In this study, micro-computed tomography (CT) is utilized to detect defects of Ti-6Al-4V specimens fabricated by selective laser melting (SLM) and electron beam melting (EBM), which are two popular metal additive manufacturing methods. SLM and EBM specimens were fabricated with random defects at a specific porosity. The capability of micro-CT to evaluate inclusion defects in the SLM and EBM specimens is discussed. The porosity of EBM specimens was analyzed through image processing of CT single slices. An empirical method is also proposed to estimate the porosity of reconstructed models of the CT scan.

Ultrasonic peening treatment (UPT) has been proved to be an effective way of improving residual stresses distribution in weld structures. Thus, it shows a great potential in stress modification for metal parts fabricated by additive manufacturing technology. In this paper, an investigation into the ultrasonic treatment process of AlSi10Mg specimens fabricated by selective laser melting (SLM) process was conducted by means of experimental and numerical simulation. The specimens were prepared using a SLM machine, and UPT on their top surface was carried out. The residual stresses were measured with an X-ray stress diffraction device before and after UPT. Meanwhile, a finite element simulation method for analyzing the influence of UPT on the residual stress field of specimens was proposed and validated by experiments. Firstly, the thermal mechanical coupling numerical simulation of the SLM process of the specimen was carried out in order to obtain the residual stress distribution in the as-fabricated specimen. Then, the transient dynamic finite element simulation model of the UPT process of the specimen was established, and the UPT effect analysis was implemented. In the UPT simulation, the residual stress was applied as a pre-stress on the specimen, and the specimen’s material mechanical property was described by the Johnson–Cook model, whose parameters were determined by Split Hopkinson Pressure Bar (SHPB) experiment. The residual stress distribution before and after UPT predicted by the finite element model agree well with the measurement results. This paper concludes with a discussion of the effects of ultrasonic peening time, as well as the frequency and amplitude of the peening needle on residual stress.

Nylon filament is a widely used thermoplastic material in extrusion-based 3D printing, favored for its strength, durability, and excellent printability. It enables the fabrication of parts with complex geometries, high design flexibility, and cost-effective production, making it ideal for both prototyping and functional components. However, one significant drawback of nylon is its hygroscopic nature—it readily absorbs moisture from the surrounding environment, often at a rapid rate. This moisture uptake can negatively impact the filament’s performance during printing, leading to poor surface finish, reduced mechanical strength, and altered thermal behavior in the final printed parts. To better understand the effects of moisture absorption, this study investigates the mechanical and thermal properties of nylon parts printed using filaments with varying levels of moisture content. The nylon filament was conditioned in a controlled humidity chamber for different durations to simulate moisture exposure over time. Specimens were then printed using these conditioned filaments, and a series of tests were performed to assess their mechanical integrity and thermal stability. By analyzing the test results, the study aims to establish a correlation between filament moisture content and part quality, offering valuable insights into the degradation mechanisms and guiding best practices for filament handling and storage in nylon 3D printing applications.

This study measures the rheological properties of two stainless steel 316L powders which are used for the powder-bed-fusion based additive manufacturing process. The purpose is to evaluate the newly acquired powder in comparison with the used and recycled powder, so that both powders can be mixed with each other to supplement the powder usage. The powder rheology properties, such as dynamic property, bulk property, and shear property, are tested and compared. The results and analysis confirm the compatibility of powder mixing.