A fatigue crack driving force parameter with load ratio effects

Kujawski, Daniel

doi:10.1016/s0142-1123(01)00158-x

Cited by 196 publications

(92 citation statements)

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“…Tanto para as curvas com R = 0,7 quanto para as com R = 0,1, o ajuste matemático de Hartman e Schijve [14], em geral, proporcionou o modelamento mais adequado. Efetuando os cálculos para a utilização do parâmetro K⃰ [15], foram encontrados para α os valores médios apresentados na Tabela 3 e "plotados" os gráficos apresentados na Figura 7. Pode-se observar que nas curvas da/dN x K⃰ o efeito da razão R diminui consideravelmente, porém, para a maioria dos aços, a região próxima ao ∆KTH está bastante dispersa.…”

Section: Resultsunclassified

“…onde: da/dN: taxa de crescimento de trinca por fadiga ∆K: força motriz para crescimento de trinca por fadiga ∆KTH: limiar de força motriz KC: tenacidade à fratura R: relação entre tensões na fadiga C, D, λ, m, n, p, q: constantes de ajustes A Equação 7 apresenta um parâmetro de força motriz, K⃰ , proposto por Kujawski [15], que não invoca dados de fechamento de trinca, mas consolida os dados para diferentes razões R em uma única banda de dispersão. Isto é, este parâmetro tenta unificar as curvas da taxa de crescimento de trinca por fadiga para diferentes razões R, minimizando os efeitos de R. * = ( á ) (∆ + ) 1− (7) onde α é um parâmetro de correlação e ∆K + = ∆K para R ≥ 0.…”

Section: Materiais E Métodosunclassified

“…Deve-se, então, fazer um gráfico com os valores de α versus log da/dN, obtendo-se assim um valor médio para α. Quando este α médio é determinado, a Equação 7 pode ser usada para reunir os dados de crescimento de trinca por fadiga com diferentes razões R em uma curva "mestre" ou faixa de dispersão [15]. …”

Section: Materiais E Métodosunclassified

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Efeito Da Razão R Entre Tensões Na Resistência Ao Crescimento De Trinca Por Fadiga De Cinco Aços De Aplicação Em Trilho Ferroviário

Vilela¹,

Godefroid²,

Cândido³

et al. 2017

Anais Do Congresso Anual Da ABM

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ResumoNeste trabalho foi avaliado o comportamento de propagação de trinca por fadiga de cinco aços utilizados na fabricação de trilhos empregados na construção e manutenção de vias permanentes brasileiras, por meio da realização de ensaios de propagação de trinca por fadiga (da/dN x ΔK), utilizando-se a razão de tensões de carregamento R = 0,7 e comparação com os resultados obtidos com R = 0,1. Vários modelos de previsão do comportamento em fadiga foram avaliados. Observou-se a influência de R nos valores mais próximos ao limiar ΔKTH, com diminuição considerável no valor de ΔKTH para R = 0,7. Dentre os modelos matemáticos usados no ajuste das curvas sigmoidais da/dN x ΔK, o que forneceu melhor ajuste foi o ajuste de Hartman e Schijve. O parâmetro K⃰ proposto por Kujawski reduziu os efeitos de R na tentativa de unificar os dados em uma única e estreita banda de dispersão, porém, na Região I da curva, os dados ainda ficaram bastante dispersos. Palavras-chave: Resistência ao crescimento de trinca por fadiga; Razão R; Modelos de ajuste; Trilho ferroviário. EFFECT OF LOAD RATIO, R, ON FATIGUE CRACK GROWTH RESISTANCE OF FIVE STEELS FOR RAILROAD APPLICATION AbstractThis study evaluated the fatigue crack propagation of five steels used in the manufacture of rails used in the construction and maintenance of Brazilian railroads, conducting fatigue crack propagation tests (da/dN x ∆K) with load ratio R = 0.7 and comparing with results obtained with R = 0.1. Many models are used to evaluate the fatigue behavior of the steels. It is noticed the influence of R closer to ∆KTH values, with considerable decrease in ∆KTH value for R = 0.7. Among the mathematical models used in the setting of sigmoidal curves da/dN x ∆K, the setting of Hartman and Schijve provided the best fit. The K⃰ parameter proposed by Kujawski reduced the effects of R in an attempt to unify the data into single, narrow band dispersion; however in Region I of the curve the data were still widespread.

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Section: Resultsunclassified

Section: Materiais E Métodosunclassified

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Efeito Da Razão R Entre Tensões Na Resistência Ao Crescimento De Trinca Por Fadiga De Cinco Aços De Aplicação Em Trilho Ferroviário

Vilela¹,

Godefroid²,

Cândido³

et al. 2017

Anais Do Congresso Anual Da ABM

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“…The effect of stress ratio on FCGR has been investigated by other researchers (e.g., [21][22][23][24][25]) and different driving forces have been identified for FCGR. As stated earlier, the study on FCGR of AM60B in our research group was initiated by Nur Hossain and Taheri [17].…”

Section: Fatigue Crack Growth In Am60bmentioning

confidence: 99%

Microstructure and Fatigue Characteristic of AM60B Magnesium Alloy

Taheri‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

You

Mehrzadi

2012

Metals

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This paper summarizes and reviews the findings of our research on AM60B magnesium alloy conducted in past 8 years. It essentially covers three categories: microstructural study, environmental effect, and fatigue crack growth rate of AM60B. The experimental and numerical studies on the influence of casting defects on this particular material's properties are reviewed in the first part. It has been shown that the non-uniform solidification of the casting results in variations of the microstructure in different layers (skin and core) of the alloy which affects the mechanical properties in those regions. Moreover, the influence of microstructure on fatigue crack initiation and propagation response of the alloy is presented. The influence of several casting defects on the failure mechanism of the material are also numerically analyzed and discussed. The influence of elevated and cold temperatures on the fatigue response of the alloy is reviewed in the second part. Our findings show that the temperature does not have a significant effect on the number of cycles to failure. However, but at some stress level, this effect cannot be dismissed. The fatigue crack growth rate (FCGR) response of the alloy at a wide range of stress ratios is also investigated in the last part. The FCGR of the alloy showed a noticeable dependency on the stress ratio. A model is proposed for estimating the FCGR of the alloy, which could provide a good prediction of alloy's FCGR over a wide range of negative and positive stress ratios. The integrity of the new model is also compared against other models. Finally, the influence of compressive loading on fatigue life of the specimens under constant and random amplitude cyclic loading is investigated experimentally. OPEN ACCESSMetals 2012, 2 412

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“…Among the fracture mechanics-based approaches, Walker [15] and more recently Vasudevan et al [16], Kujawsky [17,18] and Stoychev and Kujawsky [19] proposed the parameter:…”

Section: Introductionmentioning

confidence: 99%

The specific heat loss combined with the thermoelastic effect for an experimental analysis of the mean stress influence on axial fatigue of stainless steel plain specimens

Meneghetti

Ricotta²,

Atzori³

2014

Frattura Ed Integrità Strutturale

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ABSTRACT. The energy dissipated to the surroundings as heat in a unit volume of material per cycle, Q, was recently proposed by the authors as fatigue damage index and it was successfully applied to correlate fatigue data obtained by carrying out fully reversed stress-and strain-controlled fatigue tests on AISI 304L stainless steel plain and notched specimens. The use of the Q parameter to analyse the experimental results led to the definition of a scatter band having constant slope from the low-to the high-cycle fatigue regime. In this paper the energy approach is extended to analyse the influence of mean stress on the axial fatigue behaviour of unnotched cold drawn AISI 304L stainless steel bars. In view of this, stress controlled fatigue tests on plain specimens at different load ratios R (R=-1; R=0.1; R=0.5) were carried out. A new energy parameter is defined to account for the mean stress effect, which combines the specific heat loss Q and the relative temperature variation due to the thermoelastic effect corresponding to the achievement of the maximum stress level of the stress cycle. The new two-parameter approach was able to rationalise the mean stress effect observed experimentally. It is worth noting that the results found in the present contribution are meant to be specific for the material and testing condition investigated here.

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A fatigue crack driving force parameter with load ratio effects

Cited by 196 publications

References 20 publications

Efeito Da Razão R Entre Tensões Na Resistência Ao Crescimento De Trinca Por Fadiga De Cinco Aços De Aplicação Em Trilho Ferroviário

Efeito Da Razão R Entre Tensões Na Resistência Ao Crescimento De Trinca Por Fadiga De Cinco Aços De Aplicação Em Trilho Ferroviário

Microstructure and Fatigue Characteristic of AM60B Magnesium Alloy

The specific heat loss combined with the thermoelastic effect for an experimental analysis of the mean stress influence on axial fatigue of stainless steel plain specimens

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