Claude Belzile

The processes of metal additive manufacturing (AM) are no longer confined to rapid prototyping applications and are seeing increasing use in many fields for the production of tools and finished products. The ability to design parts with practically zero waste, high precision, complex geometry, and on-demand fabrication are among the advantages of this manufacturing approach. One of the drawbacks of this technique is the productivity rate, as the parts are made layer by layer, which also increases the production cost. Moreover, even the working space is limited, especially for the powder bed fusion technique. In view of these disadvantages and in order to guarantee the profitability of this process, it should be oriented to the production of complex components that have a limited volume with a design adapted to additive manufacturing. One solution with which to circumvent these drawbacks is to combine the 3D printing process with conventional manufacturing processes. When designing products, one may choose to use additive manufacturing to create locally complex parts and assemble them with parts produced by conventional processes. On the other hand, and due to the limited AM printing chamber space, it may be necessary to print large parts in multiple smaller parts and then assemble them. In order to investigate the weldability of stainless steel 316L parts produced by laser powder bed fusion (L-PBF), the mechanical behavior of different welding assemblies is tested. Five configurations are studied: non-welded AM specimens, two AM parts welded together, one AM part and one laser cut part welded together, two laser-cut parts welded together, and non-welded laser cut specimens. Welding is performed using the Pulsed Gas Metal Arc Welding process (GMAW-P). Specimen strength is assessed through static and fatigue tests. The results demonstrate that 316L AM parts are weldable, and the tensile and fatigue properties of L-PBF 316L welded components and welded laser cut components are comparable. GMAW-P welding led to lower fatigue results for AM components than for other configurations, but the difference is not important. It was observed that welding defects may have a direct impact on mechanical properties.

The objective of this study is to verify whether low amounts of fine sand added to a muddy sediment matrix can be detected and quantified with accuracy using a Mastersizer 3000 (Malvern Panalytical) laser diffraction particle-size analyzer equipped with a Hydro LV large volume liquid dispersion module. To achieve this goal, a postglacial sediment sample was sieved to recover naturally co-occurring sand and clay–silt fractions. Sand in the range of 1%–7% by weight was added to the clay–silt at three concentrations (88, 132, and 276 mg dry weight) and each sample was duplicated. A very strong linear relationship was found between the measured % volume of sand added and the actual weight of sand added to the mud. Sand representing as low as 1% by weight could be detected. On average, there was only a 0.7% absolute difference between the measured and actual % sand values (range 0.02%–1.65%). Sample concentration had a negligible impact on the measured % sand. A range of plausible values for the refractive and absorption indexes, essential parameters for the Mie theory calculation of the size distribution from the measured light scattering, also had very small impact on the measured % sand. The demonstrated possibility of detecting a small input of fine sand to muddy sediment provides a basis for studies using grain-size data to reconstruct past and modern detrital inputs and sediment transport variations.