Nondestructive Damage Detection of Two Dimensional Plate Structures Using Modal Strain Energy Method

AbstractA nondestructive detection method of surface cracks in two dimensional plate structures using modal strain energy method is investigated in this paper. Experimental modal analysis (EMA) is conducted on an aluminum alloy 6061 thin plate to obtain the mode shapes before and after damage under a completely free boundary condition. The measured mode shapes are used to compute the strain energy of the plate. Limited by the measured points, a differential quadrature method is employed to compute the partial differential terms in strain energy formula. A damage index is then defined based on strain energy ratio of the plate before and after damage. This damage index is employed to identify the location of surface crack in plate structure. A finite element analysis (FEA) is also performed to access this approach and demonstrate a feasible process for the experimental work. Good correlation between FEA and EMA results is obtained. The damage index obtained from both FEA and EMA successfully identify the location of surface crack in the aluminum plate. Only few measured mode shapes of the plate are required in this method, which provides a quick, flexible, inexpensive and nondestructive technique to identify the damagein local and global 2D plate structures.

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Development of scanning damage index for the damage detection of plate structures using modal strain energy method

Mechanical Systems and Signal Processing ◽

10.1016/j.ymssp.2008.05.001 ◽

2009 ◽

Vol 23 (2) ◽

pp. 274-287 ◽

Cited By ~ 52

Author(s):

Huiwen Hu ◽

Chengbo Wu

Keyword(s):

Damage Detection ◽

Energy Method ◽

Strain Energy ◽

Damage Index ◽

Plate Structures ◽

Modal Strain Energy ◽

Modal Strain Energy Method ◽

Strain Energy Method

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Infrastructure Sustainability

Rethinking Sustainable Development - Advances in Environmental Engineering and Green Technologies ◽

10.4018/978-1-61692-022-7.ch013 ◽

2011 ◽

pp. 186-201

Author(s):

Hoi Wai Shih ◽

David Thambiratnam ◽

Tommy Chan

Keyword(s):

Energy Method ◽

Strain Energy ◽

Health State ◽

Modal Strain Energy ◽

Structural Health ◽

Modal Strain Energy Method ◽

Modal Flexibility ◽

Before And After ◽

Composite Bridges ◽

Strain Energy Method

Assessing the structural health state of urban infrastructure is crucial in terms of infrastructure sustainability. This chapter uses dynamic computer simulation techniques to apply a procedure using vibration-based methods for damage assessment in multiple-girder composite bridges. In addition to changes in natural frequencies, this multi-criteria procedure incorporates two methods, namely, the modal flexibility and the modal strain energy method. Using the numerically simulated modal data obtained through finite element analysis software, algorithms based on modal flexibility and modal strain energy change, before and after damage, are obtained and used as the indices for the assessment of structural health state. The feasibility and capability of the approach is demonstrated through numerical studies of a proposed structure with six damage scenarios. It is concluded that the modal strain energy method is capable of application to multiple-girder composite bridges, as evidenced through the example treated in this chapter.

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Assessment of Modal Strain Energy Method: Advantages and Limitations

Volume 1: Advanced Computational Mechanics; Advanced Simulation-Based Engineering Sciences; Virtual and Augmented Reality; Applied Solid Mechanics and Material Processing; Dynamical Systems and Control ◽

10.1115/esda2012-82281 ◽

2012 ◽

Author(s):

Hasan Koruk ◽

Kenan Y. Sanliturk

Keyword(s):

Mode Shape ◽

Energy Method ◽

Strain Energy ◽

Reference Method ◽

Mode Shapes ◽

Complex Eigenvalue ◽

Modal Strain Energy ◽

Modal Strain Energy Method ◽

Shape Complexity ◽

Strain Energy Method

The Modal Strain Energy Method (MSEM) is widely used in practice for the prediction of damping levels in structures. MSEM is based on a fundamental assumption that the damped and the undamped mode shapes of a structure are identical. Therefore, when MSEM is to be used, it is essential to ensure that this assumption is an acceptable assumption. However, detailed information on the accuracy of the method as a function of the system parameters including modal (or mode shape) complexity is quite limited. In this paper, the performance of MSEM is assessed in terms of the damping levels of the structure, proportionality of damping distribution and/or the modal complexity. To do so, an effective finite element based MSE approach is proposed first. Then, a proportionally damped structure with different damping levels is modeled and the performance of MSEM is assessed as a function of the structural damping level. After that, a non-proportionally damped structure is studied in order to examine the performance of the method with respect to mode shape complexity. In all cases, a more accurate reference method, based on complex eigenvalue approach, is used for comparison purposes. Furthermore, a few definitions of mode shape complexity are utilized in order to quantify the mode shape complexity. The results show that as long as the mode shapes are real or close to being real, MSEM can predict the damping levels as well as the natural frequencies of a damped structure with good accuracy. However, the accuracy that can be achieved with MSEM decreases as mode shape complexity increases.

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