Fatigue evaluation of welded joints using a wireless monitoring system

Abstract

This paper examines the applicability of the hot spot method using a small wireless system and the effect of data loss during data communication on fatigue evaluation. Fatigue failure is a phenomenon that progresses due to repeated loading. Since it is not practical to monitor all structural members, it is important to monitor the structural integrity of damage-prone areas. In addition, due to cost and installation space constraints, the use of inexpensive, compact IoT devices is effective. Compact wireless fatigue monitoring methods using strain gauges have been proposed, and systems based on the nominal stress method have been considered. However, there are cases where the nominal stress cannot be defined due to the complex structure of the weldment, making fatigue evaluation difficult. In such cases, the hot spot method, which measures the structural stress concentration, is effective. However, the application of the hot spot method to a small wireless monitoring system has not been sufficiently studied. In this paper, a small wireless monitoring system was fabricated and its applicability to fatigue evaluation of welded joints was confirmed. From the test results, it was confirmed that the data loss was caused by the data communication condition of the small wireless system and the accumulated fatigue damage degree was underestimated. It is necessary to select an appropriate small wireless monitoring system considering the information on fatigue and stress state required for the target structure. This selection should consider the trade-off between transmitting raw data and performing edge processing before transmission. The former provides richer information but can cause data loss and high-power consumption due to the large volume of transmission. On the other hand, the latter reduces data loss and saves power, but can provide less information.