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M. Lambrigger - One of the best experts on this subject based on the ideXlab platform.

  • Weibull master curves and Fracture Toughness testing Part I Master curves for quasi-static uniaxial tensile and bend tests
    Journal of Materials Science, 1999
    Co-Authors: M. Lambrigger
    Abstract:

    Three types of specimen-size-independent Weibull master curves, characterizing strength and failure of macroscopically homogeneous, brittle materials have been derived. These Weibull master curves are significant if an uniaxial tensile stress is applied to the investigated specimens, as, for example, in the case of quasi-static uniaxial tensile tests or, under some restrictions, in the case of quasi-static three- or four-point bend tests. In addition, the existence of three types of Apparent Fracture Toughness master curves, which can be applied to any material undergoing brittle cleavage Fracture such as ceramics, intermetallics, or structural steels at low homologous temperatures, has been established. Furthermore, the same is also valid for the specimen-size-independent Weibull master curves. The Apparent Fracture Toughness master curves can be obtained, by performing Fracture Toughness tests, or simply by applying a mathematical transformation to the corresponding Weibull master curves, which have been evaluated from quasi-static uniaxial tensile or bend tests.

  • Weibull master curves and Fracture Toughness testing Part II Evaluation of data of quasi-static three-point bend tests of tetragonal zirconia, zirconia/alumina and silicon nitride
    Journal of Materials Science, 1999
    Co-Authors: M. Lambrigger
    Abstract:

    It has already been displayed that a variety of Apparent Fracture Toughness master curves and Weibull master curves exist, which enables an extensive description of the Fracture Toughness of the investigated solids. Therefore, the concept of Weibull master curves has been generalized. In this paper, it is shown that characteristic magnitudes, derived from both experimental Weibull master curves and experimental Apparent Fracture Toughness master curves, can be defined in a new way, by quantifying the amount of microcracking and crack-tip shielding that occurs when materials undergo stable crack growth prior to failure (when a sufficient external load is applied). Experimental data of three-point bend tests of ceria partially stabilized tetragonal zirconia, yttria partially stabilized zirconia/β-alumina-composite, and coarse-grained β-silicon nitride gathered at room temperature have been evaluated. The Weibull master curves, which are obtained by scaling the cumulative failure distribution functions with the corresponding mean-values, have been found to be most appropriate for investigating the Fracture Toughness by quasistatic uniaxial tensile or bend tests.

  • Apparent Fracture Toughness master curve of a zirconia-alumina composite
    Philosophical Magazine A, 1998
    Co-Authors: M. Lambrigger
    Abstract:

    Recently, the existence of specimen-size-independent Weibull master curves characterizing strength and failure of macroscopically homogeneous, brittle materials, if the Weibull modulus m > 1, has been demonstrated by the present author. Furthermore, an Apparent Fracture Toughness master curve M(a) has been derived from experimental Weibull master curves, which can even be applied to materials undergoing an amount of stable crack growth prior to failure. The objective of the present paper is to show that another type of specimen-size-independent Weibull master curves K(y,m), which is obtained by scaling the cumulative failure probability distribution function P(sigma) with the physically, highly significant mean stress = integral(0)(1) sigma dP, can be constructed for every Weibull modulus m > 0. Moreover, an Apparent Fracture Toughness master curve T(b), being physically highly significant and evident, can be derived from the Weibull master curves K(y, m) for every m > 0. T(b) provides characteristic magnitudes, which facilitate a thorough comprehension of the Fracture Toughness of the investigated solids. Therefore the Apparent Fracture Toughness master curve T(b) of an 8 wt% yttria partially stabilized zirconia-20vol.% beta-alumina composite has been evaluated, using data from three-point bend tests performed at room temperature.

  • Apparent Fracture Toughness master curves derived from specimen-size-independent Weibull master curves
    Materials Science and Engineering: A, 1998
    Co-Authors: M. Lambrigger
    Abstract:

    The objective of this paper is to show that Apparent Fracture Toughness master curves can be derived from experimental Weibull master curves of materials undergoing an amount of stable crack growth prior to failure, facilitating the identification of the type of toughening mechanisms operating in the investigated materials. (C) 1998 Elsevier Science S.A. All rights reserved.

A. M. Afsar - One of the best experts on this subject based on the ideXlab platform.

  • analysis of Apparent Fracture Toughness of a thick walled cylinder with an fgm coating at the inner surface containing a radial edge crack
    Journal of The Korean Society for Composite Materials, 2010
    Co-Authors: A. M. Afsar, Sheikh Rasel, Jung-il Song
    Abstract:

    This study analyzes the Apparent Fracture Toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate Apparent Fracture Toughness. The approach is demonstrated for a cylinder with a TiC/ FGM coating and some numerical results of Apparent Fracture Toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the Apparent Fracture Toughness are investigated in details. It is found that all of these factors play an important role in controlling the Apparent Fracture Toughness of the cylinder.

  • Effect of FGM coating thickness on Apparent Fracture Toughness of a thick-walled cylinder
    Engineering Fracture Mechanics, 2010
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    Abstract This study describes the effect of FGM coating thickness on Apparent Fracture Toughness (AFT) of a thick-walled cylinder containing two diametrically-opposed edge cracks emanating from the inner surface of the cylinder. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion because of cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress intensity factor (SIF) addressed in a previous study, an approach is developed to calculate AFT. Some numerical results of AFT are presented for a TiC/Al2O3 FGM coating at the inner surface of an Al2O3 thick-walled cylinder.

  • analysis of Apparent Fracture Toughness of a thick walled fgm cylinder with two diametrically opposed edge cracks
    Fatigue & Fracture of Engineering Materials & Structures, 2009
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    This study focuses on the analysis of Apparent Fracture Toughness of a thick-walled functionally graded material (FGM) cylinder with two diametrically opposed edge cracks emanating from the inner surface of the cylinder. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to non-uniform coefficient of thermal expansion after cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress-intensity factor developed in our previous study, an approach is presented to evaluate Apparent Fracture Toughness. To demonstrate the approach, some numerical results of Apparent Fracture Toughness are presented for a TiC/Al 2 O 3 FGM cylinder. The effects of material distribution, cylinder wall thickness, application temperature and number of cracks on Apparent Fracture Toughness are investigated in details. It is found that all these factors play an important role in controlling Apparent Fracture Toughness of a thick-walled FGM cylinder.

  • Analysis of Apparent Fracture Toughness of a thick‐walled FGM cylinder with two diametrically opposed edge cracks
    Fatigue & Fracture of Engineering Materials & Structures, 2009
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    This study focuses on the analysis of Apparent Fracture Toughness of a thick-walled functionally graded material (FGM) cylinder with two diametrically opposed edge cracks emanating from the inner surface of the cylinder. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to non-uniform coefficient of thermal expansion after cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress-intensity factor developed in our previous study, an approach is presented to evaluate Apparent Fracture Toughness. To demonstrate the approach, some numerical results of Apparent Fracture Toughness are presented for a TiC/Al 2 O 3 FGM cylinder. The effects of material distribution, cylinder wall thickness, application temperature and number of cracks on Apparent Fracture Toughness are investigated in details. It is found that all these factors play an important role in controlling Apparent Fracture Toughness of a thick-walled FGM cylinder.

  • Inverse problem of material distribution for desired Fracture characteristics in a thick-walled functionally graded material cylinder with two diametrically-opposed edge cracks
    Engineering Fracture Mechanics, 2009
    Co-Authors: A. M. Afsar, M. Anisuzzaman, Jung-il Song
    Abstract:

    Abstract This study concerns the inverse problem of evaluating the optimum material distribution for desired Fracture characteristics in a thick-walled functionally graded material (FGM) cylinder containing two diametrically-opposed edge cracks emanating from the inner surface of the cylinder. The thermal eigenstrain developed in the cylinder material due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress intensity factors developed in a previous study, an inverse method is developed to optimize material distribution intending to realize prescribed Apparent Fracture Toughness in the FGM cylinder. To present some numerical results, a TiC/Al2O3 FGM cylinder is considered and the inverse problems are solved to evaluate material distributions for two examples of prescribed Apparent Fracture Toughness. The effect of cylinder wall thickness on the material distribution and comparison of material distributions corresponding to a single and two cracks are also discussed. The numerical results reveal that the Apparent Fracture Toughness of FGM cylinders can be controlled by choosing the material distributions properly.

Jung-il Song - One of the best experts on this subject based on the ideXlab platform.

  • analysis of Apparent Fracture Toughness of a thick walled cylinder with an fgm coating at the inner surface containing a radial edge crack
    Journal of The Korean Society for Composite Materials, 2010
    Co-Authors: A. M. Afsar, Sheikh Rasel, Jung-il Song
    Abstract:

    This study analyzes the Apparent Fracture Toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate Apparent Fracture Toughness. The approach is demonstrated for a cylinder with a TiC/ FGM coating and some numerical results of Apparent Fracture Toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the Apparent Fracture Toughness are investigated in details. It is found that all of these factors play an important role in controlling the Apparent Fracture Toughness of the cylinder.

  • Effect of FGM coating thickness on Apparent Fracture Toughness of a thick-walled cylinder
    Engineering Fracture Mechanics, 2010
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    Abstract This study describes the effect of FGM coating thickness on Apparent Fracture Toughness (AFT) of a thick-walled cylinder containing two diametrically-opposed edge cracks emanating from the inner surface of the cylinder. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion because of cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress intensity factor (SIF) addressed in a previous study, an approach is developed to calculate AFT. Some numerical results of AFT are presented for a TiC/Al2O3 FGM coating at the inner surface of an Al2O3 thick-walled cylinder.

  • analysis of Apparent Fracture Toughness of a thick walled fgm cylinder with two diametrically opposed edge cracks
    Fatigue & Fracture of Engineering Materials & Structures, 2009
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    This study focuses on the analysis of Apparent Fracture Toughness of a thick-walled functionally graded material (FGM) cylinder with two diametrically opposed edge cracks emanating from the inner surface of the cylinder. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to non-uniform coefficient of thermal expansion after cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress-intensity factor developed in our previous study, an approach is presented to evaluate Apparent Fracture Toughness. To demonstrate the approach, some numerical results of Apparent Fracture Toughness are presented for a TiC/Al 2 O 3 FGM cylinder. The effects of material distribution, cylinder wall thickness, application temperature and number of cracks on Apparent Fracture Toughness are investigated in details. It is found that all these factors play an important role in controlling Apparent Fracture Toughness of a thick-walled FGM cylinder.

  • Analysis of Apparent Fracture Toughness of a thick‐walled FGM cylinder with two diametrically opposed edge cracks
    Fatigue & Fracture of Engineering Materials & Structures, 2009
    Co-Authors: A. M. Afsar, Jung-il Song
    Abstract:

    This study focuses on the analysis of Apparent Fracture Toughness of a thick-walled functionally graded material (FGM) cylinder with two diametrically opposed edge cracks emanating from the inner surface of the cylinder. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to non-uniform coefficient of thermal expansion after cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress-intensity factor developed in our previous study, an approach is presented to evaluate Apparent Fracture Toughness. To demonstrate the approach, some numerical results of Apparent Fracture Toughness are presented for a TiC/Al 2 O 3 FGM cylinder. The effects of material distribution, cylinder wall thickness, application temperature and number of cracks on Apparent Fracture Toughness are investigated in details. It is found that all these factors play an important role in controlling Apparent Fracture Toughness of a thick-walled FGM cylinder.

  • Inverse problem of material distribution for desired Fracture characteristics in a thick-walled functionally graded material cylinder with two diametrically-opposed edge cracks
    Engineering Fracture Mechanics, 2009
    Co-Authors: A. M. Afsar, M. Anisuzzaman, Jung-il Song
    Abstract:

    Abstract This study concerns the inverse problem of evaluating the optimum material distribution for desired Fracture characteristics in a thick-walled functionally graded material (FGM) cylinder containing two diametrically-opposed edge cracks emanating from the inner surface of the cylinder. The thermal eigenstrain developed in the cylinder material due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress intensity factors developed in a previous study, an inverse method is developed to optimize material distribution intending to realize prescribed Apparent Fracture Toughness in the FGM cylinder. To present some numerical results, a TiC/Al2O3 FGM cylinder is considered and the inverse problems are solved to evaluate material distributions for two examples of prescribed Apparent Fracture Toughness. The effect of cylinder wall thickness on the material distribution and comparison of material distributions corresponding to a single and two cracks are also discussed. The numerical results reveal that the Apparent Fracture Toughness of FGM cylinders can be controlled by choosing the material distributions properly.

Majid R. Ayatollahi - One of the best experts on this subject based on the ideXlab platform.

  • Size and Geometry Effects on Rock Fracture Toughness: Mode I Fracture
    Rock Mechanics and Rock Engineering, 2013
    Co-Authors: Majid R. Ayatollahi, J. Akbardoost
    Abstract:

    In this paper, the effects of specimen size and geometry on the Apparent mode I Fracture Toughness (K c) of an Iranian white marble (Neyriz) are studied. A number of Fracture tests were conducted on center-cracked circular disk (CCCD) specimens with different radii to investigate the size effects on K c. The experimental results demonstrate that the Apparent Fracture Toughness increases in bigger specimens. In order to explain the experimental results, the modified maximum tangential stress (MMTS) criterion is used, where higher order terms of the Williams’ series expansion are included in the maximum tangential stress criterion. It is shown that the MMTS criterion provides good estimates for the Apparent Fracture Toughness of Neyriz marble, obtained from Fracture tests of edge-cracked triangular specimens. It is, therefore, concluded that the proposed criterion is able to account for the size and geometry effects on the Fracture resistance of rocks simultaneously.

  • Fracture analysis of V-notched components – Effects of first non-singular stress term
    International Journal of Solids and Structures, 2011
    Co-Authors: Majid R. Ayatollahi, M. Dehghany, Morteza Nejati
    Abstract:

    The effect of the first non-singular stress term on the Fracture behavior of notched structures was investigated under symmetric geometry and loading conditions. According to the Williams series expansion, for a large domain of notch angles the non-singular stress terms of sharp notches are functions of complex eigenvalues and their corresponding complex coefficients. Hence, a new representation of stress field near the notch tip was developed in which the higher order terms are expressed as several explicit functions of real and imaginary parts of both the complex eigenvalues and their complex coefficients. A critical stress criterion was then applied to the new stress formulations to assess the influence of the first non-singular stress term on the Apparent Fracture Toughness. Several finite element analyses were also performed on two laboratory specimens in order to show the effects of first non-singular term on the near field stress distribution of notched specimens. The results demonstrated that neglecting the first non-singular stress term could lead to significant errors in predicting the Apparent Fracture Toughness of notched components.

  • Effects of lateral load on warm prestressing in a center crack plate
    Materials Science and Engineering: A, 2006
    Co-Authors: Majid R. Ayatollahi, A. Aliniaziazi
    Abstract:

    The load bearing capacity of cracked components increases if an appropriate compressive residual stress field is created near the crack tip. Warm prestressing is a well-known technique for introducing such a residual stress field. In this paper, the finite element method is used to study the effect of the load applied parallel to the crack (or the lateral load) in warm prestressing of a cracked specimen. The specimen is a square plate containing a center crack and the lateral load is applied in the preloading stage. The numerical results suggest that the lateral load in the preloading stage can influence significantly the Apparent Fracture Toughness after the warm prestressing. It is shown that the improvement in the Apparent Fracture Toughness due to a compressive lateral load is more significant than the improvement due to a tensile lateral load.

Sergio Cicero - One of the best experts on this subject based on the ideXlab platform.

  • Critical Distance Default Values for Structural Steels and a Simple Formulation to Estimate the Apparent Fracture Toughness in U-Notched Conditions
    MDPI AG, 2018
    Co-Authors: Sergio Cicero, V. Madrazo, Juan Diego Fuentes, Isabela Procopio, Pablo González
    Abstract:

    The structural integrity assessment of components containing notch-type defects has been the subject of extensive research in the last few decades. The assumption that notches behave as cracks is generally too conservative, making it necessary to develop assessment methodologies that consider the specific nature of notches, providing accurate safe predictions of failure loads or defect sizes. Among the different theories or models that have been developed to address this issue the Theory of Critical Distances (TCD) is one of the most widely applied and extended. This theory is actually a group of methodologies that have in common the use of the material Toughness and a length parameter that depends on the material (the critical distance; L). This length parameter requires calibration in those situations where there is a certain non-linear behavior on the micro or the macro scale. This calibration process constitutes the main practical barrier for an extensive use of the TCD in structural steels. The main purpose of this paper is to provide, through a set of proposed default values, a simple methodology to accurately estimate both the critical distance of structural steels and the corresponding Apparent Fracture Toughness predictions derived from the TCD

  • Effect of fibre content and notch radius in the Fracture behaviour of short glass fibre reinforced polyamide 6: An approach from the Theory of Critical Distances
    Composites Part B: Engineering, 2016
    Co-Authors: F.t. Ibáñez-gutiérrez, Sergio Cicero, Isidro A. Carrascal, I. Procopio
    Abstract:

    Abstract This paper presents an analysis of the notch effect on the Fracture behaviour of short glass fibre reinforced polyamide 6 (SGFR-PA6) with different amounts of fibre content. The research is based on the results obtained in an experimental programme composed of 125 Fracture specimens, combining five different fibre contents and five different notch radii. Concerning the Apparent Fracture Toughness, a clear notch effect has been observed, with an increase in the Fracture resistance when the notch radius increases. Moreover, the Apparent Fracture Toughness has been reasonably predicted through the Theory of Critical Distances. The results have also shown a direct relation between the Apparent Fracture Toughness and the fibre content. The research is completed with the Scanning Electron Microscopy analysis of the evolution of the Fracture micromechanisms when both the notch radius and the fibre contents increase.

  • On the Use of the Notch Master Curve for Apparent Fracture Toughness Predictions of Notched Ferritic Steels Operating Within the Ductile-to-Brittle Transition Zone
    Volume 6B: Materials and Fabrication, 2015
    Co-Authors: Sergio Cicero, T. Garcia, V. Madrazo
    Abstract:

    This paper presents the Notch-Master Curve as a model for the prediction of the Apparent Fracture Toughness of ferritic steels in notched conditions and operating at temperatures corresponding to their ductile-to-brittle transition zone.The Notch-Master Curve combines the Master Curve of the material in cracked conditions and the notch corrections provided by the Theory of Critical Distances.In order to validate the model, the Fracture resistance results obtained in Fracture tests performed on notched CT and SENB specimens are presented. The results gathered here cover four ferritic steels (S275JR, S355J2, S460M and S690Q), three different notch radii (0.25 mm, 0.50 mm and 2.0 mm) and three different temperatures within the corresponding ductile-to-brittle transition zone.The results demonstrate that the Notch Master Curve provides good predictions of the Fracture resistance in notched conditions for the four materials analyzed.Copyright © 2015 by ASME

  • On the Line Method Apparent Fracture Toughness evaluations: Experimental overview, validation and some consequences on Fracture assessments
    Theoretical and Applied Fracture Mechanics, 2015
    Co-Authors: Sergio Cicero, T. Garcia, V. Madrazo
    Abstract:

    Abstract This paper analyses the capacity of the Line Method to provide evaluations of the Apparent Fracture Toughness, which is the Fracture resistance exhibited by materials in notched conditions. With this aim, the experimental results obtained in 555 Fracture tests are homogeneously presented and compared to the Line Method evaluations. It is remarked that the Line Method provides adequate estimates of the Apparent Fracture Toughness, and also that it conveniently addresses the physics of the notch effect. All this makes the Line Method a valuable scientific and engineering tool for the Fracture assessment of materials containing notches.

  • Analysis of notch effect in the Apparent Fracture Toughness and the Fracture micromechanisms of ferritic–pearlitic steels operating within their lower shelf
    Engineering Failure Analysis, 2014
    Co-Authors: Sergio Cicero, V. Madrazo, T. Garcia
    Abstract:

    Abstract The Fracture resistance of materials is generally higher in notched conditions that in cracked conditions. In other words, when the notch radius increases there is also an increase in the Apparent Fracture Toughness, which is that exhibited in notched conditions. This paper presents an analysis of the notch effect on two ferritic–pearlitic steels operating within their corresponding lower shelf, and develops an experimental programme, composed of 28 CT characterisation specimens and 72 CT validation specimens, together with finite elements analysis with the aim of validating the Apparent Fracture Toughness predictions provided by the Theory of Critical Distances. The results have shown how this theory provides reasonable predictions of the Apparent Fracture Toughness of the material The research is completed with the analysis of the evolution of Fracture micromechanisms when the notch radius increases, revealing a direct relation between this evolution and the Apparent Fracture Toughness observations.