Effect of stress concentrators on fracture resistance of specimens fabricated by direct metal laser sintering

We studied samples of 17-4 PH stainless steel with stress concentrators fabricated via direct metal laser sintering (DMLS). Tests were carried out both on these samples and on smooth specimens. The mechanical properties of the samples under cyclic and static loading were also determined. Moreover, the surface morphology of the destroyed samples was studied by optical and electron microscopy. It was found that the resistance to cyclic loading in samples with grooves of radius R = 0.5, 1.0, and 2.5 mm is higher than that of a smooth sample. The decrease in cyclic and static strength characteristics was influenced by the metal structure of the samples. It was found that the sample with a coarse-grained structure favors crack development. Lastly, the specimen with a sharp concentrator of radius R = 0.5 mm was characterized to have a highly dispersed structure, which reduces crack development under cyclic loading. The novelty of this work lies in the fact that for the first time the ambiguous influence of stress concentrators was established depending on the type of loading. All these factors have an impact on the strength of the samples in cyclic and static tests.