Research On Damage Identification Method Of Concrete Slab Based On Piezoelectric Rayleigh Wave

Reinforced concrete structure is one of the most widely used building structures in the field of civil engineering.It has own unique performance advantages.For example,the advantages of high bearing capacity,fire resistance and high temperature resistance,sufficient material supply make reinforced concrete structure widely used in construction engineering.However,due to the existence of external factors such as load,temperature change and support settlement,defects such as cracks and holes on the surface of concrete are often appeared.Although these surface defects can not pose a direct threat to the building structure,if they are not handled in time,it is likely to cause the protective layer to fall off,the steel bars are exposed,and the steel bars are corroded over time,which will further affect the safety and durability of the whole structure.Therefore,in order to ensure the safety of people’s life and property,it is necessary to identify the damage of building structure in time locate the damage position of the structure reasonably,of the structure reasonably,and effectively determine the degree of structural damage,so as to avoid subsequent damage to the service structure due to the development of concrete cracks.Thus,people’s life and property security is guaranteed.In this paper,concrete slabs are used as the research object,based on the combination of Rayleigh wave non-destructive testing technology and piezoelectric wave method of piezoelectric smart materials from theoretical analysis,numerical simulation,and experimental demonstration,the surface is free of cracks and contains cracks of different depths.Analyze and study the concrete slabs,so as to effectively determine the damage degree of the concrete slabs.The main contents of this paper are as follows:(1)Introduce the development status of Rayleigh wave non-destructive testing technology and piezoelectric materials at home and abroad,analyze the advantages and disadvantages of existing damage identification methods,and determine the feasibility and effectiveness of damage identification of concrete structures based on piezoelectric Rayleigh wave method.The wave theory is analyzed to clarify the propagation mechanism and signal conversion relationship of each component stress wave(P-wave,S-wave,Rayleigh wave)on the surface and inside of concrete.The relationship between energy amplitude and propagation time of each component stress wave is established,and the change of Rayleigh wave energy amplitude and propagation time with the appearance and growth of surface crack depth is quantitatively studied.(2)The finite element analysis software ABAQUS is used to establish the concrete slab model of non damage and different damage conditions,and the performance parameters of concrete slab and piezoelectric ceramic(PZT)are defined.The 3D solid model of concrete slab is established by C3D8 R element,and the piezoelectric ceramic model is established by C3D8 E element,and its polarization direction is defined.A three-dimensional time-domain viscoelastic artificial boundary is established at the boundary of the model to effectively absorb the reflected and diffracted waves generated by the stress waves of each component at the boundary of the concrete slab,and to simulate the application and reception of excitation signals on the surface of the concrete slab.Based on the wave theory,the energy amplitude of Rayleigh wave will be attenuated and the propagation time will be delayed in the process of Rayleigh wave propagation.Taking the crack depth and frequency(wavelength)as variables,the potential time curves of concrete slabs with different crack depths are measured,and the multiple working conditions are normalized and the correlation curves are drawn The damage degree is analyzed from voltage amplitude and propagation time.(3)The concrete slab without damage and different damage degree was tested by using function generator,signal amplifier,PZT and digital oscilloscope.At the boundary,damping clay,sponge and other materials are used to absorb and reduce noise.The excitation signals are applied and received on the surface of concrete slabs,and the voltage time curve of concrete slabs under different depth crack conditions are accurately measured.The relationship between the voltage amplitude and propagation time of Rayleigh wave and the crack depth is established by normalizing the experimental results.The crack depth is effectively determined by the change of energy amplitude and propagation time of Rayleigh wave and the damage identification of concrete slab based on piezoelectric Rayleigh wave are completed.