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Alexander M Korsunsky - One of the best experts on this subject based on the ideXlab platform.
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neutron strain scanning for experimental validation of the artificial intelligence based Eigenstrain contour method
Mechanics of Materials, 2020Co-Authors: Fatih Uzun, Chrysanthi Papadaki, Zifan Wang, Alexander M KorsunskyAbstract:Abstract The demand for energy generation with low carbon emissions evoked the development of ultra-super critical technology that allows operating steam turbines at high temperature and pressure conditions. However, operating at extreme conditions necessitates careful consideration of structural integrity which is affected by residual stresses. Welding is used for joining of components of steam turbines, but this process causes the formation of residual stresses of complex form. Careful investigation is necessary to understand the distribution of potentially detrimental residual stress fields. Eigenstrain theory was previously used for the development of the artificial intelligence based Eigenstrain (AI-eig) contour method that allowed advanced modelling of the behaviour of Inconel alloy 740H under thermo-mechanical loading conditions. Models created using this method are capable of evaluating the residual stress fields in the whole specimen or in the parts and slices created using electric discharge machining (EDM). In the previous applications of the AI-eig contour method, the determination of the distribution of Eigenstrain in as-welded and heat-treated specimens was followed by the calculation of volumetric residual stresses. In this study, long- and short-transverse components of the residual strains determined by the AI-eig contour method applied to EDM-cut surfaces of the parts of as-welded and heat-treated specimens were validated using the neutron strain scanning method. The results demonstrate the effectiveness of the integrative modelling approach that enables the determination of Eigenstrains in the whole specimen and the calculation of residual strains before and after the machining process.
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the use of profilometry techniques and Eigenstrain theory for the analysis of creep behavior in nickel superalloy welds
Materials Today: Proceedings, 2020Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract This paper presents a summary of recently developed experimental and computational tools to reconstruct residual stress fields and analyze creep in nickel superalloy welds used in aerospace engineering components. This approach combines experimental data with Eigenstrain theory to reconstruct stress fields at the macroscopic scale and provided reliable means for numerical prediction of creep behavior of welded components under complex loading conditions. Experimental data in the form of profilometry scans was interpreted using a range of iterative Eigenstrain methods that included the adaptation of the contour method and artificial intelligence models for Eigenstrain-creep analysis. The integration of principles of artificial intelligence with Eigenstrain models allowed highly accurate results to be obtained which were validated by comparison with experimental data obtained using independent techniques such as neutron diffraction. The use of artificial intelligence models is discussed for residual stress reconstruction and creep behavior prediction in annular aeroengine parts manufactured using inertia friction welding. To extend the range of experimental data taken into consideration, the height Digital Image Correlation (hDIC) technique was introduced that utilizes information regarding triaxial displacements obtained from profilometry, allowing deeper and more reliable analysis to be conducted. The hDIC technique was validated using operando tensile testing data.
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The use of Eigenstrain theory and fuzzy techniques for intelligent modeling of residual stress and creep relaxation in welded superalloys
Materials Today: Proceedings, 2020Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract Ni-base superalloys are used in a wide range of applications where components made from these alloys are exposed to extreme conditions of high temperature and high pressure, and dependable performance is critical for mission success, the safety of human lives, and multi-million commercial investment. To ensure robustness and reliability of highly demanding engineering solutions, it is crucial to advance the development of cutting-edge computational design tools based on artificial intelligence and fuzzy techniques, combined with the application of materials characterization and materials design. In the present study, the use of the contour method in combination with Eigenstrain theory provided new insights into 3D residual stress states in Ni-base superalloy samples. As-welded and heat-treated specimens were made using bead-on-plate design to investigate the effect of complex fabrication conditions on welds process in large components. The widely used relief of residual stresses during post-weld heat treatment was simulated using Eigenstrain-creep model. Furthermore, artificial intelligence (AI) based Eigenstrain-contour and Eigenstrain-creep models, that use fuzzy techniques, were developed by the present authors for materials used in advanced ultra-supercritical coal-powered plants, showing good match with experiments. The present study reports the combination of Eigenstrain theory with artificial intelligence for the modelling of welding residual stresses and simulation of post-weld heat treatment process and highlights the benefits of AI-based Eigenstrain-contour and Eigenstrain-creep methods on the development of robust and reliable aeroengine components.
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On the analysis of post weld heat treatment residual stress relaxation in Inconel alloy 740H by combining the principles of artificial intelligence with the Eigenstrain theory
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract Post weld heat treatment (PWHT) process has an important role on fabrication of advanced ultra-supercritical power plant turbines. This process relieves the residual stresses formed as a result of welding by converting elastic strains into creep strains. In order to analyse the residual stress relief mechanism during the PWHT process, a novel simulation approach based on experimental data was developed for the analysis of residual stress states from complex manufacturing processes which are welding and heat treatment. This model uses permanent plastic strains (Eigenstrains) formed as a result of welding process to set the initial mechanical state of the sample. The distribution of Eigenstrains in the whole body was determined using displacement data obtained from contour measurements. The use of Eigenstrains to set the initial residual stress state of the creep model reduced the number of uncertainties. This allowed the use of the principles of artificial intelligence for the development of a new fuzzy finite element model (fFEM) that determines the Eigenstrain-creep model parameters through an evolution process. Subsequent to the determination of the model parameters, conditions of the PWHT process are investigated to analyse residual stress relaxation in Inconel Alloy 740H weldments.
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on the application of principles of artificial intelligence for Eigenstrain reconstruction of volumetric residual stresses in non uniform inconel alloy 740h weldments
Finite Elements in Analysis and Design, 2019Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract The Eigenstrain theory provides a range of fruitful concepts for advanced modelling of the behaviour of materials and components obtained using sophisticated manufacturing routes, their response to thermal and mechanical loading, and deformation under fatigue and creep conditions. In recent years the method has been shown to be able to provide predictions of residual stresses for a limited range of processing and simulated service conditions for which experimental data is available. The authors recently presented advances in the use of Eigenstrain-based analysis to include accurate determination of the domain and boundaries of Eigenstrain fields in the weld zone. This approach allowed effective modelling of large-scale components and the determination of volumetric distributions of residual stresses through the use of additional model coefficients that need to be determined. Due to the non-linear dependence of the prediction on these parameters, the algorithm of the decision-making process has a profound influence on the cost of the simulation, and the reliability of its output. To address this challenge, the principles of Artificial Intelligence were adopted for use in the Eigenstrain contour method to develop fuzzy Finite Element Model (fFEM) for the Eigenstrain the reconstruction of residual stresses in large structures. The deterministic finite element Eigenstrain model uses contour measurements for reconstruction process, and the developed fFEM behaves as an artificial agent to determine the coefficients of the deterministic finite element Eigenstrain model. As an example application, as-welded and post-weld heat-treated specimens of non-uniform weldments of Inconel Alloy 740H were investigated using the proposed model. The results were verified using displacement measurements and residual stress calculations of the contour method. The determination of model coefficients by artificial agent allowed effective reconstruction of volumetric residual stresses in complex shaped components using limited data without the requirement of costly and destructive multi-cut experimental procedures.
Fatih Uzun - One of the best experts on this subject based on the ideXlab platform.
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neutron strain scanning for experimental validation of the artificial intelligence based Eigenstrain contour method
Mechanics of Materials, 2020Co-Authors: Fatih Uzun, Chrysanthi Papadaki, Zifan Wang, Alexander M KorsunskyAbstract:Abstract The demand for energy generation with low carbon emissions evoked the development of ultra-super critical technology that allows operating steam turbines at high temperature and pressure conditions. However, operating at extreme conditions necessitates careful consideration of structural integrity which is affected by residual stresses. Welding is used for joining of components of steam turbines, but this process causes the formation of residual stresses of complex form. Careful investigation is necessary to understand the distribution of potentially detrimental residual stress fields. Eigenstrain theory was previously used for the development of the artificial intelligence based Eigenstrain (AI-eig) contour method that allowed advanced modelling of the behaviour of Inconel alloy 740H under thermo-mechanical loading conditions. Models created using this method are capable of evaluating the residual stress fields in the whole specimen or in the parts and slices created using electric discharge machining (EDM). In the previous applications of the AI-eig contour method, the determination of the distribution of Eigenstrain in as-welded and heat-treated specimens was followed by the calculation of volumetric residual stresses. In this study, long- and short-transverse components of the residual strains determined by the AI-eig contour method applied to EDM-cut surfaces of the parts of as-welded and heat-treated specimens were validated using the neutron strain scanning method. The results demonstrate the effectiveness of the integrative modelling approach that enables the determination of Eigenstrains in the whole specimen and the calculation of residual strains before and after the machining process.
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The use of Eigenstrain theory and fuzzy techniques for intelligent modeling of residual stress and creep relaxation in welded superalloys
Materials Today: Proceedings, 2020Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract Ni-base superalloys are used in a wide range of applications where components made from these alloys are exposed to extreme conditions of high temperature and high pressure, and dependable performance is critical for mission success, the safety of human lives, and multi-million commercial investment. To ensure robustness and reliability of highly demanding engineering solutions, it is crucial to advance the development of cutting-edge computational design tools based on artificial intelligence and fuzzy techniques, combined with the application of materials characterization and materials design. In the present study, the use of the contour method in combination with Eigenstrain theory provided new insights into 3D residual stress states in Ni-base superalloy samples. As-welded and heat-treated specimens were made using bead-on-plate design to investigate the effect of complex fabrication conditions on welds process in large components. The widely used relief of residual stresses during post-weld heat treatment was simulated using Eigenstrain-creep model. Furthermore, artificial intelligence (AI) based Eigenstrain-contour and Eigenstrain-creep models, that use fuzzy techniques, were developed by the present authors for materials used in advanced ultra-supercritical coal-powered plants, showing good match with experiments. The present study reports the combination of Eigenstrain theory with artificial intelligence for the modelling of welding residual stresses and simulation of post-weld heat treatment process and highlights the benefits of AI-based Eigenstrain-contour and Eigenstrain-creep methods on the development of robust and reliable aeroengine components.
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the use of profilometry techniques and Eigenstrain theory for the analysis of creep behavior in nickel superalloy welds
Materials Today: Proceedings, 2020Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract This paper presents a summary of recently developed experimental and computational tools to reconstruct residual stress fields and analyze creep in nickel superalloy welds used in aerospace engineering components. This approach combines experimental data with Eigenstrain theory to reconstruct stress fields at the macroscopic scale and provided reliable means for numerical prediction of creep behavior of welded components under complex loading conditions. Experimental data in the form of profilometry scans was interpreted using a range of iterative Eigenstrain methods that included the adaptation of the contour method and artificial intelligence models for Eigenstrain-creep analysis. The integration of principles of artificial intelligence with Eigenstrain models allowed highly accurate results to be obtained which were validated by comparison with experimental data obtained using independent techniques such as neutron diffraction. The use of artificial intelligence models is discussed for residual stress reconstruction and creep behavior prediction in annular aeroengine parts manufactured using inertia friction welding. To extend the range of experimental data taken into consideration, the height Digital Image Correlation (hDIC) technique was introduced that utilizes information regarding triaxial displacements obtained from profilometry, allowing deeper and more reliable analysis to be conducted. The hDIC technique was validated using operando tensile testing data.
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On the analysis of post weld heat treatment residual stress relaxation in Inconel alloy 740H by combining the principles of artificial intelligence with the Eigenstrain theory
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract Post weld heat treatment (PWHT) process has an important role on fabrication of advanced ultra-supercritical power plant turbines. This process relieves the residual stresses formed as a result of welding by converting elastic strains into creep strains. In order to analyse the residual stress relief mechanism during the PWHT process, a novel simulation approach based on experimental data was developed for the analysis of residual stress states from complex manufacturing processes which are welding and heat treatment. This model uses permanent plastic strains (Eigenstrains) formed as a result of welding process to set the initial mechanical state of the sample. The distribution of Eigenstrains in the whole body was determined using displacement data obtained from contour measurements. The use of Eigenstrains to set the initial residual stress state of the creep model reduced the number of uncertainties. This allowed the use of the principles of artificial intelligence for the development of a new fuzzy finite element model (fFEM) that determines the Eigenstrain-creep model parameters through an evolution process. Subsequent to the determination of the model parameters, conditions of the PWHT process are investigated to analyse residual stress relaxation in Inconel Alloy 740H weldments.
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on the application of principles of artificial intelligence for Eigenstrain reconstruction of volumetric residual stresses in non uniform inconel alloy 740h weldments
Finite Elements in Analysis and Design, 2019Co-Authors: Fatih Uzun, Alexander M KorsunskyAbstract:Abstract The Eigenstrain theory provides a range of fruitful concepts for advanced modelling of the behaviour of materials and components obtained using sophisticated manufacturing routes, their response to thermal and mechanical loading, and deformation under fatigue and creep conditions. In recent years the method has been shown to be able to provide predictions of residual stresses for a limited range of processing and simulated service conditions for which experimental data is available. The authors recently presented advances in the use of Eigenstrain-based analysis to include accurate determination of the domain and boundaries of Eigenstrain fields in the weld zone. This approach allowed effective modelling of large-scale components and the determination of volumetric distributions of residual stresses through the use of additional model coefficients that need to be determined. Due to the non-linear dependence of the prediction on these parameters, the algorithm of the decision-making process has a profound influence on the cost of the simulation, and the reliability of its output. To address this challenge, the principles of Artificial Intelligence were adopted for use in the Eigenstrain contour method to develop fuzzy Finite Element Model (fFEM) for the Eigenstrain the reconstruction of residual stresses in large structures. The deterministic finite element Eigenstrain model uses contour measurements for reconstruction process, and the developed fFEM behaves as an artificial agent to determine the coefficients of the deterministic finite element Eigenstrain model. As an example application, as-welded and post-weld heat-treated specimens of non-uniform weldments of Inconel Alloy 740H were investigated using the proposed model. The results were verified using displacement measurements and residual stress calculations of the contour method. The determination of model coefficients by artificial agent allowed effective reconstruction of volumetric residual stresses in complex shaped components using limited data without the requirement of costly and destructive multi-cut experimental procedures.
Djaffar Boussaa - One of the best experts on this subject based on the ideXlab platform.
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Effects of superimposed Eigenstrains on the overall thermoelastic moduli of composites
Mechanics of Materials, 2017Co-Authors: Djaffar BoussaaAbstract:Abstract This study investigates the effects that an initial local Eigenstrain field, when superimposed on the thermal Eigenstrain field, has on the overall thermal expansion coefficients and heat capacities of thermoelastic composites. The study can also be seen as an investigation into how a local residual stress field affects these overall moduli, as initial Eigenstrains are generally a source of residual stresses. The approach taken is thermodynamic. Expressions that include the superimposed Eigenstrain field are developed for the overall moduli within the framework of small strain thermoelasticity with temperature dependent materials. These expressions, which are written in terms of the concentration tensors and residual fields (stress and strain fields given rise to by the Eigenstrains under zero overall stress and strain, respectively), contain correction terms that are absent in the expressions developed within linear thermoelasticity. Taking into account the temperature dependence of the constituent moduli is shown to be essential to capture the effects of the superimposed Eigenstrain field. A Ti–6Al–4V/ZrO 2 composite is investigated for which the correction terms are found to be negligible for the heat capacities but significant for the thermal expansion coefficients. This suggests that, for applications with large temperature changes, using the linear-thermoelasticity-based expressions can affect the accuracy of the estimates of the overall moduli, and therefore the accuracy of thermostructural analyses of composite structures. The proposed expressions can be of use to estimate the overall thermoelastic moduli in contexts in which the strains remain small, temperature changes are large, and superimposed Eigenstrains may be present.
Arash Yavari - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Elastic Inclusions in Anisotropic Solids
Journal of Elasticity, 2018Co-Authors: Ashkan Golgoon, Arash YavariAbstract:In this paper we study the stress and deformation fields generated by nonlinear inclusions with finite Eigenstrains in anisotropic solids. In particular, we consider finite Eigenstrains in transversely isotropic spherical balls and orthotropic cylindrical bars made of both compressible and incompressible solids. We show that the stress field in a spherical inclusion with uniform pure dilatational Eigenstrain in a spherical ball made of an incompressible transversely isotropic solid such that the material preferred direction is radial at any point is uniform and hydrostatic. Similarly, the stress in a cylindrical inclusion contained in an incompressible orthotropic cylindrical bar is uniform hydrostatic if the radial and circumferential Eigenstrains are equal and the axial stretch is equal to a value determined by the axial Eigenstrain. We also prove that for a compressible isotropic spherical ball and a cylindrical bar containing a spherical and a cylindrical inclusion, respectively, with uniform Eigenstrains the stress in the inclusion is uniform (and hydrostatic for the spherical inclusion) if the radial and circumferential Eigenstrains are equal. For compressible transversely isotropic and orthotropic solids, we show that the stress field in an inclusion with uniform Eigenstrain is not uniform, in general. Nevertheless, in some special cases the material can be designed in order to maintain a uniform stress field in the inclusion. As particular examples to investigate such special cases, we consider compressible Mooney-Rivlin and Blatz-Ko reinforced models and find analytical expressions for the stress field in the inclusion.
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Finite Eigenstrains in Nonlinear Elastic Solid Wedges
2018Co-Authors: Ashkan Golgoon, Souhayl Sadik, Arash YavariAbstract:Eigenstrains in nonlinear solids are created due to anelastic effects such as non-uniform temperature distributions, growth, remodeling, and defects. Eigenstrains understanding is indispensable, as they can generate residual stresses and strongly affect the overall response of solids. Here, we study the residual stress and deformation fields of an incompressible isotropic infinite wedge with a circumferentially-symmetric distribution of finite Eigenstrains. We construct a material manifold, whose Riemannian metric explicitly depends on the Eigenstrain distribution, thereby we turn the problem into a classical nonlinear elasticity problem, where we find an embedding of the Riemannian material manifold into the ambient Euclidean space. In particular, we find exact solutions for the residual stress and deformation fields of a neo-Hookean wedge having a symmetric inclusion with finite radial and circumferential Eigenstrains. Moreover, we numerically solve a similar problem when a symmetric Mooney-Rivlin inhomogeneity with finite Eigenstrains is placed in a neo-Hookean wedge. Generalization of the Eigenstrain problem to other geometries are also discussed.
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The anelastic Ericksen problem: universal Eigenstrains and deformations in compressible isotropic elastic solids.
Proceedings. Mathematical physical and engineering sciences, 2016Co-Authors: Arash Yavari, Alain GorielyAbstract:The elastic Ericksen problem consists of finding deformations in isotropic hyperelastic solids that can be maintained for arbitrary strain-energy density functions. In the compressible case, Ericksen showed that only homogeneous deformations are possible. Here, we solve the anelastic version of the same problem, that is, we determine both the deformations and the Eigenstrains such that a solution to the anelastic problem exists for arbitrary strain-energy density functions. Anelasticity is described by finite Eigenstrains. In a nonlinear solid, these Eigenstrains can be modelled by a Riemannian material manifold whose metric depends on their distribution. In this framework, we show that the natural generalization of the concept of homogeneous deformations is the notion of covariantly homogeneous deformations-deformations with covariantly constant deformation gradients. We prove that these deformations are the only universal deformations and that they put severe restrictions on possible universal Eigenstrains. We show that, in a simply-connected body, for any distribution of universal Eigenstrains the material manifold is a symmetric Riemannian manifold and that in dimensions 2 and 3 the universal Eigenstrains are zero-stress.
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Circumferentially-symmetric finite Eigenstrains in incompressible isotropic nonlinear elastic wedges
International Journal of Non-Linear Mechanics, 2016Co-Authors: Ashkan Golgoon, Souhayl Sadik, Arash YavariAbstract:Abstract Eigenstrains are created as a result of anelastic effects such as defects, temperature changes, bulk growth, etc., and strongly affect the overall response of solids. In this paper, we study the residual stress and deformation fields of an incompressible, isotropic, infinite wedge due to a circumferentially symmetric distribution of finite Eigenstrains. In particular, we establish explicit exact solutions for the residual stresses and deformation of a neo-Hookean wedge containing a symmetric inclusion with finite radial and circumferential Eigenstrains. In addition, we numerically solve for the residual stress field of a neo-Hookean wedge induced by a symmetric Mooney–Rivlin inhomogeneity with finite Eigenstrains.
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On the stress singularities generated by anisotropic Eigenstrains and the hydrostatic stress due to annular inhomogeneities
Journal of the Mechanics and Physics of Solids, 2015Co-Authors: Arash Yavari, Alain GorielyAbstract:Abstract The problems of singularity formation and hydrostatic stress created by an inhomogeneity with Eigenstrain in an incompressible isotropic hyperelastic material are considered. For both a spherical ball and a cylindrical bar with a radially symmetric distribution of finite possibly anisotropic Eigenstrains, we show that the anisotropy of these Eigenstrains at the center (the center of the sphere or the axis of the cylinder) controls the stress singularity. If they are equal at the center no stress singularity develops but if they are not equal then stress always develops a logarithmic singularity. In both cases, the energy density and strains are everywhere finite. As a related problem, we consider annular inclusions for which the Eigenstrains vanish in a core around the center. We show that even for an anisotropic distribution of Eigenstrains, the stress inside the core is always hydrostatic. We show how these general results are connected to recent claims on similar problems in the limit of small Eigenstrains.
Helmut J. Böhm - One of the best experts on this subject based on the ideXlab platform.
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On the role of the transformation Eigenstrain in the growth or shrinkage of spheroidal isotropic precipitations
Acta Materialia, 2005Co-Authors: Franz Dieter Fischer, Helmut J. BöhmAbstract:Abstract The jumps of the strain and stress tensors on the surface of elastic homogeneous or inhomogeneous ellipsoidal inclusions embedded in an elastic matrix are obtained from results reported in the literature. They are used to derive closed-form expressions for the thermodynamic force in such matrix–inclusion systems that are subjected to a generally defined homogeneous transformation Eigenstrain. A detailed study is presented for an isotropic spheroidal inclusion in an isotropic matrix in which the most important parameters are the inclusion’s aspect ratio α and an Eigenstrain triaxiality parameter d ˜ . The fluctuations of the thermodynamic force are investigated for a set of specific transformation Eigenstrain tensors and are presented for inclusion shapes ranging from disk-like to fiber-like spheroids.
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Evaluation of elastic strain energy of spheroidal inclusions with uniform volumetric and shear Eigenstrains
Scripta Materialia, 1997Co-Authors: Helmut J. Böhm, Franz Dieter Fischer, G. ReisnerAbstract:The calculation of the elastic strain energy due to a uniform Eigenstrain in an inclusion continues to be of high concern for various problems in material science such as nucleation conditions or transformation conditions for the inclusion. It is the main goal of this note to show that very easily programmable equations can be formulated for a general uniform Eigenstrain tensor consisting of three different normal and three different shear strains. Although the authors appreciate the recently published results very much, they do not see any necessity to demonstrate in detail specific results since the following derivation presents a consistent way to calculate the specific strain energy in very few steps. Specifically, a modified notation helps to split the usually lengthy expression into a group of easily expressible terms multiplied by the mixed product terms of the normal Eigenstrains and the squares of the shear Eigenstrains. Since all entities are expressed with respect to a coordinate frame attached to the inclusion any coordinate transformation can be avoided.