Estimation of beam material random field properties via sensitivity-based model updating using experimental frequency response functions

Structural parameter estimation is affected not only by measurement noise but also by unknown uncertainties which are present in the system. Deterministic structural model updating methods minimise the difference between experimentally measured data and computational prediction. Sensitivity-based methods are very efficient in solving structural model updating problems. Material and geometrical parameters of the structure such as Poisson’s ratio, Young’s modulus, mass density, modal damping, etc. are usually considered deterministic and homogeneous. In this paper, the distributed and non-homogeneous characteristics of these parameters are considered in the model updating. The parameters are taken as spatially correlated random fields and are expanded in a spectral Karhunen-Loève (KL) decomposition. Using the KL expansion, the spectral dynamic stiffness matrix of the beam is expanded as a series in terms of discretized parameters, which can be estimated using sensitivity-based model updating techniques. Numerical and experimental tests involving a beam with distributed bending rigidity and mass density are used to verify the proposed method. This extension of standard model updating procedures can enhance the dynamic description of structural dynamic models

Significance Of Assessment Experiences During Initial Teacher Training In Physical Education

This study investigates how students in the final semester of their teacher training program (licensure) at the Center of Physical Education and Sports (CEFD), Espírito Santo Federal University, Brazil, (re)interpret their assessment experiences, an integral component of their teacher training. It employs the narrative as a theoretical and methodological perspective, and it utilizes student portfolios, as well as focus groups and semi-structured individual interviews as inputs for data generation. Ten students in their eighth, or final, semester participated in this study. These were the total respondents to a "call for volunteers" among the 2014 graduating class. The results suggest that the students believe the assessment processes of their teaching practices in physical education are disjointed. They feel that the disciplines that allow them to review their own performance during teacher training are more efficient and play a stronger role in their education.221627

A spectral approach for damage quantification in stochastic dynamic systems

Intrinsic to all real structures, parameter uncertainty can be found in material properties and geometries. Many structural parameters, such as, elastic modulus, Poisson's rate, thickness, density, etc., are spatially distributed by nature. The Karhunen-Loève expansion is a method used to model the random field expanded in a spectral decomposition. Once many structural parameters can not be modelled as a Gaussian distribution the memoryless nonlinear transformation is used to translate a Gaussian random field in a non-Gaussian. Thus, stochastic methods have been used to include these uncertainties in the structural model. The Spectral Element Method (SEM) is a wave-based numerical approach used to model structures. It is also developed to express parameters as spatially correlated random field in its formulation. In this paper, the problem of structural damage detection under the presence of spatially distributed random parameter is addressed. Explicit equations to localize and assess damage are proposed based on the SEM formulation. Numerical examples in an axially vibrating undamaged and damaged structure with distributed parameters are analysed

Coupled Plate Energy Models At Mid- And High-frequency Vibrations

At mid- and high-frequency bands, displacement-based approaches such as the finite element method (FEM) create too large models, while energy-based methods, such as statistical energy analysis, produce smaller ones, but without spatial variation. Energy flow analysis (EFA) can produce compact models that include spatial variation; however, their analytical solution makes them difficult to handle for built-up structures. To overcome this issue, the energy finite element method (EFEM), a finite element solution of EFA, was proposed. A more accurate alternative to EFEM is the energy spectral element method (ESEM). It is a matrix methodology applied to EFA similar in style to FEM, with one significant difference being the use of the analytical solution as interpolation functions. Simulated results obtained by EFEM and ESEM are analysed and compared with each other and with the spectral element method, which is used as a reference. © 2013 Elsevier Ltd. All rights reserved.1344861Lyon, R.H., Dejong, G.R., (1995) Theory and Application of Statistical Energy Analysis, , Butterworth-Heinemann BostonWohlever, J.C., Bernhard, R.J., Mechanical energy flow models of rods and beams (1992) J Sound Vib, 153, pp. 1-19Bouthier, O.M., Bernhard, R.J., Simple models of the energetic of transversely vibrating plates (1995) J Sound Vib, 182, pp. 149-166Bouthier, O.M., Bernhard, R.J., Simple models of the energy flow in vibrating membranes (1995) J Sound Vib, 182, pp. 129-147Bitsie, F., Bernhard, R.J., Sensitivity calculations for structural-acoustic EFEM predictions (1998) Noise Control Engineering Journal, 46 (3), pp. 91-96Cho, P.E., Bernhard, R.J., Energy flow analysis of coupled beams (1998) Journal of Sound and Vibration, 211 (4), pp. 593-605Doyle, J.F., (1997) Wave Propagation in Structures: Spectral Analysis Using Fast Discrete Fourier Transforms, , Springer New YorkPereira, V.S., Dos Santos, J.M.C., Models of space energetics of coupled plates for high frequency vibrations (2008) Proceedings of the Ninth International Conference on Computational Structures Technology, , Athens, GreeceSantos, E.R.O., Arruda, J.R.F., Dos Santos, J.M.C., Modelling of coupled structural systems by an energy spectral element method (2008) J Sound Vib, 316, pp. 1-24Plunt, J., Fredo, C., Sanderson, M., On the use and misuse of the statistical energy analysis for vehicle noise control (1993) Proceedings of the SAE Noise and Vibration Conference, , Michigan: USALee, U., Lee, J., Spectral-element method for Levy-type plates subject to dynamic loads (1999) J Eng Mech ASCE, 125 (2), pp. 243-247Park, D.-H., Hong, S.-Y., Kil, H.-G., Jeon, J.-J., Power flow models and analysis of in-plane waves in finite coupled thin plates (2001) Journal of Sound and Vibration, 244 (4), pp. 651-668. , DOI 10.1006/jsvi.2000.3517Noiseux, D.U., Measurement of power flow in uniform beams and plates (1969) J Acoust Soc Am, 47 (1), pp. 238-24

Dynamic Analysis Of Frame Structures At High Frequencies Using Energy Finite Elements And Spectral Elements

The Energy Finite Element Method (EFEM) is based upon an approximation of the partial differential equations that result from the energy balance and energy coupling relations for different structural configurations and wave types. The coupling relations are used to describe the energy exchange among various subsystems. The EFEM can be expressed in a standard finite element (FE) approach, which is similar to a heat conduction problem. The Spectral Element Method (SEM) is based upon the exact solution of the partial differential equations in the frequency domain. Elements are assembled using the direct stiffness method. Therefore, a spectral element is equivalent to an infinite number of finite elements for a homogeneous medium. For this reason, the SEM, when it can be used, is more adequate to predict the dynamic response at higher frequencies than the FE method. In this paper, these two methods are used to predict the dynamic response of frame-type structures at high frequencies. Responses simulated with EFEM involving longitudinal and transversal waves in coupled beams are analyzed and compared with the solutions obtained by SEM. Experimental results from the INCE T-shaped beam are presented and compared with the simulated results.427712779Moens, I., (2001) On the Use and Validity of the Energy Finite Element Method for High Frequency Vibrations, , PhD thesis, Leuven Catholic University, BelgiumWohlever, J.C., (1988) Vibration Power Flow Analysis of Rods and Beams, , PhD thesis, Purdue University, Lafayette, USADoyle, J.F., (1989) Wave Propagation in Structures, , Prentice-Hall, New York, USACho, P.E., (1993) Energy Flow Analysis of Coupled Structures, , PhD thesis, Purdue University, Lafayette, USAPlunt, J., Fredo, C., Sanderson, M., On the Use and Misuse of Statistical Energy Analysis for Vehicle Noise Control (1993) Proceedings of the SAE Noise and Vibration Conference, pp. 319-328Lyon, R.H., (1995) Theory and Application of Statistical Energy Analysis, , M.I.T. Press, Second EditionCimerman, B., Bharj, T., Borello, G., Overview of the Experimental Approach to Statistical Energy Analysis (1997) SAE Noise and Vibration Conference, 169, pp. 1-6Pavic, G., Vibration Damping, Energy and Power Flow (2001) Proceedings of the 17th International Congress on Acoustics, Vibrations and Structural Acoustics, 1, p. 2. , Rome, ItalyHambric, S.A., Comparison of Finite Element Predictions and Experimental Measurements of Structure- Borne Powers in a T-Shaped Beam Proceedings of Inter-noise 95, Newport-Beach, CA, USA, July,10- 12, (1995)Santos, E.O., Donadon, L.V., Arruda, J.R.F., Santos, D., Analysis of Coupled Structural Systems using Energy Finite Elements and Spectral Elements, 12th International Congress on Sound and Vibration, Lisbon (2005) J. M. C., pp. 11-14Jul

Structural Damage Detection Using Energy Flow Models

The presence of a crack in a structure modifies the energy dissipation pattern. As a consequence, damaged structures can present high localized damping. Experimental tests have revealed that crack nucleation and growth increase structural damping which makes this phenomenon useful as a damage locator. This paper examines the energy flow patterns caused by localized damping in rods, beams and plates using the Energy Finite Element Method (EFEM), the Spectral Element Method (SEM) and the Energy Spectral Element Method (ESEM) in order to detect and locate damage. The analyses are performed at high frequencies, where any localized structural change has a strong influence in the structural response. Simulated results for damage detection in rods, beams, and their couplings calculated by each method and using the element loss factor variation to model the damage, are presented and compared. Results for a simple thin plate calculated with EFEM are also discussed