Built-up edge mechanisms in the machining of duplex stainless steels

 The thesis work was aimed at resolving long established issues with difficult-to-machine materials. The main thesis contribution, is the academic community now has a better understanding of how the issue of built-up edge is occurring when machining duplex stainless steel alloys, which will aid in the machining sector

Effect of layer thickness and cross-section geometry on the tensile and compression properties of 3D printed ABS

This study examines the influence of deposition layer thickness on the mechanical properties of printed ABS material when manufacturing using Fused Filament Fabrication (FFF). Tensile and compression testing was performed to ASTM standards on samples printed with layer thickness between 0.2 mm and 0.8 mm. Results found material strength and stiffness was greatest using smaller layer thicknesses, compared with larger layer thicknesses e.g. σy(0.2mm) = 31.5 MPa, UTS0.2mm = 38.2 MPa, compared with σy(0.8mm) = 23.0 MPa, UTS0.8mm = 31.0 MPa. The recorded changes in mechanical properties are explained by mechanisms relating to manufacturing residual porosity, the number of deposited layers promoting interlayer bonding strength, and the extrusion process resulting in material shear hardening. Findings have implications on the ability to reduce the overall part print time using a method of increased material deposition, and may have profound implications on comparative part integrity when utilising large volume deposition printing formats with unmodified ABS polymer. The findings from this study also highlight the need for current mechanical testing standards to accommodate appropriate guidelines for the testing of 3D printed material, given the wide variance of measured tensile and compression properties based on layer thickness and printed geometry

Metallurgical and Machinability Characteristics of Wrought and Selective Laser Melted Ti-6Al-4V

This research work presents a machinability study between wrought grade titanium and selective laser melted (SLM) titanium Ti-6Al-4V in a face turning operation, machined at cutting speeds between 60 and 180 m/min. Machinability characteristics such as tool wear, cutting forces, and machined surface quality were investigated. Coating delamination, adhesion, abrasion, attrition, and chipping wear mechanisms were dominant during machining of SLM Ti-6Al-4V. Maximum flank wear was found higher in machining SLM Ti-6Al-4V compared to wrought Ti-6Al-4V at all speeds. It was also found that high machining speeds lead to catastrophic failure of the cutting tool during machining of SLM Ti-6Al-4V. Cutting force was higher in machining SLM Ti-6Al-4V as compared to wrought Ti-6Al-4V for all cutting speeds due to its higher strength and hardness. Surface finish improved with the cutting speed despite the high tool wear observed at high machining speeds. Overall, machinability of SLM Ti-6Al-4V was found poor as compared to the wrought alloy

Machinability of metallic and ceramic biomaterials : a review

The machining process is the most common method for metal cutting, especially in the fabrication of biomaterials and artificial implants. In modern industry, the goal of production is to manufacture products at a low cost, with the highest quality in the shortest time. The main focus of the research presented here is to provide a review of the machinability of metallic and ceramic biomaterials in traditional machining processes, such as turning, milling and grinding. Thereafter, machining strategies, machinability and surface characteristics post machining are discussed. To provide a better understanding of the machining process, various cutting tools and fluids are analysed. Finally, the current research gap and directions of prospect investigations are highlighted