Experimental Investigation of Spur Gear Tooth Crack Location and Depth Detection using Short-time Averaging Method and Statistical Indicators

Gear systems are one of the most functional power transmission systems in the industry. Crack is one of the common defects in gears which is caused by excessive loading, sudden impact and shortcomings in the gears construction. Initially, the crack will not result in structure collapse, but its growth can lead to irreparable damage. Therefore, detecting the crack and determining its location and depth are very important in this respect. In this paper, two encoders are used to obtain the spur gear pair transmission error speed. Moreover, the short-time averaging method (STAM) has been proposed thereby detecting the crack location and some statistical indicators have been used to estimate the crack depth in the spur gear tooth. For this purpose, a dynamical model in which mesh stiffness varying with time has been deployed to achieve the transmission error speed of the gear system. Additionally, a gear test rig including a single-stage gearbox, two encoders, and also an electronic board has been used. Encoders were installed on input and output shafts and the angular position of each shaft in time was saved in the computer using the electronic board. In addition, the transmission error speed was obtained by analyzing the received signals. Then, short-time averaging method was used to identify the crack location. Ultimately, some indicators such as ABS-max, FM0, Energy Ratio (ER) and Residual Signal Average were applied to the simulated results and experimental signals to fine the crack depth ratio. According to  the results of this study, it seems safe to conclude that the STAM is a useful method in cracked tooth detection and the indicators have acceptable accuracy to find the crack depth ratio.