PSI - Issue 56

Radim Halamaa et al. / Procedia Structural Integrity 56 (2024) 111–119 Halama et al / Structural Integrity Procedia 00 (2023) 000 – 000

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1. Introduction Selective laser melting (SLM) is an additive manufacturing (AM) technology used to print functional parts from metallic powders using a high-energy laser beam. AM brings freedom in complex geometry and enhanced possibilities of design as bionic structures. Light structures can be produced by application of a lattice structure; see the review of Obadimu and Kourousis (2021). The fatigue properties of AM materials must be considered when evaluating materials for industrial use. Compared to the static tensile properties of the parts produced by AM, fatigue performance is less reported in recent research studies, especially in the low cycle domain; see Brandl et al. (2012) and Raja et al. (2022). The AlSi10Mg alloy is one of the most popular materials used in light structures produced by SLM and commonly used in the aviation and automotive industries due to its high heat resistance and fatigue properties, see Glodež (2020) . Influence of scanning strategies on the stress-strain behavior and its prediction by a crystal plasticity model is studied for instance in Chakrabarty and Chakraborty et al. (2023). Crack propagation properties of additively manufactured AlSi10Mg were explored in Chakrabarty and Sahu et al. (2023). The possibility of heat treatment to reduce the residual stresses, that are natural in the AM process, keeping the cellular microstructure is studied by Měsíček et al. (2022). In computational fatigue analysis, the cyclic stress-strain curve is an important material characteristic, which is usually constructed by an approximation of stress peaks from low-cycle fatigue tests performed for particular (plastic) strain amplitudes. This paper shows a new possibility of estimating the cyclic stress-strain curve using full field data from optical measurement of strain on the curved part of the specimen. The first example of such an application was described by Halama et al. (2017). The procedure described in this study was applied to two proportional loading cases performed under tension-compression and pure torsion, and to the 90 degree out-of-phase axial-torsion test. Nomenclature 0−3 parameters of the four-parametric approximation function G shear modulus

radius of the curved part of the specimen coordinate of the DIC point in the -direction coordinate of the DIC point in the -direction 0 , 0 optimized parameters 1 , 2 , 3 principal strains equivalent strain calculated according to von Mises , axial plastic strain amplitude, shear plastic strain amplitude , axial stress amplitude, shear stress amplitude 2. Accelerated technique description

The selective laser melting is an expensive manufacturing technology. The limitation in build space dimensions requires to carefully plan number of parts and their orientation. In anisotropy investigation, one needs a lot of specimens for monotonic and fatigue testing. Therefore, it is necessary to obtain maximum information from each test, and the accelerated technique of cyclic stress-strain curve estimation is very beneficial.