The plasticity length scale parameters associated with rotational and stretch gradients in LIGA nickel MEMS structures plated from sulfamate bath are presented in this paper. These are obtained from micro-bend and micro-tensile experiments on LIGA nickel films with different thicknesses. The composite length-scale parameter, l c is measured to be ~ 4.8 µm for as-plated films (25, 50, 100 and 175 µm thick). The implications of the results are then discussed for the modeling of plasticity in LIGA nickel structures.
The effects of application of recycled scraps on the composition, microstructure and mechanical properties of SRR99 alloy were studied. The compositions of recycle master alloy are similar to that of the fresh alloy. However, nitrogen content, the size and amount of microporosity increase significantly with the recycle material proportion. Granular, lamellar and strip-like MC particles mainly represent in the interdendritic regions of the revert alloy. With the addition of the recycled material proportion, the amount of the granular ones rapidly drop and the lamellar ones gently enhance. The stress rupture life decline with the addition of the recycled material proportion. The oxide and sulphide inclusions in revert superalloy can be effectively captured and removed by a foam ceramic filter so that the tensile and stress rupture property has been significantly improved.
This paper presents the results of an experimental study of the indentation size effects at the nano, sub-micron, and micron-scales. The size dependence of the indentation hardness in these regimes is shown to exhibit a bi-linear behavior when the data are fitted to Taylor Dislocation Hardening (TDH) model. The deformation in indent sizes corresponding to the onset of the transition from micro and deep nano indents to shallow nano indents represent dislocation substructures at the sub-micron and micron scales whereas the deformation at the nano-scale represents dislocation source-limited behavior.
This paper presents a statistical framework for the modeling of fatigue in gamma-based titanium aluminide intermetallics. Following an initial description of the physics of fatigue crack growth, a deterministic fracture mechanics model is presented for the estimation approaches are of fatigue life. This is used as a basis for the development of a probabilistic model for the estimation of fatigue life due to variabilities in the initial flow size. The predicted variabilities are compared with measured variabilities from multiple fatigue life experiments performed on three cast lamellar gamma alloys. The implications of the results are then discussed for the estimation of material reliability in gamma-based titanium aluminide intermetallics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.