Abstract
In this work, local properties such as hardness and fatigue crack grow rate in the heat-affected zone of four laser-welded butt joints in thin high-strength low-alloy steel were examined, so as to explain and predict fatigue lives at high stress levels through the fracture mechanics approach. The different welded series presented a similar fatigue crack growth rate in the heat-affected and fusion zones, but lower than base metal due to the higher hardness of the bainitic–martensitic microstructure verified in the welded series. The results showed that at high stress levels in the as-welded condition, the fatigue initiation stage can be neglected and assume some types of cracks, with an initial crack of 0.07 mm and appropriate fatigue crack growth rates, estimates of fatigue life close to the experimental results were obtained.
Highlights
The fatigue behavior of steel welds has been widely studied, but there are still gaps in the knowledge of this complex subject due to several factors that affect the fatigue strength and even more so due to concerns related to thin thicknesses and unconventional welding processes
When allowing the increase in fatigue assessment classes of welded joints (FAT), when the imperfections have been verified with nondestructive testing (NDT) or when an improvement method has been used [8], there is no differentiation in the increase according to the tensile strength of the materials
The differences were small, each welded series presented at the crack start and propagation sites (CGHAZ and fusion zone (FZ)) had higher hardness than the base metal (BM)
Summary
The fatigue behavior of steel welds has been widely studied, but there are still gaps in the knowledge of this complex subject due to several factors that affect the fatigue strength and even more so due to concerns related to thin thicknesses and unconventional welding processes. The presence of defects acting as a fatigue pre-crack are the main reason to a substantial reduction in fatigue strength in welded joints This determines that the initiation period can be neglected [8,18] and that fracture mechanics seem to be the appropriate approach to determine the fatigue life [9]. Murakami [23] proposed an expression for fatigue limit predictions of materials containing small defects or cracks as a function of the hardness and the size of small defects; Åman et al [24], in a recent work, modified the aforementioned expression in order to analyze the consequence of a small defect at the notch root. In the present study the influence of welding parameters on fatigue crack growth rate (FCGR) of laser butt welds in thin plates of high-strength low-alloy steel were analyzed. FCGR parameters were obtained through fatigue crack growth tests and complementary tests and analysis such as metallographic, hardness, crack closure and fractography were performed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
