Expedited Optimization of AM Materials Using Miniaturized Testing

Mechanics of the small punch test: a review and qualification of additive manufacturing materials

“…As the changes in SLM material microstructures can range from minor to major depending on the variations employed in processing, a high sensitivity evaluation method is vital. As SPT has been shown to be responsive to material property changes and anisotropy in small volumes caused by processing variations, this then becomes a highly attractive option for optimizing processing parameter settings and post-processing routines [31,74,104]. The Pareto plot and the resultant curves from the parametric study show that a model such as that utilized here, and consequently the small punch test, is sensitive enough to track incremental changes in material properties due to processing variations typical of AM materials.…”

“…A significant gap in SPT fatigue testing exists which needs a modified methodology capable of reversed loading in order to fill it, which presents a large challenge given the confined dimensions of the test system. Present works are directed at starting to fill these gaps, as shown in [31,179], including test control variations for cyclic loading, as well as introduction of a dual-punch test setup to introduce fully reversed cyclic loading in an effort to replicate traditional fatigue testing damage. Concurrent work completed by Lancaster et al, utilized a similar dual punch setup to fatigue test variants of Ti-6Al-4 V manufactured by both electron beam melting and conventional forging [180].…”

“…This data and its fit is also be affected by the locations of the samples with respect to the original donor component as a whole, as location within the original structure will affect the porosity and level of sintering which are artefacts of the PM manufacturing process, since samples nearer to the surface will undergo more direct pressure and sintering than those at the center, and thus have a less brittle nature [43]. Consequently, it may be necessary to consider both methodologies when evaluating the suitability of SPT for AM materials, as fracture morphology and response for AM samples can vary due to the degree of material anisotropy present depending on parameters such as orientation and post-processing treatments [31].…”

“…Literature on the topic is limited when the subject matter is combined with additive manufacturing techniques such as SLM, due to the somewhat recent emergence of both topics. The ability of the SPT to predict the anisotropy of as-manufactured AM materials, specifically those made with SLM, has been shown in the literature, with fracture morphology being highly dependent on manufacturing orientation [31,32]. Additionally, Dao et al showed an orientation dependency for stainless steel 316 L manufactured via SLM when subjected to small punch creep tests [33].…”