Damage Detection For Annular Concrete Specimens By Piezoceramic Transducers

With the development of water conservancy and hydropower in China,the number and length of concrete hydraulic tunnels are increasing.After a certain year of service,concrete hydraulic tunnels often have different degrees of diseases.The occurrence of diseases and defects will have an adverse impact on the normal operation of the tunnel,and may even lead to disastrous consequences of loss of human life and property.Therefore,it is of great significance to study the real-time structural health monitoring method for the diseases and defects of concrete hydraulic tunnel in engineering practice.This paper takes a section of concrete hydraulic tunnel as the research object to carry out a series of studies.The main contents are as follows:(1)The working mechanism of piezoelectric smart sensor under alternating voltage excitation is discussed.It is assumed that the piezoelectric smart sensor is a linear elastic model and only deforms in the thickness direction.In this paper,the natural frequency of piezoelectric intelligent sensor excited by alternating voltage is obtained by deriving the relationship between stress,strain,potential shift and other variables.Thus,it provides a theoretical reference for the follow-up research work,and preliminarily determines the optimal excitation frequency range of piezoelectric intelligent sensor.(2)This paper discusses the propagation of stress wave in concrete,and simulates the propagation process of stress wave by abaqus2022 finite element commercial software.In order to ensure that the simulation of stress wave propagation is closer to the test situation,the random aggregate model is adopted in the concrete structure,and the regular shapes of aggregates such as regular sphere,ellipsoid and regular polyhedron are discussed respectively.This work provides theoretical support for subsequent experiments.(3)Based on the relevant conclusions of the existing literature on plane aluminum plate and concrete plate,this test explores the detection of damage length of ring specimen when it is damaged by crack.Considering the material attenuation and geometric attenuation,it is assumed that the stress wave attenuation satisfies the Rayleigh damping model.According to the law of significant difference in energy attenuation between crack tip and crack middle section,the positioning,quantitative and shape description methods are used to quantitatively evaluate the absolute size of concrete cracks.