PSI - Issue 37

2

R. Fernandes et al. / Procedia Structural Integrity 37 (2022) 462–468 R. Fernandes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

463

Nomenclature  strain  a,t

total strain amplitude elastic strain amplitude plastic strain amplitude fatigue ductility coefficient fatigue strength coefficient fatigue strength exponent fatigue ductility exponent cyclic hardening coefficient stress stress amplitude

 a,e  a,p

 f 

 a  f

b c k

k p

material constant

n

cyclic hardening exponent

N N f

number of cycles

number of cycles to failure

due to their high strength, low density, good fracture toughness, and attractive cost (Heinz, 2000). These superior mechanical properties make them ideal for applications which experience repeated loading histories (Borrego, 2000; Jesus, 2014; Branco, 2019). Although engineering applications are usually designed in a such a way that materials only deform in an elastic manner, local plastic deformation can occur at the geometric discontinuities, and, therefore, an accurate structural integrity assessment requires a deep knowledge of the cyclic plastic behaviour (Carpinteri, 2016; Macek, 2017; Zhu, 2019; Liao, 2019; Pejkowski, 2019; Cruces, 2019; Nejad, 2021). Additive manufacturing has attracted the interest of several strategic sectors, such as aerospace, automotive, medical and energy industries because of its potential to reduce costs, the possibility to reduce the steps associated with the production process and high design freedom (Blakey-Milner, 2021). Within the current additive manufacturing processes, laser-beam powder bed fusion is one of the most popular. It combines unique features with cost effectiveness, allowing the manufacturing of functional parts, in a layer-by-layer fashion, directly from 3D digital files. One of the main disadvantages is its susceptibility to different types of anomalies (such as porosities, inclusions, lack of fusion, etc.) increasing the uncertainty concerning the mechanical behaviour (Branco, 2021; Garcias, 2021; Jesus, 2021; Razavi, 2021). In the past few years, some effort has been put on the understanding of mechanical behaviour for different engineering metals processed by laser-beam powder bed fusion, particularly on the triangular relationship between process parameters, microstructural features, and mechanical properties (Shamsaei, 2015). Regarding the AlSi10Mg aluminium alloy manufactured by laser-beam powder bed fusion, although the research focused on the effect of processing routes on microstructure and monotonic properties is relatively abundant, only very few studies have addressed the effect of processing routes of cyclic deformation behaviour (Bao, 2021). Therefore, the main goal of the present paper is to study the cyclic deformation behaviour of AlSi10Mg aluminium alloy manufactured by laser-beam powder bed fusion for different processing states, namely in the as-built, stress-relieved, and T6 conditions. In order to meet this objective, low-cycle fatigue tests are performed under fully-reversed conditions, at room temperature, for strain amplitudes ranging from 0.2-1.5%. 2. Material and methods The material used in this study was an AlSi10Mg aluminium alloy manufactured via laser-beam powder bed fusion. The specimens, represented in Figure 1, were built vertically from the platform, with a scan speed of 1.8 m/s