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The prediction of fatigue life of asphalt mixtures using four-point bending tests

Pais, Jorge; Minhoto, Manuel
Fonte: ARRB Group Ltd and Authors 2010 Publicador: ARRB Group Ltd and Authors 2010
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
691.6452%
Fatigue resistance is used in the analysis and design of pavements to predict their life cycle. The results of fatigue tests are expressed in terms of the number of cycles for the tensile strain level applied. Two constants (k1 and k2) take part in this relationship. To know these two constants, at least two fatigue tests are needed, performed at different strain levels to obtain those constants. However, based on laboratory results analysis, k1 and k2 can be correlated and, in this case, the relationship between the fatigue life and the strain level has only one constant, which can be evaluated using the results obtained by a fatigue test. This paper presents the evaluation of the k1 and k2 relationship for Portuguese mixtures based on the results obtained from more than 50 different asphalt mixtures and the prediction of only one of those constants with fatigue test results. The paper also presents an analysis of the fatigue life using fatigue laws with only one constant.

Fatigue life predictions in polymer particle composites

Antunes, F. V.; Ferreira, J. M.; Costa, J. D.; Capela, C.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
Português
Relevância na Pesquisa
683.4916%
This paper presents a study on fatigue life predictions in three polymer particle composites with different volume fractions of filler and different particle sizes. Central hole notched specimens were analysed using a fracture mechanics approach. A solution for the stress intensity factor of corner cracks at a hole was obtained using the finite element method and considering quarter-circular and quarter-elliptical cracks of different sizes. The solution was compared with a literature solution and significant differences were found. Fatigue crack propagation tests were performed at room temperature and constant loading amplitude, for stress ratios R=0 and R=-0.75. Finally, fatigue lives, crack shape evolution and final crack length were predicted assuming an initial crack size and considering that the crack maintains a quarter-elliptical shape. The comparison with experimental fatigue lives indicated the presence of initial defects larger than the silica particles; however, these large sizes can be explained by the residual stresses measured near the hole.; http://www.sciencedirect.com/science/article/B6V35-454FDJ5-7/1/4231c9abb6a4b1b364cde431359b1e14

Fatigue life and failure modes of crowns systems with a modified framework design

LORENZONI, Fabio C.; MARTINS, Leandro M.; SILVA, Nelson R. F. A.; COELHO, Paulo G.; GUESS, Petra C.; BONFANTE, Estevam A.; THOMPSON, Van P.; BONFANTE, Gerson
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
692.8984%
Objectives: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. Methods: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n = 10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n = 10 each). Fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300 N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. Results: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups...

The beta-Birnbaum-Saunders distribution An improved distribution for fatigue life modeling

CORDEIRO, Gauss M.; LEMONTE, Artur J.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
675.54086%
Birnbaum and Saunders (1969a) introduced a probability distribution which is commonly used in reliability studies For the first time based on this distribution the so-called beta-Birnbaum-Saunders distribution is proposed for fatigue life modeling Various properties of the new model including expansions for the moments moment generating function mean deviations density function of the order statistics and their moments are derived We discuss maximum likelihood estimation of the model s parameters The superiority of the new model is illustrated by means of three failure real data sets (C) 2010 Elsevier B V All rights reserved; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP (Brazil)

Um modelo para previsão de vida à fadiga de juntas soldadas submetidas a carregamentos combinados.; A fatigue life prediction model of welded joints under combined cyclic loading.

Goes, Keurrie Cipriano
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/04/2010 Português
Relevância na Pesquisa
593.1905%
O presente trabalho teve como objetivo desenvolver uma metodologia prática e confiável para previsão de vida à fadiga de juntas soldadas a cordão pelo processo MIG/MAG, quando estas estão submetidas a carregamentos cíclicos combinados. A máxima tensão linear no pé da solda, região típica de início de trinca, conhecida como hot spot foi utilizada para prever a vida através do método de Fadiga de Alto Ciclo S x N (Tensão x Vida), largamente empregado em códigos de projeto de estruturas soldadas. O Método dos Elementos Finitos foi utilizado para determinação das tensões estruturais resultantes do carregamento e das descontinuidades geométricas presentes nos cordões de solda. A análise de fadiga foi efetuada em ambiente virtual, através de um software (programa) de fadiga capaz de importar as tensões atuantes na região da solda para cada carregamento, combinando-as e obtendo assim a vida à fadiga decorrente da somatória dos diferentes tipos de carregamento ao qual a junta foi submetida. As propriedades monotônicas e cíclicas dos materiais da junta foram obtidas da literatura e de um extenso banco de dados disponível no software de fadiga. Estas propriedades foram ajustadas com base em ensaios de laboratório nas juntas investigadas. A medição ou modelagem das tensões residuais inerentes ao processo de soldagem não fazem parte do escopo deste trabalho. Contudo...

Tensões residuais induzidas por shot-peening e durabilidade de molas em lâmina.; Residual stresses induced by shot-peening and fadigue life of leaf springs.

Scuracchio, Bruno Geoffroy
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/11/2012 Português
Relevância na Pesquisa
589.4884%
O aumento da vida em fadiga em peças submetidas a esforços cíclicos devido à aplicação de processos de tratamento mecânico superficial já é bastante conhecido, tanto no meio industrial quanto no meio acadêmico. Para molas, o processo de shot-peening se torna etapa essencial no processo de fabricação, porém um estudo sistemático do efeito do shot-peening na vida em fadiga se faz necessário. O objetivo deste trabalho é aprofundar o conhecimento nos processos de jateamento superficial do tipo shot-peening para molas em lâminas de veículos, através da análise de tensões residuais por difração de raios-x e ensaios de fadiga em uma série de amostras que sofreram dez diferentes receitas de processos de jateamento. Dos dez diferentes processos, o de jateamento com granalha esférica fundida de aço com 1,0mm de diâmetro seguido de um segundo jateamento com granalha esférica fundida de aço de 0,3mm de diâmetro levou a uma maior vida em fadiga das amostras. A análise por difração de raios-x comprovou que a importância das tensões residuais de compressão se dá até a uma profundidade de 0,05mm, influenciando diretamente no modo de nucleação de trincas de fadiga. Acima desta profundidade, as tensões residuais induzidas por shot-peening não têm influência no modo de propagação destas trincas...

Avaliação da vida à fadiga em materiais homogêneos e juntas soldadas incluindo efeitos de fechamento de trinca.; Fatigue life evaluation of homogeneous materials and welded joints including effects of crack closure.

Sarzosa Burgos, Diego Felipe
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/04/2012 Português
Relevância na Pesquisa
592.8168%
Esta tese investiga o efeito do fechamento de trinca sobre as previsões da vida à fadiga em materiais homogêneos e juntas soldadas. É apresentada uma metodologia para a simulação numérica do fenômeno de fechamento de trinca induzido por plasticidade utilizando o método dos elementos finitos. Ensaios laboratoriais de propagação de trinca por fadiga do aço ASTM A516 Gr. 70 à temperatura ambiente foram realizados usando corpos de prova típicos da mecânica da fratura nas condições soldada e homogênea. Estes resultados foram usados para validar a metodologia numérica do cálculo da carga de abertura de trinca. Comparações entre a vida de propagação experimental e as estimativas obtidas por meio da integração da lei de propagação, incluindo o efeito do fechamento de trinca, foram feitas usando vários critérios para o cálculo da carga de abertura. As análises numéricas permitem estimar a carga de abertura de trinca analisando a evolução do campo de tensões, deformações e deslocamentos na região próxima à trinca, que está influenciada pelo contato das faces da trinca. Menores níveis de proteção da trinca devido ao fechamento foram obtidos para o corpo com heterogeneidade mecânica quando comparado ao corpo homogêneo na modelagem numérica. Durante o ensaio de propagação o corpo homogêneo apresentou taxas de propagação de trinca relativamente menores quando comparadas ao espécime soldado. A não inclusão do efeito do fechamento de trinca resulta em previsões da vida à fadiga conservadoras em aproximadamente 20% para todos os casos estudados neste trabalho. Análises tridimensionais do fenômeno de fechamento de trinca revelam que o crescimento da trinca por fadiga no estagio II parece estar controlado pelo retardo que acontece na superfície do corpo de prova. Incluído o efeito do fechamento de trinca nas previsões...

Influência do processo de fabricação do disco na vida em fadiga de rodas para veículos comerciais fabricadas com o aço S355JR; The influence of the disc manufacturing process on the fatigue life of the commercial vehicle wheels manufactured using S355JR steel

Spagnol, Nicholas João Ramos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/09/2014 Português
Relevância na Pesquisa
687.08336%
A disputa por espaço no mercado automotivo tem sido intensificada a cada ano. A cobrança por componentes mais leves e de menor custo aliados à preocupação ambiental têm exigido a busca de novas alternativas de materiais e/ou processos produtivos mais eficientes. Uma das respostas a estas tendências é o aumento significativo no uso de aços de alta resistência baixa liga e dual phase nos últimos anos a fim de reduzir peso dos componentes. Entretanto, o custo destes aços no Brasil está entre 20 a 40% maior que os aços baixo carbono. Desta forma, para alguns segmentos está descartada esta hipótese, pois o mercado brasileiro exige redução de peso aliada à redução de custo. Sendo assim, a melhoria do processo produtivo ganha força nesta disputa. O processo de repuxamento (spinning) tem sido utilizado há anos para produção do componente disco de rodas para veículos comerciais e é um processo de trabalho à frio severo, o que pode resultar em aumento das propriedades mecânicas do material e redução do uso de matéria-prima em função da porcentagem da redução de espessura proposta. Sendo assim, neste trabalho foram analisadas 3 condições de repuxamento de disco, 41% de redução de espessura, 52% de redução de espessura e 64% de redução de espessura a fim de se obter o limite de redução de espessura do material S355JR por meio do processo de repuxamento do disco sem que haja perda das propriedades mecânicas do mesmo e...

The prediction of fatigue life of asphalt mixtures using four-point bending tests

Pais, Jorge C.; Minhoto, Manuel J. C.
Fonte: ARRB Group Publicador: ARRB Group
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 Português
Relevância na Pesquisa
589.6082%
Fatigue resistance is used in the analysis and design of pavements to predict their life cycle. The results of fatigue tests are expressed in terms of the number of cycles for the tensile strain level applied. Two constants (k1 and k2) take part in this relationship. To know these two constants, at least two fatigue tests are needed, performed at different strain levels to obtain those constants. However, based on laboratory results analysis, k1 and k2 can be correlated and, in this case, the relationship between the fatigue life and the strain level has only one constant, which can be evaluated using the results obtained by a fatigue test. This paper presents the evaluation of the k1 and k2 relationship for Portuguese mixtures based on the results obtained from more than 50 different asphalt mixtures and the prediction of only one of those constants with fatigue test results. The paper also presents an analysis of the fatigue life using fatigue laws with only one constant.

The effect of using rest periods in 4PB tests on the fatigue life of grouted macadams

Oliveira, J. R. M.; Pais, Jorge C.; Thom, N. H.; Zoorob, S.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2009 Português
Relevância na Pesquisa
686.9902%
Four-point bending tests are commonly used to assess the fatigue resistance of bi-tuminous bound materials that are used in road pavements. However, it is difficult to establish a reliable relationship between the laboratory test results and the field performance of the mate-rial. In order to predict the real life of the pavement, shift factors are normally used to convert the fatigue results obtained in the laboratory onto the actual fatigue life of the material in the field. Those shift factors depend on the type of test used, the testing conditions and the type of mixture used. In this study, an attempt was made to establish a shift factor for grouted mac-adams, based on four-point bending fatigue test results carried out with rest periods between the loading cycles. The result obtained was used to define a fatigue criterion for pavement design with grouted macadams.

Improvement of permanent deformation and fatigue life of bituminous mixtures by using modified bitumens

Pereira, Paulo A. A.; Pais, Jorge C.; Azevedo, M. C. M.
Fonte: Tapir Academic Press Publicador: Tapir Academic Press
Tipo: Conferência ou Objeto de Conferência
Publicado em //2000 Português
Relevância na Pesquisa
675.54086%
This paper describes the results of a study aiming the evaluation of pavement performance improvement by using a polymer modified bitumen as binder. Two dense graded bituminous mixtures were produced in laboratory. The first one was produced with conventional bitumen and the second one with polymer-modified bitumen. Permanent deformation tests were carried out in a shear servo-hydraulic machine using the repetitive simple shear test at constant height. Fatigue life tests were carried out in an axial servo-hydraulic testing system using a flexural beam. A comparison between these two mixtures was made for tensile strains calculated for a typical flexible pavement structure where these two mixtures were considered.

Effects of cellular growth on fatigue life of directionally solidified hypoeutectic Al-Fe Alloys

Ribeiro,Pryscilla Liberato; Silva,Bismarck Luiz; Silva,Wanderson Santana da; Spinelli,José E
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 Português
Relevância na Pesquisa
688.4408%
Al-Fe hypoeutectic alloys are a family of casting alloys characterized by cell growth, low cost and appreciable formability. It is well known that fatigue strength is a requirement of prime importance considering the nature of load typically observed during operations involving the risers used in oil extraction. The aim of this study is to examine the influence of cell size and its intercellular phase distribution on the fatigue life (Nf) of the directionally solidified Al-0.5, 1.0 and 1.5wt% Fe alloys. A water-cooled vertical upward unidirectional solidification system was used to provide the castings. Microscopy light and SEM microscopy were used. It was found that fatigue life decreases as cell spacing (λ c) increases. Smaller cell spacing allows a homogeneous distribution of Al-Fe fibers to happen within the intercellular regions, which tends to improve the mentioned fatigue property. Hall-Petch type correlations [Nf= Nf0+A(λc -1/2)-B(λc -1); where A and B are constants] seems to be able to encompass the fatigue life variation along the Al-Fe alloys.

Non-linear individual and interaction phenomena associated with fatigue crack growth.

Codrington, John David
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008 Português
Relevância na Pesquisa
596.76883%
The fatigue of materials and structures is a subject that has been under investigation for almost 160 years; yet reliable fatigue life predictions are still more of an empirical art than a science. The traditional safe-life approach to fatigue design is based upon the total time to failure of a virtually defect free component. This approach is heavily reliant on the use of safety factors and empirical equations, and therefore much scatter in the fatigue life predictions is normally observed. Furthermore, the safe-life approach is unsuitable for many important applications such as aircraft, pressure vessels, welded structures, and microelectronic devices. In these applications the existence of initial defects is practically unavoidable and the time of propagation from an initial defect to final failure is comparable with the total life of the component. In the early 1970’s, the aircraft industry pioneered a new approach for the analysis of fatigue crack growth, known as damage tolerant design. This approach utilises fracture mechanics principles to consider the propagation of fatigue cracks from an initial crack length until final fracture, or a critical crack length, is reached. Since the first implementation of damage tolerant design...

Non-local energy based fatigue life calculation method under multiaxial variable amplitude loadings

SAINTIER, Nicolas; PALIN-LUC, Thierry; BÉNABÈS, Jérôme; COCHETEUX, Francis
Fonte: Elsevier Publicador: Elsevier
Português
Relevância na Pesquisa
689.6082%
Reliable design of industrial components against high cycle multiaxial fatigue requires a model capable of predicting both stress gradient and load type effects. Indeed, taking into account gradient effects is of prior importance for the applicability of fatigue models to real structures. In this paper, a fatigue life assessment method is proposed for proportional and non-proportional multiaxial variable amplitude loadings in the range 104 –107 cycles. This method derives from the fatigue criterion initially proposed by Palin-Luc and Lasserre (1998) [2] and revisited by Banvillet et al. (2003) [16] for multiaxial constant amplitude loading. The new proposal consists of a complete reformulation and extension of the previ- ously cited energy based fatigue strength criteria. It includes two major improvements of the existing criteria. The first one consists in a fatigue criterion for multiaxial variable amplitude loadings while only constant amplitude loadings were considered in the above cited works. The second one is an extension to an incremental fatigue life assessment method for proportional and non-proportional multiaxial variable amplitude loadings. No cycle counting technique is needed whatever the variable amplitude load- ings type considered (uniaxial or multiaxial). The predictions of the method for constant and variable amplitude multiaxial loadings are compared with experimental results on specimens from literature and from new experiments on a ferrito-perlitic steel. The above mentioned method has been implemented as a post-processor of a finite element software. An application to a railway wheel is finally presented.; Thèse CIFRE avec la SNCF...

MODELLING OF STRESS GRADIENT EFFECT ON FATIGUE LIFE USING WEIBULL BASED DISTRIBUTION FUNCTION

KAROLCZUK, Aleksander; PALIN-LUC, Thierry
Fonte: PMTS Publicador: PMTS
Português
Relevância na Pesquisa
688.1309%
In the present paper, a new approach is developed in order to take into account the stress gradient effect on fatigue life of structural components. The proposed approach is based on the weakest link concept in which the shape coefficient of the Weibull distribution becomes a function of a local damage parameter. The function simulates the experimentally observed relationship between the shape of the fatigue life distribution and the stress level. Such an approach allows one to calculate the global probability distribution of the fatigue life for notched structural components in a wide range of fatigue life regime: 104-107 cycles typically. For comparison purposes, the approach is applied to calculate the number of cycles to crack initiation of structural elements under three probability levels: 5%, 63% and 95%. The calculated lifetimes are compared with the lifetimes obtained from experiments performed on notched cruciform specimens and notched round specimens subjected to constant amplitude loading.

Low cycle fatigue life improvement of AISI 304 by initial and intermittent wire brush hammering

MAKHLOUF, Kamel; SIDHOM, Naziha; KHLIFI, Ammar; SIDHOM, Habib; BRAHAM, chedly
Fonte: Elsevier Publicador: Elsevier
Português
Relevância na Pesquisa
691.05875%
The effects of hammering by wire brush as a method of improving low cycle fatigue life of highly ductile austenitic stainless steel AISI 304 have been investigated through an experimental study combining imposed strain fatigue tests and assessment of surface characteristic changes under cyclic loading by SEM examinations and XRD analysis. It has been shown that the fatigue life of wire brush hammered surface was increased by 307% at an imposed strain rate of 0.2% and only 17% at an imposed strain rate of 0.5%, comparatively to the turned surface. This increase in fatigue life is explained in terms of fatigue damage that is related to crack networks characteristics and stability which are generated during fatigue on both turned and wire brush hammered surfaces. The improvement of brushed surface is attributed to the role of the surface topography, the near surface stabilized compressive residual stresses and superfi-cial cold work hardening on the fatigue crack network nucleation and growth. It is found that wire brush hammering produces a surface texture that favors, under cyclic loading, nucleation of randomly dispersed short cracks of the order of 40 lm in length stabilized by the compressive residual stress field that reached a value of r0 =

Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

Mostefa,Bendouba; Abdelkrim,Aid; Ali,Benhamena; Mohamed,Benguediab
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 Português
Relevância na Pesquisa
589.50312%
Hole cold expansion (HCE) is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model.

Statistical model prediction of fatigue life for diffusion bonded Inconel 600

Nowicki, Timothy
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
590.3572%
Diffusion bonding is a solid-state joining process, used in a wide range of fields, allowing the joining of both metallic and ceramic materials to create complicated parts and geometries [1]. Diffusion bonded material has been found to contain inherent defects caused by the bond process that have been loosely associated to the lower tensile and fatigue strengths of the parent material [2]. The process is relatively new, and little research has been done to characterize these defects or their relationship to bond quality, with the exception of a recent study that did relate tensile strength to the bond quality [3]. Previous work resulted in successful diffusion bonding of Inconel 600, a high strength super alloy [4], optimization of bond process parameters, and the development of a method for qualitative analysis of bond quality [3]. The first goal of the present research is to develop a 2-dimensional characterization of the diffusion bonding defects for use in predicting fatigue life. Then, by treating the defects as pre-existing cracks, fracture mechanics can be used to predict life to failure based on initial material quality. A Monte Carlo Simulation will be used to capture the variability in the defects and quality of the bond. The overall goal of this research will be to enhance the previous qualitative bond quality assessment by using defect measurements taken with the SEM. This will allow for not only a more quantitative relationship between bond quality and tensile strength...

Fatigue life analysis of a steel trapezoidal box girder bridge using measured strains

Soto Fuentes, Jose Luis
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
589.50312%
Shenton, Harry W.; The Newport Viaduct is a 1,984 feet long bridge owned by the Delaware Department of Transportation located in Newport, DE. During an in-depth inspection in 2006, approximately 665 cracks were discovered near the internal cross frame diaphragm connection plates and the girder webs. A 2.5 inch gap exists between the termination of the diaphragm connection plate and the flanges of the girder. This is a known fatigue prone detail subject to out of plane deformations which lead to the formation of distortion induced fatigue cracks. Previous research done on the Newport Viaduct used global finite element models to estimate the fatigue life of the web gap details and analyze potential retrofit options. The purpose of this project is to measure site specific strains caused by variable traffic loads and use this data to carry out a fatigue life analysis of the web gap details. In order to assist in the fatigue life analysis, localized finite element models of the web gap details were created. Given geometric differences, separate models were created for the top and bottom web gap details. The finite element models were created using FEMAP and solved using ABAQUS. The analysis results showed a high stress gradient in the web gap region with a maximum near the weld toe. Moreover...

Fatigue life prediction of shot peened components

Cláudio,R.A.; Silva,J.M.; Branco,C.M.; Byrne,J.
Fonte: Sociedade Portuguesa de Materiais Publicador: Sociedade Portuguesa de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 Português
Relevância na Pesquisa
687.08336%
Shot peening is one of the most effective surface treatments in order to prevent crack initiation and early crack propagation. Part of the studies to determine the fatigue performance of shot peening are based on experimental tests. Almost no work is published related with the prediction of shot peening behaviour. The present paper evaluates the ability of the current methodologies, used to predict fatigue life, on components treated with shot peening. The Finite Element Method was used to determine the stress, strain and strain energy due to shot peening of some specimens tested experimentally. These results were used to apply methods to predict the total fatigue life. A final discussion is presented about the ability of the methods used, to predict the fatigue life of the specimens tested experimentally.