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Finite Element Modeling And Experimental Study Of Brittle Fracture In Tempered Martensitic Steels For Thermonuclear Fusion Applications
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Book Synopsis Finite Element Modeling and Experimental Study of Brittle Fracture in Tempered Martensitic Steels for Thermonuclear Fusion Applications by : Pablo Federico Mueller
Download or read book Finite Element Modeling and Experimental Study of Brittle Fracture in Tempered Martensitic Steels for Thermonuclear Fusion Applications written by Pablo Federico Mueller and published by . This book was released on 2009 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Investigations and Numerical Modeling of Mechanical Properties of Tempered Martensitic Steel Eurofer97 at Various Loading Rates, Temperatures and After Spallation Irradiation by : Serafin Knitel
Download or read book Investigations and Numerical Modeling of Mechanical Properties of Tempered Martensitic Steel Eurofer97 at Various Loading Rates, Temperatures and After Spallation Irradiation written by Serafin Knitel and published by . This book was released on 2018 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'auteur: tempered martensitic steel ; thermo-nuclear fusion reactor ; ductile to brittle transition ; static and dynamic fracture toughness ; irradiation embrittlement ; inverse method ; finite element modeling ; local approach of brittle fracture.
Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1076 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Finite Element Model for Brittle Fracture and Fragmentation by :
Download or read book Finite Element Model for Brittle Fracture and Fragmentation written by and published by . This book was released on 2016 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new computational model for brittle fracture and fragmentation has been developed based on finite element analysis of non-linear elasticity equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-strained edges based on the principal direction of strain tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.
Book Synopsis Hybrid Experimental/numerical Analysis and Finite Element Modeling of Fracture of Aggregate Composite by : Sean He
Download or read book Hybrid Experimental/numerical Analysis and Finite Element Modeling of Fracture of Aggregate Composite written by Sean He and published by . This book was released on 1993 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Microstructural-based Modeling Framework for High Temperature Behavior of Ferritic- Martensitic Steels Using Crystal Plasticity and Grain Boundary Finite Element Approaches by : Omar Mohd Nassif
Download or read book Microstructural-based Modeling Framework for High Temperature Behavior of Ferritic- Martensitic Steels Using Crystal Plasticity and Grain Boundary Finite Element Approaches written by Omar Mohd Nassif and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferritic/martensitic 9-12Cr steel alloys, have had widespread use as structural materials in power plants. Among this family of alloys, Grade 91 (Gr91) steel was a landmark in the development of 9-12Cr alloys. However, the unique microstructure complexity of the alloy has raised doubt regarding the techniques of data extrapolation in estimating its service-life for operation in next-generation power plants at higher temperatures and presssures. Conservatism becomes essential when the alloy is to be used in components lasting the life-cycle of power plants without replacement.This dissertation develops a physically-based microstructural model for creep rupture at 600 degrees Celsius for Gr91 steel as well as fundamental modeling tools that apply more broadly to microstructural modeling in metals. Key features of the Gr91 modeling framework capture the mechanical behavior of its prior austenite grains (PAG) and grain boundaries. Ultimately, a constitutive expression was adopted that captured the response from experiments conducted in the creep strain rate regime. An initial model intended to simulate low-cycle fatigue was first developed using the idea of geometrically necessary dislocations (GNDs) in crystal plasticity (CP) framework. That necessitated evaluating strain gradients and a patch-recovery method was implemented to recover a linear elastic deformation gradient field across the domain in linear elements. A Lie-group to Lie-algebra mapping was used to preserve orthogonality when projecting the rotation tensor from the elements' Gauss points to the nodes. A statistically-stored dislocation density model was investigated to span the regimes of moderate strain rates (tension tests) to low strain rates (creep tests). Calibration of this model was possible against tension tests, but its application to creept tests suggested that other dislocation mechanisms were present during the primary creep regime of Gr91. Therefore, the CP model in the PAGs was changed to represent dislocation climb-glide motion and recovery along with linear viscous diffusional creep for point defect diffusion. This revised model more closely captured the measurements of creep response. Lastly, a robust Discontinuous Galerkin method is proposed to model the grain boundary interface elements to address traction oscillations observed for cohesive models. Stability and convergence are assessed along with non-conforming meshes.
Book Synopsis Temperature-dependent Material Modeling for Structural Steels by : Mina Seif
Download or read book Temperature-dependent Material Modeling for Structural Steels written by Mina Seif and published by . This book was released on 2016 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents the formulation and application of a newly developed temperature-dependent material model for structural steels. First it presents a model for computing the stress-strain behavior of structural steel for conditions appropriate to fire. The model accounts for the change in yield strength with temperature, the change in the amount of post-yield strain hardening with both temperature and room-temperature yield strength, and the change in strength with increasing strain rate. Then, this NIST stress-strain model is used for predicting flexural buckling of steel columns subjected to elevated temperature. The main focus of this part of the study is to evaluate the applicability of the NIST model for predicting the behavior of steel gravity columns at elevated temperatures using the finite-element method. Besides the stress-strain behavior, another key issue in evaluating the response of structural systems to fire effects is the modeling of fracture, which is required to capture failure modes such as tear out in connection plates and bolt shear. Fracture can be simulated in explicit finite element analysis using element erosion, in which elements are removed from the analysis when specified failure criteria are satisfied. A finite element material modeling methodology is presented for structural steels and bolts at elevated temperatures that incorporates erosion-based modeling of fracture. The failure criterion was calibrated against high- temperature experimental data on elongation of tensile coupons at fracture, and its dependence on temperature and mesh size was investigated. Finally, these temperature-dependent material models for structural steel and bolts that incorporate erosion-based modeling of fracture were implemented to study the performance of steel moment frame assemblies at elevated temperatures.
Book Synopsis Evolution of Microstructure during Long‐term Creep of a Tempered Martensite Ferritic Steel by : Ali Aghajani Bazazi
Download or read book Evolution of Microstructure during Long‐term Creep of a Tempered Martensite Ferritic Steel written by Ali Aghajani Bazazi and published by Cuvillier Verlag. This book was released on 2009-12-08 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tempered martensite ferritic steels are used for critical components in fossil fired power plants that operate in the creep range. The materials contain a high density of dislocations and precipitates form on all types of internal interfaces, the majority of which represent subgrain boundaries. Most previous studies suffer from either only relating to short term creep experiments or from being incomplete in not considering all relevant elements of the microstructure. No systematic effort was made to investigate the evolution of microstructures under conditions of long term creep. In the present study the evolution of the microstructure of a 12% Cr tempered martensite ferritic steel was investigated under conditions of long term aging and creep. Transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD) techniques were used to characterize materials from interrupted creep tests (0.5%, 1%, 1.6% and rupture at 11.9%; creep conditions: 550°C, 120 MPa, rupture time: 139 971 h). It is shown that subgrains coarsen, that the close correlation between carbides and subgrain boundaries loosens during long term creep, and that the frequency of small angle boundaries increases. In addition, the evolution of dislocation densities during long term aging and creep was studied using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). During aging the dislocation density remains constant, while during long term creep the dislocation density continuously decreases. All these elementary deformation processes have already been discussed in short term creep studies. The present study shows that they also govern long term creep, however, during long term creep, precipitation and coarsening reactions occur which are not observed during short term creep. Cr rich M23C6, VX carbides and Laves phase were identified as the major precipitates in the microstructure of the 12% Chromium tempered martensite ferritic steel. Their chemical compositions, sizes, volume fractions and number densities were evaluated in all interrupted specimens. M23C6 particles coarsen and establish their equilibrium concentration after 51072 hours. VX particles are stable. The Laves phase particles do not reach thermodynamic equilibrium as they form and grow during long term creep. This is due to Silicon which is found in the Laves phase particles and which diffuses slowly in the steel matrix.
Book Synopsis Phenomenological Constitutive Modeling and Numerical Analysis of Fracture Toughness for Shape Memory Alloys by : Mohammed Yousuf Alsawalhi
Download or read book Phenomenological Constitutive Modeling and Numerical Analysis of Fracture Toughness for Shape Memory Alloys written by Mohammed Yousuf Alsawalhi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nickel titanium (NiTi) alloys possess unique characteristics that provide them the ability to recover large mechanical strains up to 8%. Pseudoelasticity and the shape memory effect are phenomena associated with SMA behavior. Shape recovery is driven by thermomechanical loading/unloading during the martensitic phase transformation. NiTi behavior also exhibits the property of asymmetry in transformation stress and transformation strain between the tension and compression responses as a result of forward and reverse phase transformations, as well as the reorientation and detwinning of the martensite phase. Furthermore, the process of heat generation during phase transformation near a crack tip effects the local temperature variations and thus the fracture toughness of the material. A new thermomechanical constitutive modeling approach for shape memory alloys (SMAs) that undergo a martensite to austenite phase transformation is presented. The novelty of this new formulation is that a single transformation surface is implemented in order to capture the main aspects of SMAs including forward transformation, reverse transformation, and martensite reorientation. Specific forms for the transformation surface and the transformation potential are devised and results for the behaviors captured by the model are provided for a range of thermomechanical loadings. The validity of the model is assessed with experimental studies of complex thermomechanical proportional and non proportional load paths at different temperatures using numerical simulations. The phenomenological constitutive model is implemented in finite element calculations and applied to the pseudoelastic and shape memory effects of a beam in pure bending. Fracture analysis is implemented within finite element computations to model the toughening due to the austenite to martensite phase transformation and martensite reorientation during steady mode I crack growth. Several dimensionless parameters relating the thermomechanical parameters of the constitutive model, the crack growth velocity, and the prevailing sample temperature are identified and applied to study the thermomechanical crack tip fields and the toughening enhancement due to the forward and reverse phase transformations in the vicinity of the crack tip. The first part of this dissertation involves validation of the model by comparisons of numerical simulations with experimental data and by developing consistent tangent moduli and applying the model to simple structural analysis of pure beam bending. First, uniaxial tensile and compressive stress-strain responses are simulated at four different temperatures: below the martensite finish temperature, between the martensite start and austenite start temperatures, between the austenite start and austenite finish temperatures, and above the austenite finish temperature. The numerical model reproduces the major aspects of the experimental measurements including the stress and strain levels. The transformation stress and transformation strain asymmetry between the tensile and compressive responses is also implemented in the model. The second problem investigates the performance of the model for a NiTi tube under a square axial-shear strain load path. The asymmetric model outperforms the symmetric model by reproducing the main features observed in the experiments. However, there is a notable difference in the magnitudes of stresses, mainly the shear stress, due to the anisotropy of the SMA material which is not accounted for in this model. The third problem examines the behavior of the constitutive model for tension-torsion of SMA wires for temperatures at the martensite and austenite phases. Again, the asymmetric model performs better than the symmetric model in terms of fitting the model response to the experimental measurements. The exclusion of anisotropy from the constitutive model has noticeable impact on the axial strain behavior at high temperatures. Lastly, the final problem investigates the pseudoelastic and shape memory behaviors of a beam under pure bending. The analysis in each case captures the moment-curvature and the temperature-curvature responses, as well as the axial stress distribution through the cross-section of the beam. The asymmetric model produced asymmetry in the axial stress distribution that fits the behavior of real SMAs. The second part of this dissertation involves fracture computations to analyze the toughening due to the stress-induced martensitic transformation and martensite reorientation during steady mode I crack growth. First, analyses are performed on the sizes and shapes of the various transformed zones near the crack tip for a range of temperatures analyzed. Secondly, the uniaxial stress-strain response is impacted by the thermomechanical parameters in the constitutive model which results in a relatively strong dependence of the transformation toughening on the material parameters. Next, numerical simulations are used to illustrate the effects of crack growth speed and heat capacity on the toughening. Finally, different sample temperatures show the strong impact on the toughness enhancement due to phase transformation. The last part of this dissertation discusses different approaches for material modeling, including different formulations associated with the transformation potentials and the associated integration routines. The first approach introduces a new internal variable that is a function of the other two in an attempt to control the pure shear stress-strain response as being a mixture between the tensile and compressive responses. The second approach introduces two stress invariants that are a linear or non-linear combination of the strain invariant. Here the objective is to control how fast the strain invariant goes towards uniaxial tension in a pure shear loading in order to allow the pure shear response to be a controlled mixture between the tensile and compressive responses as opposed to having similar behavior to the tensile response. The last approach for the integration algorithm utilizes a classical elastic prediction-transformation correction return mapping. This method simplifies the number of unknowns solved in the integration routine to just one. Therefore, a 1-D Newton-Raphson (NR) scheme is used which allows for more robust numerical calculations
Book Synopsis An Experimental Investigation of the Conditions for Brittle Fracture in Steel by : David K. Felbeck
Download or read book An Experimental Investigation of the Conditions for Brittle Fracture in Steel written by David K. Felbeck and published by . This book was released on 1951 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Modeling and Experimental Study of Deformation and Hot Tearing in Steel by : Charles Andrew Monroe
Download or read book A Modeling and Experimental Study of Deformation and Hot Tearing in Steel written by Charles Andrew Monroe and published by ProQuest. This book was released on 2008 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-phase model is presented that predicts solid deformation and damage as well as melt pressure, feeding flow, and shrinkage porosity. A viscoplastic constitutive theory with damage is used to model the solid deformation. Damage is a scalar quantity based on ductile fracture theory which is calculated from the inelastic volume deformation. This associative model smoothly transitions from rate-dependent behaviour at high temperatures to rate-independent behaviour at lower temperatures. The damage created by mechanically induced voiding is proposed as a new hot tear criterion. Hot tears are believed to initiate from locations with significant damage. The liquid feeding and shrinkage porosity is coupled to the solid deformation which enables the final damage prediction to be more accurate than previous hot tear criteria. This model has been successfully implemented in a general-purpose casting simulation code. Novel steel casting experiments have been designed and performed which measure the deformation and force from solidification to shakeout. Under certain experimental conditions, hot tears form in the test castings and the deformation and force during hot tear formation is also measured. The measured and predicted deformations and forces show good agreement with the simulation results. Furthermore, the damage predictions show good correspondence with hot tear indications on radiographs of the test castings.
Book Synopsis The Application of 3-dimensional Finite Element Methods to Fracture Mechanics and Fatigue Life Prediction by : A. C. Pickard
Download or read book The Application of 3-dimensional Finite Element Methods to Fracture Mechanics and Fatigue Life Prediction written by A. C. Pickard and published by . This book was released on 1986 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Metal Surfaces by : Roberto Montanari
Download or read book Metal Surfaces written by Roberto Montanari and published by MDPI. This book was released on 2021-08-31 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection covers the physical and chemical phenomena of metal surfaces, including surface modifications and treatments. It is targeted at researchers working in materials science and also at newcomers to the research field of metal surfaces and surface analysis.
Book Synopsis Experimental Investigation and Finite Element Modeling of Hemispherically Stretched Steel Sheet by : Julie Renee Knibloe
Download or read book Experimental Investigation and Finite Element Modeling of Hemispherically Stretched Steel Sheet written by Julie Renee Knibloe and published by . This book was released on 1988 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :Great Britain. Navy Department. Advisory Committee on Structural Steels Publisher : ISBN 13 : Total Pages :144 pages Book Rating :4.:/5 (41 download)
Book Synopsis Brittle Fracture in Steel Structures by : Great Britain. Navy Department. Advisory Committee on Structural Steels
Download or read book Brittle Fracture in Steel Structures written by Great Britain. Navy Department. Advisory Committee on Structural Steels and published by . This book was released on 1970 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Combined Experimental and Finite Element Study of Crack Closure Effects in Modified 1070 Steel by : TS. Srivatsan
Download or read book A Combined Experimental and Finite Element Study of Crack Closure Effects in Modified 1070 Steel written by TS. Srivatsan and published by . This book was released on 2000 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The significance and even the existence of crack closure is being questioned by several researchers. The objective of this study was to determine if crack closure occurs and to quantify its significance. An approach combining experimental measurement techniques with finite element analysis techniques was utilized. For two values of compact tension specimen thickness, a series of tests were conducted to determine the effect of maximum stress intensity, load ratio, constraint, and single tensile overload on the crack closure and fatigue crack growth behavior of a modified 1070 steel. Test results indicated that constraint has a significant influence on crack closure and crack growth rate behavior. Thin specimens exhibited consistently lower crack growth rates and higher crack closure levels than the thick specimens, except for tests conducted at a high load ratio, where crack closure did not occur. The thin specimens also exhibited a more significant overload effect. A new finite element modeling technique, which uses substructuring techniques to model the load cycling and crack propagation of an entire compact tension specimen, was developed. Comparison of stationary crack and propagating crack finite element models revealed that plasticity-induced crack closure produces a significant amount of crack tip shielding, which effectively reduces the strain range and mean strain experienced at the crack tip.
Book Synopsis Deformation and Failure Models of High Strength Steels for Finite Element Simulations by : Marvin Nahrmann
Download or read book Deformation and Failure Models of High Strength Steels for Finite Element Simulations written by Marvin Nahrmann and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
