## 1 Introduction  
Acoustic emission (AE) technology is widely applied in structural health monitoring (SHM) and nondestructive evaluation (NDE) due to its remarkable advantages such as dynamic, sensitivity, integrity, and timeliness [1; 2; 3]. The purpose of AE detection is to obtain information about the AE source from the collected AE signals and then to estimate information about material or structural damage [4]. Many scholars have conducted research in this area. [PERSON] et al. [5] measured the AE characteristics of collapsing holes and the movements of dislocations in Mg-Ho alloys during structural collapse, and the analysis showed that porous collapse is fully consistent with Bath's law, while dislocation movements are not. [PERSON] et al. [6] used the profile analysis of AE signals and characteristic parameters to distinguish dislocation movements and dynamic entanglements in fcc 316L stainless steel. [PERSON] et al. [7] carried out ring shear friction experiments within a certain shear rate range, and their results revealed that both shear rate and particle size affect the mechanical behavior of shear resistance, specimen compaction and slip displacement, as well as the release of acoustic energy. [PERSON] [8] clarified the local structure of jammed twin boundary patterns using computer simulation and found that the friction in ferroelastomer and martensite is associated with movement of the boundary and other microstructures. [PERSON] et al. [9] numerically simulated the microstructure changes of ferroelastic or martensitic materials during mechanical shear and their AE spectrum characteristics during strain-induced yield and detwinning. The types of AE signals generated with different strengths were analyzed from the perspective of energy. [PERSON] et al. [10] concluded through simulations that the AE rise time better reflects the atomic avalanche time profile than the duration of the AE signal. These studies have demonstrated the potential of AE for condition monitoring and structural damage identification. However, stiffeners are widely used on the surfaces of cylindrical shells such as engine casing or thin-walled vessels to reduce the structural weight. Complicated phenomena, such as scattering, interference, and mode conversion, occur when the fault AE signal passes through these stiffeners. These stiffeners interfere with the fault AE signal and limit the effective range, thus reducing the accuracy of fault diagnosis. Therefore, in order to clarify the interaction mechanism between the stiffeners on the cylindrical shell, such as engine casings and thin-walled vessels, and the AE signal and to improve the ability of AE technology in fault detection, it is essential to investigate the influence of stiffeners attached to cylindrical shell structures on AE signal propagation characteristics. There are many studies in the literature on the propagation characteristics of AE signal in a cylindrical structure. [PERSON] et al. [11,12] investigated the reflection of the axially symmetric guided elastic wave L(0,2) from notches in pipes, and maps of reflection coefficient as a function of the circumferential extent and depth of the defect have been presented. [PERSON] et al. [13] conducted a series of experiments and simulations to measure the reflection of the axially symmetric mode and of the mode-converted non-axially symmetric modes with an increase in the circumferential extent of the notch, which can be used in pipeline NDE to discriminate the axially symmetric reflectors such as circumferential welds and any non-axially symmetric defects. [PERSON] et al. [14] carried out numerical simulations on the propagation characteristics of L(0,2) and T(0,1) mode guided waves in pipes and their interaction with defects and demonstrated the propagation process of the ultrasonic guided waves in pipes and the modal conversion of each guided wave. [PERSON] et al.