Abstract
Additive manufacturing (AM) has recently gained much interest from researchers and industry practitioners due to the many advantages it offers as compared to the traditional subtractive manufacturing methods. These include the ability to fabricate net shaped complex geometries, integration of multiple parts, on-demand fabrication, and efficient raw material usage, among other benefits. Some of distinguishing features of AM metals, as compared to traditional subtractive manufacturing methods, include surface roughness, porosity and lack of fusion defects, residual stresses due to the thermal history of the part during the fabrication process, and anisotropy of the properties. Most components made of AM processes are subjected to cyclic loads, therefore, fatigue performance is an important consideration in their usage for safety critical applications. In addition, the state of stress at fatigue critical locations are often multiaxial. Considering the fact that many of the distinguishing features of AM metals are directional, the subject of multiaxial fatigue presents an important study area for a better understanding of their fatigue performance. This paper presents an overview of the aforementioned issues using recent data generated using AM Ti-6Al-4V and 17-4 PH stainless steel. Specimens were made by laser-based powder bed fusion and subjected to axial, torsion, and in-phase as well as out-of-phase loadings. A variety of conditions such as surface roughness, thermo-mechanical treatment, and notch effects are included. Many aspects are considered including damage mechanisms and crack paths, cyclic deformation, fatigue crack nucleation and growth, and stress concentration effects.
Highlights
Additive Manufacturing (AM) offers a number of advantages compared to the conventional subtractive manufacturing methods such as the capability of fabricating complex geometries, which are difficult or not feasible to build using conventional methods
In order to use AM parts in critical applications, such as those in aerospace and biomedical industries, cyclic properties and fatigue performance are of utmost important considerations as such parts are commonly subjected to cyclic loads in their operational environments
Such effects are more pronounced in AM, where geometry complexities result in stress concentrations, multidirectional residual stresses from the fabrication process are inevitable, and produced defects are typically directional resulting in anisotropy
Summary
Additive Manufacturing (AM) offers a number of advantages compared to the conventional subtractive manufacturing methods such as the capability of fabricating complex geometries, which are difficult or not feasible to build using conventional methods. Biaxial and multiaxial stresses are common for many components, even under nominal uniaxial loading conditions where the stress state can be multiaxial due to the complexities in the geometry such as notches, or presence of multidirectional residual stresses [1] Such effects are more pronounced in AM, where geometry complexities result in stress concentrations, multidirectional residual stresses from the fabrication process are inevitable, and produced defects are typically directional resulting in anisotropy. Shape, location, density, and orientations are significantly affected by the utilized processing parameters, build direction, and even the number of samples per build These defects, most commonly Lack of Fusion (LOF) and porosity, significantly affect fatigue performance of the fabricated parts. A brief discussion of some of the other important issues not considered in this paper is presented and an outlook for future research is provided
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
