Detection of Subsurface Defects in Metal Materials Using Infrared Thermography; Image Processing and Finite Element Modeling

Abstract

This study experimentally investigates effect of fatigue strength improvement of the Portable Pneumatic Needle-Peening treatment (PPP treatment) as a needle peening on out-of-plane gusset welded joints by using plate bending fatigue tests. This study also examined effect of the travel speed and the number of treatment passes of the PPP treatment with regards to its fatigue strength improvement. After the fatigue tests, the observation of the fracture surface with Scanning Electron Microscope was carried out in order to clarify the crack initiation. From those test results, it may be concluded that the effect of fatigue strength improvement might be governed by treatment passes with sufficient travel speed. In addition, this study carried out additional fatigue tests that focus on fatigue crack closer by using the PPP treatment. As a result of additional fatigue tests for fatigue crack closure, it might be said that the effect of fatigue crack closure is effective when the distance between fatigue cracks and treatment area is less than 2.0 mm.