Impact location estimation in anisotropic structures

In this article, an acoustic emission–based impact location estimation algorithm is presented for use with composite structures. The algorithm is formulated as a constrained optimization problem by utilizing sensor locations and times of arrival of impact signals at the sensors. The impact locations are estimated without any information about wave propagation velocity in the structure. A modification of the algorithm to overcome difficulties produced by waveform reflections enables accurate estimation of impact locations close to the structure’s boundaries. The capability of this algorithm to accurately estimate impact locations is demonstrated numerically and experimentally. Experiments performed at different temperatures showed that the algorithm is robust to temperature changes. An automatic time-of-arrival estimation method is also presented. The performance capabilities of the method and its computational simplicity make this approach an attractive alternative to other methods available in the literature for practical structural health monitoring applications.

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Passive Impact Location Estimation Using Piezoelectric Sensors

Structural Health Monitoring ◽

10.1177/1475921709102090 ◽

2009 ◽

Vol 8 (5) ◽

pp. 357-367 ◽

Cited By ~ 8

Author(s):

Daniel Guyomar ◽

Mickaël Lallart ◽

Thomas Monnier ◽

Xingjun Wang ◽

Lionel Petit

Keyword(s):

Location Estimation ◽

Piezoelectric Sensors ◽

Impact Location

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New polarized-light microscope for fast and orientation independent measurement of birefringent fine structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146254 ◽

1993 ◽

Vol 51 ◽

pp. 82-83

Author(s):

Rudolf Oldenbourg

Keyword(s):

Light Microscope ◽

Polarized Light ◽

Video Camera ◽

Limited Range ◽

Image Point ◽

Computer Assisted ◽

Optical Modulators ◽

Anisotropic Structures ◽

Long Time ◽

Computer Assisted Image

The polarized light microscope has the unique potential to measure submicroscopic molecular arrangements dynamically and non-destructively in living cells and other specimens. With the traditional pol-scope, however, single images display only those anisotropic structures that have a limited range of orientations with respect to the polarization axes of the microscope. Furthermore, rapid measurements are restricted to a single image point or single area that exhibits uniform birefringence or other form of optical anisotropy, while measurements comparing several image points take an inordinately long time.We are developing a new kind of polarized light microscope which combines speed and high resolution in its measurement of the specimen anisotropy, irrespective of its orientation. The design of the new pol-scope is based on the traditional polarized light microscope with two essential modifications: circular polarizers replace linear polarizers and two electro-optical modulators replace the traditional compensator. A video camera and computer assisted image analysis provide measurements of specimen anisotropy in rapid succession for all points of the image comprising the field of view.

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