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Item type:Publication, Access status: with files , Fatigue crack initiation and propagation in plain and notched PBF-LB/M, WAAM, and wrought 316L stainless steel specimensAdditively manufactured (AM) components—either made by laser-powder bed fusion or wire and arc additive manufacturing—typically contain process-related defects on and near surfaces that can be removed by machining. Various studies have shown that post-treatment, such as machining significantly improves the fatigue strength of AM parts. To this day, however, hardly any studies have investigated the fatigue strength of post-treated additively manufactured components with notches. In this study, fatigue tests were performed on plain and notched specimens to determine and compare the crack initiation and crack propagation behavior due to different manufacturing-related effects. Tests were performed on specimens produced by the two aforementioned AM processes and compared to specimens taken from wrought sheets. The fatigue strength of AM materials is influenced by microstructure, defects, residual stress, and notches. PBF-LB/M specimens exhibit the highest fatigue strength in plain, notch-free conditions, attributed to differences in microstructure and static strength affecting fatigue crack initiation. Notched specimens show larger differences among materials, with PBF-LB/M having shorter fatigue crack propagation life related to line-type defect clusters, while the plain PBF-LB/M specimens are less affected as their fatigue strength is primarily determined by fatigue crack initiation.Publicationtype: Journal Article60 86 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Mechanical behavior of additively and conventionally manufactured 316L stainless steel plates joined by gas metal arc weldingCombining several additive manufactured (AM) parts to larger parts by welding may be required due the limited building volume of powder bed AM methods. Laser powder bed fusion (LPBF) has a great potential because it enables the production of nearly full-density components through AM processes; however, additional residual stresses and production defects are induced by LPBF. These residual stresses affect the residual stress state of welded AM parts. In combination with the production related defects, both alter the mechanical and—in particular—the fatigue behavior of these welded joints. In this study, various tests are performed to characterize the butt joints of 316L AM steel plates made by gas metal arc welding. To this goal, joints are produced with weld seams parallel and vertical to the layer orientation of AM plates. The results are compared to joints of conventionally rolled steel plates produced with the same welding parameter. The residual stress states in initial (unloaded) condition and after cyclic loading were determined by X-ray diffraction techniques for AM and rolled plates. Complex residual stress states were determined at the welds made of AM steel plates compared to the welds made of rolled steel plates; however, the residual stress level in the heat affected zone of the butt-welded AM steel plates was similar to the welds made of hot-rolled steel plates. After cyclic loading with a high load level, high residual stress relaxations were observed in the parent materials. The fatigue design curve for butt joints from international standards is exceeded by all three test series, but the fatigue strength of the butt joints made by LBPF and hot rolling vary significantly. This is thought to be related to differences between the AM and conventional joints in microstructure, static strength, residual stress level, and small crack-like defects that partially interact with stress concentrations at the weld transition.Publicationtype: Journal Article41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Residual stress analysis of butt welds made of additively and traditionally manufactured 316L stainless steel plates(2022-03-29); ; ; ; Publicationtype: Conference Paper not in Proceedings38