In this study, the degree of mechanical anisotropy was investigated through tensile testing of specimens built in different orientations and designed according to the ASTM D638 standard. The mechanical properties that were evaluated include Young’s modulus, ultimate tensile strength (UTS), and percentage elongation. Additionally, physical properties, such as mean surface roughness (Ra), density and dimension of the cross-sectional area, were also measured. These properties were then compared with the available standard data to see how SLA performs comparing to the traditional manufacturing methods. The obtained modulus of elasticity and UTS values of the printed samples were 2481 ± 50 MPa and 51.9 ± 1.3 MPa respectively, which were very similar to the standard data (2550 and 52 MPa, respectively) as provided by the material suppliers. The percentage elongation values (4.8% ± 0.4%) were a bit lower than the expected value of 6%. However, the surfaces of all the printed samples were quite smooth, with a surface roughness range of 2.28 ± 0.59 µm. A design of experiments was created to study the influence of the independent variables such as build orientation and angular orientation on the mechanical properties. Extensive statistical analysis, using the Taguchi method and analysis of variance (ANOVA), was performed to examine the effect of these independent variables on the mechanical properties. The SLA printed parts can be classified as isotropic since the build orientation and the angular orientation did not have a statistically significant impact on the mechanical properties. The effect of aging on the mechanical properties was also evaluated and it shows that the specimens that had been aged for a longer time resulted in superior mechanical properties. For example, the UTS increased from 24 to 54 MPa when the sample aligned parallel to the XY plane was aged from 1 week to 6 months, respectively. This significant increase implies that aging has a substantial effect on the mechanical properties of the parts fabricated by stereolithography. The resin used for this study, Visijet Sl Clear, produced very consistent mechanical properties in different directions.

Ti6Al4V is one of the vital metal alloys used in various industries including aerospace, especially at high-temperature applications, because of having high strength-to-weight ratio, and high melting temperature. Manufacturing these metal parts by the conventional subtractive methods have been challenging due to the difficulty involved with the cutting and machining it. However, additive manufacturing (AM) offers a convenient way for shaping this metal into the desired complex parts. Although different powder bed fusion (PBF) AM processes are time and cost effective, degradation of mechanical properties during high-temperature applications could be a concern for parts produced by them. Therefore, this study focuses on the anisotropic and high-temperature elastic and plastic behaviors of Ti6Al4V parts made using electron beam powder bed fusion (EB-PBF) process. Mechanical properties, like modulus of elasticity, 0.2% yield strength, ultimate tensile strength (UTS), and percent elongation, have been determined at 200 °C, 400 °C, and 600 °C temperatures from the samples produced in different build orientations. Considerable anisotropic behavior and temperature dependency were observed for all the analyzed properties. At 600 °C, various softening mechanisms such dislocation glide, grain boundary slip, and grain growth were anticipated to be activated reducing the flow stress and increasing the elasticity. Fractography analysis on fractured surfaces of the samples reveals various defects, including partially melted or unmelted powder particles near the surface and subsurface areas. Those internal and external defects are analyzed further using X-ray computed tomography (CT) and surface profilometer to show their effect on the anisotropic behaviors.

Powder bed fusion of copper has been extensively investigated using both laser-based (PBF-LB/M) and electron beam-based (PBF-EB/M) additive manufacturing technologies. Each technique offers unique benefits as well as specific limitations. Near-infrared (NIR) laser-based LPBF is widely accessible; however, the high reflectivity of copper limits energy absorption, thereby resulting in a narrow processing window. Although optimized parameters can yield relative densities above 97%, issues such as keyhole porosity, incomplete melting, and anisotropy remain concerns. Green lasers, with higher absorptivity in copper, offer broader process windows and enable more consistent fabrication of high-density parts with superior electrical conductivity, often reaching or exceeding 99% relative density and 100% International Annealed Copper Standard (IACS). Mechanical properties, including tensile and yield strength, are also improved, though challenges remain in surface finish and geometrical resolution. In contrast, Electron Beam Powder Bed Fusion (EB-PBF) uses high-energy electron beams in a vacuum, eliminating oxidation and leveraging copper’s high conductivity to achieve high energy absorption at lower volumetric energy densities (~80 J/mm³). This results in consistently high relative densities (>99.5%) and excellent electrical and thermal conductivity, with additional benefits including faster scanning speeds and in situ monitoring capabilities. However, EB-PBF processes in general face their own limitations, such as surface roughness and powder smoking. This paper provides a comprehensive review of the current state of laser-based (PBF-LB/M) and electron beam-based (PBF-EB/M) powder bed fusion processes for the additive manufacturing of copper, summarizing key trends, material properties, and process innovations. Both approaches continue to evolve, with ongoing research aimed at refining these technologies to enable the reliable and efficient additive manufacturing of high-performance copper components.

The powder bed fusion additive manufacturing process has received widespread interest because of its capability to manufacture components with a complicated design and better surface finish compared to other additive techniques. Process optimization to obtain high quality parts is still a concern, which is impeding the full-scale production of materials. Therefore, it is of paramount importance to identify the best combination of process parameters that produces parts with the least defects and best features. This work focuses on gaining useful information about several features of the bead area, such as contact angle, porosity, voids, melt pool size and keyhole that were achieved using several combinations of laser power and scan speed to produce single scan lines. These features are identified and quantified using process learning, which is then used to conduct a comprehensive statistical analysis that allows to estimate the effect of the process parameters, such as laser power and scan speed on the output features. Both single and multi-response analyses are applied to analyze the response parameters, such as contact angle, porosity and melt pool size individually as well as in a collective manner. Laser power has been observed to have a more influential effect on all the features. A multi-response analysis showed that 150 W of laser power and 200 mm/s produced a bead with the best possible features.

Classical mechanics theory is used to develop an analytical model for determining pile displacement due to temperature variations, in integral abutment bridges (IABs). The advantage of this model, as opposed to simple techniques proposed by AASHTO, is that it includes the forces that develop in the bridge due to soil pressure constraining the piles. A three-dimensional, nonlinear finite-element model (FEM) of the superstructure and substructure is developed to determine the displacement and cyclic behavior of piles. FEM is used to analyze the cyclic stress-strain behavior of piles and determine their inelastic deformation. Both the analytical model and FEM are used to calculate the displacements in piles for variety of bridge lengths under thermos-mechanical loading due to daily and seasonal temperature variations. Displacement calculations using the analytical model are then compared with the finite element and AASHTO results. The results show that although the new analytical model takes into account soil pressure on the piles, it does not include the soil pressure on the abutment. Therefore, the amount of deformation that FEM shows for expansion of the bridge is less than that determined by the analytical model. However, results of the analytical model are less than the AASHTO results. This shows that in conservative designs AASHTO can be used comfortably. If more accurate, less conservative design is desirable, the analytical model and FEM are proposed. FEM results show that maximum lateral displacement in (contraction) occurs during the winter. The displacement of piles in the summer and during high temperature times of the day shows a nonmonotonic trend with respect to depth providing buckling behavior in the piles. The piles’ displacement is completely monotonic during the winter and cold times of the night. For the bridge studied maximum stress occurs in the pile that is furthest from the center of the bridge. The cyclic stress-strain loop and inelastic deformation, both found from the FEM, are studied closely to identify the most likely location of a fatigue crack. Since plastic deformation occurs in piles, low cycle fatigue is expected. The most likely crack location is found in the flange of the pile right below the concrete abutment.