Mala M. Sharma

Anisotropic Mechanical Properties of ABS Parts Fabricated by Fused Deposition Modelling

Layered manufacturing (LM) methods have traditionally been used for rapid prototyping (RP) purposes, with the primary intention of fabricating models for visualization, design verification, and kinematic functionality testing of developing assemblies during the product realization process (Caulfield et al., 2007). Without any need for tooling or fixturing, LM allows for the computer-controlled fabrication of parts in a single setup directly from a computerized solid model. These characteristics have proven beneficial in regard to the objective of reducing the time needed to complete the product development cycle (Chua et al., 2005).

Pitting and Stress Corrosion Cracking Susceptibility of Nanostructured Al-Mg Alloys in Natural and Artificial Environments

The stress corrosion cracking (SCC) behavior of two developmental nanocrystalline 5083 alloys with varied composition and processing conditions was studied. The results were compared to a commercial aluminum AA 5083 (H111) alloy. The pitting densities, size and depths, and residual tensile strengths were measured after alternate immersion in artificial seawater and atmospheric exposure under different loading conditions. Optical and scanning electron microscopy (SEM) with EDX was used to analyze the fracture surfaces of failed specimen after removal at selected intervals and tensile testing. One of the nanostructured Al-Mg alloys exhibited significantly superior pitting resistance when compared to conventional microstructured AA 5083. Under conditions where pitting corrosion showed up as local tunnels toward phase inclusions, transgranular cracking was observed, whereas under conditions when pitting corrosion evolved along grain boundaries, intergranular cracking inside the pit was observed. Pit initiation resistance of the nano alloys appears to be better than that of the conventional alloys. However, long-term pit propagation is a concern and warrants further study. The objective of this investigation was to obtain information regarding the role that ultra-fine microstructures play in their degradation in marine environments and to provide insight into the corrosion mechanisms and damage processes of these alloys.

Characterization, Deposition Mechanisms, and Modeling of Metallic Glass Powders for Cold Spray

This chapter describes recent efforts to understand the effects that chemical and physical properties of metallic glass (MG) powder particles have on the synthesis of their cold-sprayed coatings. Understanding the mechanical response of MG is fundamental to evaluate the conditions at which their powder particles can be deposited by cold spray. The characteristics of the feedstock powders are evaluated and used to ascertain ideal cold spray parameters. This information is also used to model the deposition mechanism of metallic glasses in the cold spray process. FE analysis and simulation is used to identify the phenomena behind the formation of MG coatings (i.e., homogenous or inhomogeneous deformation). The model defined considers strain rate and temperature dependence of MGs under different conditions.