Investigation on a predetermined point of failure for stainless steel 316L pressure loaded components made by laser powder bed fusion through stress analysis and experimental testing

Abstract

AbstractThe qualification process of pressure vessels in general is subject to governmental restrictions. Thus, introducing additive manufacturing (AM) components to the market is challenging due to incomplete standardization. To increase component safety and trust, predetermined points of failure can be integrated by design using direct manufacturing methods. A predetermined point of failure using a surface notch is one option to avoid dangerous part failure (e.g. explosion) and increase safety. For implementation, a design approach with experimental proof of concept is striven to guide manufacturers and demonstrate the behavior of the material and the component as a whole. Finite element analysis is used for investigations on the influence of surface notch geometries applied to wall structures on structural stress super-elevation. Analytical strength assessment using FKM guideline and experimental validation of PBF-LB/M-manufactured specimen behavior by static axial tensile and burst testing is carried out. Fracture surface and plastic elongation evaluation using light microscopy and 3-D surface scanning clarify the material behavior. The analytical and experimental approval of an integrated predetermined point of failure for static overload is achieved without reducing the maximum burst pressure value. The integration fulfills all theoretical requirements for structural strength. All tested specimens meet the expectations regarding static strength and failure behavior. As expected, component elongation decreases using surface notches for failure provocation. Results lead to a proposed guideline for the application of an integrated predetermined point of failure by the use of a surface notch.