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 Thermal Barrier Coatings (13)
 PEM Fuel Cell Membranes (13)
 Fatigue/Fracture (10)
 Mechanical Properties of Materials (6)
 Finite element analysis (3)

 Biomaterials (3)
 Proton exchange membrane fuel cells (3)
 Composite materials (3)
 Elastic– plastic material; Finite elements; Thermal barrier coatings; Thermal cycling; Oxidation (2)
 Durability (2)
 Composite; contact; debond; delamination; doubler; edge; panel; patch; shell; structure (1)
 Elastic– plastic material; Finite elements; Thermomechanical testing; Thermal barrier coatings; Thermal cycling; Oxidation (1)
 Elastoplasticity (1)
 Beam; Bifurcation; Bimaterial; Buckling; Composite; Laminate; Patched structures; Plate; Postbuckling; Slingshot buckling; Snapthrough; Stability; Temperature; Thermal buckling (1)
 Clusterchannel model; fluoropolymers; hydrophilic polymers; mechanical properties; micromechanical modeling; PFSA membranes; structure– property relations; swelling; temperature; Young’s modulus (1)
 Epoxy adhesives (1)
 Barb pullout method; Interface toughness; Delamination; EBPVD TBC (1)
 Cyclic crack growth; Plastic dissipated energy; Crack tunneling; ABAQUS; Plasticity induced crack closure (PICC) (1)
 Carbon (1)
 Cyclic crack growth; Plastic dissipated energy; Reverse plastic zone; Paris law; ABAQUS (1)
 Aluminum (1)
 Finite element; Cyclic loading; Cycle jump; Thermal barrier coatings; Failure evolution (1)
 Failure; fatigue analysis; fatigue behavior; fuel cells; ionomers; mechanical properties; PFSA membrane (1)
 Bimaterial interface; Fracture mechanics; Fatigue crack growth; Cycle jump technique (1)
 Elasticity (1)
 Finite element method; Objectoriented programming; Cyclic loading; Crack propagation; Multilayered structures; Fatigue; ABAQUS (1)
 Analytical model; Elastic– plastic material; Finite elements; Thermal barrier coatings; Thermal cycling; Oxidation (1)
 Design (1)
 Biomimicking (1)
 Double cantilever beam; crack kinking; elastic foundation model; finite element analysis (1)
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Numerical Evaluation Of ParisRegime Crack Growth Rate Based On Plastically Dissipated Energy, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Numerical Evaluation Of ParisRegime Crack Growth Rate Based On Plastically Dissipated Energy, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Anette M Karlsson
The crack growth rate during cyclic loading is investigated via numerical simulations. The crack advancement is governed by a propagation criterion that relates the increment in plastically dissipated energy ahead of the crack tip to a critical value. Once this critical value is satisfied, crack propagation is modeled via a node release scheme. Thus, the crack growth rate is an output from the numerical simulation. The crack growth rate predicted by the proposed scheme is compared with published experimental crack growth data in the Parisregime for selected metals. A good match is found between the experimentally observed crack growth rates ...
The Effects Of Patch Properties On The Debonding Behavior Of Patched BeamPlates, Anette M. Karlsson
The Effects Of Patch Properties On The Debonding Behavior Of Patched BeamPlates, Anette M. Karlsson
Anette M Karlsson
The debonding characteristics of patched structures are investigated in this study by means of an analytical model. In particular, the effects the layup sequence and edge tapering of a carbonreinforced epoxy patch, as well as the beveling of an aluminum patch, have on the initiation, stability, and extent of the debonding are considered. The results presented show that both the degree of edgetapering and the patch properties must be carefully selected in order to optimize the patched structure. It is also shown that when designing a patched system, it is important to model the correct boundary and load conditions to ...
High Strength And LightWeight Materials Inspired By The Exoskeleton Of Arthropods, Anette M. Karlsson
High Strength And LightWeight Materials Inspired By The Exoskeleton Of Arthropods, Anette M. Karlsson
Anette M Karlsson
This work investigates the multiscaled structure and the constitutive behavior of the exoskeleton of arthropods (Japanese beetle) along with the response of biomimicked structures. Image analysis (SEM and TEM) revealed three loadbearing regions comprised of chitinprotein fiber layers orientated parallel to the cuticle surface. The chitin fibers in the exocuticle and mesocuticle are organized in a helicoidal structure (layers stacked with a small rotational angle relative to their adjacent layers). The endocuticle has a distinct pseudoorthogonal pattern, characterized by a thin transitional helicoidal region inserted between two orthogonal layers. Idealized mechanics based models showed that the pseudoorthogonal structure redistributes the ...
On The Detachment Of StepTapered Doublers: Part 2—Evolution Of Pressure Loaded Structures, Anette M. Karlsson, W. J. Bottega
On The Detachment Of StepTapered Doublers: Part 2—Evolution Of Pressure Loaded Structures, Anette M. Karlsson, W. J. Bottega
Anette M Karlsson
Onedimensional edge debonding of layerwise steptapered patches from both flat and cylindrical structures subjected to applied pressure is studied in the context of the general formulation presented in Part 1. Numerical simulations based on analytical solutions of the problems of interest are performed and intricate results presented in the form of threshold curves/delamination paths for various taper angles and support conditions. Configurations corresponding to full contact of the debonded segments, edge contact of the debonded segments and no contact of the debonded segments of the evolving composite structure are included in the model and found to significantly affect the ...
Conical Indentation Of A Viscoelastic Sphere, J. K. Phadikar, T. A. Bogetti, V. N. Kaliakin, Anette M. Karlsson
Conical Indentation Of A Viscoelastic Sphere, J. K. Phadikar, T. A. Bogetti, V. N. Kaliakin, Anette M. Karlsson
Anette M Karlsson
Instrumented indentation is commonly used for determining mechanical properties of a range of materials, including viscoelastic materials. However, most—if not all—studies are limited to a flat substrate being indented by various shaped indenters (e.g., conical or spherical). This work investigates the possibility of extending instrumented indentation to nonflat viscoelastic substrates. In particular, conical indentation of a sphere is investigated where a semianalytical approach based on “the method of functional equations” has been developed to obtain the force–displacement relationship. To verify the accuracy of the proposed methodology selected numerical experiments have been performed and good agreement was ...
The Presence Of Edge Contact And Its Influence On The Debonding Of Patched Panels, Anette M. Karlsson, W. J. Bottega
The Presence Of Edge Contact And Its Influence On The Debonding Of Patched Panels, Anette M. Karlsson, W. J. Bottega
Anette M Karlsson
A formulation is presented which accounts for configurations of debonding patched cylindrical panels for which the edge of the debonded segment of the patch maintains sliding contact with the corresponding base structure. The formulation is incorporated with that which accounts for configurations for which a contact zone is present and for which no contact between the debonded segments of the patch and base structure occurs during debonding. Analyses are performed for two types of loading conditions: Applied circumferential tension and applied internal pressure. Results of numerical simulations based on analytical solutions of the problems of interest are presented in the ...
On Thermal Buckling Of Patched BeamPlates, Anette M. Karlsson, W. J. Bottega
On Thermal Buckling Of Patched BeamPlates, Anette M. Karlsson, W. J. Bottega
Anette M Karlsson
The behavior of uniformly heated plates is considered for the situation where a patch is adhered over a region of the structure. A variational formulation results in a selfconsistent set of equations and conditions, which governs the response of the system. The nonlinear problems are solved analytically, yielding exact results within the context of the mathematical model employed. A stability criterion is established for the class of problems considered, based on the second variation of the potential energy of the composite structure, and issues of stability are assessed in this context. Three nondimensional parameters that characterize the response of the ...
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
Anette M Karlsson
This paper presents an in situ SEM experimental study on cyclic crack propagation in closedcell polymer foams. The microscopic failure mechanisms in precracked PVC and PES specimens of 60 and 90 kg/m3 densities were examined under lowcycle fatigue loading. In the PVC foam, crack propagation occurred incrementally by successive failure of cell boundaries in front of the crack tip. The crack occasionally jumped to cell boundaries above or below the main crack resulting in nonself similar growth. Crack propagation in the PES foam occurred incrementally by extensive plastic tearing and subsequent tensile failure of the cell edge in front ...
TimeDependent Mechanical Response Of A Composite Pfsa Membrane, Narinder S. Khattra, Zongwen Lu, Anette M. Karlsson, Michael H. Santare, F. Colin Busby, Thomas Schmiedel
TimeDependent Mechanical Response Of A Composite Pfsa Membrane, Narinder S. Khattra, Zongwen Lu, Anette M. Karlsson, Michael H. Santare, F. Colin Busby, Thomas Schmiedel
Anette M Karlsson
The mechanical response of a composite fuel cell membrane, made from layers of reinforced and unreinforced PFSA material, is investigated via both experimental and numerical means. First, the timedependent mechanical properties for the reinforced layers are measured for a range of environmental and loading conditions. A threenetwork, viscoelasticplastic constitutive model is developed to characterize the mechanical response of this reinforced membrane material. This constitutive model is then used in finite element simulations of a fuel cell unit (consisting of composite membrane, electrodes, gas diffusion layer and bipolar plates) where the effect of relative humidity (RH) cycling on the stress response ...
On The Behavior Of A Class Of Patched Plates During Cooling, Anette M. Karlsson, W. J. Bottega
On The Behavior Of A Class Of Patched Plates During Cooling, Anette M. Karlsson, W. J. Bottega
Anette M Karlsson
The behavior of patched beamplates during uniform cooling is considered. A nonlinear formulation is adopted and the problems of interest are solved analytically yielding exact results within the context of the mathematical model employed. Three nondimensional parameters corresponding to (i) a loading parameter, (ii) a critical temperature and (iii) a critical membrane force, are seen to characterize the response of the composite structure. Stability is considered and critical behavior includes bifurcation and asymptotic buckling, nontrivial “groundstates”, and demarcation and transition in deflection direction. Extensive numerical simulations based on analytical solutions are performed. Results are presented for various loading and support ...
Implementation Of A Plastically Dissipated Energy Criterion For Three Dimensional Modeling Of Fatigue Crack Growth, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Implementation Of A Plastically Dissipated Energy Criterion For Three Dimensional Modeling Of Fatigue Crack Growth, Parag G. Nittur, Anette M. Karlsson, Leif A. Carlsson
Anette M Karlsson
Fatigue crack growth is simulated using three dimensional elasticplastic finite element analysis. The crack extension per load cycle, da/dN, as well as crack front profile changes (crack tunneling) under cyclic loading is not specified as an input but evaluated based on a condition that relates plastically dissipated energy to a critical value. Simulation of cyclic crack propagation in a middlecrack tension M(T) specimen using this implementation captures the well established, experimentally obtained crack growth rate reduction accompanying a single overload event. The analysis predicts that the single overload also affects the crack front profile, where a tunneling crack ...
TimeDependent Mechanical Behavior Of Proton Exchange Membrane Fuel Cell Electrodes, Zongwen Lu, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh
TimeDependent Mechanical Behavior Of Proton Exchange Membrane Fuel Cell Electrodes, Zongwen Lu, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh
Anette M Karlsson
The electrodes used for Proton Exchange Membrane Fuel Cells (PEMFCs) are typically painted or sprayed onto the membrane during manufacturing, making it difficult to directly characterize their mechanical behavior as a standalone material. An experimentalnumerical hybrid technique is devised to extract the electrode properties from the experimentally measured properties of Nafion® 211 membrane1 and a membrane electrode assembly (MEA) based on Nafion® 211 membrane at various temperatures, humidities, and strain rates. Within the linear regime, the ruleofmixtures assuming an isostrain condition is used to calculate the ratedependent Young's modulus of the electrodes. Beyond the linear regime, reverse analysis is ...
On The Detachment Of StepTapered Doublers : Part 1—Foundations, W. J. Bottega, Anette M. Karlsson
On The Detachment Of StepTapered Doublers : Part 1—Foundations, W. J. Bottega, Anette M. Karlsson
Anette M Karlsson
Onedimensional edge debonding of layerwise steptapered patches from both flat and cylindrical structures is examined. The problems are approach from a unified point of view, as propagating boundary problems in the calculus of variations, with the models for both flat and curved structures being formulated simultaneously. The effects of a contact zone adjacent to the bonded region are incorporated as is the phenomenon of edgepoint contact. The formulation results in a selfconsistent representation of the various intact and debonded segments of the composite structure comprised of a multilayer patch and a base structure. It concurrently yields the conditions which establish ...
On The Microstructural Development In PlatinumModified NickelAluminide Bond Coats, S. Darzens, Anette M. Karlsson
On The Microstructural Development In PlatinumModified NickelAluminide Bond Coats, S. Darzens, Anette M. Karlsson
Anette M Karlsson
A numerical procedure for simulating the distortions exhibited by a thermally grown oxide (TGO) upon temperature cycling has been adapted to incorporate the microstructure of the bond coat. The focus is on the dual phase β/γ′ microstructure that develops upon oxidation of a system with a Ptaluminide bond coat. The results reveal that the presence of the γ′phase next to the TGO reduces its distortion locally, because of the superior hightemperature strength of γ′, relative to β. Conversely, in regions where the βphase exists adjacent to the TGO, it distorts and the TGO propagates downward, while simultaneously lengthening ...
On The Effective Elastic Properties Of Macroscopically Isotropic Media Containing Randomly Dispersed Spherical Particles, D. Cojocaru, Anette M. Karlsson
On The Effective Elastic Properties Of Macroscopically Isotropic Media Containing Randomly Dispersed Spherical Particles, D. Cojocaru, Anette M. Karlsson
Anette M Karlsson
computational scheme for estimating the effective elastic properties of a particle reinforced matrix is investigated. The randomly distributed samesized spherical particles are assumed to result in a composite material that is macroscopically isotropic. The scheme results in a computational efficient method to establish the correct bulk and shear moduli by representing the threedimensional (3D) structure in a twodimensional configuration. To this end, the statistically equivalent area fraction is defined in this work, which depends on two parameters: the particle volume fraction and the number of particles in the 3D volume element. We suggest that using the statistically equivalent area fraction ...
MechanicsBased Model For NonAffine Swelling In Perfluorosulfonic Acid (Pfsa) Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson
MechanicsBased Model For NonAffine Swelling In Perfluorosulfonic Acid (Pfsa) Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson
Anette M Karlsson
A mechanicsbased model is developed to predict the swelling pressure in perfluorosulfonic acid (PFSA) ionomer membranes during water uptake. The PFSA membrane is represented as a twophase system, where the waterfilled hydrophilic domains are dispersed throughout the hydrophobic polymer matrix. Two representative volume elements (RVEs) are used to represent the nanostructure: (i) a spherical RVE with a spherical hydrophilic domain at the center, and (ii) a cylindrical RVE with a cylindrical hydrophilic domain. The model starts with the nonaffine swelling behavior of the membrane and interprets this as a structural reorganization of the RVEs to characterize the microscopic deformation. Swelling ...
A Double Cantilever Beam Specimen For Foam Core Fracture Characterization, Elio E. Saenz, Adrián HernándezPérez, Leif A. Carlsson, Anette M. Karlsson
A Double Cantilever Beam Specimen For Foam Core Fracture Characterization, Elio E. Saenz, Adrián HernándezPérez, Leif A. Carlsson, Anette M. Karlsson
Anette M Karlsson
This article presents the analysis and test results for a new sandwich double cantilever beam specimen for foam fracture characterization. The foam is sandwiched between two stiff and strong aluminum adherends. The specimen is analyzed using a modified version of the classical Kanninen elastic foundation model. Finite element analysis is conducted to determine the stress state near the crack tip and compliance of the double cantilever beam sandwich specimen. Model predictions are compared to experimental compliance data and crack growth paths for double cantilever beam specimens with polyvinyl chloride and polyethersulfone foams. The elastic foundation model and finite element analysis ...
The Effect Of The Thermal Barrier Coating On The Displacement Instability In Thermal Barrier Systems, Anette M. Karlsson, T. Xu, A. G. Evans
The Effect Of The Thermal Barrier Coating On The Displacement Instability In Thermal Barrier Systems, Anette M. Karlsson, T. Xu, A. G. Evans
Anette M Karlsson
Thermal barrier systems are susceptible to instability of the thermally grown oxide (TGO) at the interface between the bond coat and the thermal barrier coating (TBC). The instabilities have been linked to thermal cycling and initial geometrical imperfections, as well as to misfit strains due to both oxide growth and thermal expansion misfit. Numerical simulations are used to investigate the role of the thermomechanical properties of the TBC in this instability. It is found that the TBC constrains the deformation, whereupon instabilities develop preferentially in regions where cracklike imperfections either preexist in the TBC or are created because of the ...
Mechanical Behavior Of BioInspired Laminated Composites, Liang Cheng, Adam Thomas, James L. Glancey, Anette M. Karlsson
Mechanical Behavior Of BioInspired Laminated Composites, Liang Cheng, Adam Thomas, James L. Glancey, Anette M. Karlsson
Anette M Karlsson
To investigate if the relative high strength and stiffness of biological composites can be translated into manmade materials, innovative bioinspired laminated composites with commercial materials (glass epoxy prepreg) were designed and manufactured by incorporating the distinctive helicoidal morphology observed in the exoskeletons of crustaceans. The helicoidal structure is characterized by a stacking sequence consisting of a gradual rotation of each lamina in the multilayered laminated composites. Variations of the helicoidal structure were designed and produced to address some important issues encountered in the practical composites manufacturing process, including midplane symmetry. In addition, composite structures with a general quasiisotropic configuration were ...
Simulated Properties Of Kagomé And Tetragonal Truss Core Panels, S. Hyun, Anette M. Karlsson, S. Torquato, A. G. Evans
Simulated Properties Of Kagomé And Tetragonal Truss Core Panels, S. Hyun, Anette M. Karlsson, S. Torquato, A. G. Evans
Anette M Karlsson
The finite element method has been used to simulate the properties of panels with Kagomé and tetragonal cores under compressive and shear loading. The simulation has been performed for two different materials: a Cualloy with extensive strain hardening and an Alalloy with minimal hardening. It is shown that the Kagomé core is more resistant to plastic buckling than the tetragonal core under both compression and shear. One consequence is that the Kagomé structure has the greater load capacity and a deferred susceptibility to softening. Another is that the Kagomé core is isotropic in shear: contrasting with the soft orientations exhibited ...
On Internal Cone Cracks Induced By Conical Indentation In Brittle Materials, J. Yan, Anette M. Karlsson, X. Chen
On Internal Cone Cracks Induced By Conical Indentation In Brittle Materials, J. Yan, Anette M. Karlsson, X. Chen
Anette M Karlsson
The conditions for cone cracks to develop due to a conical indentation are investigated. Axisymmetric numerical simulations, based on the finite element method, are conducted, assuming a linearelastic, perfectly plastic material. A superposition scheme is employed to simulate a range of crack geometries, including various lengths and orientations. The results indicate that the class of cracks investigated is prone to develop internally in brittle materials. Based on a reversed analysis, a new technique is proposed for measuring the fracture toughness in bulk material and thick coatings through one simple indentation test when the cone crack appears.
Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn
Micromechanics Model Based On The Nanostructure Of Pfsa Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson, William B. Johnson, Simon Cleghorn
Anette M Karlsson
A micromechanics model is developed to predict Young’s modulus of perfluorosulfonic acid (PFSA) membranes at various temperatures and water contents. The morphology of PFSA membranes is characterized by a twophase structure, where hydrophilic clusters expand to hold water molecules during swelling, whereas the hydrophobic polymer network maintains the structural stability. A representative volume element (RVE) is proposed based on the descriptions for the nanostructure of PFSA membranes available in the literature. On the basis of mechanics model, we estimate Young’s modulus in tension of PFSA membranes as a function of water volume fraction for various temperatures. The results ...
Multiaxial ThermoMechanical Fatigue On Material Systems For Gas Turbines, M. Bartsch, B. Baufeld, M. Henzelmann, Anette M. Karlsson, S. Dalkilic, L. Chernova
Multiaxial ThermoMechanical Fatigue On Material Systems For Gas Turbines, M. Bartsch, B. Baufeld, M. Henzelmann, Anette M. Karlsson, S. Dalkilic, L. Chernova
Anette M Karlsson
Material systems made from nickel based superalloys with protective coatings have been tested in thermomechanical fatigue with superposed thermal gradients, which generated multiaxial stress states. The testing conditions were selected for simulating the fatigue loading in the wall of an internally cooled gas turbine blade of an aircraft engine. After thermomechanical testing the damage behaviour of the materials has been investigated by means of microscopic methods. The laboratory experiments have been accompanied by numerical simulations. Based on the results of the simulations and observed damage features the test parameters in subsequent laboratory tests have been controlled to facilitate the validation ...
Obtaining Mode Mixity For A Bimaterial Interface Crack Using The Virtual Crack Closure Technique, A. Agrawal, Anette M. Karlsson
Obtaining Mode Mixity For A Bimaterial Interface Crack Using The Virtual Crack Closure Technique, A. Agrawal, Anette M. Karlsson
Anette M Karlsson
We review, unify and extend work pertaining to evaluating mode mixity of interfacial fracture utilizing the virtual crack closure technique (VCCT). From the VCCT, components of the strain energy release rate (SERR) are obtained using the forces and displacements near the crack tip corresponding to the opening and sliding contributions. Unfortunately, these components depend on the crack extension size, Δ, used in the VCCT. It follows that a mode mixity based upon these components also will depend on the crack extension size. However, the components of the strain energy release rate can be used for determining the complex stress intensity ...
A Model Study Of Displacement Instabilities During Cyclic Oxidation, Anette M. Karlsson, C. G. Levi, A. G. Evans
A Model Study Of Displacement Instabilities During Cyclic Oxidation, Anette M. Karlsson, C. G. Levi, A. G. Evans
Anette M Karlsson
The shape changes that occur at imperfections on the surface of an aluminaforming alloy, subject to thermal cycling, have been simulated and measured. Observations have been made by emplacing a surface groove into a FeCrAlY material. Upon thermal cycling, large shape distortions have been observed: whereas, for comparable isothermal oxidation, the shape changes are minimal. The simulations predict similar responses. Upon cycling, upward displacements (pileup) occur around the perimeter, accompanied by downward displacements at the center. Yet, minimal displacements arise upon isothermal oxidation. To realize cyclic displacements comparable in magnitude to those found experimentally, large values of the inplane growth ...
A Numerical Model For The Cyclic Instability Of Thermally Grown Oxides In Thermal Barrier Systems, Anette M. Karlsson, A. G. Evans
A Numerical Model For The Cyclic Instability Of Thermally Grown Oxides In Thermal Barrier Systems, Anette M. Karlsson, A. G. Evans
Anette M Karlsson
Morphological instability of the thermally grown oxide (TGO) is a fundamental source of failure in some thermal barrier systems. The instabilities occur when initial nonplanarity in the TGO grows in amplitude as the system experiences thermal cycling. By numerical means, this study explores how these instabilities are linked to constituent properties. The associated phenomena involve oxidation of the TGO, plastic flow of the bond coat, thermal expansion misfit between the TGO, bond coat and substrate, and stress relaxation in the TGO at high temperature. A key implication of the simulations is that the incidence of reverse yielding upon reheating differentiates ...
On Tgo Creep And The Initiation Of A Class Of Fatigue Cracks In Thermal Barrier Coatings, Mercedes T. Hernandez, Anette M. Karlsson, Marion Bartsch
On Tgo Creep And The Initiation Of A Class Of Fatigue Cracks In Thermal Barrier Coatings, Mercedes T. Hernandez, Anette M. Karlsson, Marion Bartsch
Anette M Karlsson
The initiation of a class of fatigue cracks observed in thermal barrier coatings (TBCs) subjected to thermal gradient mechanical fatigue testing is investigated. The coating system is based on a NiCoCrAlY bond coat and a partially yttria stabilized zirconia top coat. To explain the development of the cracks of interest, the thermomechanical response of the bond coat and the thermally grown oxide (TGO) is examined and quantified through finite element analyses. The models include nonlinear and timedependent behavior such as creep, TGO growth stress, and thermomechanical cyclic loading. The simulations suggest that stressredistribution due to creep can lead to tensile ...
The NonDestructive And NanoMicrostructural Characterization Of ThermalBarrier Coatings, Y. H. Sohn, B. Jayaraj, S. Laxman, B. Franke, J. W. Byeon, Anette M. Karlsson
The NonDestructive And NanoMicrostructural Characterization Of ThermalBarrier Coatings, Y. H. Sohn, B. Jayaraj, S. Laxman, B. Franke, J. W. Byeon, Anette M. Karlsson
Anette M Karlsson
The durability of thermal barrier coatings (TBCs) plays an important role in the service reliability and maintainability of hotsection components in advanced turbine engines for aerospace and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary nondestructive evaluation (NDE) techniques for quality control and liferemain assessment of TBCs. This paper discusses recent achievements in understanding the residual stress, phase constituents, and electrochemical resistance (or capacitance) of TBC constituents—with an emphasis on the thermally grown oxide. Results from NDE by PSLS and EIS are correlated to the nano and microstructural development of ...
On Establishing Elastic–Plastic Properties Of A Sphere By Indentation Testing, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
On Establishing Elastic–Plastic Properties Of A Sphere By Indentation Testing, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
Anette M Karlsson
Instrumented indentation is a popular technique for determining mechanical properties of materials. Currently, the evaluation techniques of instrumented indentation are mostly limited to a flat substrate being indented by various shaped indenters (e.g., conical or spherical). This work investigates the possibility of extending instrumented indentation to nonflat surfaces. To this end, conical indentation of a sphere is investigated where two methodologies for establishing mechanical properties are explored. In the first approach, a semianalytical approach is employed to determine the elastic modulus of the sphere utilizing the elastic unloading response (the “unloading slope”). In the second method, reverse analysis based ...
An ObjectOriented Approach For Modeling And Simulation Of Crack Growth In Cyclically Loaded Structures, D. Cojocaru, Anette M. Karlsson
An ObjectOriented Approach For Modeling And Simulation Of Crack Growth In Cyclically Loaded Structures, D. Cojocaru, Anette M. Karlsson
Anette M Karlsson
We present an objectoriented modeling frame for simulating crack propagation due to cyclic loadings. Central to the approach is that the crack propagates when a userdefined propagation criterion is fulfilled, i.e., the crack propagation rate is not prescribed but predicted. The approach utilizes the commercial finite element software package ABAQUS and its associated Python based scripting interface. The crack propagation is simulated by a generalized node release technique. If the propagation criteria are satisfied in the end of a cycle, the crack is allowed to propagate. The incremental crack growth is inferred from an iterative investigation of the propagation ...