Purpose
In the development of powder bed additive manufacturing (AM) process parameters, the characterization of mechanical properties is generally performed through relatively large mechanical test samples that represent a bulk response. This provides an accurate representation of mechanical properties for equivalently sized or larger parts. However, as feature size is reduced, mechanical properties transition from a standard bulk response to a thin wall response where lower power border scans and surface roughness have a larger effect.
Design/methodology/approach
For this study, samples of wall thickness varying between 4.0 and 0.25 mm were built in 304L on the selective laser melting (SLM) platform and Ti-6Al-4V on the electron beam melting (EBM) platform. Samples were then mechanically tested, and fractography was performed for analysis.
Findings
This study experimentally identifies the threshold between bulk and thin wall mechanical properties for 304L SS on the SLM platform and Ti-6Al-4V on the EBM platform. A possible method for improving those properties and shifting the transition from bulk to thin wall response to smaller wall thicknesses by manipulation of scan pattern was investigated.
Originality/value
This study is a novel investigation into the effect of reduced wall thickness on the mechanical properties of a part produced by powder bed AM.
Dyes are a category of substances capable of inducing allergic contact dermatitis found in a variety of foods, drugs, textiles, cosmetics, and hair dyes. This study tested 33 dyes in guinea pigs using a modified Buehler and Klecak method for open epicutaneous testing. The dyes were tested at an induction concentration of 10% and challenge concentrations of 10.0%, 5.0%, and 2.5%. Nine of the 33 dyes tested produced positive allergic reactions in the guinea pig model (2‐amino‐4‐nitrophenol, 2‐amino‐5‐nitrophenol, acid yellow 23, acid orange 3, basic black 3, basic orange 1, disperse orange 3, solvent black 27, and solvent black 34). When eight of the nine positive dyes were retested using a 1% induction concentration, five dyes produced allergic contact dermatitis at a 1% challenge concentration (2‐amino‐4‐nitrophenol, 2‐amino‐5‐nitrophenol, acid yellow 23, disperse orange 3, and solvent black 34), two at a 0.5% challenge concentration (2‐amino‐5‐nitrophenol and solvent black 34), and one at a 0.25% challenge concentration (2‐amino‐5‐nitrophenol). DNCB at a 0.5% induction/challenge concentration was used as a positive control. With the exception of disperse orange 3 and acid yellow 23, the seven additional dyes that elicited positive allergic reactions in the guinea pig model have not been previously reported.
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