## 1 Introduction  
Additive manufacturing (AM) is quickly growing in the automotive and aerospace industries because it not only offers rapid prototyping but also almost unlimited possibilities of innovative structural design to save weight and optimize performance. AM processes offer the ability to fabricate parts with complex geometry that are very challenging or even impossible to produce by subtractive manufacturing methods. In addition, on-site fabrication of replacement parts and efficient production of parts in small numbers are among the other advantages of AM methods, enabling lean and effective logistics for maintenance. Owing to these reasons, nowadays, AM methods have gained popularity in various industries.  
With the development of more advanced AM technologies, such as laser-based powder bed fusion (LB-PBF), including selective laser melting (SLM) and direct metal laser sintering (DMLS), and directed energy deposition (DED) methods, the mechanical properties of AM materials are getting closer to and sometimes even exceeding the conventional materials [1; 2; 3]. Extensive efforts have also been devoted to studies on fatigue performance of AM materials, which are summarized in recent reviews [4; 5]. Both tensile and fatigue properties are pertinent to the development of material allowables and design values for certification of the designed products. By these requirements, it is quite challenging to fully characterize the effects of all the variables that influence the resulting performance in the intended application of AM materials through conventional testing.  
AM materials commonly have manufacturing defects, such as lack of fusion (LOF) defects, porosities, and un-melted particles, which inevitably affect the fatigue behaviour of AM materials [5; 6]. The process and design parameters could influence the density,size, shape, and location of the internal defects, surface roughness and residual stresses. In addition, the complex thermal cycles during the fabrication of AM parts, accompanied by the variations in the part geometry, can influence the orientation and geometry of the defects as well. Therefore, it can be said that individually built coupons may not fully represent local variations in parts. Therefore, the applicability and fitness of the use of coupon-generated bulk material allowables and design values have to be demonstrated for each individual component [7]. This requires a quantitative correlation of the fatigue properties with surface finish and microstructure per manufacturing process.  
The present paper summarizes the results of a study assignment during a graduate course MECH 5602 at Carleton University, Ottawa, ON, Canada. The participating students curated the fatigue data for various AM materials such as SLM Al-Si-10 Mg, DLMS Ti-6 Al-4V, and LB-PBF 17-4 PH from the literature, and analyzed the data using a modified Tanaka-Mura-Wu model [8; 9]. The effects of surface roughness, microstructure and post-heat treatment, e.g., hot isostatic pressing (HIP), on fatigue life are examined with respect to low cycle fatigue (LCF) and high cycle fatigue (HCF). Preliminary statistical analysis is also conducted for defining the fatigue strength allowables.