Analysis of mechanical behavior of additively manufactured metallic materials under static and cyclic loading

Abstract

Additive manufacturing (AM) or 3D printing has been continuously developed. The obvious advantage of AM technologies is the ability to adjust the print parameters, which affect the properties of AM parts, costs, and time in the manufacturing process. Most AM technologies use a lattice structure to form the internal part of AM part to reduce material consumption resulting in the weight reduction of the part. The effect of various print parameters on the mechanical properties of parts fabricated by AM technology has been widely studied, especially under a static load. However, the part may be subjected to repeated loads, leading to fatigue failure. This study focuses on investigating the mechanical properties of metal parts produced by an AM technology under static and cyclic loads by performing the tensile and fatigue tests. Specimens were fabricated using Bound Metal Deposition (BMD) technique with 316L and 17-4PH stainless steel with different relative densities to study the effect of relative densities on mechanical properties, manufacturing costs and time. Because the BMD technique uses a lattice structure with a triangular pattern to form the internal part of AM part, this study therefore examines the mechanical properties of the lattice structure under tensile load. Isotropic property of the lattice structure with a triangular pattern is also investigated including other lattice patterns. In addition, this study uses the analytical method from the literature and finite element analysis to validate the results. It is found that the specimens with a higher relative density have higher mechanical properties. However, the relationship between relative density and mechanical properties is a non-linear function. When validating the results with the analytical method from the literature, it is found that the analytical method can be used to predict the mechanical properties correctly only in the low relative density range. In term of efficiency, the specimens with a higher relative density give greater results when considering performance and sustainability parameters. For investigating the degree of anisotropy of lattice structures, the triangular lattice exhibits the isotropy behavior in terms of elastic modulus same as the hexagonal lattice. However, it has a higher modulus and strength. The triangular lattice is therefore a good choice for producing AM parts. The results from this study can be applied to the design of AM parts to be able to ensure they can carry the applied load appropriately. However, the performance of AM specimens in this study was only investigated for in-plane tensile loading. Other implementations, such as compression, bending, and impact loading, may yield different results. Therefore, it is important to investigate and study various loads for comprehensive design purposes.