Experimental Study And 3-D Numerical Simulation Of The Effect Of Pore Structure On The Stress Wave Transmission

Since the birth of smart piezoelectric materials, they have been widely used because of their excellent properties, such as inverse piezoelectric effect, stability, high sensitivity and low cost, especially in the area of structural health monitoring(SHM). However, most of SHM aims at the damage of structures, while there is little research on the effect of inner concrete components(including pore structures) have on piezoelectric stress wave. Therefore, in this paper, platform of piezoelectric intelligent monitoring was established to study the relationship between pore, piezoelectric amplitude and wave velocity. And the samples were scanned with CT scanning technique. The simulation models were established by MIMICS software and then compared with experiment results. Details are as follows:CT scanning technique was employed to conduct statistical analysis of specimen pore. 3 groups of cement specimens which have different porosity were prepared in this paper to avoid the effect of aggregate on stress wave. In experiments, all sections of 3 kinds of specimens were obtained by CT scanning. And Matlab image processing techniques were used to conduct image enhancement, image segmentation, and image edge detection processing. Then 3 kinds of specimens were analyzed statically in terms of pore parameters, such as pore size, equivalent radius of the pore, pore edge, degree of irregular shape and size irregular degree by Oringin software to obtain the distribution and function of 5 kinds of parameters.Piezoelectric intelligent system was used to monitor the effect of porosity on stress wave amplitude and wave velocity. NI monitoring system and Sine monitoring system were established to monitor pore specimens in high frequency and low frequency, respectively. In this study, the piezoelectric intelligent aggregate is pasted into the two ends of specimen. Three specimens in the same group were monitored to obtain the wave velocity with NI monitoring system and amplitude with two monitoring system. The results show that no matter high frequency or low frequency, amplitudes become lower with larger frequency, but velocity of wave is in opposite trend for the same specimen: for the same frequency, amplitudes and wave velocity decrease with growing pore.Simulation model was established based on CT image pore model of the specimen. MIMICS was used to process and integrate CT images of three kinds of pore specimens and three kinds of 3-D models were established. Then the above models were imported into ABAQUS to conduct post-processing. The simulation results have the same trend with experiment results, while there exists some difference. The key reason is the discreteness of experiment and the difference between 3D model by numerical simulation and the real paste. On the other hand, the result of simulation shows that there is stress concentration at the edge of pore and the distribution of the pore is non-uniform.