Abstract
The impact elastic wave method (IEW) has been applied to evaluate the thickness and internal defects of the target structure based on the dominant frequency of the response wave that is formed by the repeated reflections in the thickness direction. However, it is difficult to evaluate the size and position of the defect by IEW if the size and depth are relatively small and deep, respectively, and further, it is known that the technique is inapplicable if the target is not a plate-like structures. Therefore, the authors propose a new technique that uses Difference value as a new evaluation index to overcome the limitations of the conventional methods. Difference value shows the change of the response waveform in the time domain; it is computed by using a response waveform of the structures in sound condition as a reference. In this paper, the practicality of the Difference value is investigated by performing experiments using concrete specimens. The results of the experiments demonstrate that Difference value changes by the influence of internal defects, and Difference value evaluates the location of the relatively small defect that is difficult to evaluate by the conventional technique.
Highlights
Non-Destructive Testing for Concrete StructuresConcrete is one of the most common construction materials. It is widely used for the construction of structures because the unit price of materials is low and on-site construction is easy [1]
Based on the above discussion, it is revealed that Differential Value Analysis (DVA) evaluates the position of the sheath correctly by choosiFniggtuhereap1p6rosphrioawte sN.a cross-section view of the specimen and configuration sheath of specimen_2 and specimen_4
Even if the thickness condition is complied with, the evaluation of internal defects becomes difficult because the difference value of the defects area is not characteristically increased with condition and surface do not change
Summary
Concrete is one of the most common construction materials. It is widely used for the construction of structures because the unit price of materials is low and on-site construction is easy [1]. It has been applied to evaluate the thickness and internal defects of the target structure based on the dominant frequency of the response wave that is formed by the repeated reflections in the thickness direction. It is suitable for testing concrete structures because the frequency of the excitation is relatively low, and the elastic wave emitted by the excitation is not attenuated [4,8]. Since a relatively low frequency band is used for the input, the effect of elastic waves due to dispersibility is very small [27] This makes it suitable for the NDT of concrete structures with large thickness and composite materials. FiFgiugruere6.6.CCoonncecpept toof fDDififfefreernencecevvalaulueeAAnnalaylysissisininTiTmime eDDomomaiani:n:(a()a)NNoovvooidid; ;(b(b) )WWitihthvoviodi;d;(c()c)ExEaxmamplpeleofofrersepsopnosnese wwavaevfeofromrmcocmompapraisriosno.n
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