1 THE LOCALIZATION METHOD OF DAMAGE SOURCE IN BOLTED JOINTS STRUCTURES BASED ON TWO ACOUSTIC EMISSION SENSORS Junfei Tai, Tian He and Xiaoran Wang School of Transportation Science and Engineering, Beihang University, Beijing, China email: taijunfei@buaa.edu.cn Hong Wang Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms， Beijing Institute of Control Engineering, Beijing, China e-mail: hongwang1981@163.com Bolted joint is a basic form of connection which is widely used in engineering. The failure of the joint may lead to serious accidents. The stress concentration near the distributed bolts in connection struc- ture is possible to cause structural damage. The acoustic emission (AE) wave generated by the struc- tural damage can be used to localize the damage source. In this paper, a localization method of bolted joints damage with two AE sensors is developed based on arrival time difference (ATD) database presented by simulation. Firstly, the finite element model with the double-row bolt connection struc- ture is established to obtain the damage signals at difference positions, and the localizing method of bolted joints damage with only two AE sensors is proposed with ATD database. Secondly, the optimal method of sensors’ positions is explored, which is relative to the layout of two sensors. Finally, the feasibility of presented localization method of bolted joints damage with two AE sensors is verified by experiments. The results show that the presented bolted joints damage localization method based on two AE sensors has good applicability and high success rate. Keywords: acoustic emission, bolted joints damage, source localization, finite element simulation 1. Introduction Bolted joint is an irreplaceable form of structural connection [1]. Usually, the connecting holes in the structure with holes is rather susceptible to stress concentrations. Especially for composite materials, the holes in structure mean the destruction of internal fibers, resulting in more severe stress on the fiber around the holes. Damage of bolted joints can lead to serious accidents, so the damage monitoring for joining is an important part of structural safety. Among many structure damage monitoring technologies, acoustic emission technique (AET), as an online monitoring technique, has developed rapidly in recent years. Its ability to passively monitor ultrasonic stress waves in structures makes it have a huge applica- tion prospect in structure health management [2,3], especially the damage localization. Tobias [4] is a pioneer in the field of AE source localization, who proposed time difference of arrival (TDOA) method, the most convenient and commonly used method for localization of AE source. The operation of TDOA is based on the ATD of signals received by different sensors. Hence, the accurate wave velocity and ATD