Constance W. Ziemian

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).

Computer aided decision support for fused deposition modeling

Parts formed using fused deposition modeling (FDM) can vary significantly in quality depending on the manufacturing process plan. Altering the plan profoundly affects the character of the resulting part. Although the designer and the machine user may have preferences regarding the part build and the relative importance of build outcomes such as production speed, dimensional accuracy, and surface quality, setting process variables to ensure desired results is a complex task. A multi‐objective decision support system has been developed to aid the user in setting FDM process variables in order to best achieve specific build goals and desired part characteristics. The method uses experimentation to quantify the effects of FDM process variables on part build goals, and to predict build outcomes and expected part quality. The system offers the user the ability to quantify the trade‐offs among conflicting goals while striving towards the best compromise solution.

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.

Tensile and fatigue behavior of layered acrylonitrile butadiene styrene

Purpose – This paper aims to define the effect of specimen mesostructure on the monotonic tensile behavior and tensile-fatigue life of layered acrylonitrile butadiene styrene (ABS) components fabricated by fused deposition modeling (FDM). Design/methodology/approach – Tensile tests were performed on FDM dogbone specimens with four different raster orientations according to ASTM standard D638-03. Resulting ultimate tensile stresses (UTS) for each raster orientation were used to compute the maximum stress for fatigue testing, i.e. 90, 75, 60 and 50 or 45 per cent nominal values of the UTS. Multiple specimens were subjected to tension – tension fatigue cycling with stress ratio of R = 0.10 in accordance with ASTM standard D7791-12. Findings – Both tensile strength and fatigue performance exhibited anisotropic behavior. The longitudinal (0°) and default (+45/−45°) raster orientations performed significantly better than the diagonal (45°) or transverse (90°) orientations in regards to fatigue life, as displaye...

Shake‐table simulation study of small scale layered models

– The purpose of this paper is to investigate the correlation between the dynamic behavior of a full‐scale steel prototype and a small‐scale plastic model fabricated using fused deposition modeling (FDM)., – Based on the use of a known input excitation, the small‐scale model is tested on a shake‐table. Experimental results are compared with results of a full prototype study and with computational models in an effort to assess the feasibility of testing small‐scale FDM models., – Time History Records present strong correlation with prototype data and are reproducible using computational methods. Matching the first natural frequency of the studied structure proved to be a large part of achieving the desired response., – Including the direct measurement of floor displacements will potentially highlight different aspects of model behavior not observed by recording accelerations only. Further investigation into the damping properties of acrylonitrile butadiene styrene plastic is recommended towards further understanding the model response., – Although this paper is based on a simple structure, the benefits of layered manufacturing (LM) methods include speed and ease of generating geometrically complex solids. The implications of the success of this pilot study include the ease in which the dynamic response of complex structures can be assessed using small‐scale LM models., – This project obtained baseline information on the dynamic behavior of FDM plastic parts. It provides assessment of the value of using small‐scale LM models to accurately predict the dynamic response of structures subjected to earthquake excitation.

Influence of Impact Conditions on Feedstock Deposition Behavior of Cold-Sprayed Fe-Based Metallic Glass

Cold spray is a promising method by which to deposit dense Fe-based metallic glass coatings on conventional metal substrates. Relatively low process temperatures offer the potential to prevent the crystallization of amorphous feedstock powders while still providing adequate particle softening for bonding and coating formation. In this study, Fe48Mo14Cr15Y2C15B6 powder was sprayed onto a mild steel substrate, using a variety of process conditions, to investigate the feasibility of forming well-bonded amorphous Fe-based coatings. Particle splat adhesion was examined relative to impact conditions, and the limiting values of temperature and velocity associated with successful softening and adhesion were empirically established. Variability of particle sizes, impact temperatures, and impact velocities resulted in splat morphologies ranging from well-adhered deformed particles to substrate craters formed by rebounded particles and a variety of particle/substrate interface conditions. Transmission electron microscopy studies revealed the presence of a thin oxide layer between well-adhered particles and the substrate, suggesting that bonding is feasible even with an increased oxygen content at the interface. Results indicate that the proper optimization of cold spray process parameters supports the formation of Fe-based metallic glass coatings that successfully retain their amorphous structure, as well as the superior corrosion and wear-resistant properties of the feedstock powder.