The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform

Rhys Jones - One of the best experts on this subject based on the ideXlab platform.

  • Crack Growth at fastener holes containing intergranular Cracking
    Fatigue & Fracture of Engineering Materials & Structures, 2017
    Co-Authors: Rhys Jones, Adam Bowler, Michael Dorman, D. Edwards
    Abstract:

    This paper examines the Growth of Cracks at a fastener hole containing intergranular Cracking with a focus on ‘dome nut hole’ coupons that are representative of a critical location in the Royal Australian Air Force AP-3C Orion wing. It is shown that Crack Growth under operational flight loads can be captured using the NASGRO formulation and that the scatter in these various tests can also be captured by allowing for small variations in the value of the cyclic stress intensity fatigue threshold. In this context, it is shown that Crack Growth can be captured using both a cycle-by-cycle analysis and also a United States Air Force ‘characteristic K’ approach. We also see that, for the operational load spectra considered, the Crack Growth History is approximately exponential so that the United States Air Force risk assessment computer program (PRobability Of Fracture) can be used to assess the risk of failure by fracture. The results of this study also suggest that, provided that intergranular Cracking does not turn and break through to a free surface, it should have little effect on Crack Growth at a fastener hole.

  • Scatter in the Growth of small Cracks in AA7050-T7451
    2017
    Co-Authors: Pu Huang, Rhys Jones, Simon Barter, Daren Peng
    Abstract:

    This paper presents the results of study into the scatter associated with twenty three Cracks that have arisen and subsequently grown from small surface etched pits in AA 7050-T7451. To this end a number of dog-bone shaped specimens with multiple surface pits were tested. The loading spectrum used marker bands to enable the Crack Growth History to be determined via quantitative fractography. A total of twenty three Cracks were observed and analysed. This gave a family of small Crack da/dN versus DeltaK curves. It is shown that these curves form a single curve in the mid-range DeltaK region. This paper also illustrates how the scatter in these Crack Growth curves can be captured using the Hartman-Schijve equation, with the constant as determined from tests on long Cracks, allowing for small changes in the threshold term DeltaKthr.

  • Crack Growth from naturally occurring material discontinuities in operational aircraft
    Procedia Engineering, 2015
    Co-Authors: Rhys Jones, Pu Huang, Daren Peng, Raman R K Singh
    Abstract:

    Abstract This paper focuses on problems associated with aircraft sustainment related issues and illustrates how Cracks that grow from small naturally occurring material discontinuities in operational aircraft behave. The example discussed in this paper, which is associated with Crack Growth under a representative maritime aircraft load spectrum, when taken in conjunction with previous studies into Cracks growing under combat aircraft load spectra illustrates how for Cracks that grow from naturally occurring material discontinuities under such operational load spectra there is generally little Crack closure so that the Crack Growth History from its initial equivalent pre-Crack size (EPS) through to final failure can be easily and accurately computed.

  • Damage tolerance analysis of a helicopter component
    International Journal of Fatigue, 2009
    Co-Authors: Ung Hing Tiong, Rhys Jones
    Abstract:

    Abstract Fatigue critical helicopter components are, in general, subjected to complex high frequency dynamic loading. Due to these high frequencies small flaws can propagate to failure in a short period of time. Consequently, the demonstration of damage tolerance for those components must include the analysis of near-threshold Crack propagation, i.e. Growth in the low-to-mid stress intensity factor range (Δ K ) regime. To this end this paper presents a fatigue Crack Growth analysis of a helicopter airframe component, that was used as part of a round-robin study into helicopter fatigue, performed using a non-similitude based Crack Growth law, termed the Generalised Frost–Dugdale law. The resultant computed Crack Growth History is in excellent agreement with the measured Crack length histories.

  • Understanding Crack Growth in fuselage lap joints
    Theoretical and Applied Fracture Mechanics, 2008
    Co-Authors: Rhys Jones, Lorrie Molent, Susan Pitt
    Abstract:

    Abstract The problem of multi-site damage and multiple interacting Cracks is one experienced by many aircraft manufacturers and operators. This paper focuses on understanding the phenomena, and on developing a predictive capability that can form the engineering framework for maintaining continued airworthiness. To this end the present paper uses a simple formulation based on the Frost–Dugdale Crack Growth law to study the problem of Cracking at fastener holes in fuselage lap joints and shows that the predicted Crack Growth History is in good agreement with both experimental results and with fleet data.

Susan Pitt - One of the best experts on this subject based on the ideXlab platform.

  • Understanding Crack Growth in fuselage lap joints
    Theoretical and Applied Fracture Mechanics, 2008
    Co-Authors: Rhys Jones, Lorrie Molent, Susan Pitt
    Abstract:

    Abstract The problem of multi-site damage and multiple interacting Cracks is one experienced by many aircraft manufacturers and operators. This paper focuses on understanding the phenomena, and on developing a predictive capability that can form the engineering framework for maintaining continued airworthiness. To this end the present paper uses a simple formulation based on the Frost–Dugdale Crack Growth law to study the problem of Cracking at fastener holes in fuselage lap joints and shows that the predicted Crack Growth History is in good agreement with both experimental results and with fleet data.

  • Crack Growth of physically small Cracks
    International Journal of Fatigue, 2007
    Co-Authors: Rhys Jones, Lorrie Molent, Susan Pitt
    Abstract:

    This paper shows how, for physically small Cracks, the unified Crack Growth model, also referred to as Unigrow, can be related to the generalized Frost and Dugdale Crack Growth model. We also show how this formulation can be used to predict the Crack Growth History of a range of experimental tests.

  • Crack patching: Predicting fatigue Crack Growth
    Theoretical and Applied Fracture Mechanics, 2006
    Co-Authors: Rhys Jones, Kumanan Krishnapillai, Susan Pitt
    Abstract:

    This paper examines the Crack Growth History of a range of test specimens, and Cracks repaired with a composite patch, and shows that in the low to mid range ΔK region there is a near linear relationship between the log of the Crack length and the number of cycles. A simple methodology for predicting Crack Growth is then presented and validated by comparison with a range of experimental studies.

  • Recent developments in fatigue Crack Growth assessment
    International Journal of Fatigue, 2006
    Co-Authors: Lorrie Molent, Rhys Jones, Simon Barter, Susan Pitt
    Abstract:

    Abstract This paper examines the fatigue Crack Growth histories, at low to mid range Δ K ’s, for a range of aircraft aluminium alloys, test specimens and service loaded components. It concludes that the Crack Growth History shows that, as a first approximation, there is a log–linear relationship between the apparent Crack length or depth and the life ( N ), respectively. This leads to the further observation that, for the range of materials and spectra considered here, there is a linear relationship between the Crack Growth rate and the Crack length when plotted on a log–log scale.

  • Crack patching: an experimental evaluation of fatigue Crack Growth
    Composite Structures, 2005
    Co-Authors: Rhys Jones, Lorrie Molent, Simon Barter, Susan Pitt
    Abstract:

    This paper examines the Crack Growth History of a range of test specimen and service Cracking, for Cracks repaired with a composite patch and shows that for small to medium Crack lengths there is a linear relationship between the log of the Crack length and the service History (number of cycles).

Mohammad H. Haque - One of the best experts on this subject based on the ideXlab platform.

  • A Multi-Scale Viscoelastic Cohesive Layer Model for Predicting Delamination in HTPMC
    Volume 1: Advances in Aerospace Technology, 2014
    Co-Authors: Samit Roy, Priyank Upadhyaya, Mohammad H. Haque
    Abstract:

    In this paper, a novel numerical-experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified model is fully rate-dependent and does not require a pre-assigned traction-separation law. The actual shape of traction separation law depends on: (a) the strain rate via the viscoelastic constitutive relationship, (b) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (c) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-Integral approach was adapted to extract cohesive stresses near the Crack tip. A principal-stretch dependent internal damage state variable defines the damage in the cohesive layer. Within the cohesive layer, pristine and cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the cohesive layer helps mitigate numerical instabilities caused by elastic energy released due to Crack Growth, thereby enabling the FEA model to simulate the load-deflection response of the composite structure well beyond peak load. The present cohesive-layer based FEA model was able to accurately predict not only the macro level load-displacement curve, but also the micro level Crack Growth History in IM-7/BMI laminate before and after thermal aging, using only three parameters.Copyright © 2014 by ASME

  • A novel numerical-experimental approach for predicting delamination in high temperature polymer matrix composites
    Composite Structures, 2013
    Co-Authors: Priyank Upadhyaya, Samit Roy, Mohammad H. Haque
    Abstract:

    Abstract In this paper, a novel numerical–experimental methodology is outlined to determine cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract cohesive stresses near the Crack tip. A principal-stretch dependent internal damage state variable defines the damage in the cohesive layer. Within the cohesive layer, pristine and cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to simulate interlaminar delamination. The present cohesive-layer based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level Crack Growth History in IM-7/BMI laminate before and after thermal aging.

Lorrie Molent - One of the best experts on this subject based on the ideXlab platform.

  • Experimentally derived Crack Growth models for different stress concentration factors
    International Journal of Fatigue, 2008
    Co-Authors: J. Huynh, Lorrie Molent, Simon Barter
    Abstract:

    Abstract This paper summarises the investigation into a unique set of fatigue Crack Growth data involving coupons containing three different stress concentration factors (Kt) tested at various stress levels. Crack Growth History data were determined through the use of quantitative fractography (QF). These coupons were made of 7050 aluminium alloy, and were tested with the same representative F/A-18 aircraft fatigue usage wing root bending moment spectrum. These data were used in the analysis of fatigue Crack Growth from the various Kts and also in the development of Crack Growth models capable of predicting the fatigue Crack Growth History at one Kt from data obtained at a different Kt. These models were based on the stress dependency of the Paris parameter C.

  • Understanding Crack Growth in fuselage lap joints
    Theoretical and Applied Fracture Mechanics, 2008
    Co-Authors: Rhys Jones, Lorrie Molent, Susan Pitt
    Abstract:

    Abstract The problem of multi-site damage and multiple interacting Cracks is one experienced by many aircraft manufacturers and operators. This paper focuses on understanding the phenomena, and on developing a predictive capability that can form the engineering framework for maintaining continued airworthiness. To this end the present paper uses a simple formulation based on the Frost–Dugdale Crack Growth law to study the problem of Cracking at fastener holes in fuselage lap joints and shows that the predicted Crack Growth History is in good agreement with both experimental results and with fleet data.

  • Crack Growth of physically small Cracks
    International Journal of Fatigue, 2007
    Co-Authors: Rhys Jones, Lorrie Molent, Susan Pitt
    Abstract:

    This paper shows how, for physically small Cracks, the unified Crack Growth model, also referred to as Unigrow, can be related to the generalized Frost and Dugdale Crack Growth model. We also show how this formulation can be used to predict the Crack Growth History of a range of experimental tests.

  • Recent developments in fatigue Crack Growth assessment
    International Journal of Fatigue, 2006
    Co-Authors: Lorrie Molent, Rhys Jones, Simon Barter, Susan Pitt
    Abstract:

    Abstract This paper examines the fatigue Crack Growth histories, at low to mid range Δ K ’s, for a range of aircraft aluminium alloys, test specimens and service loaded components. It concludes that the Crack Growth History shows that, as a first approximation, there is a log–linear relationship between the apparent Crack length or depth and the life ( N ), respectively. This leads to the further observation that, for the range of materials and spectra considered here, there is a linear relationship between the Crack Growth rate and the Crack length when plotted on a log–log scale.

  • Crack patching: an experimental evaluation of fatigue Crack Growth
    Composite Structures, 2005
    Co-Authors: Rhys Jones, Lorrie Molent, Simon Barter, Susan Pitt
    Abstract:

    This paper examines the Crack Growth History of a range of test specimen and service Cracking, for Cracks repaired with a composite patch and shows that for small to medium Crack lengths there is a linear relationship between the log of the Crack length and the service History (number of cycles).

Samit Roy - One of the best experts on this subject based on the ideXlab platform.

  • Multi-scale modeling of high-temperature polymer matrix composites for aerospace applications
    Structural Integrity and Durability of Advanced Composites, 2015
    Co-Authors: Samit Roy
    Abstract:

    In this chapter, a novel numerical–experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified multi-scale model is fully rate-dependent and does not require a preassigned traction–separation law. The actual shape of traction–separation law depends on (1) the strain rate via the viscoelastic constitutive relationship, (2) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (3) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract cohesive stresses near the Crack tip. A principal stretch-dependent internal damage state variable defines the damage in the cohesive layer. Within the cohesive layer, pristine and cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics-based viscoelastic cohesive layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the cohesive layer helps mitigate numerical instabilities caused by elastic energy released due to Crack Growth, thereby enabling the FEA model to simulate the load–deflection response of the composite structure well beyond peak load. The present cohesive layer-based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level Crack Growth History in IM-7/BMI laminate before and after thermal aging, using only three parameters.

  • A Multi-Scale Viscoelastic Cohesive Layer Model for Predicting Delamination in HTPMC
    Volume 1: Advances in Aerospace Technology, 2014
    Co-Authors: Samit Roy, Priyank Upadhyaya, Mohammad H. Haque
    Abstract:

    In this paper, a novel numerical-experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified model is fully rate-dependent and does not require a pre-assigned traction-separation law. The actual shape of traction separation law depends on: (a) the strain rate via the viscoelastic constitutive relationship, (b) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (c) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-Integral approach was adapted to extract cohesive stresses near the Crack tip. A principal-stretch dependent internal damage state variable defines the damage in the cohesive layer. Within the cohesive layer, pristine and cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the cohesive layer helps mitigate numerical instabilities caused by elastic energy released due to Crack Growth, thereby enabling the FEA model to simulate the load-deflection response of the composite structure well beyond peak load. The present cohesive-layer based FEA model was able to accurately predict not only the macro level load-displacement curve, but also the micro level Crack Growth History in IM-7/BMI laminate before and after thermal aging, using only three parameters.Copyright © 2014 by ASME

  • A novel numerical-experimental approach for predicting delamination in high temperature polymer matrix composites
    Composite Structures, 2013
    Co-Authors: Priyank Upadhyaya, Samit Roy, Mohammad H. Haque
    Abstract:

    Abstract In this paper, a novel numerical–experimental methodology is outlined to determine cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract cohesive stresses near the Crack tip. A principal-stretch dependent internal damage state variable defines the damage in the cohesive layer. Within the cohesive layer, pristine and cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to simulate interlaminar delamination. The present cohesive-layer based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level Crack Growth History in IM-7/BMI laminate before and after thermal aging.