Inspection For The Deep Concrete Deck Internal Defects Based On Acoustic Emission Array Beamforming

Now, concrete material has been the most widely used building materials,Because of the long-time action of load or abrupt disaster in the term of usage, theconcrete structure will appear the safety problem and endanger people’s life, Healthymonitoring of concrete structure must be carried on in order to avoiding theseaccidents occurring. Acoustic emission (AE) testing technology had been extensivelyapplied in healthy monitor aspect of concrete structure as a kind of real-time anddynamic of nondestructive testing technology.To make sure the defects encouraged in the acoustic emission sensor array, theconventional acoustic emission testing technology need a number of sensors to coverthe full surface of the structure, This approach was very difficult to carried on in thelarge concrete structure and cost much. So combining with array beamforming,Designing a uniform circular array based on fewer sensors (about4~8) to detectionthe large-scale concrete structure (radius:3~4m) was proposed in this paper. Themain content of this theory includes some aspects as follows.（1）The uniform circular array beamforming and the uniform rectangular arraybeamforming were simulated by programming, First, the influence of what thenumber of array、the space between AE sensors and the wavelength of the AE signalto the performance of array beamforming was analyzed, and then their performanceswere discussed based on the same number of AE sensors, last we decided thegeometry and number of the AE array with better performance.（2）The conventional Beamforming (CBF) and the Minimum variancedistortionless response (MVDR) direction-finding algorithm were analyzed throughsimulation based on uniform circular array of8sensors, and the two algorithm’sdirection-finding performance was compared from the array directivity、highestside-lobe level and angle resolution.（3）The parameters of acoustic emission detector were determined through theexperiment of broking pencil leads, including the threshold、time parameters and thespeed of the AE signal propagating in concrete structure. （4）Using the method of time-frequency analyze (Short Time FourierTransform, STFT; Wavelet Transform, WT; Hilbert-Huang Transform, HHT) toanalyse the character of AE signal, observing the frequency range of AE signal ofconcrete materials and attenuation law, and making further Denoising Processaccording to the character of the AE signal.（5）An experiment was performed on concrete slab of one building top, Auniform circular array of eight AE sensors with radius of0.06m was placed in thecenter of the area of detection, and a simulated AE signal was produced in whereabout3~4m from the centre of the uniform circular array, Using beamformingalgorithm to find which direction the AE signal from, Meanwhile, In combinationwith the double uniform circular array to location the acoustic emission source. andthen the results of the experiment were analyzed.