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Knipling, Keith Edward. "High-cycle fatigue / low-cycle fatigue interactions in Ti-6Al-4V." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/41290.
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The largest single cause of failure in fan and compressor components in the cold frontal sections of commercial and military gas turbine engines has been attributed to high cycle fatigue (HCF). Additionally, both high-cycle fatigue (HCF) and lowcycle fatigue (LCF) loadings are widely recognized as unavoidable during operation of these components and because the classic Linear Damage Rule (LDR) neglects to account for the synergistic interaction between these damage contributors, dangerous over predictions of lifetime can result.
Combined low-cycle fatigue / high-cycle fatigue (HCF/LCF) loadings were investigated in smooth Ti-6Al-4V. The specimens were subjected to a variable amplitude block loading history comprised of completely-reversed (R = -1) tensioncompression overloads followed by constant-amplitude zero-tension (R = 0) minor cycles. Axial specimens were excised from forgings representative of turbine engine fan blade forgings, and consisted of approximately 60% primary α in a matrix of lamellar α + β.
Data are reported for smooth specimens of Ti-6Al-4V subjected to both constant amplitude and variable amplitude loadings. The axial specimens were prepared according to two distinct specimen conditions: low stress ground and longitudinallypolished (LSG+LP) and stress-relieved and chemically milled (SR+CM) conditions. Significantly longer lives were observed for the LSG+LP specimen condition under both constant and variable amplitude loading, due to the presence of a beneficial compressive surface residual stress. The presence of this residual stress was confirmed by x-ray diffraction, and its magnitude was of the order of 180 MPa (~20% of the yield stress). In either specimen condition, no appreciable effect of periodic overloads on the life of subsequent minor cycles was observed.Master of Science
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Bérard, Jean-Yves Adrien. "Low cycle fatigue behavior of a low carbon steel." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/20130.
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Romo, Arango Sebastian A. "Low-Cycle Fatigue of Low-Alloy Steel Welded Joints." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1573054310351145.
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Charles, C. M. "Low cycle fatigue mechanisms in CMSX-4." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597493.
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This thesis investigates the low-cycle fatigue behaviour of CMS-4. The focus is on R=0 load controlled fatigue, with an emphasis on deformation at 750°C. A particular aim of this research is to identify how fatigue proceeds at stress concentrators. Here, high stresses in plain bars have been compared with similar maximum stresses around the known stress concentration of a Kt-2 notch. Fatigue tests were conducted on both plain and notched specimens, across a range of stresses and temperatures, and the deformation has been imaged using TEM. The plain bars show a range of deformation mechanisms, which have been described and analysed. Of particular interest is the presence of widely spaced dipoles of single dislocations, previously noted in tensile studies. These have been imaged on slip planes, and it is shown that they are not formed by the mutual attraction of two independent dislocations, as has been previously thought. Rather, they are two sides of an á110ñ loop, separated by a region of APB. These loops are expected to expand and contract within the precipitates, and it is shown that this could account for a significant degree of plastic strain within the plain bars. Although the fracture patterns and lifetimes are very similar to those seen in the plain bars, no microstructural evidence of significant deformation is seen from TEM examination of the notched bars. Visible dislocation density is consistently extremely low, and it is seen that there is no correlation between deformation in the bulk of the plain bars, the notched bars, and failure. Hence, a new mechanism of initiation is proposed for failure below 950°C. It is proposed that initiation below 950°C is related to the extrusion of g channels at the surface of internal porosity, and the concomitant formation of subsurface voids.
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Megharbi, Ahmed. "Low cycle fatigue of FPSO ship structure." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2894.
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The phenomenon of low cycle fatigue (LCF) is characterised by high stress range, close to or above yield, and relatively low number of cycles to failure, typically below 104. In the case of tankers and Floating, Production, Storage and Offloading units (FPSO), nominal stress amplitudes lower than the yield stress may result in plastic strains due to the high stress concentrations that are typical in many of the hulls’ structural details. FPSOs are more susceptible to damage due to LCF compared to tankers, cargo and other ocean going ships. The main reasons are; the unique structure of FPSO in terms of the presence of internal turret and topsides load which affects the structural response of FPSO to dynamic and quasi-static loads, the frequent loading and unloading patterns of FPSO (i.e. unlike oil tankers which are either in full load or ballast condition) which causes the FPSO to experience the maximum hogging and sagging still water bending moment every single cycle and the condition of the sea at which the FPSO is operating (site specific environment) where even benign condition may subject the FPSO to extremely diverse wave induced loads. An increasing number of FPSOs are being used in the oil and gas industry due to the practical advantages they offer as compared to fixed installations, however, many FPSO show signs of cracks at critical locations in the first five years of service. It is believed that this is primarily due to LCF. It is therefore imperative to address LCF at the design stage. Finite Element Analysis (FEA) has been used to demonstrate that extremely high stress levels, exceeding three times the yield stress of the material, may occur at some critical locations during FPSO operations. Due to this ‘new’ form of damage in ship structures classification societies, shipyards and other organizations are addressing the issue of LCF by issuing various guidance notes and recommended practices in order to assess the damage due to LCF. This research contains a very extensive and useful literature review of the state-of-theart in LCF assessment methods available in literature and various class societies. Representative operational loading conditions (most onerous) have been presented for LCF Assessment of FPSO. LCF tests of typical longitudinal attachment were performed. This important structural element is seldom tested compared to the transverse attachment or cruciform. Experimental and numerical results compare well. A novel method of predicting LCF life has been proposed and a new S-N curve is proposed to be used for LCF assessment.
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Zhang, Yahui. "Low cycle fatigue of shape memory alloys." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLY004/document.
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Dans cette thèse, nous proposons une analyse globale multi-échelles de la fatigue à faible nombre de cycles des matériaux à mémoire de forme (MMF). Dans un premier temps, une large campagne d’essais a été menée pour différents chargements thermomécaniques comprenant des tests de fatigue sous contrainte et déformation imposée et pour différentes fréquences de chargement. A partir des résultats des essais, un critère de fatigue, basé sur l’énergie de déformation, a été développé ; on montre que l’énergie de déformation est un paramètre pertinent pour prédire la fatigue des MMF en tenant compte du couplage thermomécanique et du type de chargement : contrainte ou déformation imposée. Ensuite, en prenant appui sur la répartition de l’énergie de l’hystérésis en dissipation et énergie stockée, on avance une interprétation physique du mécanisme de la fatigue des MMF. Dans la troisième partie, on propose une modélisation multi-échelles de l’initiation des fissures de fatigue dans les MMF à partir de la notion de plasticité de transformation (PlTr). Dans ce cadre, on montre que la fatigue de MMF est contrôlée par la (PlTr) et que la température maximale lors de la transformation de phase est le paramètre à retenir pour prédire la rupture par fatigue des MMF. Le modèle permet également de prédire le lieu d’initiation des premières fissures de fatigue. Enfin, un procédé – fondé sur l’«éducation» des MMF – permettant d’améliorer la résistance à la fatigue est proposéThe thesis proposes a multi-scale comprehensive analysis of low cycle fatigue of shape memory alloys (SMAs). First, low cycle fatigue of SMAs is experimentally investigated; comprehensive tensile-tensile fatigue tests under both stress and strain controlled loadings at different frequencies are carried out and results are discussed. Second, a new strain energy-based fatigue criterion is developed; it is shown that the use of total strain energy is a relevant parameter to predict fatigue lifetime of SMAs for different thermomechanical conditions and under different types (strain-control or stress-control) loadings. A physical interpretation of the mechanism related to the low-cycle fatigue of SMAs is then provided based on the conversion of hysteresis work into dissipation and stored energy. Third, fatigue crack initiation during cyclic stress-induced phase transformation is modeled based on transformation induced plasticity (TRIP); it is shown that the maximum temperature during the cyclic loading is a relevant indicator of the fatigue of SMA. Furthermore, the effect of the macroscopic mechanical load on the the fatigue lifetime is addressed as well as the spatial location of crack initiation. Finally, a mechanical training process that allows enhancing resistance to low cycle fatigue of SMAs is proposed
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Zhang, Yahui. "Low cycle fatigue of shape memory alloys." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLY004.
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Dans cette thèse, nous proposons une analyse globale multi-échelles de la fatigue à faible nombre de cycles des matériaux à mémoire de forme (MMF). Dans un premier temps, une large campagne d’essais a été menée pour différents chargements thermomécaniques comprenant des tests de fatigue sous contrainte et déformation imposée et pour différentes fréquences de chargement. A partir des résultats des essais, un critère de fatigue, basé sur l’énergie de déformation, a été développé ; on montre que l’énergie de déformation est un paramètre pertinent pour prédire la fatigue des MMF en tenant compte du couplage thermomécanique et du type de chargement : contrainte ou déformation imposée. Ensuite, en prenant appui sur la répartition de l’énergie de l’hystérésis en dissipation et énergie stockée, on avance une interprétation physique du mécanisme de la fatigue des MMF. Dans la troisième partie, on propose une modélisation multi-échelles de l’initiation des fissures de fatigue dans les MMF à partir de la notion de plasticité de transformation (PlTr). Dans ce cadre, on montre que la fatigue de MMF est contrôlée par la (PlTr) et que la température maximale lors de la transformation de phase est le paramètre à retenir pour prédire la rupture par fatigue des MMF. Le modèle permet également de prédire le lieu d’initiation des premières fissures de fatigue. Enfin, un procédé – fondé sur l’«éducation» des MMF – permettant d’améliorer la résistance à la fatigue est proposéThe thesis proposes a multi-scale comprehensive analysis of low cycle fatigue of shape memory alloys (SMAs). First, low cycle fatigue of SMAs is experimentally investigated; comprehensive tensile-tensile fatigue tests under both stress and strain controlled loadings at different frequencies are carried out and results are discussed. Second, a new strain energy-based fatigue criterion is developed; it is shown that the use of total strain energy is a relevant parameter to predict fatigue lifetime of SMAs for different thermomechanical conditions and under different types (strain-control or stress-control) loadings. A physical interpretation of the mechanism related to the low-cycle fatigue of SMAs is then provided based on the conversion of hysteresis work into dissipation and stored energy. Third, fatigue crack initiation during cyclic stress-induced phase transformation is modeled based on transformation induced plasticity (TRIP); it is shown that the maximum temperature during the cyclic loading is a relevant indicator of the fatigue of SMA. Furthermore, the effect of the macroscopic mechanical load on the the fatigue lifetime is addressed as well as the spatial location of crack initiation. Finally, a mechanical training process that allows enhancing resistance to low cycle fatigue of SMAs is proposed
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Powell, Brian Edward. "The influence of minor cycles on low cycle fatigue crack growth." Thesis, University of Portsmouth, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354380.
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Fatigue crack propagation rates have been measured for two titaniumbased aeroengine disc alloys using compact tension test pieces. The loading block employed simulates two features of the engine flight pattern. A major stress cycle represents the start-stop operation which leads to low cycle fatigue. In-flight vibrations, which may give rise to high cycle fatigue, are represented by superimposed minor cycles of high frequency. This combined loading is applied in a specially developed test facility consisting of an electromagnetic vibrator mounted above a servohydrau1ic actuator. When the minor cycles are inactive the fractographic cracking processes are those associated with major cycle crack growth. Once active, the minor cycle growth may either generate extensive cyclic cleavage or increase the separation of the fatigue striations associated with the periodic major cycles. The contribution of the minor cycles to the total growth rate is dependent on their relative number and size. In gas turbine and compressor discs and blades, components which experience large numbers of minor cycles per flight, the damage associated with active minor cycles is dominant. Consequently, the onset of minor cycle damage effectively determines the useful life of such components. The threshold values associated with the minor cycles have been used to predict the onset of minor cycle activity. Similarly the method of linear superposition has been used to predict the subsequent fatigue crack growth rates. These predictions are successful for Ti-6Al-4V, whilst for Ti-5331S they are either found to be accurate or safe. Although Ti-5331S displays a marginally greater resistance to the onset of minor cycle crack growth, of greater significance is its reduced crack growth rates prior to this event. As a consequence components fabricated from Ti-5331S will exhibit longer fatigue crack propagation lives when subjected to the conjoint action of high and low cycle fatigue.
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Payne, R. Kelly. "Low cycle fatigue of modified 9Cr-1Mo weldments." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/10991.
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Bérard, Jean-Yves Adrien. "A micromechanical approach to biaxial low cycle fatigue." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/20157.
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Praisarnti, Chonrada. "Low-cycle fatigue of NiTi rotary instruments in hypochlorite." Thesis, View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38727365.
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Hall, Rodney H. F. "Crack growth under combined high and low cycle fatigue." Thesis, University of Portsmouth, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290404.
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Rosenblad, Louise, and Filippa Hallbäck. "Low Cycle Fatigue Weld Optimization using Chaboche Material Model." Thesis, KTH, Hållfasthetslära (Avd.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232520.
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In this master thesis a method for optimizing welds has been investigated. The method was developed by the use of a finite element (FE)-model of a silencer. The silencer is exposed to both dynamic and thermal loads. Focus has been on using topology optimization for the welds. The main driver for developing a method for weld optimization is to investigate whether the stresses close to the welds could be decreased if some weld material were to be removed. Another motive for conducting the study is to understand the potential for decreased computation time for modeling welds (continuous welds) should the component have more intermittent welds. Given the loads that the component is subjected to, a plastic material model would be preferable. However as of today, a material model in an optimization is limited to being linear elastic and hence it is not possible to use a plastic material model in an optimization, even though that would better to capture the real conditions of the silencer. Thus, as part of this thesis an investigation aiming to find a transfer function between a plastic material model and an elastic material model was conducted. An important part of an optimization is to have a relevant requirement to optimize against. This requirement could be calculated from the transfer function and then be used in an optimization.Summarizing the findings, a transfer function between a plastic and elastic material model was identified, but only for a specific model and position. The identified function can translate and enable the stricter conditions used in a plastic material model to be adapted to an elastic material model. To get a functional transfer function the Super Neuber needs to be calculated for every element in a time efficient way. This might be done by finding a relation of the geometry and the Super Neuber parameter but this will require more investigations. If the Super Neuber parameters for the model are found then the fatigue requirement can be translated to an elastic stress constraint which will give a more accurate optimization.The method for weld optimization has been evaluated but without a requirement calculated from the transfer function. By changing from continuous to intermittent welds the stresses caused by the thermal load can be decreased.
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Liu, Jinxiang. "Investigation of low cycle fatigue in shot peened components." Düsseldorf VDI-Verl, 2009. http://d-nb.info/996623914/04.
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Abduljabbar, Fouad Abdulbaky. "Low-cycle fatigue of NiTi rotary instruments in hypochlorite." Thesis, Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43224039.
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Stekovic, Svjetlana. "Low Cycle Fatigue and Thermo-Mechanical Fatigue of Uncoated and Coated Nickel-Base Superalloys." Doctoral thesis, Linköpings universitet, Konstruktionsmaterial, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9820.
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High strength nickel-base superalloys have been used in turbine blades for many years because of their superior performance at high temperatures. In such environments superalloys have limited oxidation and corrosion resistance and to solve this problem, protective coatings are deposited on the surface. The positive effect of coatings is based on protecting the surface zone in contact with hot gas atmosphere with a thermodynamically stable oxide layer that acts as a diffusion barrier. During service life, mechanical properties of metallic coatings can be changed due to the significant interdiffusion between substrate and coating. There are also other degradation mechanisms that affect nickel-base superalloys such as low cycle fatigue, thermo-mechanical fatigue and creep. The focus of this work is on a study of low cycle fatigue and out-of-phase thermo-mechanical fatigue behaviour of three uncoated and coated nickel-base superalloys. Polycrystalline IN792 and two single crystals CMSX-4 and SCB were coated with four different coatings; an overlay coating AMDRY997 (NiCoCrAlYTa), a platinum aluminide modified diffusion coating RT22 and two innovative coatings with a NiW interdiffusion barrier in the interface called IC1 and IC3. A low cycle fatigue and thermo-mechanical fatigue device was designed and set-up to simulate service loading of turbine blades and vanes. The low cycle fatigue tests were run at 500oC and 900oC while the thermo-mechanical fatigue tests were run between 250oC and 900oC.To simulate long service life, some coated specimens were exposed at 1050oC for 2000 h before the tests. The main conclusions are that the presence of the coatings is, in most cases, detrimental to LCF lives of the superalloys at 500oC while the coatings do improve the LCF lives of the superalloys at 900oC. Under TMF loading conditions, the coatings have negative effect on the lifetime of IN792. On single crystals, they are found to improve TMF life of the superalloys, especially at lower strains. The tests also indicate that long-term aging influences the fatigue and fracture behaviour of coated superalloys by oxidation and diffusion mechanisms when compared to non-aged specimens. The aged specimens exhibit longer life in some cases and shorter life during other test conditions. Fatigue cracks were in most cases initiated at the surface of the coatings, growing transgranularly perpendicular to the load axis.
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Šteković, Svjetlana. "Low cycle fatigue and thermo-mechanical fatigue of uncoated and coated nickel-base superalloys /." Linköping : Department of Managenet and Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9820.
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Rundström, Finn, and Albert Ericsson. "Optimisation of Low Cycle Fatigue : Life in Turbine Rear Frame." Thesis, KTH, Maskinkonstruktion (Inst.), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100713.
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Syftet med detta examensarbete är att undersöka vilka faktorer som styr livslängdsbegränsningarna i bakre turbinstativet (TRF) i GEnx -motorn, mestadels med inriktning på området kring motorfästena, och om möjligt hindra dessa problem att uppstå. Arbetet har huvudsakligen utförts med hjälp av FE -programmet Ansys och utgått från modeller tidigare konstruerade på Volvo Aero Corporation. Tre större studier beträffande lågcyklisk utmattning har utförts: Först och främst har ca 80 finita element -modeller byggts med lokala ändringar av området runt motorfästena, där godstjockleken har varierats, ibland tillsammans med olika sorters flänsar. Denna sudie resultarade i en ökning av livslängden till 280% av den ursprungliga. Utöver detta har globala ändringar studerats; i detta fall i form av sex modeller med olika vinklar på ledskenorna. Slutsatsen är att nuvarande vinkel är den mest optimala. Slutligen har även en känslighetsanalys av de termiska randvillkoren utförts för att undersöka inverkan av osäkerheten hos de ursprungliga termiska antaganden som gjorts. Ett tydligt samband mellan de termiska randvillkoren och livslängden påvisades runt motorfästet, medan det var svårt att dra några slutsatser beträffande navet..The aim of this is master thesis where the aim is to analyse the factors that limits the fatigue life of the GEnx TRF engine and, if possible, ways to prevent such problems to should be presented. Thermal and structural analyses have been carried out using the finite element program Ansys. Models from previous studies at Volvo Aero Corporation have been used. There have been three main studies, all of them concerning LCF life: Firstly, about 80 finite element models with local changes of the lug section have been performed; the thickness in the lug section has been varied, sometimes together with different types of flanges. This study increased the life to 280% of the original model. Secondly, global changes have been studied; in this case six different strut angles have been analysed. It was found that the current strut angle is the optimal one. Finally, a sensitivity study of the thermal boundary conditions has been carried out in order to investigate the importance of the uncertainty of the initial thermal assumptions. A good correlation between the life and thermal boundary conditions was found around the mount lugs whilst it is hard to draw any conclusions in the hub
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Cheung, Shun-pan Gary. "Low-cycle fatigue of nickel-titanium rotary root-canal instruments /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36666671.
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Raji, Hauwa. "Low cycle fatigue in floating production storage and offloading units." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=13230.
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Cheung, Shun-pan Gary, and 張順彬. "Low-cycle fatigue of nickel-titanium rotary root-canal instruments." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45015533.
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Gordon, Paul Mark. "Low Cycle Fatigue Behavior of Concrete with Recycled Concrete Aggregates." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/577.
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A comparison of concrete containing recycled concrete coarse aggregates and natural coarse aggregates subjected to high strain, low cycle compressive fatigue is presented. Using a strain based feedback control loop, concrete cylinders are compressed at 15µε/s to a specified strain then unloaded to zero stress for 10 cycles. After cycling, all samples are loaded to a strain of 0.008. Direct concrete material variables are the water to cement (w/c) ratio, taken as 0.60, 0.45, and 0.39, and percent coarse recycled concrete aggregate content, varied from zero to 100 percent. The primary testing variable is the specified unloading strain. Unloading strains include 60, 75, 90, 100, and 120 percent of the strain at peak stress. Ten batches of concrete were made, generating a total of 224 samples for testing. Findings confirm previous research showing a reduction in strength with increasing recycled concrete coarse aggregate content, an equivalent concrete with only 25 percent replacement of natural coarse aggregates and an equivalent strength concrete with a decrease in the w/c ratio and 100 percent recycled concrete coarse aggregates. Fatigue testing indicates that each cycle’s maximum stress remains unchanged, but the stiffness degrades more rapidly with increasing recycled aggregate content and a constant w/c ratio.
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Radonovich, David Charles. "Methods of Extrapolating Low Cycle Fatigue Data to High Stress Amplitudes." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3460.
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Modern gas turbine component design applies much effort into prediction and avoidance of fatigue. Advances in the prediction of low-cycle fatigue (LCF) cracks will reduce repair and replacement costs of turbine components. These cracks have the potential to cause component failure. Regression modeling of low-cycle fatigue (LCF)test data is typically restricted for use over the range of the test data. It is often difficult to characterize the plastic strain curve fit constants when the plastic strain is a small fraction of the total strain acquired. This is often the case with high strength, moderate ductility Ni-base superalloys. The intent of this project is to identify the optimal technique for extrapolating LCF test results into stress amplitudes approaching the ultimate strength. The proposed method to accomplish this is by finding an appropriate upper and lower bounds for the cyclic stress-strain and strain-life equations. Techniques investigated include: monotonic test data anchor points, strain-compatibility, and temperature independence of the Coffin-Manson relation. A Ni-base superalloy (IN738 LC) data set with fully reversed fatigue tests at several elevated temperatures with minimal plastic strain relative to the total strain range was used to model several options to represent the upper and lower bounds of material behavior. Several high strain LCF tests were performed with stress amplitudes approaching the ultimate strength. An augmented data set was developed by combining the high strain data with the original data set. The effectiveness of the bounding equations is judged by comparing the bounding equation results with the base data set to a linear regression model using the augmented data set.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering MSME
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Liu, Wei. "Grain size effect on low cycle fatigue behavior of copper polycrystals." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0022/MQ51744.pdf.
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Wang, Bin. "The prediction of low cycle fatigue for die casting with FEM." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57753.pdf.
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Liu, Changqi. "The low cycle fatigue behavior of aluminum alloy based particulate composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056483090.
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Gong, Meng. "Failure of spruce under compressive low-cycle fatigue loading parallel to grain." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0032/NQ65458.pdf.
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Cheng, Deborah Wen-hsin. "Compressive high cycle at low strain fatigue behavior of bovine trabecular bone." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38042.
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Tola, Tola Adrian Patricio. "Analytical and Experimental Investigation of Low-Cycle Fatigue Fracture in Structural Steel." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/100051.
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The mechanism of metal material failure due to inelastic cyclic deformations is commonly described as Low-Cycle Fatigue (LCF). Fracture in steel structures caused by earthquakes can be associated with this mechanism. Mathematical expressions describing the material deterioration due to LCF are often referred to as LCF laws. The accurate determination of the safety of steel structures against earthquake-induced failure requires the use of LCF laws which have been sufficiently validated with experimental test data.
The present study combined experimental testing and computational simulation to enhance the understanding of structural steel fracture due to LCF. The experiments were conducted in specimens extracted from the flat and corner regions of two rectangular steel hollow sections with different thickness. A total of 60 cylindrical specimens with a circumferential notch were subjected to different combinations of axial and torsional loading. The loading protocols and notch geometry were designed to produce different stress states at the location of fracture initiation. Finite element analyses were conducted to obtain the stress state and inelastic strains at the fracture initiation location. This information was then used for the calibration of five existing LCF laws. The calibration also allowed the comparative evaluation of the capability of the different laws to capture fracture initiation for different stress states, with a single set of values for the various parameters.
The accuracy of the calibrated LCF laws to predict fracture initiation in a large-scale test was also investigated. To this end, a test was conducted on a rectangular steel tube subjected to cyclic axial loading. A finite element analysis of this test was conducted, and predictions of the instant and location of fracture initiation using the calibrated LCF laws were compared with the experimental observations.Doctor of Philosophy
The mechanism of material failure due to repeated cycles of large deformations is denoted as Low-Cycle Fatigue (LCF); this failure mechanism can occur in steel structures subjected to loading conditions such as those induced by earthquakes. Mathematical expressions that evaluate the material deterioration due to LCF are often used to predict the instant and location of fracture initiation in small-scale and large-scale tests. An experimental program was conducted for the study of fracture associated with LCF. A total of 60 specimens were fabricated with material extracted from the flat and corner regions of two rectangular steel tubes; the applied loads elongated and/or twisted the specimens until they ruptured. Computational simulations of these tests were conducted to obtain key information at the location of the observed fracture initiation. This information was used to adjust five mathematical expressions suggested by previous researchers that could predict the same instant of fracture initiation observed in the experiments. The accuracy of the predictions from each of these mathematical expressions was evaluated. The accuracy of these mathematical expressions to predict fracture initiation in a large-scale test was also investigated. To this end, an experiment was conducted on a rectangular steel tube subjected to repeated cycles of deformation. A computational simulation of this test was also developed, and predictions of the instant and location of fracture initiation were compared with the experimental observations.
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Roy, Alexander M. "Prediction of low and high cycle multiaxial fatigue of superelastic nitinol stents via uniaxial fatigue based equations." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527412.
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Lester, Charles Gilbert IV. "Analysis of fatigue behavior, fatigue damage and fatigue fracture surfaces of two high strength steels." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42795.
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Building fuel efficient automobiles is increasingly important due to the rising cost of energy. One way to improve fuel efficiency is to reduce the overall automobile weight. Weight reductions using steel components are desirable because of easy integration into existing manufacturing systems. Designing components with Advanced High Strength Steels (AHSS) has allowed for material reductions, while maintaining strength requirements. Two Advanced High Strength steel microstructures investigated in this research utilize different strengthening mechanisms to obtain a desired tensile strength grade of 590MPa. One steel, HR590, utilizes precipitation strengthening to refine the grain size and harden the steel. The other steel, HR590DP, utilizes a dual phase microstructure consisting of hardened martensite constituents in a ferrite matrix. The steels are processed to have the same tensile strength grade, but exhibit different fatigue behavior. The central objective of this research is to characterize and compare the fatigue behavior of these two steels. The results show the dual phase steel work hardens at a low fatigue life. The precipitation strengthened microstructure shows hardening at low strain amplitudes, softening at intermediate strain amplitudes and little to no effect at high strain amplitudes. These different fatigue responses are characterized and quantified in this research. Additionally, observations showing the fracture surfaces and the bulk microstructure are analyzed.
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Peters, Donald Michael Dirk. "The effects of shot peening on low cycle fatigue life of 7075-T6 aluminium alloy round bar." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/2929.
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The aim in this dissertation was to improve our understanding of the effectiveness of shot peening in prolonging fatigue life, of 7075-T6 Aluminium Alloy round bar, taking into consideration surface residual stress, microstructural and micro-hardness parameters. Three point bending, high stress, moderately low cycle, fatigue tests were conducted to study the effects of shot peening and associated surface residual compressive stresses on fatigue life. The influence of shot peening on the microstructure was explored, including the application of mechanical small plastic straining and surface skimming, to vary the surface residual compressive stresses and induce strain hardening. Tests were performed to measure residual stress-depth distribution, plastic straining, micro-hardness, and the microstructure analysed on scanning electron microscopy (SEM) fractographs. The Juvinall and Marshek life prediction model was used in conjunction with the Gerber equation for non-zero mean stress applications to generate a proposed life prediction model for this material which is user-friendly. The proposed life prediction model has a linear equation format with the flexibility to conservatively accommodate most of the various types, and combinations, of treatments applied in this research by the use of customised constants. The results show that there was good correlation between actual and predicted fatigue life as well as useful insights into the role of the microstructure in explaining fatigue life behaviour.
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Reyher, Boris [Verfasser]. "Zur Modellierung von Low Cycle Fatigue-Effekten bei zyklisch beanspruchten Stahlbauteilen / Boris Reyher." Aachen : Shaker, 2006. http://d-nb.info/1170529356/34.
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Daubenspeck, Brian R. "Extrapolation techiques for very low cycle fatigue behavior of a ni-base superalloy." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1390.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Mechanical, Materials, and Aerospace Engineering
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Stevens, Katherine Anne. "The low-cycle fatigue behavior of an alpha-two + Beta Titanium Aluminide Alloy /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486462702466278.
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Brooks, Rebecca Ruth. "Fatigue damage mechanisms in the nickel-based superalloy UDIMET720." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387637.
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Schäfer, Hans Joachim. "Auswertealgorithmus auf der Basis einer Modifikation des goniometrischen Modells zur stetigen Beschreibung der Wöhlerkurve vom Low-Cycle-Fatigue- bis in den Ultra-High-Cycle-Fatigue-Bereich." Aachen Mainz, 2008. http://d-nb.info/99179804X/04.
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Orozco-Smith, Evelyn M. "Analysis of low cycle fatigue properties of single crystal nickel-base turbine blade superalloys." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014339.
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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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Stahl, Douglas Ray. "The effect of temperature, microstructure and stress state on the low cycle fatigue behavior of waspaloy." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10268.
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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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Anguo, Wang. "The effect of grain size on the low-cycle fatigue behaviours of a CrMnFeCoNi high entropy alloy." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/21129.
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High-entropy alloys (HEAs) alloys are alloys formed by at 5 or more elements, which have high strength, excellent ductility, and wear, corrosion and creep resistance. While the above-mentioned properties are very important and widely studied, fatigue properties are a more critical issue in most industrial applications. Fatigue causes over 90% of failure. Yet, the fatigue properties of HEAs have been less investigated. So, it worth to study the fatigue properties. It has been well-known that grain size plays a critical role in determining the mechanical properties of HEAs. However, the grain size effects on fatigue properties of HEAs has not been clear. This project aims to study the effect of grain size on the low-cycle fatigue (LCF) properties of a CrMnFeCoNi HEA. Results show that the fatigue life increased with decreasing grain size and/or decreasing strain amplitude. Fatigue-induced structural evolution of the HEA was complicated. Deformation of samples with fine and coarse grain sizes occurred mainly via planar slip at low strain levels, while wavy slip dominated the deformation of samples with the intermediate grain size. Planar slip was suppressed at a high strain regime. Dislocation cell structures, which are classic wavy slip microstructures, were commonly seen in intermediate grains at the high strain regime. The fatigue cracking behaviour at twin boundaries (TBs) in the HEA was also explored. Irrespective of grain size, the change from slip band cracking to TB cracking occurred with increasing the difference in the Schmid factors between matrix and twin. However, the required critical difference of Schmid factors for the transition of the dominant cracking mode decreases with decreasing grain size due to the reduced slip band spacing that increases the impingement sites on the TBs and facilitates the coalescence of defects and voids to initiate TBs cracks
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Findley, Kip Owen. "Physically-based models for elevated temperature low cycle fatigue crack initiation and growth in Rene." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04292005-092902/.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2006.McDowell, David, Committee Member ; Gokhale, Arun, Committee Member ; Saxena, Ashok, Committee Chair ; Johnson, Steven, Committee Member ; Sanders, Thomas, Committee Member.
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Schayes, Claire. "Low cycle fatigue of the Fe-3Si steel : damage mechanisms and strain localisation by EBSD." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10002/document.
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L’objectif de ce travail de thèse était d’étudier le comportement en fatigue oligocyclique de l’acier Fe-3Si utilisé pour les rotors des nouveaux alterno-démarreurs développés par Valeo. L’étude pris en compte la relation entre la réponse mécanique et la microstructure, les mécanismes de fatigue, l’évaluation de la déformation à une échelle mésoscopique et une optimisation du dimensionnement du rotor. Les essais de fatigue, menés sur des éprouvettes d’épaisseur 350μm, ont montré un durcissement cyclique du matériau et le mode de propagation de la fissure, fragile, souligne sa faible ténacité. La formation de structure de dislocations observées par Microscopie Electronique en Transmission (TEM) et par cECCI (Controlled Electron Channelling Contrast Imaging) est dépendante de la déformation et la variation de déformation totale Δεt=0.7% apparaît comme une valeur de transition. En-dessous de Δεt =0.7%, des arrangements homogènes de dislocations et un amorçage de la fissure transgranulaire sont observés. Au-dessus de Δεt =0.7%, des structures veines-canaux et murs-canaux sont observés et l'amorçage de fissure est intergranulaire. Une étude EBSD (Electron Back-Scattered Diffraction) basée sur les paramètres KAM, GROD et GOS menée sur les éprouvettes fatiguées montre un gradient de déformation dans les grains et une localisation de la déformation aux joints de grain au-dessus de Δεt =0.7%. Enfin, en prenant en compte les propriétés en fatigue de l’acier Fe-3Si dans la base de données matériaux de la modélisation par éléments finis, des légères modifications de la géométrie du rotor ont été effectuées ce qui améliore les performances électromagnétiques de la machineThe objective of the PhD work was to investigate the low cycle fatigue (LCF) behaviour of Fe-3Si steel employed for rotors of new starter-alternators developed by Valeo. The study took into account the relation between mechanical response and microstructure, the fatigue mechanisms, the assessment of strain at a mesoscopic scale and an optimisation of the rotor design. Low cycle fatigue tests performed on 350μm thick specimen pointed out a cyclic hardening of the material. The brittle crack propagation mode underlined the low toughness of the material. The formation of dislocations structures observed by Transmission Electron Microscopy (TEM) and controlled Electron Channelling Contrast Imaging (cECCI) was strain dependant. The total strain variation Δεt =0.7% appeared as a transition value. Below Δεt =0.7%, homogeneous arrangement of dislocations and transgranular crack initiation are observed. Above Δεt =0.7%, a mixture of veins-channels and wall-channels were observed inside the grains and cracking became intergranular. An Electron Back-Scattered Diffraction (EBSD) study was then performed on the specimen fatigued above Δεt=0.7% and approached with KAM, GROD and GOS parameters. It pointed out the strain gradient within grain and highlighted the strain localisation at grain boundaries. Finally, by taking into account LCF properties of the Fe-3Si steel in the material database of the finite element modelling, slight modifications of the rotor geometry have been performed which improves the electromagnetic performances of the machine
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Li, Yugang. "Shot-peening and low-cycle fatigue of titanium alloys : instrumented indentation and X-ray diffraction." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0031/document.
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Deux problèmes surviennent lorsque nous étudions les effets du grenaillage de précontrainte sur le processus de la fatigue. Le premier est la caractérisation des contraintes résiduelles (CR) et de l’écrouissage. Le second est l’évolution de CR et de l’écrouissage pendant le cyclage.Pour résoudre le premier problème, cette thèse propose une méthode pour mesurer les contraintes et l’écrouissage par nanoindentation. Ici, l’écrouissage est représenté par la déformation plastique cumulée (PP). A l’aide d’une série de simulations par éléments finis (MEF) en supposant le comportement du matériau connu, les réponses obtenues par indentation permettent d’obtenir simultanément contrainte et déformation plastique. Bien que satisfaisante d’un point vue numérique, les performances expérimentales obtenues sur un alliage de titane temps T40 restent insuffisantes. Cependant, si le profil de contrainte est connu, on peut toutefois obtenir le profil de déformation plastique. Les biais induits par la préparation de la surface ont été analysés en détail. Pour le second problème, une série d'essais de fatigue ont été effectués sur un alliage Ti-18. Quatre traitements ont été testés sur 100 cycles sous 3 amplitudes différentes de déformation. Des mesures par diffraction des rayons X ont montré que la relaxation des contraintes et l’adoucissement cyclique augmentent avec l'amplitude de déformation. Les essais d’indentation ont montré un adoucissement de la couche grenailléeThere are two problems when investigating the effects of shot-peening on fatigue process. The first one is characterizing residual stresses (RS) and strain hardening (WH) on the sample surface. The second one is the evolution of RS and WH during fatigue. In order to solve the first problem, this thesis proposes a “simultaneous function method” to measure RS and WH with nanoindentation. Accumulated plastic strain (PP) is used to represent WH. Then, by establishing functions of normalized indentation responses through a series of finite element method (FEM) simulations, normalized indentation responses obtained from nanoindentation experiments can be used to extract RS and PP values, assuming that the constitutive behavior is known. Although the simultaneous function method shows fairly high accuracy from a pure numerical view point, experiments performed on T40 commercial pure titanium are not completely satisfying. However, if the residual stress profile is known, the method can be used to derive the work hardening profile.In order to study the second problem, a series of strain-controlled fatigue tests are performed on Ti-18 alloy. Fatigue specimens of 4 material states, including raw, shot-peened, prestrained and prestrained + shot-peened, were tested under 3 different strain amplitudes over 100 cycles. X-ray diffraction tests on the sample surfaces showed that the RS relaxation and the cyclic softening increase together with the strain amplitude. IIT tests showed that shot-peening may induce a softening of the surface of Ti-18 alloy samples
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Xiao, Yi. "Fatigue des alliages aluminium-lithium." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37610833r.
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Acar, Fikri. "Low Cycle Fatigue Effects In The Damage Caused By The Marmara Earthquake Of August 17, 1999." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605534/index.pdf.
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This study mainly addresses the problem of estimating the prior earthquake damage on the response of reinforced concrete structures to future earthquakes. The motivation has arisen from the heavy damages or collapses that occurred in many reinforced concrete structures following two major earthquakes that recently occurred in the Marmara Region, Turkey.
The analysis tool employed for this purpose is the package named IDARC2D. Deterioration parameters of IDARC's hysteretic model have been calibrated using a search method. In the calibration process experimental data of a total of twenty-two beam and column specimens, tested under constant and variable amplitude displacement histories, has been used. Fine-tuning of deterioration parameters is essential for more realistic predictions about inelastic behavior and structural damage. In order to provide more realistic damage prediction, three ranges of parameters are proposed. Some damage controlling structural parameters have been assessed via a large number of two-dimensional section analyses, inelastic time history and damage analyses of SDOF systems and seismic vulnerability analyses of reinforced concrete buildings. Inelastic time history and damage analyses of numerous SDOF systems have been carried out to determine whether the loading history has an effect on damage and dissipated hysteretic energy. Then this emphasis is directed to the analyses of MDOF systems. In the analyses of the SDOF systems, various forms of constant and variable amplitude inelastic displacement reversals and synthetic ground motions composed of one of the four earthquake records preceded or followed by its modified records acted as a prior or successive earthquake, have been used. The analyses of two five-story R/C buildings have been caried out using synthetic accelerograms comprised of base input provided by the two recorded ground motions. It is shown that both damage progression and cumulative hysteretic energy dissipated along a path seem to depend on the number and amplitude of cycles constituting the path. However, final damage and accumulated hysteretic energy dissipated along a loading path are independent of the ordering of the same number and amplitude cycles along the path. There is a nonlinear relationship between the earthquake excitation intensity and final damage attained in the end. Increase in the acceleration amplitude leads to exponential increase in damage. As the prior earthquake intensity increases the damage from the succeding main earthquake decreases. A definite ground motion acting as prior and successive earthquake causes substantially different amount of damage. Prior earthquake damage does not substantially affect the maximum drift response in future larger earthquakes. A MDOF frame type structure with aprior damage suffers less overall damage in an earthquake in comparison with the one without a prior damage.
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Oakley, Sharon Yvonne. "On the high- and low-cycle fatigue of aero-engine compressor blades following foreign object damage." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403979.
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Saiedi, Mohammad Reza. "Behaviour of CFRP-Prestressed Concrete Beams under Sustained Loading and High-Cycle Fatigue at Low Temperature." Thesis, Kingston, Ont. : [s.n.], 2009. http://hdl.handle.net/1974/5365.
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Jiang, Haichun [Verfasser], Sandra [Akademischer Betreuer] Korte-Kerzel, and Jürgen Rainer [Akademischer Betreuer] Hirsch. "Low cycle fatigue in precipitation-strengthened AA6016 alloy / Haichun Jiang ; Sandra Korte-Kerzel, Jürgen Rainer Hirsch." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1211591034/34.
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