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Material Identification

The finite element model updating method that is implemented in FEMtools can be used for identifying the elastic properties of isotropic, orthotropic and anisotropic materials. If the material properties or beam section properties are selected as global updating parameters, and the modes of vibration of a test specimen (obtained by measurement) are used as reference responses, then the updating procedure will iteratively adjust starting values until predicted dynamic behavior corresponds with observed one.

Application Cases

Identification of Layered Materials

This approach is a non-destructive material testing method that is especially useful for composites and laminated materials. The method easily adapts to be used in temperature-controlled environments to obtain properties as function of temperature (or other controlled conditions).

Identification of layered materials was explored in the following doctoral thesis and papers:

  • Tom Lauwagie, Vibration-Based Methods for the Identification of the Elastic Properties of Layered Materials, Doctoral thesis, University of Leuven, October 2005.
    Download (PDF, 8.0 MB)
  • T. Lauwagie, H. Sol, W. Heylen, Handling Uncertainties in Mixed Numerical-Experimental Techniques for Vibration Based Material Identification. Journal of Sound and Vibration, Volume 291, Issues 3-5, 4 April 2006, Pages 723-739.
  • Lauwagie T., Heylen W., Sol H., Van der Biest O., Roebben G., The Uncertainty Budget of Mixed-Numerical-Experimental-Techniques for the Identification of Elastic Material Properties from Resonant Frequencies. Proceedings of the  International Seminar on Modal Analysis 2004 (ISMA), pp. 1313-1324.
    Download (PDF, 349 KB)
  • Lauwagie T., Heylen W., Sol H., Van der Biest O., Validation of a Vibration Based Identification Procedure for Layered Materials. Proceedings of the  International Seminar on Modal Analysis 2004 (ISMA), pp. 1325-1336.
    Download (PDF, 695 KB)
  • T. Lauwagie, H. Sol, W. Heylen, G. Roebben, Determination of the In-Plane Elastic Properties of the Different Layers of Laminated Plates by Means of Vibration Testing and Model Updating. Journal of Sound and Vibration, Volume 274, Issues 3-5, 22 July 2004, Pages 529-546.
  • T. Lauwagie, H. Sol, G. Roebben, W. Heylen, Y. Shi, O. Van der Biest, Mixed Numerical-Experimental Identification of Elastic Properties of Orthotropic Metal Plates. NDT & E International, Volume 36, Issue 7, October 2003, Pages 487-495.
  • T. Lauwagie, E. Dascotte, Layered Material Identification using Multi-Model Updating. Proceedings of the 3rd International Conference on Structural Dynamics Modeling - Test, Analysis, Correlation and Validation - Madeira Island, Portugal, June 2002.
    Download (PDF, 160 KB)
  • Lauwagie T., Sol H., Roebben G., Heylen W., Shi Y., Validation of the Resonalyser Method: An Inverse Method for Material Identification. Proceedings of the  International Seminar on Modal Analysis 2002 (ISMA), pp. 687-694.
    Download (PDF, 296 KB) 

Identification of Beam Section Properties

The identification process can also be applied on cross-sectional properties of beams, for example for pultruded composite beams with arbitrary cross-sectional shapes. This identification process was explored in the following thesis and papers:

  • Erik Euler, Identification of the Material Properties of Slender Composite Structures, MSc thesis, University of Brussels, 2004. Download (PDF, 2.7 MB) 
  • E. Euler, H. Sol, E. Dascotte, Identification of Material Properties of Composite Beams: Inverse Method Approach, Presented at the 2006 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, June 4-7, 2006, St. Louis, MO, USA.
    Download (PDF, 360 KB)

Identification of Ogden Material Properties

The Ogden material model is frequently used in finite element programs to simulate the behavior of non-linear elastomers. The values of the material parameters of the Ogden model are highly material dependent. The main challenge in using the Ogden model in finite element simulations, is to find reliable estimates for the values of the Ogden material parameters. The relation between an imposed displacement and the resulting reaction force can be used to identify these material parameters using a mixed numerical-experimental approach. In this approach, the objective is to fit the simulated reaction force curve onto the measured reaction force curve. The computationally most efficient way of doing that is by using a gradient-based optimization strategy.

Such identification routine was implemented using FEMtools Script for the process identification part, FEMtools Optimization for the optimizer routines, and used MSC.Marc to compute the reaction force curves. More information can be found in the following application note:

More References Related to Material Identification

  • W.-C. Wang, K.-H. Lai, Hybrid Determination of Equivalent Characteristics of Perforated Plates. Experimental Mechanics, Vol. 43, No. 2, 163-172 (2003)
  • Lauwagie T., Sol H., Dascotte E., Damage Identification in Beams using Inverse Methods. Proceedings of the  International Seminar on Modal Analysis 2002 (ISMA), pp. 715-722.
    Download (PDF, 145 KB)
  • Sol H., Lauwagie T., Guillaume P., Identification of Distributed Material Properties using Measured Modal Data, Proceedings of the  International Seminar on Modal Analysis 2002 (ISMA), pp. 695-704.
    Download (PDF, 213 KB)
  • H. Hua, H. Sol, Finite Element Model Updating of a Short Fiber Reinforced Composite Material Structure. International Conference on Structural Dynamics Modeling, NAFEMS/DTA, July 1993, Cranfield, UK.

 

For more information on the topics and cases that are presented, contact info@femtools.com.

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