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D.a. Hills - One of the best experts on this subject based on the ideXlab platform.
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refinements in the characterisation of mode mixity and small scale yielding at Sharp Notch roots
Engineering Fracture Mechanics, 2014Co-Authors: R C Flicek, D.a. Hills, Daniele DiniAbstract:Abstract This paper uses a modified formulation of Williams’ asymptotic solution to examine the plastic zone near the root of Sharp V-Notches. A method for assessing whether the plastic zone is ‘mode I like’ or ‘mode II like’ or mixed-mode in character is presented. Small scale yielding limits are also calculated. This analysis is then applied to monotonic, mixed-mode experimental test data reported in the literature. The results indicate that: (i) most tests were carried out within 5 % small scale yielding and (ii) the plastic zone of practical engineering components is likely to be either mainly mode I or mixed-mode in character.
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Sharp Notch Roots; The length scale implicit in the solution
2011Co-Authors: D.a. Hills, D. DiniAbstract:Reentrant Notches whose internal angle exceeds about 257 o induce two singular eigensolutions, from the classical Williams procedure, where the symmetric term is always more strongly singular than the antisymmetric term. This implies the presence of a length scale within the singular solution, and it means that Notch root process zones are not self-similar but vary in character according to their size; small ones will be mode-I like, larger ones mode-II like, larger ones still not existing under small scale yielding conditions. Here we explore explicitly within the framework of the singular solution (i.e. a semi-infinite Notch) the conditions under which mode I type behaviour exists, or mode II behaviour, or the solution is mixed in character. These general results are then applied to example finite problems, and used to show the range of loads under which pure mode I, small scale yielding singular behaviour is to be expected. This is of practical relevance because it means that, even if both eigenmodes are excited in a particular example problem, the process zone may practically be considered to be mode I in nature. It is shown that, in each of the example problems examined so far, there is a wide range of conditions where this is so, and this property may be used to simplify the way we treat the effects of Sharp corners, whether at Notches or at the edges of complete contacts, as characterizers of the local process zone.
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Characteristics of the process zone at Sharp Notch roots
International Journal of Solids and Structures, 2011Co-Authors: D.a. Hills, D. DiniAbstract:AbstractThe classical Williams solution for the state of stress at the tip of a semi-infinite Notch is re-visited and the two-term singular solution re-written in a form making the mode mixity and load magnitude explicit. This is used to show that, for a 270° solid angle, the majority of Notch problems exhibit a process zone which is entirely or substantially mode I in character, which in turn means that the Notch strength may practically be governed by a single elastic parameter. A method for finding the practical limit on the load and stress intensity ratio where this holds is described
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further consideration of closure at the root of a Sharp Notch
Journal of Strain Analysis for Engineering Design, 2008Co-Authors: D.a. Hills, Daniele DiniAbstract:The true contact length and corresponding contact pressure distribution arising at the root of a semi-infinite Sharp Notch, subject to compression, is found.
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Crack tip stress intensity factors for a crack emanating from a Sharp Notch
Engineering Fracture Mechanics, 2008Co-Authors: A.g. Philipps, Saravanan Karuppanan, C.m. Churchman, D.a. HillsAbstract:Accurate calibrations are provided for the crack tip stress intensity factor for a crack of finite length emanating from the symmetric tip of a Sharp Notch, of arbitrary angle, in terms of the generalised stress intensity quantifying remote loading of the Notch. The solution is applied to example problems and shown to be accurate for cases where the crack is much shorter then the Notch depth.
David Hudak - One of the best experts on this subject based on the ideXlab platform.
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on estimating the fracture toughness of al 7si mg alloys by Sharp Notch tensile test results
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Murat Tiryakioğlu, David HudakAbstract:Abstract Plane-strain fracture toughness and Notch-yield ratio data reported in the literature for Al–7Si–0.6Mg alloy castings were reanalyzed. A new empirical equation was developed to estimate K Ic from Notch tensile strength. Statistical analysis showed that the distribution of K Ic in A357-T6 castings is two-parameter Weibull. By using the moments method to estimate the Weibull modulus, empirical equations for lower bound estimates of K Ic were introduced. It is proposed that the empirical equations developed in this study be used to estimate K Ic from round Sharp-Notch tensile test results from Al–7Si–0.6Mg alloy castings.
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On estimating the fracture toughness of Al–7Si–Mg alloys by Sharp-Notch tensile test results
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Murat Tiryakioğlu, David HudakAbstract:Abstract Plane-strain fracture toughness and Notch-yield ratio data reported in the literature for Al–7Si–0.6Mg alloy castings were reanalyzed. A new empirical equation was developed to estimate K Ic from Notch tensile strength. Statistical analysis showed that the distribution of K Ic in A357-T6 castings is two-parameter Weibull. By using the moments method to estimate the Weibull modulus, empirical equations for lower bound estimates of K Ic were introduced. It is proposed that the empirical equations developed in this study be used to estimate K Ic from round Sharp-Notch tensile test results from Al–7Si–0.6Mg alloy castings.
David A Hills - One of the best experts on this subject based on the ideXlab platform.
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Sharp Notch roots subject to in plane and anti plane loading an alternative normalisation of the eigenfields their application to example problems
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: R. Ramesh, David A HillsAbstract:Abstract The state of stress at a Sharp Notch is characterised by the classical Williams eigenfunction expansion for in-plane loading, and a corresponding anti-plane solution. Excluding the case when the internal Notch angle is 2 π (a crack), the solutions have differing orders of singularity, and hence, between any pair of modes of loading, there is an internal implied length scale. Here we bring out those length scales, and show how the three generalised stress intensity factors may be replaced by equivalent parameters having a much more direct physical interpretation. The revised form of the semi-infinite Notch solutions are then applied to example geometries, showing how the characteristics of the Notch-root process zone may be inferred without further calculation.
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Sharp Notch roots subject to in-plane and anti-plane loading: An alternative normalisation of the eigenfields & their application to example problems
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: R. Ramesh, David A HillsAbstract:Abstract The state of stress at a Sharp Notch is characterised by the classical Williams eigenfunction expansion for in-plane loading, and a corresponding anti-plane solution. Excluding the case when the internal Notch angle is 2 π (a crack), the solutions have differing orders of singularity, and hence, between any pair of modes of loading, there is an internal implied length scale. Here we bring out those length scales, and show how the three generalised stress intensity factors may be replaced by equivalent parameters having a much more direct physical interpretation. The revised form of the semi-infinite Notch solutions are then applied to example geometries, showing how the characteristics of the Notch-root process zone may be inferred without further calculation.
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analytical representation of the non square root singular stress field at a finite angle Sharp Notch
International Journal of Solids and Structures, 2014Co-Authors: George G Adams, David A HillsAbstract:Abstract The stress field near the tip of a finite angle Sharp Notch is singular. However, unlike a crack, the order of the singularity at the Notch tip is less than one-half. Under tensile loading, such a singularity is characterized by a generalized stress intensity factor which is analogous to the mode I stress intensity factor used in fracture mechanics, but which has order less than one-half. By using a cohesive zone model for a notional crack emanating from the Notch tip, we relate the critical value of the generalized stress intensity factor to the fracture toughness. The results show that this relation depends not only on the Notch angle, but also on the maximum stress of the cohesive zone model. As expected the dependence on that maximum stress vanishes as the Notch angle approaches zero. The results of this analysis compare very well with a numerical (finite element) analysis in the literature. For mixed-mode loading the limits of applicability of using a mode I failure criterion are explored.
Murat Tiryakioğlu - One of the best experts on this subject based on the ideXlab platform.
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on estimating the fracture toughness of al 7si mg alloys by Sharp Notch tensile test results
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Murat Tiryakioğlu, David HudakAbstract:Abstract Plane-strain fracture toughness and Notch-yield ratio data reported in the literature for Al–7Si–0.6Mg alloy castings were reanalyzed. A new empirical equation was developed to estimate K Ic from Notch tensile strength. Statistical analysis showed that the distribution of K Ic in A357-T6 castings is two-parameter Weibull. By using the moments method to estimate the Weibull modulus, empirical equations for lower bound estimates of K Ic were introduced. It is proposed that the empirical equations developed in this study be used to estimate K Ic from round Sharp-Notch tensile test results from Al–7Si–0.6Mg alloy castings.
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On estimating the fracture toughness of Al–7Si–Mg alloys by Sharp-Notch tensile test results
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Murat Tiryakioğlu, David HudakAbstract:Abstract Plane-strain fracture toughness and Notch-yield ratio data reported in the literature for Al–7Si–0.6Mg alloy castings were reanalyzed. A new empirical equation was developed to estimate K Ic from Notch tensile strength. Statistical analysis showed that the distribution of K Ic in A357-T6 castings is two-parameter Weibull. By using the moments method to estimate the Weibull modulus, empirical equations for lower bound estimates of K Ic were introduced. It is proposed that the empirical equations developed in this study be used to estimate K Ic from round Sharp-Notch tensile test results from Al–7Si–0.6Mg alloy castings.
W. H. Wu - One of the best experts on this subject based on the ideXlab platform.
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Calculation of mixed-mode stress field at a Sharp Notch tip using M1ɛ-integral
Computational Mechanics, 2003Co-Authors: J. H. Chang, W. H. WuAbstract:Direct computation of the mixed-mode stress field at a Sharp Notch tip appears to be difficult in that the mode I and mode II asymptotic stresses are in general governed by different orders of singularity. In this paper, we first present a path-independent integral termed M1ɛ. The relation between M1ɛ and the generalized stress intensity factors is then derived and expressed as function of the Notch angle. Once the M1ɛ-integrals are accurately computed, the generalized SIF's and, consequently, the asymptotic mixed-mode stress field can thus be properly determined. No extra complementary solutions are required in the formulation. Further, no particular singular elements are required when the integration is performed by using finite elements.
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Calculation of mixed-mode stress field at a Sharp Notch tip using M _1ɛ-integral
Computational Mechanics, 2003Co-Authors: J. H. Chang, W. H. WuAbstract:Direct computation of the mixed-mode stress field at a Sharp Notch tip appears to be difficult in that the mode I and mode II asymptotic stresses are in general governed by different orders of singularity. In this paper, we first present a path-independent integral termed M _1ɛ. The relation between M _1ɛ and the generalized stress intensity factors is then derived and expressed as function of the Notch angle. Once the M _1ɛ-integrals are accurately computed, the generalized SIF's and, consequently, the asymptotic mixed-mode stress field can thus be properly determined. No extra complementary solutions are required in the formulation. Further, no particular singular elements are required when the integration is performed by using finite elements.
