Propagation characteristics of acoustic emission signals affected by the length and the position of cracks

To address problem that closed crack detection of remanufacturing blank is more difficult, the acoustic emission technology is used to study propagation characteristics of acoustic emission signals due to the length and the position of cracks in remanufacturing blanks. The wave transmission theory in crack medium and the finite difference time domain method are used to simulate the influence of two factors on acoustic signals which indicates that the attenuation effect due to crack lengths is more obvious than that due to crack locations. The energy and amplitude attenuation coefficients (0.28 and 0.15, respectively) of the acoustic signals for the crack length less than 3 mm are greater than those for the crack length greater than 6 mm (1.48 and 0.9, respectively). The relative energy and amplitude attenuation rates of crack length 6 mm are 0.62 dB and 0.2 dB more than those of crack length 0.5 mm, 14.7dB and 8 dB are decreased crack length 15 mm. The energy relative attenuation rates of the crack location are between -6.4 to -6.6 dB and its relative amplitude attenuation rates are between -1.4 to -1.7 dB. The influence of crack length on the acoustic emission signal is also discussed in experiments. The experiment result shows that the attenuation coefficient of the crack length less than 2 mm is bigger than that of the length more than 6 mm, which indicates that it is consistent with the simulation. Therefore, the acoustic emission parameters and the crack length have a definite corresponding relationship. The acoustic emission technique can effectively detect the crack in remanufacturing blank, especially for the detection of micro crack less than 3 mm. © 2015, Science Press. All right reserved.