PSI - Issue 50

V. Ilinykh Artem et al. / Procedia Structural Integrity 50 (2023) 113–118 Illinykh Artem V. et al./ Structural Integrity Procedia 00 (2023) 000 – 000

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technology is by far the most suitable in the additive manufacturing of complex products from various alloys and metals (Martin et al., 2017). It allows to create products with high precision and complex geometric shapes which is a labor-intensive process with traditional production technologies. The main disadvantages of this technology are the high cost of production and the relatively small size of manufactured products. After production by laser melting method parts and products have a significant anisotropy of mechanical properties (Herzog et al., 2016) which is due to the nature of the layer-by-layer synthesis processes and the strategy of scanning the layer with a laser beam. The deformation and strength properties are different depending on the considered direction inside the material. The layer-by-layer synthesized material can be represented as a transversally isotropic material. Such a material has an advantageous direction in which the mechanical properties differ significantly from the mechanical properties in perpendicular planes. For the experimental study of the mechanical properties of materials, samples with different cross-sectional shapes are used (Lewandowski et al., 2016). Because of the anisotropy of properties three growth directions are considered for standard round sections: X, Y, and Z; and for rectangular samples - 6 directions: XYZ, XZY, YXZ, YZX, ZXY and ZYX (Zhao et al., 2016). To obtain the basic mechanical characteristics such as conditional yield stress and tensile strength, static tensile tests to failure are carried out. To obtain the modulus of elasticity and Poisson's ratio, it is sufficient to carry out tests in the elastic zone at low loads without destroying the sample. The mechanical properties of the resulting products are significantly affected by both the manufacturing technology and the operating modes of the equipment: laser beam energy density, scanning speed, subsequent thermal and mechanical processing (Kimura et al., 2016). So in the article by Demkovich et al. (2016) using the example of the AK9ch alloy it was shown that the material in the synthesized state has the best strength indicators while any subsequent heating leads to a deterioration in these indicators. And in the article by Nesma et al. (2016) it is shown how for an alloy obtained by the method of selective laser sintering from ASP35(AlSi10Mg) powder mechanical characteristics were obtained higher in values than when smelted by the traditional method. However, with poor selection of parameters the appearance of a large number of defects (cracks, cavities, etc.) is observed which negatively affects the mechanical properties of the material (Haijun et al., 2015). A big problem in the manufacture of complex shape parts is the presence of significant residual stresses. These stresses can have high values leading to a change in the geometry or destruction of the part at the manufacturing stage (Fedorenko et al., 2021). There are many articles containing mechanical tests of a wide range of materials obtained by selective laser melting; see e.g. Zhang et al (2016), but due to the fact that in structures of complex geometry under the action of loads a complex stress state arises then complex experimental studies are required including testing for torsion by Ilinykh et al (2021) or pure shear. However, few data on shear characteristics can be found for such a material obtained by an additive method. Therefore, experiments are relevant with the implementation of shear deformations and shear stresses. This article discusses the results of tensile and torsion tests of samples made from ASP35 powder. The samples were made from cylindrical blanks grown by selective laser melting in the directions: 0, 30, 45, 60, and 90º to the substrate plane (Pankov at al., 2021). It is of interest to compare the values of the anisotropy coefficient of mechanical properties in tension and torsion. 2. Materials and methods Tensile experiments were carried out at the Center of Experimental Mechanics of PNRPU on an Instron 8801 servo-hydraulic testing system. To measure longitudinal strains, an Instron 2620-603 mounted extensometer (Fig. 1a) with a limiting strain of 10% was used. Figure 1 (b) shows tensile cylindrical samples. The use of threaded grips makes it possible to produce samples of smaller size which makes it possible to reduce the cost of their manufacture. Before the start of the experiment a sample was installed in the grips of the test system in the sample protection mode which makes it possible to avoid overloading when it is fixed in the grips. Next a strain gauge was hung on the sample. The sample was stretched at a rate of 1 mm per minute until the sample failed. Based on the results of processing the obtained experimental data, the following mechanical characteristics were determined: Young's modulus (E, GPa), proportionality limit ( σ pc, MPa), conditional tensile yield strength ( σ 0.2, MPa), tensile strength ( σ b, MPa), relative elongation ( δ , %) and relative narrowing ( Ψ , %) .