Advanced Three Dimensional Simulations And Cohesive Modeling Of Fatigue Crack Growth
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Advanced Three Dimensional Simulations And Cohesive Modeling Of Fatigue Crack Growth
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Author : Ani Ural
language : en
Publisher:
Release Date : 2004
Advanced Three Dimensional Simulations And Cohesive Modeling Of Fatigue Crack Growth written by Ani Ural and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Simulations Of Failure Via Three Dimensional Cracking In Fuel Cladding For Advanced Nuclear Fuels
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Author :
language : en
Publisher:
Release Date : 2014
Simulations Of Failure Via Three Dimensional Cracking In Fuel Cladding For Advanced Nuclear Fuels written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Enhancing performance of fuel cladding and duct alloys is a key means of increasing fuel burnup. This project will address the failure of fuel cladding via three-dimensional cracking models. Researchers will develop a simulation code for the failure of the fuel cladding and validate the code through experiments. The objective is to develop an algorithm to determine the failure of fuel cladding in the form of three-dimensional cracking due to prolonged exposure under varying conditions of pressure, temperature, chemical environment, and irradiation. This project encompasses the following tasks: 1. Simulate 3D crack initiation and growth under instantaneous and/or fatigue loads using a new variant of the material point method (MPM); 2. Simulate debonding of the materials in the crack path using cohesive elements, considering normal and shear traction separation laws; 3. Determine the crack propagation path, considering damage of the materials incorporated in the cohesive elements to allow the energy release rate to be minimized; 4. Simulate the three-dimensional fatigue crack growth as a function of loading histories; 5. Verify the simulation code by comparing results to theoretical and numerical studies available in the literature; 6. Conduct experiments to observe the crack path and surface profile in unused fuel cladding and validate against simulation results; and 7. Expand the adaptive mesh refinement infrastructure parallel processing environment to allow adaptive mesh refinement at the 3D crack fronts and adaptive mesh merging in the wake of cracks. Fuel cladding is made of materials such as stainless steels and ferritic steels with added alloying elements, which increase stability and durability under irradiation. As fuel cladding is subjected to water, chemicals, fission gas, pressure, high temperatures, and irradiation while in service, understanding performance is essential. In the fast fuel used in advanced burner reactors, simulations of the nuclear fuels are critical to understand the burnup, and thus the fuel efficiency.
Extended Finite Element Predictions For Three Dimensional Modeling Of Fatigue Crack Growth In Cold Worked Holes
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Author : Mohammad Salman Yasin
language : en
Publisher:
Release Date : 2020
Extended Finite Element Predictions For Three Dimensional Modeling Of Fatigue Crack Growth In Cold Worked Holes written by Mohammad Salman Yasin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with Steel categories.
Cold working has been widely used for enhancing the fatigue life of open holes. The process imparts compressive residual stresses around the hole which slows down the progression of crack under cyclic loading conditions. In the present study, fatigue crack growth in open holes in R260 grade steel, a typical railroad material, has been analyzed using the Extended Finite Element Method (XFEM). Along with the experimental studies, numerical simulation emerges as a powerful tool to predict the fatigue crack growth in rail steel and may deliver important insights to consider more situations by saving time and cost. XFEM modifies the standard displacement-based approximation by adding enrichment functions in the crack region. The investigation explored the capability of the XFEM, for a plate containing plain hole (baseline), pad coined, or split-sleeve cold-worked hole using the commercial finite element package, Abaqus, as a means of fatigue crack growth under constant amplitude loading. The effect of residual stress redistribution has been added to the numerical model to accurately predict the crack evolution. Stress Intensity Factors (SIF) are obtained from the XFEM calculations and the crack growth is estimated until the SIF reaches the fracture toughness of the modeled coupon material. The obtained simulation results are in good agreement with the fatigue experimental results in terms of the fatigue crack growth rates for plain hole (baseline), pad coined, or split-sleeve cold-worked holes. Results from the performed analysis show that cold working of an open hole increases the fatigue life when compared to the one without residual stresses due to the delay of crack initiation and propagation. The results also indicated fatigue life increase almost by a factor of three during crack propagation due to split-sleeve cold expansion in correlation to the baseline and pad coined sample.
Three Dimensional Finite Element Simulation Of Fatigue Crack Growth And Closure
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Author : Stephen G. Cupschalk
language : en
Publisher:
Release Date : 1987
Three Dimensional Finite Element Simulation Of Fatigue Crack Growth And Closure written by Stephen G. Cupschalk and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Stress corresion categories.
Cohesive Zone Model For Carbon Nanotube Adhesive Simulation And Fracture Fatigue Crack Growth
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Author : Haodan Jiang
language : en
Publisher:
Release Date : 2010
Cohesive Zone Model For Carbon Nanotube Adhesive Simulation And Fracture Fatigue Crack Growth written by Haodan Jiang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Cohesion categories.
"The Cohesive Zone Model (CZM) describes material separation with a traction-separation law and links the micro-structural failure mechanism to the continuum deformation field. The evolvement of the CZM and its specific features were introducted in the first chapter of this dissertation and followed by applications for interface decohesion and crack growth study. Chapter II adopted a bilinear CZM for description of the decohesion properties of the innovative carbon nanotube (CNT) dry adhesive. Macroscopic modeling of the uncoupled normal and shear adhesive behaviors were implemented using finite element method. The cohesive zone model completes a multi-scale modeling scheme together with coarse grained molecular dynamics (CGMD). Three-dimensional simulations of quasi-static fracture process were studied next by formulating an exponential cohesive law. Crack growth under monotonic loading was modeled and cohesive parameters were calibrated by comparing with experiments. The CZM simulation captured the crack initiation as well as the process of crack propagation. A damage-updated irreversible cohesive law was formulated in Chapter IV for simulations of cyclic crack growth. Material degradation was described with a damage evolution mechanism, revealing the history dependence of fatigue crack growth. The irreversible CZM was verified through one-element model under load-controlled and displacement-controlled fatigue loading and was further validated with fatigue crack growth simulations for different speciment modes. Simulation results captured the gradual damage accumulation and stable fatigue crack propagation, consistent with the power law method. Further application of the irreversible CZM for overload effect during fatigue crack propagation was presented in Chapter V. Stress redistribution caused by the overload in a compact-tension-shear (CTS) specimen was investigated. Fatigue crack growth retardation was studied in terms of overload ratios and the mode of the overload. A damage extrapolation scheme was formulated for the high-cycle fatigue loading and greatly reduced the computation cost. The last chapter investigated crack path deviation phenomena with possible CZM simulation approaches. Numerical issues and mesh-related convergence problem were referred for future investigation."--Abstract.
Extended Finite Element Method
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Author : Amir R. Khoei
language : en
Publisher: John Wiley & Sons
Release Date : 2015-02-23
Extended Finite Element Method written by Amir R. Khoei and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-02-23 with Science categories.
Introduces the theory and applications of the extended finite element method (XFEM) in the linear and nonlinear problems of continua, structures and geomechanics Explores the concept of partition of unity, various enrichment functions, and fundamentals of XFEM formulation. Covers numerous applications of XFEM including fracture mechanics, large deformation, plasticity, multiphase flow, hydraulic fracturing and contact problems Accompanied by a website hosting source code and examples
Advanced Modeling For Fatigue Growth Of Small Surface Cracks
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Author : T. A. Cruse
language : en
Publisher:
Release Date : 1988
Advanced Modeling For Fatigue Growth Of Small Surface Cracks written by T. A. Cruse and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with Fracture mechanics categories.
The primary result of the sponsored research is the development and application of the boundary element method for two- and three-dimensional fatigue crack growth analysis. The two-dimensional formulation developed previously (AFOSR Contract No. F49620-84-C-0042) was extended to investigate the crack tip behavior of long and short cracks under cyclic loading. The influence of residual plasticity on stress intensity factor was used to obtain an unambiguous estimate of the plastic zone size. It was demonstrated that the effect of the plastic wake on the stress intensity factor for crack opening (closure) and the effect of the residual stress on the retardation are identical manifestations of the same plasticity process. The boundary integral equations also provide insight to the mathematical equivalence of these two effects. Keywords: Fracture mechanics, Fatigue crack growth, Crack retardation, Crack closure, Crack opening displacement, Boundary element method. (jes).
Finite Element Simulations Of Three Dimensional Microstructurally Small Fatigue Crack Growth In 7075 Aluminum Alloy Using Crystal Plasticity Theory
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Author :
language : en
Publisher:
Release Date : 2005
Finite Element Simulations Of Three Dimensional Microstructurally Small Fatigue Crack Growth In 7075 Aluminum Alloy Using Crystal Plasticity Theory written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
This thesis discusses plasticity-induced crack closure based finite element simulations of small fatigue cracks in three dimensions utilizing crystal plasticity theory. Previously, modeling has been performed in two dimensions using a double-slip crystal plasticity material model. The goal of this work is to extend that research using a full three-dimensional FCC crystal plasticity material model implementation that accounts for all twelve FCC slip systems. Discussions of Python scripts that were written to perform analyses with the commercial finite element code ABAQUS are given. A detailed description of the modeling methodology is presented along with results for single crystals and bicrystals. The results are compared with finite element and experimental results from the literature. A discussion of preliminary work for the analysis of crack growth around an intermetallic particle is also presented.
Finite Element Simulations Of Three Dimensional Microstructurally Small Fatigue Crack Growth In 7075 Aluminum Alloy Using Crystal Plasticity Theory
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Author : Stephen Riley Johnston
language : en
Publisher:
Release Date : 2005
Finite Element Simulations Of Three Dimensional Microstructurally Small Fatigue Crack Growth In 7075 Aluminum Alloy Using Crystal Plasticity Theory written by Stephen Riley Johnston and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Aluminum alloys categories.
This thesis discusses plasticity-induced crack closure based finite element simulations of small fatigue cracks in three dimensions utilizing crystal plasticity theory. Previously, modeling has been performed in two dimensions using a double-slip crystal plasticity material model. The goal of this work is to extend that research using a full three-dimensional FCC crystal plasticity material model implementation that accounts for all twelve FCC slip systems. Discussions of Python scripts that were written to perform analyses with the commercial finite element code ABAQUS are given. A detailed description of the modeling methodology is presented along with results for single crystals and bicrystals. The results are compared with finite element and experimental results from the literature. A discussion of preliminary work for the analysis of crack growth around an intermetallic particle is also presented.
Generalized Finite Element Methods For Three Dimensional Crack Growth Simulations
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Author : Jeronymo P. Pereira
language : en
Publisher:
Release Date : 2010
Generalized Finite Element Methods For Three Dimensional Crack Growth Simulations written by Jeronymo P. Pereira and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Three-dimensional (3-D) crack growth analysis is crucial for the assessment of structures such as aircrafts, rockets, engines and pressure vessels, which are subjected to extreme loading conditions. The analysis of 3-D arbitrary crack growth using the standard Finite Element Method (FEM) encounters several difficulties. The singularities at crack fronts require strongly refined finite element meshes that must fit the discontinuity surfaces while keeping the aspect ratio of the elements within acceptable bounds. Fully automatic generation of meshes in complex 3-D geometries satisfying these requirements is a daunting task. Partition-of-unity methods, such as the Generalized FEM (GFEM), are promising candidates to surmount the shortcomings of the standard FEM in crack growth simulations. These methods allow the representation of discontinuities and singularities in the solution via geometrical descriptions of crack surfaces, that are independent of the volume mesh, coupled with suitable enrichment functions. As a result, volume meshes need not fit crack surfaces. This work proposes an hp-version of the GFEM (hp-GFEM) for crack growth simulations. This method provides enough flexibility to build high-order discretizations for crack growth simulations. At each crack growth step, high-order approximations on locally refined meshes are automatically created in complex 3-D domains while preserving the aspect ratio of elements, regardless of crack geometry. The hp-GFEM uses explicit surface meshes composed of triangles to represent non-planar 3-D crack surfaces. By design, the proposed methodology allows the crack surface to be arbitrarily located within the GFEM mesh. To track the crack surface evolution, the proposed methodology considers an extension of the Face Offsetting Method (FOM). Based on the hp-GFEM solution, the FOM provides geometrically feasible crack front descriptions by updating the vertex positions and checking for self-intersections of the edges. The hp-GFEM with FOM allows the simulation of arbitrary crack growth independent of the volume mesh. Numerical simulations using the hp-GFEM coupled with the FOM are corroborated by experimental data and experimental observations. As an alternative to large-scale crack growth simulations, this work combines the proposed hp-GFEM with the generalized finite element method with global-local enrichment functions (GFEMgl). The proposed method allows crack growth simulations with arbitrary path in industrial level complexity problems while keeping the global mesh unchanged. Furthermore, this method allows crack growth simulations without solving the entire problem from scratch at each crack growth step. The GFEMgl for crack growth explores solutions from previous crack growth steps, hierarchical property of the enrichment functions as well as static condensation of the global-local degrees of freedom to expedite the solution process. Numerical examples demonstrate the robustness, efficiency and accuracy of the proposed GFEMgl for crack growth simulations.