The Experts below are selected from a list of 1857 Experts worldwide ranked by ideXlab platform
Stéphane Bordas - One of the best experts on this subject based on the ideXlab platform.
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error controlled adaptive extended finite element method for 3d linear elastic crack propagation
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Y Jin, Stéphane Bordas, O A Gonzalezestrada, Olivier PierardAbstract:We present a simple error estimation and mesh adaptation approach for 3D linear elastic crack propagation simulations using the eXtended Finite Element Method (X-FEM). A global extended recovery technique (Duflot and Bordas, 2008) is used to quantify the interpolation error. Based on this error distribution, four strategies relying on two different mesh optimality criteria are compared. The first aims at homogenizing the error distribution. The second minimizes the total number of elements given a target global error level. We study the behaviour of these criteria in the context of cracks treated by an X-FE approach. In particular, we investigate the convergence rates at the element-level depending its enrichment type. We conclude on the most suitable refinement criterion and propose and verify a strategy for mesh adaptation on 3D Damage Tolerance Assessment problems.
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global energy minimization for multi crack growth in linear elastic fracture using the extended finite element method
2014Co-Authors: Danas Sutula, Stéphane BordasAbstract:In computational fracture mechanics as applied, for example, to Damage Tolerance Assessment, it has been common practice to determine the onset of fracture growth and the growth direction by post-processing the solution of the linear elastostatics problem, at a particular instance in time. For mixed mode loading the available analytically derived criteria that can be used for determining the onset of crack growth typically rely on the assumptions of an idealized geometry e.g. a single crack subjected to remote loading [1, 2] and that the kink angle of the infinitesimal crack increment is quite small [3]. Moreover, the growth direction given by a criterion that is based on an instantaneous local crack tip field can only be valid for infinitesimally small crack growth increments. Consequently, the maximum hoop stress criterion [4] and other similar criteria [5] disregard the changes in the solution that take place as fractures advance over a finite size propagation. Hence, due to the error committed in time-integration, fractures may no longer follow the most energetically favorable paths that theoretically could be achieved for a specific discrete problem. In our approach, we investigate multiple fracture evolution under quasistatic conditions in an isotropic linear elastic solid based on the principle of minimum potential elastic energy, which can help circumvent the aforementioned difficulties. The technique enables a minimization of the potential energy with respect to all crack increment directions minding their relative interactions. The directions are optimized (in the energy sense) by considering virtual crack rotations to find the energy release rates and its first derivatives in order to determine, via an iterative process, the directions that yield zero energy release rates with respect to all virtual rotations [6]. We use the extended finite element method (XFEM) [7, 8] for discretization of a 2D continua in order to model an elaborate crack evolution over time, similar in principle to [9], although we consider here
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enriched finite elements and level sets for Damage Tolerance Assessment of complex structures
Engineering Fracture Mechanics, 2006Co-Authors: Stéphane Bordas, B MoranAbstract:The extended finite element method (X-FEM) has recently emerged as an alternative to meshing/remeshing crack surfaces in computational fracture mechanics thanks to the concept of discontinuous and asymptotic partition of unity enrichment (PUM) of the standard finite element approximation spaces. Level set methods have been recently coupled with X-FEM to help track the crack geometry as it grows. However, little attention has been devoted to employing the X-FEM in real-world cases. This paper describes how X-FEM coupled with level set methods can be used to solve complex three-dimensional industrial fracture mechanics problems through combination of an object-oriented (C++) research code and a commercial solid modeling/finite element package (EDS-PLM/I-DEAS®). The paper briefly describes how object-oriented programming shows its advantages to efficiently implement the proposed methodology. Due to enrichment, the latter method allows for multiple crack growth scenarios to be analyzed with a minimal amount of remeshing. Additionally, the whole component contributes to the stiffness during the whole crack growth simulation. The use of level set methods permits the seamless merging of cracks with boundaries. To show the flexibility of the method, the latter is applied to Damage Tolerance analysis of a complex aircraft component.
D Roach - One of the best experts on this subject based on the ideXlab platform.
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Damage Tolerance Assessment of bonded composite doubler repairs for commercial aircraft applications
Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2002Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded composite doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded composite doublers for general use. The associated documentation package provides guidance regarding the design, analysis, installation, Damage Tolerance, and nondestructive inspection of these doublers. This report describes a series of fatigue and strength tests which were conducted to study the Damage Tolerance of Boron-Epoxy composite doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with composite doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of composite doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determinemore » strength values and failure modes. It was demonstrated that even in the presence of extensive Damage in the original structure (cracks, material loss) and in spite of non-optimum installations (adhesive disbonds), the composite doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.« less
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Damage Tolerance Assessment of bonded composite doubler repairs for commercial aircraft applications
Other Information: PBD: Aug 1998, 1998Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded composite doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded composite doublers for general use. The associated documentation package provides guidance regarding the design, analysis, installation, Damage Tolerance, and nondestructive inspection of these doublers. This report describes a series of fatigue and strength tests which were conducted to study the Damage Tolerance of Boron-Epoxy composite doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with composite doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of composite doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determine strength values and failure modes. It was demonstrated that even in the presence of extensive Damage in the original structure (cracks, material loss) and in spite of non-optimum installations (adhesive disbonds), the composite doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.
Y Jin - One of the best experts on this subject based on the ideXlab platform.
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error controlled adaptive extended finite element method for 3d linear elastic crack propagation
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Y Jin, Stéphane Bordas, O A Gonzalezestrada, Olivier PierardAbstract:We present a simple error estimation and mesh adaptation approach for 3D linear elastic crack propagation simulations using the eXtended Finite Element Method (X-FEM). A global extended recovery technique (Duflot and Bordas, 2008) is used to quantify the interpolation error. Based on this error distribution, four strategies relying on two different mesh optimality criteria are compared. The first aims at homogenizing the error distribution. The second minimizes the total number of elements given a target global error level. We study the behaviour of these criteria in the context of cracks treated by an X-FE approach. In particular, we investigate the convergence rates at the element-level depending its enrichment type. We conclude on the most suitable refinement criterion and propose and verify a strategy for mesh adaptation on 3D Damage Tolerance Assessment problems.
C. Forrester - One of the best experts on this subject based on the ideXlab platform.
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The lead crack concept applied to defect growth in aircraft composite structures
Composite Structures, 2017Co-Authors: Lorrie Molent, C. ForresterAbstract:Currently, the cyclic fatigue growth and residual strength of Damaged aircraft composite structures under operational loads is not fully understood. This leads to structures generally being designed to a no Damage growth criterion with many knock down factors included to cover unknown/untested effects. Thus, full optimisation of composite aircraft structures is unlikely to be achieved under the no Damage growth criterion. In 2009 the US Federal Aviation Administration (FAA) introduced a slow growth approach to certifying composite, adhesively bonded structures and bonded repairs which could improve the situation and is worthy of further investigation. In this paper the growth of some (limited) Damage types available in the literature are reviewed and a framework proposed to address the Damage Tolerance Assessment of these structures.
O A Gonzalezestrada - One of the best experts on this subject based on the ideXlab platform.
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error controlled adaptive extended finite element method for 3d linear elastic crack propagation
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Y Jin, Stéphane Bordas, O A Gonzalezestrada, Olivier PierardAbstract:We present a simple error estimation and mesh adaptation approach for 3D linear elastic crack propagation simulations using the eXtended Finite Element Method (X-FEM). A global extended recovery technique (Duflot and Bordas, 2008) is used to quantify the interpolation error. Based on this error distribution, four strategies relying on two different mesh optimality criteria are compared. The first aims at homogenizing the error distribution. The second minimizes the total number of elements given a target global error level. We study the behaviour of these criteria in the context of cracks treated by an X-FE approach. In particular, we investigate the convergence rates at the element-level depending its enrichment type. We conclude on the most suitable refinement criterion and propose and verify a strategy for mesh adaptation on 3D Damage Tolerance Assessment problems.
