Local fatigue assessment of butt-welded joints between additively manufactured 316L stainless steel parts

Kurzfassung

Additive manufacturing (AM) has seen a rapid increase in application for many applications in recent years; nevertheless, there are still technical limitation with respect to widespread industrial applications. One important aspect is the relative limited building volume of the laser powder bed fusion (LPBF) process. Thus, the joining of AM parts makes it possible to increase the volume of AM structures; however, it is currently unclear whether welded AM parts can be assessed using fatigue assessment concepts typically applied for welded components. In particular, local fatigue assessment concepts seem to be suitable for this task, as they are capable to assess complex part and weld geometries. In this study, local concepts based on the micro-structural support effect hypothesis are applied as they also account for support effects at weld transitions. The considered methods are the critical distance and the IBESS approach. To investigate their applicability, fatigue tests were performed on butt-welded joints of 316L AM steel plates made by gas metal arc welding. To account, for the different weld seam position relative to the LBPF building process, joints were produced with weld seams parallel and vertical to the layer orientation of AM plates. For all three test series, the local fatigue assessment concepts lead to conservative results; however, the comparison between numerical and test results also reveal some shortcomings of the chosen concepts.