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Yibing Xiang - One of the best experts on this subject based on the ideXlab platform.
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crack growth based fatigue life prediction using an equivalent Initial Flaw model part i uniaxial loading
International Journal of Fatigue, 2010Co-Authors: Yibing XiangAbstract:A general methodology is proposed in this paper for fatigue-life prediction using crack growth analysis. This is the part II of the paper and focuses on the fatigue-life prediction under proportional and nonproportional multiaxial loading. The proposed multiaxial fatigue-life prediction is based on a critical plane-based multiaxial fatigue damage model and the Equivalent Initial Flaw Size (EIFS) concept. An equivalent stress intensity factor under general multiaxial proportional and nonproportional loading is defined. The fatigue life is predicted by integration of the crack growth rate curve from the EIFS to the critical crack length. The proposed model can automatically adapt for different materials experiencing different local failure modes. The numerical fatigue-life prediction results calculated by the proposed approach are validated with experimental data for a wide range of metallic materials available in the literature. Reasonable agreements are observed between the model predictions and the experimental observations under proportional and nonproportional loading.
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crack growth based fatigue life prediction using an equivalent Initial Flaw model part i uniaxial loading
International Journal of Fatigue, 2010Co-Authors: Yibing Xiang, Zizi LuAbstract:A general methodology is proposed in this paper for fatigue life prediction using crack growth analysis. Part I of the paper focuses on the fatigue life prediction for smooth and notched specimens under uniaxial loading. Part II of the paper focuses on the fatigue life prediction under proportional and non-proportional multiaxial loading. The proposed methodology is based on a previously developed equivalent Initial Flaw Size (EIFS) concept. The EIFS is determined by the Kitagawa–Takahashi diagram and does not require back-extrapolation calculation. Fatigue lives of smooth specimens can be predicted using crack growth analysis with the Initial crack length equaling to the EIFS. An asymptotic interpolation method is used to estimate the stress intensity factor (SIF) solution for short and long cracks at notches and is used for fatigue life prediction of notched specimens. The well-known fatigue notch effect is discussed using the proposed EIFS methodology. Various experimental data of different metallic materials are used to validate the proposed methodology and reasonable agreement is observed between model predictions and experimental data.
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Probabilistic damage tolerance analysis considering shot peening effect
50th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2009Co-Authors: Yibing Xiang, Yongming LiuAbstract:Peening process is a widely used method to improve fatigue strength of metals. It has been shown that the increased fatigue performance is mainly due to compressive residual stress near specimen surface during peening processes. However, the damage tolerance analysis directly using the residual stress profile after manufacturing will have a very nonconservative prediction results. A detailed mechanism model is proposed to capture the physics of fatigue damage accumulation of shot peened specimens. The proposed methodology is based on the Equivalent Initial Flaw Size (EIFS) concept and the asymptotic stress intensity factor solution of notched specimen. Two detrimental effects of the fatigue behavior of shot peened specimens are included into the proposed methodology. One is the residual stress relaxation and the other is the increased surface roughness. Time varying residual stress and the surface notch depth (roughness) are included in the EIFS life prediction methodology for damage tolerance analysis. A simplified probabilistic damage tolerance analysis model is proposed. The developed probabilistic damage tolerance analysis methodology is compared with various experimental data under different shot peening conditions and very good agreement is observed between model predictions and experimental data.
Mh Aliabadi - One of the best experts on this subject based on the ideXlab platform.
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Statistical inference of the equivalent Initial Flaw Size for assembled plate structures with the dual boundary element method
'Elsevier BV', 2020Co-Authors: Morse L, Sharif Khodaei Z, Mh AliabadiAbstract:The statistical inference of the Equivalent Initial Flaw Size Distribution (EIFSD) is developed for the first time using the Dual Boundary Element Method (DBEM) for assembled shear deformable plate structures. As part of this inference procedure, Bayesian updating is employed to enable the continuous refinement of the EIFSD via data obtained by many simulated routine inspections of a stiffened panel from a fleet of aircraft. Fatigue crack growth is modelled using an incremental crack growth procedure that only requires modelling of the boundary of the 2.5D structure with line elements and requires no remeshing during crack growth simulations. Stochastic Kriging is employed to account for the stochastic nature of fatigue crack growth and to offset the high computational cost associated with modelling complex built-up structures. To demonstrate the efficiency of the proposed inference methodology, a numerical example featuring a stiffened panel subjected to complex loading in the form of combined tension and bending is presented. Once the EIFSD has been inferred, it can be used to optimise the intervals between routine aircraft inspections via the use of reliability analysis techniques as part of a combined reliability-EIFS approach. It is demonstrated that the proposed methodology offers the capability to reduce the costs associated with inspections
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a multi fidelity modelling approach to the statistical inference of the equivalent Initial Flaw Size distribution for multiple site damage
International Journal of Fatigue, 2019Co-Authors: Llewellyn Morse, Zahra Sharif Khodaei, Mh AliabadiAbstract:Abstract A new methodology for the statistical inference of the Equivalent Initial Flaw Size Distribution (EIFSD) using the Dual Boundary Element Method (DBEM) is proposed. As part of the inference, Bayesian updating is used to calibrate the EIFS based on data obtained from simulated routine inspections of a structural component from a fleet of aircraft. An incremental crack growth procedure making use of the DBEM is employed for the modelling of the simultaneous growth of cracks in the structure due to fatigue. Multi-fidelity modelling, in the form of Co-Kriging, is used to create surrogate models that act in place of the DBEM model for the expensive Monte Carlo sampling procedure required for the statistical inference of the EIFSD. The proposed methodology is applied to a numerical example featuring a long fuselage lap joint splice in the presence of Multiple Site Damage (MSD). Results show that the EIFSD can be accurately estimated within 10% error with data from just 50 inspections. The employed Co-Kriging models proved to be effective substitutes for the DBEM model, providing significant reductions in the computational cost associated with the implementation of the proposed statistical inference methodology.
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A multi-fidelity modelling approach to the statistical inference of the equivalent Initial Flaw Size distribution for multiple-site damage
'Elsevier BV', 2018Co-Authors: Morse L, Sharif Khodaei Z, Mh AliabadiAbstract:Abstract: A new methodology for the statistical inference of the Equivalent Initial Flaw Size distribution (EIFSD) using the Dual Boundary Element Method (DBEM) is proposed. As part of the inference, Bayesian updating is used to calibrate the EIFS based on data obtained from simulated routine inspections of a structural component from a fleet of aircraft. An incremental crack growth procedure making use of the DBEM is employed for the modelling of the simultaneous growth of cracks in the structure due to fatigue. Multi-fidelity modelling, in the form of Co-Kriging, is used to create surrogate models that act in place of the DBEM model for the expensive Monte Carlo sampling procedure required for the statistical inference of the EIFSD. The proposed methodology is applied to a numerical example featuring a long fuselage lap joint splice in presence of multiple site damage (MSD). Results show that the EIFSD can be accurately estimated with data from 50 inspections. The employed Co-Kriging models proved to be effective substitutes for the DBEM model, providing significant reductions in the computational cost associated with the implementation of the proposed statistical inference methodology. Abbreviations: EIFSD Equivalent Initial Flaw Size Distribution, MSD Multiple Site Damage, DBEM Dual Boundary Element Metho
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A multi-fidelity modelling approach to the statistical inference of the equivalent Initial Flaw Size distribution for multiple-site damage
'Elsevier BV', 2018Co-Authors: Morse L, Sharif Khodaei Z, Mh AliabadiAbstract:A new methodology for the statistical inference of the Equivalent Initial Flaw Size distribution (EIFSD) using the Dual Boundary Element Method (DBEM) is proposed. As part of the inference, Bayesian updating is used to calibrate the EIFS based on data obtained from simulated routine inspections of a structural component from a fleet of aircraft. An incremental crack growth procedure making use of the DBEM is employed for the modelling of the simultaneous growth of cracks in the structure due to fatigue. Multi-fidelity modelling, in the form of Co-Kriging, is used to create surrogate models that act in place of the DBEM model for the expensive Monte Carlo sampling procedure required for the statistical inference of the EIFSD. The proposed methodology is applied to a numerical example featuring a long fuselage lap joint splice in presence of multiple site damage (MSD). Results show that the EIFSD can be accurately estimated with data from 50 inspections. The employed Co-Kriging models proved to be effective substitutes for the DBEM model, providing significant reductions in the computational cost associated with the implementation of the proposed statistical inference methodology
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Statistical inference of the equivalent Initial Flaw Size distribution using the boundary element method under multiple sources of uncertainty
'Trans Tech Publications Ltd.', 2018Co-Authors: Morse L, Sharif Khodaei Z, Mh AliabadiAbstract:In this work, a method for determining the Equivalent Initial Flaw Size (EIFS) distribution using the Boundary Element Method (BEM) is proposed. Maximum Likelihood Estimation (MLE) is used to infer the EIFS distribution of a cracked stiffened panel under multiple sources of uncertainty, including uncertainty in the loading conditions, fatigue crack growth model parameters, and in the measurement of crack Size found from routine inspections. Results suggest that MLE is an effective tool for estimating the parameters of an EIFS distribution when no prior knowledge is available regarding the EIFS distribution or its parameters
Sankaran Mahadevan - One of the best experts on this subject based on the ideXlab platform.
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statistical inference of equivalent Initial Flaw Size with complicated structural geometry and multi axial variable amplitude loading
International Journal of Fatigue, 2010Co-Authors: Shankar Sankararaman, You Ling, Sankaran MahadevanAbstract:Abstract This paper presents several efficient statistical inference techniques to calibrate the equivalent Initial Flaw Size (EIFS) of fatigue cracks for mechanical components with complicated geometry and multi-axial, variable amplitude loading. Finite element analysis is used to address the complicated geometry and calculate the stress intensity factors. Multi-modal stress intensity factors due to multi-axial loading are combined to calculate an equivalent stress intensity factor using a characteristic plane approach. During cycle-by-cycle integration of the crack growth law, a Gaussian process surrogate model is used to replace the expensive finite element analysis, resulting in rapid computation. Experimental data (crack Size after a particular number of loading cycles) and statistical methods are used to calibrate the EIFS. The methods of least squares and maximum likelihood method are extended to evaluate the entire probability distribution of EIFS. Bayesian techniques are also implemented for this purpose. A fast numerical integration technique is developed as an efficient alternative to the expensive Markov Chain Monte Carlo sampling approach in the Bayesian analysis. An application problem of cracking in a cylindrical structure is used to illustrate the proposed methods.
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probabilistic fatigue life prediction using an equivalent Initial Flaw Size distribution
International Journal of Fatigue, 2009Co-Authors: Sankaran MahadevanAbstract:A new methodology is proposed in this paper to calculate the equivalent Initial Flaw Size (EIFS) distribution. The proposed methodology is based on the Kitagawa–Takahashi diagram. Unlike the commonly used back-extrapolation method for EIFS calculation, the proposed methodology is independent of applied load level and only uses fatigue limit and fatigue crack threshold stress intensity factor. The advantage of the proposed EIFS concept is that it is very efficient in calculating the statistics of EIFS. The developed EIFS methodology is combined with probabilistic crack growth analysis to predict the fatigue life of smooth specimens. Model predictions are compared with experimental observations for various metallic materials.
Erian A Armanios - One of the best experts on this subject based on the ideXlab platform.
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simultaneous uncertainty quantification of fracture mechanics based life prediction model parameters
International Journal of Fatigue, 2007Co-Authors: Richard J Cross, Andrew Makeev, Erian A ArmaniosAbstract:A Bayesian technique is developed for simultaneous estimation of the equivalent Initial Flaw Size (EIFS) and crack growth rate distributions in fracture mechanics based life prediction models from inspection data. The inference method separately quantifies the different sources of variability to obtain a data set independent EIFS distribution without the requirement for prior knowledge of the uncertainties in other parameters. The ability to simultaneously and accurately predict the EIFS distribution and crack growth rate noise from a small, highly-scattered data set is demonstrated in a numerical example.
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a concept for quantifying equivalent Initial Flaw Size distribution in fracture mechanics based life prediction models
International Journal of Fatigue, 2007Co-Authors: Andrew Makeev, Yuri Nikishkov, Erian A ArmaniosAbstract:A stochastic regression analysis technique for the prediction of equivalent Initial Flaw Size (EIFS) distributions based on crack Size against time data is presented. This technique correctly accounts for the variability of multiple crack growth drivers to enable a data set independent EIFS distribution. A numerical example illustrates the accuracy of the predicted EIFS distribution in the presence of noise in the crack growth rate data, and shows the applicability of the developed stochastic regression analysis technique to small data sets with large scatter.
Shan Jiang - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Life Prediction Using Strain Intensity Factor and Equivalent Initial Flaw Size
2020Co-Authors: Wei Zhang, Qiang Wang, Huili Liu, Shan JiangAbstract:ABSTRACT In this paper, an effective approach is developed to evaluate fatigue life of smooth specimens of 316 austenitic stainless steel under the fully reversed loading condition based on strain intensity factor and the equivalent Initial Flaw Size (EIFS) concept. The strain intensity factor is indicated to be a better driving parameter to correlate with the fatigue crack growth rate, especially for the fully reversed load condition and the low cycle fatigue region. EIFS is an effective approach to account for complex process of the crack initiation and small crack propagation, which can be calculated by correlating the fatigue limit strain with fatigue threshold strain intensity factor. The fatigue limit strain is obtained from experimental data by analyzing the asymptotic behavior of the fatigue life curve. The driving force of crack growth is expressed in strain intensity factor. Then the fatigue life could be calculated by integrating the crack growth rate from integral lower limit EIFS to integral upper limit critical crack length a c . The experimental data of 316 austenitic stainless steel are employed to validate the proposed model. The good agreements are observed. It has shown that strain-intensity-factor-based approach could be a good method for fatigue life evaluation
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fatigue life prediction based on crack closure and equivalent Initial Flaw Size
Materials, 2015Co-Authors: Qiang Wang, Wei Zhang, Shan JiangAbstract:Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent Initial Flaw Size (EIFS) concept are employed. Different effects of crack closure on small crack growth region and long crack growth region are considered in the proposed method. The EIFS is determined by the fatigue limit and fatigue threshold stress intensity factor △Kth. Fatigue limit is directly obtained from experimental data, and △Kth is calculated by using a back-extrapolation method. Experimental data for smooth and circular-hole specimens in three different alloys (Al2024-T3, Al7075-T6 and Ti-6Al-4V) under multiple stress ratios are used to validate the method. In the validation section, Semi-circular surface crack and quarter-circular corner crack are assumed to be the Initial crack shapes for the smooth and circular-hole specimens, respectively. A good agreement is observed between model predictions and experimental data. The detailed analysis and discussion are performed on the proposed model. Some conclusions and future work are given.