13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Accuracy of Acoustic Emission Localization for Masonry Structures Monitoring Jie Xu1*, Qinghua Han1, Giuseppe Lacidogna2, Alberto Carpinteri2 1 School of Civil Engineering, Tianjin University, Tianjin, 300072, China 2 Department of Structural, Geotechnical and Building Construction, Politecnico di Torino, Turin, 10129, Italy * Corresponding author: jie.xu@polito.it Abstract Acoustic Emission (AE) is a promising non-destructive monitoring technique to investigate the damage location and to evaluate the structural health conditions. Based on the tests performed on a masonry bridge, three ingredients sensor distribution, onset time determination and degree of inhomogeneity affecting the accuracy of AE localization are discussed. The test result shows a reasonable sensor arrangement is of great importance for the localization capability. The highest accuracy can be achieved for damage sources localized among the sensor distributions. Distances of sources far from the sensor network are less accurate. Onset time determination of an AE signal is another important factor in this technique. A widely used approach, based on the Akaike Information Criterion (AIC), is confirmed to provide more reliable onset time determination of AE signals. Moreover, the inhomogeneity of the test object may lead to errors in the ultrasonic wave travelling model. Different-scale fluctuations and structure variations in the composite structure can result in random variations of the propagation velocity and systematic errors. A new proposed parameter, the degree of inhomogeneity ξ, introduced into the classical method, can effectively decrease the crack localization unavoidable errors due to inhomogeneities in masonry material. Keywords Acoustic emission, masonry structures, crack localization, structural health monitoring. 1. Introduction Various masonry structures, such as towers, bridges and historical buildings are widely distributed all over the world. As a consequence of building with old techniques, long-time exposing to the environmental conditions and changing loading regimes, many of these masonry structures are placed in repair and strengthening programs [1, 2]. Prior to repair and rehabilitation, inspections of the structures to estimate the current state in service are essentially required. As one of the non-destructive evaluation and diagnostic techniques, Acoustic Emission (AE) technique is gradually employed in the masonry monitoring [2-5]. Within civil engineering practice, the AE technique is a widely applied non-destructive technique for the detection of damage onset and growth [6, 7]. AE is the class of phenomena whereby transient elastic waves are generated by the rapid release of strain energy when damage occurs within a material. By investigating onset times and other characteristics of acoustic signals, AE techniques provide an insight into the deterioration processes of a tested object [8]. As the onset times of AE signals at different sensors are linked to the propagation speed inside the material, algorithm can be used to locate the emitting sources and to predict their subsequent development [1, 9]. AE is widely used for monitoring metallic [10], rock [11, 12] and concrete structures [13, 14], because AE is well suited for homogeneous or qusai-homogeneous materials with good acoustic transmission. However, its application in heterogeneous materials such as masonry is much problematic [15]. This paper presented the recent research about the accuracy of the crack localization of AE technique in masonry structure, which is one of the most important and challenged topics in AE
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