developed SN curve of the component and using the Liu – Zenner modification to the Palmgren – Miner rule a reliable fatigue life in cycles is predicted.

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Highsmith, Shelby Jr. "Probabilistic fatigue crack life prediction in a directionally-solidified nickel superalloy." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5410.

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Wertz, John Nicholas. "An Energy-Based Experimental-Analytical Torsional Fatigue Life-Prediction Method." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275400649.

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Newman, John Andrew. "Life prediction of spot-welds : a fatigue crack growth approach /." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11012008-063415/.

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Senne, Jolyn Louise. "Fatigue Life of Hybrid FRP Composite Beams." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33982.

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As fiber reinforced polymer (FRP) structures find application in highway bridge structures, methodologies for describing their long-term performance under service loading will be a necessity for designers. The designer of FRP bridge structures is faced with out-of-plane damage and delamination at ply interfaces. The damage most often occurs between hybrid plys and dominates the life time response of a thick section FRP structure. The focus of this work is on the performance of the 20.3 cm (8 in) pultruded, hybrid double web I-beam structural shape. Experimental four-point bend fatigue results indicate that overall stiffness reduction of the structure is controlled by the degradation of the tensile flange. The loss of stiffness in the tensile flange results in the redistribution of the stresses and strains, until the initiation of failure by delamination in the compression flange. These observations become the basis of the assumptions used to develop an analytical life prediction model. In the model, the tensile flange stiffness is reduced based on coupon test data, and is used to determine the overall strength reduction of the beam in accordance the residual strength life prediction methodology. Delamination initiation is based on the out-of-plane stress sz at the free edge. The stresses are calculated using two different approximations, the Primitive Delamination Model and the Minimization of Complementary Energy. The model successfully describes the onset of delamination prior to fiber failure and suggests that out-of-plane failure controls the life of the structure.
Master of Science

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Kemna, John G. "Aluminum 7075-T6 fatigue data generation and probabilistic life prediction formulation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA356614.

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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, September 1998.
"September 1998." Thesis advisor(s): Edward M. Wu. Includes bibliographical references (p. 55). Also available online.

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Miller, Matthew P. "Life prediction models for high temperature fatigue based on microcrack propagation." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/16059.

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Sum, Wei Siang. "FE-based multiaxial fatigue life prediction of spline couplings undergoing fretting." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420357.

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Wong, Frank Michael Gerard. "Fatigue, fracture, and life prediction criteria for composite materials in magnets." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14093.

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Nowicki, Timothy. "Statistical model prediction of fatigue life for diffusion bonded Inconel 600 /." Online version of thesis, 2008. http://hdl.handle.net/1850/7984.

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Highsmith, Shelby. "Probabilistic fatigue crack life prediction in a directionally-solidified nickel superalloy." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180222/unrestricted/highsmith%5Fshelby%5F200312%5Fms.pdf.

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Cross, Richard J. (Richard John). "Inference and Updating of Probabilistic Structural Life Prediction Models." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19828.

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Aerospace design requirements mandate acceptable levels of structural failure risk. Probabilistic fatigue models enable estimation of the likelihood of fatigue failure. A key step in the development of these models is the accurate inference of the probability distributions for dominant parameters. Since data sets for these inferences are of limited size, the fatigue model parameter distributions are themselves uncertain. A hierarchical Bayesian approach is adopted to account for the uncertainties in both the parameters and their distribution. Variables specifying the distribution of the fatigue model parameters are cast as hyperparameters whose uncertainty is modeled with a hyperprior distribution. Bayes' rule is used to determine the posterior hyperparameter distribution, given available data, thus specifying the probabilistic model. The Bayesian formulation provides an additional advantage by allowing the posterior distribution to be updated as new data becomes available through inspections. By updating the probabilistic model, uncertainty in the hyperparameters can be reduced, and the appropriate level of conservatism can be achieved. In this work, techniques for Bayesian inference and updating of probabilistic fatigue models for metallic components are developed. Both safe-life and damage-tolerant methods are considered. Uncertainty in damage rates, crack growth behavior, damage, and initial flaws are quantified. Efficient computational techniques are developed to perform the inference and updating analyses. The developed capabilities are demonstrated through a series of case studies.

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Shenoy, Mahesh M. "Constitutive Modeling and Life Prediction in Ni-Base Superalloys." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11515.

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Microstructural features at different scales affect the constitutive stress-strain response and the fatigue crack initiation life in Ni-base superalloys. While numerous efforts have been made in the past to experimentally characterize the effects of these features on the stress-strain response and/or the crack initiation life, there is a significant variability in the data with sometimes contradictory conclusions, in addition to the substantial costs involved in experimental testing. Computational techniques can be useful tools to better understand these effects since they are relatively inexpensive and are not restricted by the limitations in processing techniques. The effect of microstructure on the stress-strain response and the variability in fatigue life were analyzed using two Ni-base superalloys; DS GTD111 which is a directionally solidified Ni-base superalloy, and IN100 which is a polycrystalline Ni-base superalloy. Physically-based constitutive models were formulated and implemented as user material subroutines in ABAQUS using the single crystal plasticity framework which can predict the material stress-strain response with the microstructure-dependence embedded into them. The model parameters were calibrated using experimental cyclic stress-strain histories. A computational exercise was employed to quantify the influence of idealized microstructural variables on the fatigue crack initiation life. Understanding was sought regarding the most significant microstructure features using explicit modeling of the microstructure with the aim to predict the variability in fatigue crack initiation life and to guide material design for fatigue resistant microstructures. Lastly, it is noted that crystal plasticity models are often too computationally intensive if the objective is to model the macroscopic behavior of a textured or randomly oriented 3-D polycrystal in an engineering component. Homogenized constitutive models were formulated and implemented as user material subroutines in ABAQUS, which can capture the macroscale stress-strain response in both DS GTD111 and IN100. Even though the study was conducted on two specific Ni-base superalloys; DS GTD111 and IN100, the objective was to develop generic frameworks which should also be applicable to other alloy systems.

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Munagala, Praveenkumar. "Fatigue life prediction of GFRP composite material at coupon and component level." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4437.

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Thesis (M.S.)--West Virginia University, 2005.
Title from document title page. Document formatted into pages; contains xi, 101 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 84-89).

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Røneid, Viggo. "LIFE PREDICTION FOR HEAVY STRUCTURES BASED ON FATIGUE CRACK INITIATION AND GROWTH." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19001.

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The main goal for this thesis has been to perform fatigue life predictions on large components.Dierent methods were to be chosen and reviwed critically. Experimental datafor girth welded pipes was assessed by means of a version of BS7910 which were modeledfrom scratch. This version was veried with results from CrackWise, and used to predictthe fatigue life for loade cases matching the selected experimental data. The fatigue assessmenttool P-FAT was used to predict the fatigue life for the same experimental data,and the results were compared. Except for some deviations recorded for embedded cracks,a generally good agreement was found between the two tools.Both the modeled BS7910 and P-FAT predicted conservative but accurate fatigue livesfor the experimental data that had signicant defects. They predicted non conservativeresults for specimens that did not have signicant defects, when the initial crack depthwas set to 0.1 mm. When the initial crack depth was set to 0.5 mm the modeled versionpredicted fatigue lives in agreement with the experimental results.Fatigue life predictions were also performed by assistance of S-N curves provided by DNVRP-C203.The results from these predictions were in agreement with the experimentaldata, except for four specimens. These four specimens had signicant aws, which reducedthe fatigue life signicantly.A review of a two-phase fatigue assessment model was made. This model uses a strainedbased approach to assess the fatigue crack initiation phase, and the fracture mechanicapproach suggested in the BS7910 to assess fatigue crack growth. This method haveshown promising results for fatigue assessment of llet welds in the literature, but themodel needs further investigation and calibration to be used to predict fatigue life ofgirth welded structures. A specic area to investigate is the proposed transition depth of0.1 mm. This depth is dubious based on the results

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Lee, J. A. "Fatigue-life prediction of fibre-reinforced plastics by using artificial neural networks." Thesis, University of Bath, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245889.

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Barnard, P. M. "Cumulative fatigue and life prediction of unidirectionally reinforced 'E'-glass/epoxy composites." Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376211.

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Girardin, Benoit. "Contact stress analysis and fatigue life prediction for a cam-roller follower system." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09052009-041041/.

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Ugwu, Ignatius Obinna. "Cement fatigue and HPHT well integrity with application to life of well prediction." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2351.

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Ng, Chuan Huat [Verfasser]. "Thermal Fatigue Tool Life and Cracking Prediction for Direct Tooling / Chuan Huat Ng." Aachen : Shaker, 2011. http://d-nb.info/1069049387/34.

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Kousky, Todd R. "Conventional and probabilistic fatigue life prediction methodologies relevant to the P-3C aircraft." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8154.

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Approved for public release; distribution is unlimited
This thesis investigates conventional and probabilistic methodologies for predicting the fatigue life of critical components in the P-3C aircraft. A probabilistic damage convolution model was developed with the intent of providing quantitative predictions of life-variability. Traditional methodologies, which are based nominally on median values, lack the capacity to adequately assess variability. Aluminum 7075-T6 was tested using a fatigue Material Test System. A fatigue data base was compiled from tests conducted at the Naval Postgraduate School and from literature sources

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Ma, Zepeng. "Fatigue models for life prediction of structures under multiaxial loading with variation in time and space." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX117/document.

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L'objet de ce travail est de proposer une approche multi-échelle de la fatigue fondée sur l'énergie, et susceptible d'estimer les durées de vie associées à des chargements multidimensionnels variables. Le fondement de la démarche consiste à supposer que l'énergie dissipée à petite échelle régit le comportement à la fatigue. À chaque point matériel, est associée une distribution stochastique de points faibles qui sont susceptibles de plastifier et de contribuer à la dissipation d'énergie sans affecter des contraintes macroscopiques globales. Ceci revient à adopter le paradigme de Dang Van en fatigue polycyclique. La structure est supposée élastique (ou adaptée) à l'échelle macroscopique. De plus, on adopte à l'échelle mésoscopique un comportement élastoplastique avec une dépendance de la fonction de charge plastique non seulement de la partie déviatorique des contraintes, mais aussi de la partie hydrostatique. On considère également un écrouissage cinématique linéaire sous l'hypothèse d'une plasticité associée. Au lieu d'utiliser le nombre de cycles comme variable incrémentale, le concept d'évolution temporelle du chargement est adopté pour un suivi précis de l'historique du chargement réel. L'effet de la contrainte moyenne est pris en compte dans la fonction de charge mésoscopique ; une loi de cumul non linéaire de dommage est également considérée dans le modèle. La durée de vie à la fatigue est ensuite déterminée à l'aide d'une loi de phénoménologique fondée sur la dissipation d'énergie mésoscopique issue du cycle d'accommodation plastique. La première partie du travail a porté sur une proposition d'un modèle de fatigie à gradient de mise en oeuvre plus simple que les précédents modèles
The aim of this work is to propose a multi-scale approach to energy-based fatigue, which can estimate lifetimes associated with variable multidimensional loading. The foundation of the approach is to assume that the energy dissipated on a small scale governs the fatigue behavior. Each material point is associated to a stochastic distribution of weak points that are likely to plasticize and contribute to the dissipation of energy without affecting global macroscopic stresses. This amounts to adopting Dang Van's paradigm of high cycle fatigue. The structure is supposed to be elastic (or adapted) on a macroscopic scale. In addition, we adopt on the mesoscopic scale an elastoplastic behavior with a dependence of the plastic load function not only of the deviatoric part of the stresses, but also of the hydrostatic part. Linear kinematic hardening is also considered under the assumption of an associated plasticity. Instead of using the number of cycles as an incremental variable, the concept of temporal evolution of the load is adopted for a precise follow-up of the history of the actual loading. The effect of mean stress is taken into account in the mesoscopic yield function; a law of nonlinear accumulation of damage is also considered in the model. Fatigue life is then determined using a phenomenological law based on mesoscopic energy dissipation from the plastic accommodative cycle. The first part of the work focused on a proposal for a fatigue model with a simpler implementation gradient than the previous models

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Elahi, Mehran. "Fatigue behavior of ceramic matrix composites at elevated temperatures under cyclic loading." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-154429/.

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Loverich, James S. "Life Prediction of Composite Armor in an Unbonded Flexible Pipe." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35873.

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Composite materials are under consideration for the replacement of steel helical tendons in unbonded flexible pipes utilized by the offshore oil industry. Higher strength to weight ratios and increased corrosion resistance are the primary advantages of a composite material for this application. The current study focuses on the life prediction of a PPS/AS-4 carbon fiber composite proposed for the above employment. In order to accomplish this task, the properties of the material were experimentally characterized at varying temperatures, aging times and loadings. An analytic technique was developed to predict tensile rupture behavior from bend-compression rupture data. In comparison to tensile rupture tests, bend-compression rupture data collection are uncomplicated and efficient; thus, this technique effectively simplifies and accelerates the material characterization process. The service life model for the flexible pipe composite armor was constructed with MRLife, a well established performance simulation code for material systems developed by the Materials Response Group at Virginia Tech. In order to validate MRLife for the current material, experimental data are compared to life prediction results produced by the code. MRLife was then applied to predict the life of the flexible pipe composite armor in an ocean environment. This analysis takes into account the flexible pipe structure and the environmental and mechanical loading history of an ocean service location. Several parameter studies of a flexible pipe in a hypothetical environment were conducted. These analyses highlight certain loadings and conditions which are particularly detrimental to the life of the material.
Master of Science

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Lim, Chemin. "Low Cycle Fatigue Life Prediction of Four Bolt Extended Unstiffened End Plate Moment Connections." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07012009-153407/.

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The end plate moment connection has been studied with various design concepts. However the low cycle fatigue (LCF) analysis was focused after 1994 the Northridge earthquake because the connection failure mode of structure was not matched with the current design concept. This concept has been applied to the design of moment resisting frames and several research studies on the LCF behavior of various connections under cyclic loading have been conducted. While the research on the behavior of end plate moment connections (EPMC) under cyclic loading has been conducted very little information on the LCF behavior is available. To evaluate the accumulation of LCF damage, the LCF life prediction, three phases of experimental tests were conducted. In order to investigate critical geometric parameters for 4E EPMCs in the LCF behavior, parametric study was conducted with pre-qualified FEM model. In the first phase of the experimental test, total 4 reduced EPMCs, T-stub, was tested to verify the elastic range of the connection system and general behavior of the connection. Three different levels of constant peak displacement loadings were applied to three full scale EPMCs for developing a LCF model in second phase of the experimental test. In the last phase, an accumulated damage model was evaluated by one full scale end plate moment connection test using random loading. All of phases were adopted three-dimensional finite element numerical analysis, and theoretical analysis to predict the experimental behavior and it successfully anticipated the behavior of connection. The results of the experimental test developed the LCF model for 4E EPMC and it predicted the LCF life of connection. The parametric study determined the three critical geometry parameters.

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Majumdar, Prasun Kanti. "Strength and Life Prediction of FRP Composite Bridge Deck." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27285.

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Fiber reinforced polymer (FRP) composites are considered very promising for infrastructure applications such as repair, rehabilitation and replacement of deteriorated bridge decks. However, there is lack of proper understanding of the structural behavior of FRP decks. For example, due to the localization of load under a truck tire, the conventionally used uniform patch loading is not suitable for performance evaluation of FRP composite deck systems with cellular geometry and relatively low modulus (compared to concrete decks). In this current study, a simulated tire patch loading profile has been proposed for testing and analysis of FRP deck. The tire patch produced significantly different failure mode (local transverse failure under the tire patch) compared to the punching-shear mode obtained using the conventional rectangular steel plate. The local response of a cellular FRP composite deck has been analyzed using finite element simulation and results are compared with full scale laboratory experiment of bridge deck and structure. Parametric studies show that design criteria based on global deck displacement is inadequate for cellular FRP deck and local deformation behavior must be considered. The adhesive bonding method is implemented for joining of bridge deck panels and response of structural joint analyzed experimentally. Strength, failure mode and fatigue life prediction methodologies for a cellular FRP bridge deck are presented in this dissertation.
Ph. D.

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Holycross, Casey M. "A multiscale analysis and extension of an energy based fatigue life prediction method for high, low, and combined cycle fatigue." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462572899.

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Aytekin, Oguz. "Numerical And Experimental Investigation Of Fatigue Life In Deep Drawn Parts." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12607386/index.pdf.

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Sheet metal forming has an important place among metal forming processes. As the usage of sheet metal increases, the fatigue simulation and optimization of these parts become more important. This thesis study examines the change of the fatigue life of a sheet metal part after forming. A sphere-like shape is deep drawn and change in thickness and residual stresses are analyzed. To understand the effect of residual stresses, deep drawn parts with and without residual stress tested against the fatigue failure. In parallel, the forming process is simulated with an implicit finite element method (FEM). The success of forming simulation is discussed in the study. Thickness changes and residual stresses calculated with FEM are included in computer aided fatigue analysis. The effect of thickness changes is examined with the results of FEM analysis. The effectiveness of the whole simulation process is discussed by comparing the outputs of experiments and computational analysis.

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Halverson, Howard Gerhard. "Improving fatigue life predictions : theory and experiment on unidirectional and crossply polymer matrix composites /." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08292008-063445/.

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Aikio, Englund Rebecca. "A study of calculation models for fatigue life prediction : A thesis accomplished together with GKN Aerospace." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-67741.

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GKN Aerospace in Trollhättan don’t use the latest ANSYS version and need to upgrade their life analysis models. The aim with this thesis is to do a study of the new models and investigate the times required for the calculations. A flight mission were chosen and this mission together with different life analysis models were run in the GKN in house program Life Analysis System. The results were analyzed and depending on the results additional runs were made or the problem were sent to the life management group at GKN Aerospace. Strain levels versus time were also plotted for the runs with the new models to get a perception where any problems occurs. The results from the model 4.10.149 had no variations between equal runs for the high pressure turbine and the low pressure turbine but there was a variation between the results when equal runs was made with the high pressure compressor. The results from model 4.10.157 and 4.10.124 and 4.10.160 and 4.10.173 had variations in the fatigue life for equal runs. The variations can depend on that the calculations converges to different solutions, the reason for this can depend on the non-linear contact elements. The variation in the results between equal runs occurs when the model uses two or more cores. The time required for the calculation becomes faster with the use of more cores. The longest duration had model 4.10.173 because of the many requirements for the calculations in this model. The problem with the variation in the results is sent to ANSYS.

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Liu, Bangyan. "Fatigue and damage tolerance analysis of composite laminates - stiffness loss, damage modellig, and life prediction." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60701.

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The prediction of fatigue life and evaluation of onset and growth of matrix cracks and delamination for general composite laminates are studied analytically using theories of damage tolerance, residual modulus degradation and residual strength degradation. Damage onset including matrix cracks and edge delamination are predicted by using a total strain energy release rate criterion which accounts for interactive effects of matrix cracks and delamination. The analytical models for modulus degradation, matrix crack density and delamination size growth as function of fatigue stress and fatigue cycles are proposed. The proposed approach provides four choices for predicting tension-tension fatigue life and for assessing fail-safety for structures made of composite laminates. The direct relation of physical damage to fatigue life and analytical equations for calculating residual elastic moduli E$ rm{ sb1, E sb2, v sb{12}}$ and G$ sb{12}$ in terms of fatigue load and fatigue cycles are proposed. The proposed approach enables prediction of fatigue behaviour of general laminates using experimental data of a basic lay-up such as unidirectional laminate. The finite element technique was utilized to model the fatigue failure process of notched laminates. A simple example of a laminate with a central hole under tension-tension fatigue loading was performed.

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Koeneman, Paul Bryant. "Viscoelastic stress analysis and fatigue life prediction of a flip-chip-on-board electronic package /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Abdulla, Warda Ibrahim. "FATIGUE BEHAVIOR AND SCALE EFFECTS IN RIVETED JOINTS." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron161651595564376.

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Jin, Ohchang. "Damage accumulation and life prediction of titanium matrix composites subjected to elevated temperatures." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19542.

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Arwidson, Jonas. "Thermal Fatigue Life Prediction of Solder Joints in Avionics by Surrogate Modeling : A Contribution to Physics of Failure in Reliability Prediction." Doctoral thesis, Linköpings universitet, Fysik och elektroteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91903.

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Manufacturers of aerospace, defense, and high performance (ADHP) equipment are currently facing multiple challenges related to the reliability of electronic systems. The continuing reduction in size of electronic components combined with increasing clock frequencies and greater functionality, results in increased power density. As an effect, controlling the temperature of electronic components is central in electronic product development in order to maintain and potentially improve the reliability of the equipment. Simultaneously, the transition to lead-free electronic equipment will most probably propagate also to the ADHP industry. Compared to well-proven tin-lead solder, the knowledge about field operation reliability of lead-free solders is still limited, as well as the availability of damage evaluation models validated for field temperature conditions. Hence, the need to fill in several knowledge gaps related to reliability and reliability prediction of lead-free solder alloys is emphasized. Having perceived increasing problems experienced in the reliability of fielded equipment, the ADHP industry has suggested inclusion of physics-of-failure (PoF) in reliability prediction of electronics as one potential measure to improve the reliability of the electronic systems. This thesis aims to contribute to the development of reliable ADHP systems, with the main focus on electronic equipment for the aerospace industry. In order to accomplish this, the thesis provides design guidelines for power distribution on a double-sided printed circuit board assembly (PBA) as a measure to improve the thermal performance without increasing the weight of the system, and a novel, computationally efficient method for PoF-based evaluation of damage accumulation in solder joints in harsh, non-cyclic field operation temperature environments. Thermal fatigue failure mechanisms and state‑of‑the‑art thermal design and design tools are presented, with focus on the requirements that may arise from avionic use, such as low weight, high reliability, and ability to sustain functional during high vibration levels and high g-forces. Paper I, II, and III describes an in-depth investigation that has been performed utilizing advanced thermal modeling of power distribution on a double-sided PBA as a measure to improve the thermal performance of electronic modules. Paper IV contributes to increasing the accuracy of thermal fatigue life prediction in solder joints, by employing existing analytical models for predicting thermal fatigue life, but enhancing the prediction result by incorporating advanced thermal analysis in the procedure. Papers V and VI suggest and elaborate on a computational method that utilizes surrogate stress and strain modeling of a solder joint, to quickly evaluate the damage accumulated in a critical solder joint from non-cyclic, non-simplified field operation temperature profiles, with accuracy comparable to finite element modeling. The method has been tested on a ball grid array package with SnAgCu solder joints. This package is included in an extensive set of accelerated tests that helps to qualify certain packages and solder alloys for avionic use. The tests include -20°C to +80°C and -55°C to +125°C thermal cycling of a statistically sound population of a number of selected packages, assembled with SnAgCu, Sn100C, and SnPbAg solder alloys. Statistical analysis of the results confirms that the SnAgCu-alloy may outperform SnPbAg solder at moderate thermal loads on the solder joints. In Papers VII and VIII, the timeframe is extended to a future, in which validated life prediction models will be available, and the suggested method is expected to increase the accuracy of embedded prognostics of remaining useful thermal fatigue life of a critical solder joint. The key contribution of the thesis is the added value of the proposed computational method utilized in the design phase for electronic equipment. Due to its ability for time-efficient operation on uncompressed temperature data, the method gives contribution to the accuracy, and thereby also to the credibility, of reliability prediction of electronic packages in the design phase. This especially relates to applications where thermal fatigue is a dominant contributor to the damage of solder joints.

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Nosti, Christopher James. "PERFORMANCE ANALYSIS AND LIFE PREDICTION FOR SMALL WIND TURBINE BLADES: A WOOD LAMINATE CASE STUDY." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/154.

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A detailed study of the fatigue life of wooden wind turbine blades for a new 10 kilowatt system was undertaken. A numerical model of the blades was created using the technical software package MATLAB in order to estimate the maximum stress occurring within the blade in response to changes in wind velocities based on a wind profile approximating the location where these turbines are expected to operate. The material properties of the wooden laminate were measured using an Instron tensile test machine and were found to be in line with published values. In parallel with this effort, a three dimensional part scanner was utilized to compare the as-built blade to the theoretical profile and large differences between these two profiles were observed. These studies were then used to guide the creation of a full scale fatigue test which subjected two blades to accelerated fatigue loads in order to monitor the damage accumulation within each blade. It was ultimately determined that this new blade design has a fatigue life greater than 20 years.

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Bartolotta, Paul Anthony. "Fatigue behavior and life prediction of a silicon carbide/titanium-24aluminum-11niobium composite under isothermal conditions." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055531339.

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Ås, Sigmund. "Fatigue Life Prediction of an Aluminium Alloy Automotive Component Using Finite Element Analysis of Surface Topography." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-758.

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A 6082 aluminium alloy has been characterized with regard to the influence of surface roughness on fatigue strength.

Fatigue life testing of smooth specimens was used to establish reference curves for the material in extruded and forged T6 condition. The extruded material was found to have better fatigue strength than the forged material, although the cyclic stress-strain response was similar for both. The forged material was tested in T5, T6 and T7 tempers, showing no significant difference in fatigue strength.

Surface roughness was created by circumferential grinding of cylindrical test specimens, and the surface topography was measured using a white light interferometry microscope. The measurements proved to be accurate, although errors were observed for certain surface features. Residual stresses were quantified by X-ray diffraction. Compressive residual stresses of around 150 MPa were found in both rough and smooth specimens. Load cycling did not significantly alter the surface residual stresses.

Stress solutions ahead of all major surface grooves were found using a linear elastic material model. Estimates of cyclic stresses and strains were calculated in the notch roots using different Neuber corrections of the linear solution. The results were compared to finite element analysis employing a bilinear kinematic hardening model. A generalized version of the Neuber correction was found to be within 20% of the nonlinear finite element results.

Several empirical models for the notch sensitivity factor were investigated. These were found to be unable to describe the notch influence on fatigue life and initiation life. In order to follow this approach, it was recommended that different test specimens should be used where the short fatigue crack growth could be monitored.

It was shown that microstructural fracture mechanics theories could be used to estimate the fatigue limit of rough surfaces. In some cases, initiation from material defects or weaknesses would override the influence of surface geometry. In one specimen, the initiation appeared to have started as at a de-bonded grain, while in other cases, initiation was thought to have started at larger second phase particles embedded in notch roots. Further work in this area should focus on statistical descriptions of surface roughness, inherent material defects, and their interaction.

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Dissertations / Theses on the topic 'Fatigue life prediction'

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