The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

Filippo Berto - One of the best experts on this subject based on the ideXlab platform.

  • Volume free Strain Energy Density method for applications to blunt V-notches
    Procedia Structural Integrity, 2020
    Co-Authors: Pietro Foti, Seyed Mohammad Javad Razavi, Liviu Marsavina, Filippo Berto
    Abstract:

    Abstract This work investigates the application of the Strain Energy Density method to rounded V-notches under mode I loading conditions and to components without stress concentrators through finite element models that do not involve the construction of the control volume in the preprocessing phase of the finite element analysis. The application of the Strain Energy Density method to components without stress concentrators like sharp V-notches requires, according to the conventional procedure of the method, two different numerical simulations; the first simulation defines the point of maximum of the first principal stress along the notch fillet; the second simulation calculates the Strain Energy Density value within the control volume built using the position of the first principal stress maximum evaluated in the first simulation. Several numerical analyses, with changing the notch angle, the notch radius, the control volume radius and the mesh refinement, were carried out to evaluate the error in calculating the Strain Energy Density value through the new procedure presented in the present work whose main advantages are to simplify the method and to decrease the calculation time that, dealing with complex geometries, is reduced by 50% requiring only one simulation instead of the two requested by the conventional procedure

  • The Strain Energy Density approach applied to bonded joints
    Procedia Structural Integrity, 2020
    Co-Authors: Paolo Ferro, Filippo Berto
    Abstract:

    Abstract Adhesively bonded joints can be treated as bi-materials characterized by a stress singularity promoted by both geometrical and constitutive discontinuities, very close to the point where the interface between two elastic solids intersects a traction-free edge. Different approaches have been proposed to predict their both static and fatigue strength. Most of them are based on the stress distribution at the interface between the adherent and the adhesive. More recently, Energy Density-based criteria have been developed to predict the static and fatigue strength of mono-material notched components, like welded joints. The most promising one is the Strain Energy Density approach in which it is assumed that failure occurs when the Strain Energy Density, averaged over a control volume of critical radius Rc surrounding the singularity point, will reach a critical value. Advantages are different. Among the others, the Strain Energy Density doesn’t depend on the singularity order and doesn’t require a fine mesh. This contribution is aimed at applying the Strain Energy Density criterion to bonded joints.

  • Rapid Strain Energy Density evaluation for V-notches under mode I loading conditions
    Engineering Failure Analysis, 2020
    Co-Authors: Pietro Foti, Majid R. Ayatollahi, Filippo Berto
    Abstract:

    Abstract This work investigates the possibility to evaluate the Strain Energy Density value with a free mesh model suggesting the use of a correcting formula a posteriori. Several numerical analyses were carried out to prove the good agreement between the method suggested and the conventional method considered until now to acquire the Strain Energy Density value that requires the construction of the so-called control volume in the pre-processing phase of the FEM code. The main advantage of the methodology shown in the present work to evaluate the Strain Energy Density value is that, accepting an error in the calculation that depends on different parameters, it is possible to apply this method directly as a post-processing tool. This allows also to decrease considerably the effort of the researcher in applying this method and to reduce the calculation time thanks to the use of a free coarse mesh.

  • Multiaxial fatigue life assessment in notched components based on the effective Strain Energy Density
    Procedia Structural Integrity, 2020
    Co-Authors: Ricardo Branco, Filippo Berto, José Costa, L.p. Borrego, Javad Razavi, Wojciech Macek
    Abstract:

    Abstract This paper presents a methodology to predict the fatigue lifetime in notched geometries subjected to multiaxial loading based on the effective Strain Energy Density concept. The modus operandi consists of defining a fatigue master curve that relates the Strain Energy Density with the number of cycles to failure from standard cylindrical specimens tested under low-cycle fatigue conditions. After that, the multiaxial loading history at the geometric discontinuity is reduced to an equivalent uniaxial loading scenario via the calculation of an averaged value of the Strain Energy, which is done by combining the equivalent Strain Energy Density concept along with the theory of critical distances. Then, this Energy is inserted into the fatigue master curve to estimate the fatigue lifetime. The method is tested in solid round bars with lateral notches subjected to in-phase bending-torsion loading. Overall, the comparison between the experimental and predicted fatigue lives shows a very good agreement. Additionally, the proposed approach enables the determination of the most likely initiation sites as well as the crack angles at the early stage of crack growth.

  • Evaluation of the Effect of the TIG-Dressing Technique on Welded Joints through the Strain Energy Density Method
    Procedia Structural Integrity, 2020
    Co-Authors: Pietro Foti, Filippo Berto
    Abstract:

    Abstract Among the various techniques employed to increase the fatigue strength of a welded joint, the TIG dressing technique acts on the weld geometry re-melting the welding toe to eliminate the presence of sharp V-notches. The main aim of this work is to investigate the effect of the TIG dressing technique on the fatigue behavior of welded joints summarizing the results of experimental tests taken from the literature through the Strain Energy Density method. The experimental tests considered were performed both on as-welded and TIG-dressed joints in order to better understand the improvement that such a technique leads to the welded joints. Finally, the data were summarized through the Strain Energy Density technique to show that the same fatigue curve, defined in terms of Strain Energy Density versus number of cycles, obtained for the as-welded joints could be used also for the TIG-dressed joints being the method not dependent on the geometry considered.

Wen-hu Huang - One of the best experts on this subject based on the ideXlab platform.

  • Strain Energy Density of a circular cavity buried in a semi-infinite slab of functionally graded materials subjected to anti-plane shear waves
    International Journal of Solids and Structures, 2007
    Co-Authors: Xue-qian Fang, Wen-hu Huang
    Abstract:

    The paper presents a theoretical method to investigate the multiple scattering of shear waves and Strain Energy Density in a semi-infinite slab of functionally graded materials with a circular cavity. The analytical solutions of wave fields are expressed by employing wave function expansion method and the expanded mode coefficients are determined by satisfying the boundary conditions of the cavity. Image method is used to satisfy the free boundary condition of the semi-infinite structure. The analytical solution of the problem is derived, and the numerical solutions of the Strain Energy Density factors around the cavity are also graphically presented. The effects of the distances between the cavity and the boundaries of the semi-infinite slab, the wave number and the non-homogeneous parameter of materials on Strain Energy Density factors are analyzed. Analyses show that the Strain Energy Density around the cavity increases with increasing non-homogeneous parameter of materials and incident wave number. The boundaries of the semi-infinite slab have great effect on both the maximum Strain Energy Density and the distribution around the circular cavity, and the effect increases with increasing incident wave number. When the distance between the semi-infinite boundary and the cavity varies, the effect of the upper and lower boundaries on the distribution of the Strain Energy Density factors around the cavity is also examined.

Xue-qian Fang - One of the best experts on this subject based on the ideXlab platform.

  • Strain Energy Density of a circular cavity buried in a semi-infinite slab of functionally graded materials subjected to anti-plane shear waves
    International Journal of Solids and Structures, 2007
    Co-Authors: Xue-qian Fang, Wen-hu Huang
    Abstract:

    The paper presents a theoretical method to investigate the multiple scattering of shear waves and Strain Energy Density in a semi-infinite slab of functionally graded materials with a circular cavity. The analytical solutions of wave fields are expressed by employing wave function expansion method and the expanded mode coefficients are determined by satisfying the boundary conditions of the cavity. Image method is used to satisfy the free boundary condition of the semi-infinite structure. The analytical solution of the problem is derived, and the numerical solutions of the Strain Energy Density factors around the cavity are also graphically presented. The effects of the distances between the cavity and the boundaries of the semi-infinite slab, the wave number and the non-homogeneous parameter of materials on Strain Energy Density factors are analyzed. Analyses show that the Strain Energy Density around the cavity increases with increasing non-homogeneous parameter of materials and incident wave number. The boundaries of the semi-infinite slab have great effect on both the maximum Strain Energy Density and the distribution around the circular cavity, and the effect increases with increasing incident wave number. When the distance between the semi-infinite boundary and the cavity varies, the effect of the upper and lower boundaries on the distribution of the Strain Energy Density factors around the cavity is also examined.

  • Strain Energy Density of a circular cavity buried in semi-infinite functionally graded materials subjected to shear waves
    Theoretical and Applied Fracture Mechanics, 2006
    Co-Authors: Xue-qian Fang
    Abstract:

    In this paper, based on the theory of multiple scattering of elastic waves, employing wave functions expansion method, multiple scattering and Strain Energy Density in semi-infinite functional graded materials with a circular cavity are investigated, the analytical solution of the problem is derived, and the numerical solution of the Strain Energy Density factors around the cavity is also presented. The effects of the distance between the cavity and the edge of the materials, the wave number and the non-homogeneous parameter of materials on Strain Energy Density factors are analyzed. From analysis, it can be seen that when the non-homogeneous parameter of materials is less than zero, it has less influence on the maximum Strain Energy Density factor around the cavity; however, it has greater influence on the distribution of Strain Energy Density factors around the cavity. When the non-homogeneous parameter of materials is greater than zero, it has greater influence on both the maximum Strain Energy Density factor and the distribution of Strain Energy Density factor around the cavity, especially in the case that the distance between the cavity and the edge is comparatively little.

Byung Man Kwak - One of the best experts on this subject based on the ideXlab platform.

  • Analogy of Strain Energy Density based bone-remodeling algorithm and structural topology optimization.
    Journal of biomechanical engineering, 2008
    Co-Authors: In Gwun Jang, Il Yong Kim, Byung Man Kwak
    Abstract:

    In bone-remodeling studies, it is believed that the morphology of bone is affected by its internal mechanical loads. From the 1970s, high computing power enabled quantitative studies in the simulation of bone remodeling or bone adaptation. Among them, Huiskes et al. (1987, "Adaptive Bone Remodeling Theory Applied to Prosthetic Design Analysis," J. Biomech. Eng., 20, pp. 1135-1150) proposed a Strain Energy Density based approach to bone remodeling and used the apparent Density for the characterization of internal bone morphology. The fundamental idea was that bone Density would increase when Strain (or Strain Energy Density) is higher than a certain value and bone resorption would occur when the Strain (or Strain Energy Density) quantities are lower than the threshold. Several advanced algorithms were developed based on these studies in an attempt to more accurately simulate physiological bone-remodeling processes. As another approach, topology optimization originally devised in structural optimization has been also used in the computational simulation of the bone-remodeling process. The topology optimization method systematically and iteratively distributes material in a design domain, determining an optimal structure that minimizes an objective function. In this paper, we compared two seemingly different approaches in different fields-the Strain Energy Density based bone-remodeling algorithm (biomechanical approach) and the compliance based structural topology optimization method (mechanical approach)-in terms of mathematical formulations, numerical difficulties, and behavior of their numerical solutions. Two numerical case studies were conducted to demonstrate their similarity and difference, and then the solution convergences were discussed quantitatively.

Pietro Foti - One of the best experts on this subject based on the ideXlab platform.

  • Volume free Strain Energy Density method for applications to blunt V-notches
    Procedia Structural Integrity, 2020
    Co-Authors: Pietro Foti, Seyed Mohammad Javad Razavi, Liviu Marsavina, Filippo Berto
    Abstract:

    Abstract This work investigates the application of the Strain Energy Density method to rounded V-notches under mode I loading conditions and to components without stress concentrators through finite element models that do not involve the construction of the control volume in the preprocessing phase of the finite element analysis. The application of the Strain Energy Density method to components without stress concentrators like sharp V-notches requires, according to the conventional procedure of the method, two different numerical simulations; the first simulation defines the point of maximum of the first principal stress along the notch fillet; the second simulation calculates the Strain Energy Density value within the control volume built using the position of the first principal stress maximum evaluated in the first simulation. Several numerical analyses, with changing the notch angle, the notch radius, the control volume radius and the mesh refinement, were carried out to evaluate the error in calculating the Strain Energy Density value through the new procedure presented in the present work whose main advantages are to simplify the method and to decrease the calculation time that, dealing with complex geometries, is reduced by 50% requiring only one simulation instead of the two requested by the conventional procedure

  • Rapid Strain Energy Density evaluation for V-notches under mode I loading conditions
    Engineering Failure Analysis, 2020
    Co-Authors: Pietro Foti, Majid R. Ayatollahi, Filippo Berto
    Abstract:

    Abstract This work investigates the possibility to evaluate the Strain Energy Density value with a free mesh model suggesting the use of a correcting formula a posteriori. Several numerical analyses were carried out to prove the good agreement between the method suggested and the conventional method considered until now to acquire the Strain Energy Density value that requires the construction of the so-called control volume in the pre-processing phase of the FEM code. The main advantage of the methodology shown in the present work to evaluate the Strain Energy Density value is that, accepting an error in the calculation that depends on different parameters, it is possible to apply this method directly as a post-processing tool. This allows also to decrease considerably the effort of the researcher in applying this method and to reduce the calculation time thanks to the use of a free coarse mesh.

  • Evaluation of the Effect of the TIG-Dressing Technique on Welded Joints through the Strain Energy Density Method
    Procedia Structural Integrity, 2020
    Co-Authors: Pietro Foti, Filippo Berto
    Abstract:

    Abstract Among the various techniques employed to increase the fatigue strength of a welded joint, the TIG dressing technique acts on the weld geometry re-melting the welding toe to eliminate the presence of sharp V-notches. The main aim of this work is to investigate the effect of the TIG dressing technique on the fatigue behavior of welded joints summarizing the results of experimental tests taken from the literature through the Strain Energy Density method. The experimental tests considered were performed both on as-welded and TIG-dressed joints in order to better understand the improvement that such a technique leads to the welded joints. Finally, the data were summarized through the Strain Energy Density technique to show that the same fatigue curve, defined in terms of Strain Energy Density versus number of cycles, obtained for the as-welded joints could be used also for the TIG-dressed joints being the method not dependent on the geometry considered.

  • Francis-99: Evaluation of the Strain Energy Density value for welded joints typical of turbine runner blades
    Journal of Physics: Conference Series, 2019
    Co-Authors: Pietro Foti, Filippo Berto
    Abstract:

    The main aim of this work is to investigate the fatigue behaviour of welded joints through an energetic approach based on the Strain Energy Density failure criteria. The geometries, taken from the literature, are typical of turbine runner blades. The results of the fatigue tests on these details were summarised through the Strain Energy Density approach. The application of this method to these geometries is the first step of a wider research with the aim to provide a suitable tool in FEM code for the lifetime estimation of components characterised by complex geometries.