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• Evaluation of finite-element calculations in a part-circular crack by coherent optics techniques

  G. Kaufmann, A. Lopergolo, S. Idelsohn, E. Barbero

  Experimental Mechanics (1987). Vol. 27 (2), pp. 154-157

  
  

  Abstract

  Two techniques, speckle photography and holographic interferometry, were used to test three-dimensional finite-element calculations in an internally pressurized cylinder with an external part-circular crack. Opening displacements along the crack line were measured by speckle photography. Radial displacements were obtained from holographic fringe patterns. Good agreement between experimental and numerical data is obtained. Stress-intensity factor variations along the crack front are calculated from numerical results.

  Abstract
  Two techniques, speckle photography and holographic interferometry, were used to test three-dimensional finite-element calculations in an internally pressurized cylinder with [...]

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• Inelastic seismic analysis of a building structure designed by argentine codes

  V. Sonzogni, A. Cardona, S. Idelsohn

  Earthquake Engineering Structural Dynamics (1984). Vol. 12 (6), pp. 721-736

  
  

  Abstract

  A reinforced concrete frame‐wall structure of a building designed in accordance to standard practice in Argentina was analysed by the procedures prescribed by current Argentine Codes. In addition, the inelastic step‐by‐step response of the structure to design spectrum‐compatible accelerograms was studied by means of a special element for inelastic dynamic analysis of reinforced concrete frames. Results obtained by the different methods of analysis are presented

  Abstract
  A reinforced concrete frame‐wall structure of a building designed in accordance to standard practice in Argentina was analysed by the procedures prescribed by current Argentine [...]

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• A comparative computational study of blood flow through prosthetic heart valves using the finite element method

  S. Idelsohn, L. Costa, R. Ponso

  Journal of Biomechanics (1985). Vol. 18 (2), pp. 97-115

  
  

  Abstract

  The steady flow of blood through three common types of prosthetic heart valves was simulated numerically using the finite element method. The velocity, pressure and stress fields were obtained for the disk-type, tilting-disk and ball-type prosthetic heart valves in aortic position, for increasing Reynolds numbers up to 900, 1500 and 2000 respectively. Computer graphics of calculated velocities are presented, showing in detail the accelerated flow, recirculation and stagnation areas developed in the prosthesis. Maximum wall shear stresses were found at 0.5, 1.4, and 1.2 diameters from the sewing ring downstream for the disk, tilting-disk and ball valves being the values of 55, 18 and 33 dyn cm−2 respectively. In the vicinity of the occluder, maximum shear stresses of 38, 30 and 47 dyn cm−2 respectively were computed. The flow characteristics and performance for each valve are compared, the results are presented in terms of energy loss and maximum shear stress. The velocity and stress fields are compared with in vitro evaluations found in the literature

  Abstract
  The steady flow of blood through three common types of prosthetic heart valves was simulated numerically using the finite element method. The velocity, pressure and stress [...]

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• Smoothed surface gradients for panel methods

  J. D'Elía, M. Storti, S. Idelsohn

  Advances in Engineering Software (2000). Vol. 31 (5), pp. 339-346

  
  

  Abstract

  A weak form to compute the dipolar and monopolar surface gradients, related to a low-order panel method, is shown. The flow problem is formulated by means of a three-dimensional potential model and the discretization is based on Morino's formulation for the perturbation velocity potential. On the body surface, this representation reduces to a boundary integral equation with the source (or monopolar) and the doublet (or dipolar) densities. The first of the two is found by application of the boundary flow condition, and the second one is the unknown over the body surface. A lower panel method is used for the analytic integrations of both the monopolar and dipolar influence coefficients. The surface velocity field is computed after solving the linear system, with a strong and a weak form of the Stokes theorem, which is oriented to fairly non-structured panel meshes. The proposed method is validated by comparing the numerical results with analytical ones for an isolated sphere and includes a prediction over a car-like configuration.

  Abstract
  A weak form to compute the dipolar and monopolar surface gradients, related to a low-order panel method, is shown. The flow problem is formulated by means of a three-dimensional [...]

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• A closed form for low-order panel methods

  J. D'Elía, M. Storti, S. Idelsohn

  Advances in Engineering Software (2000). Vol. 31 (5), pp. 347-353

  
  

  Abstract

  A closed form for the computation of the dipolar and monopolar influence coefficients related to a low-order panel method is shown. The flow problem is formulated by means of a three-dimensional potential model; the method of discretization is based on the Morino formulation for the perturbation velocity potential. On the body surface this representation reduces to an integral equation with the source (or monopolar) and the doublet (or dipolar) densities. The former is found by application of the boundary condition, and the latter is the unknown over the surface of the body. The lower panel method is used for the analytical integrations of the monopolar and dipolar influence coefficients, with special attention to avoid a logarithmic singularity in the monopolar matrix when flat fairly structured meshes that are common in ship-wave calculations are used.

  Abstract
  A closed form for the computation of the dipolar and monopolar influence coefficients related to a low-order panel method is shown. The flow problem is formulated by means [...]

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• Evaluation of Finite Element Calculations in a Cracked Cylinder Under Internal Pressure by Speckle Photography

  G. Kaufmann, A. Lopergolo, S. Idelsohn

  J. Appl. Mech (1983). Vol. 50 (4a), pp. 896-897

  
  

  Abstract

  The usefulness of using the speckle photography technique in fracture mechanics to check numerical calculations is demonstrated for an internally pressurized cylinder with a surface flaw. A pointwise technique was utilized to measure the opening displacements along the crack line and the Mode I stress-intensity factor was determined by extrapolating these results to the crack tip. Finite element calculations were performed to be compared with experimental data and good agreement was obtained.

  Abstract
  The usefulness of using the speckle photography technique in fracture mechanics to check numerical calculations is demonstrated for an internally pressurized cylinder with [...]

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• Transverse vibrations of an isotropic, simply supported rectangular plate with an orthotropic inclusion

  L. Ercoli, V. Sonzogni, S. Idelsohn, P. Laura

  Journal of Sound and Vibration (1992). Vol. 135 (2), pp. 217-221

  
  

  Abstract

  An approximate analytical solution is obtained for the title problem by using a Navier-type solution. It is shown that the fundamental frequency coefficient obtained by means of this procedure is in reasonably good agreement with the result obtained by using a finite element algorithmic methodology. Obviously the type of material disturbance considered introduces considerable change in the dynamic behavior of the structural element and this fact is clearly shown in the variation of the fundamental frequency value.

  Abstract
  An approximate analytical solution is obtained for the title problem by using a Navier-type solution. It is shown that the fundamental frequency coefficient obtained by means [...]

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• Free vibrations of rectangular plates of exponentially varying thickness and with a free edge

  V. Sonzogni, S. Idelsohn, P. Laura, V. Cortínez

  Journal of Sound and Vibration (1990). Vol. 140 (3), pp. 513-522

  
  

  Abstract

  Transverse vibrations of the structural system described in the title are analyzed by using classical plate theory and employing two different methodologies: the recently developed “optimized Kantorovich approach”; and a finite element algorithmic procedure. It is shown that the fundamental frequency coefficients obtained by using both techniques for a rather wide variation of the governing geometric parameters are in very good agreement. Lower frequency coefficients of the plate system determined by means of the finite element method are also presented.

  Abstract
  Transverse vibrations of the structural system described in the title are analyzed by using classical plate theory and employing two different methodologies: the recently [...]

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• On the self-stressing modes in free vibration analysis

  S. Idelsohn, M. Geradin

  Journal of Sound and Vibration (1982). Vol. 83 (2), pp. 143-155

  
  

  Abstract

  The type of convergence to the eigenspectrum of a structure calculated from a finite element analysis is examined in light of the variational properties of the Rayleigh quotient and of Courant's maximum-minimum principle. The influence of the self-stressing modes on the solution is firt demonstrated theoretically and then shown practically on the results obtained via a family of equilibrium elements in which the number of self-stressing modes relative to the number of vibration modes may be varied as a parameter.

  Abstract
  The type of convergence to the eigenspectrum of a structure calculated from a finite element analysis is examined in light of the variational properties of the Rayleigh quotient [...]

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• Fast fluid–structure interaction simulations using a displacement-based finite element model equipped with an explicit streamline integration prediction

  P. Ryzhakov, J. Miquel, S. Idelsohn, E. Oñate

  Comput. Methods Appl. Mech. Engrg., (2017). Vol. 315, pp. 1080-1097

  
  

  Abstract

  We propose here a displacement-based updated Lagrangian fluid model developed to facilitate a monolithic coupling with a wide range of structural elements described in terms of displacements. The novelty of the model consists in the use of the explicit streamline integration for predicting the end-of-step configuration of the fluid domain. It is shown that this prediction considerably alleviates the time step size restrictions faced by the former Lagrangian models due to the possibility of an element inversion within one time step. The method is validated and compared with conventional approaches using three numerical examples. Time step size and corresponding Courant numbers leading to optimal behavior in terms of computational efficiency are identified.

  Abstract
  We propose here a displacement-based updated Lagrangian fluid model developed to facilitate a monolithic coupling with a wide range of structural elements [...]

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