Damage detection in materials based on strain measurements
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O R I G I NA L PA P E R
ValeriiMatveenko Grigorii Serovaev
· NataliaKosheleva
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Damage detection in materials based on strain measurements
Received: 5 June 2020 / Revised: 24 August 2020 / Accepted: 21 September 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract A technique for detecting the occurrence and development of local damage in a material is presented. It is based on experimental strain values measured by a limited number of sensors and the results of numerical simulation of a stress–strain state. The technique is applicable for external loads on a controlled object that vary over time by a constant factor. The occurrence and location of damage are detected by considering changes in the ratios of strain values recorded simultaneously by two sensors. The positions of the sensors are determined using a numerical simulation of the stress–strain state. The technique was experimentally tested on various samples made of a polymer composite material and under various load cases, including cyclic loads. Fiber-optic strain sensors based on Bragg gratings were used to measure the strain. Such sensors can be glued to the surface of a sample or embedded into a polymer composite material during manufacturing. The following samples were tested: a plate with various holes to simulate damage, an L-shaped element with a stress concentration in the rib area, and a plate with a cut-out on one side under an external cyclic load. In the performed experiments, the possibility of damage detection on the basis of the presented technique was shown.
1 Introduction One of the general tasks in structural health monitoring is to detect local damage in a structure and assess its development. The importance of this problem has increased due to the replacement of traditional structural materials with composite materials, in particular, layered polymer composites, which are increasingly used in various applications from civil engineering to aerospace [1]. The structure of these materials leads to the formation of local damage areas often associated with delamination, which represents a significant danger to structures made of composite materials [2]. The occurrence and development of damage can be assessed with non-destructive testing, which preserves the integrity and structure of the sample [3]. This can be achieved on the basis of various approaches. The methods of nondestructive testing include various visual methods, the main disadvantage of which is that they do not allow detecting damage located outside the visual inspection zone [4]. Another approach is based on the interpretation of mechanical and physical quantities related to natural frequencies, vibration modes and wave processes in the material [5]. An idea of the possibilities of methods based on modal parameters (eigenfrequencies and modes of oscillations) is given in Refs. [6,7], and methods analyzing wave processes in Ref. [8]. The advantages and disadvantages of vibrational damage detection methods are presented in numerous scientific studi
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