Application of Wavelet Analysis for Measurement of Fracture Energy in Drop Weight Tear Testing of API X65 Steel

Determination of fracture energy is one of the most important aims in drop weight tear testing (DWTT) for assessment of material properties. The purpose of this study is to investigate a new experimental method for measuring fracture energy of tested steel. In doing so, the wavelet transformation was applied for API steel for the first time to analyze acceleration signals from impact tests. The acceleration signal from DWTT on API X65 steel was captured and studied using wavelet transformation. The DWT tests were conducted on three specimens with chevron notch according to API 5L standard. After impact test, noisy acceleration signal from each specimen was smoothed using discrete wavelet transformation. Then, force-displacement response was derived for each specimen from which fracture energy was calculated using the area under each plot. The obtained average fracture energy was 6326 J and the peak load was 219 kN. It was found that about 39% of the total fracture energy was used in crack initiation while 61% used in crack propagation. The comparison of the obtained results with previous data from similar research showed the effectiveness of wavelet transformation for accurate measurement of fracture energy using DWTT.