Detection and monitoring of fatigue crack growth with piezoelectric actuator and sensor

Abstract

Fatigue crack occurs when a material is subjected to recurring loading. Fatigue crack is dangerous and harmful because it is difficult to detect and monitor with naked eyes. Minor loading can even cause fatigue to the material. Therefore, it is crucial to have evaluation technique to detect and monitor fatigue cracks. Non-destructive evaluation (NDE) technique is preferred because this method provides no harm to the existing structure. The process of obtaining data to perform analysis so as to determine the product life-cycle is defined as Structural Health Monitoring (SHM). To find the structure life cycles, it is important to determine the remaining life of the structure. This field of estimating a structure’s remaining life is known as Damage Prognosis (DP). This experimental study aims to detect and monitor the fatigue crack growth. The scope of this report can be divided into two main categories: fatigue crack detection and fatigue crack growth monitoring. For fatigue crack detection, two damage indices are proposed based on the current state and baseline state comparison. It will try to identify a point when the crack initiation starts. For crack growth monitoring, two damages indices proposed in crack detection will also be applied. Based on the proposed damage indices, a linear relationship between crack length and the proposed damage indices is identified. Therefore, it is possible to approximate the crack length for a given damage index and correlation factor. It is noted that the correlation factors obtained are dependent on both specimen width and the location of the crack. Therefore, further studies should be carried out to examine the value of correlation factor and the corresponding damage index.