Mechanical Engineering
Permanent URI for this collection
Browse
Browsing Mechanical Engineering by Subject "Additive Manufacturing"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Additive Manufacturing of Novel Cemented Carbides with Self-Lubricating Properties(2020-05-11) Agyapong, Joseph; Boakye-Yiadom, SolomonIn this research, WC-17Co and WC-Co-hBN cemented carbides were processed using Selective Laser Sintering (SLS) and heat treated at 400 C, 600 C, 800 C and 1000 C for 3 hours to understand the effect of processing and post-processing heat treatment on the structure and properties of the cemented carbide. Electron microscopy and X-ray diffraction (XRD) analysis revealed that the microstructure of the as-printed WC-17Co specimen was characterized by relatively large poly-angular WC/W2C chips, WC-Co dendritic structures, W-C-Co phase and Co-rich regions. WC-Co-hBN also revealed from the microstructure polyangular WC chips which were smaller in size with no W2C phases present in the sample. During heat treatment between 0 C to 600 C, the large poly-angular chips in both WC-17Co and WC-Co-hBN disintegrated to smaller poly-angular chips as a result of the conversion of the unstable W2C phase to the more stable WC phase and the generation of W-Co-N and Co-W-B phases respectively. Heat treatment above 600 C resulted in the coalescence and growth of relatively large WC phase chips. There was significant increase in hardness of the WC-17Co samples during heat treatment when compared with the as-printed WC-17Co sample, with the sample heat-treated at 600 C being 36% harder than the as-printed sample due to the breakdown of poly-angular WC chips and the increase in volume fraction and spatial distribution of the observed W-C-Co phase regions. The increase in hardness at 600 C was coupled with the highest fracture toughness, representing a 34% increase in fracture toughness, when compared with the as-printed sample. The high fracture toughness is attributed to the evolution of the ductile W6Co6C phase in the sample after heat treatment. Nevertheless, the as-printed sample had approximately 15% higher wear resistance than the sample heat-treated at 600 C. In the WC-Co-hBN, the heat-treated samples had lower hardness values compared to the as-printed WC-Co-hBN sample. However, the hardness values were 3 times higher than the hardness value of the WC-17Co sample. This was attributed to the lower grain sizes in the WC-Co-hBN as compared to the WC-17Co samples. The wear resistance of the WC-Co-hBN samples were much higher than the WC-17Co samples with the highest being on the WC-Co-hBN sample heat treated at 1000 C. It is concluded that post-processing heat treatment of SLS printed WC-17Co alloy at 600 C can be used to improve the structure and mechanical properties of the alloy. And a further improvement of the wear properties and hardness of the material can be done by adding a volume of hBN to the alloy.Item Open Access Analysis of the Interface Properties of Multi-material 3D Printed Structures(2024-11-07) Pahari, Shauvik; Melenka, GarrettMulti-material 3D printed (MM3DP) samples offer enhanced mechanical performance with the added benefit of being customizable for specific applications. However, MM3DP structures have weak adhesion at the boundary interface. So, the interface characteristics in those structures are a critical factor in determining the strength of the structures and predicting failure. Digital image correlation (DIC) is a full-field strain measurement technique ideal for evaluating the non-uniform load response in anisotropic materials due to their heterogeneous composition. This thesis demonstrates the fabrication of MM3DP samples using two distinctly different printing methods. The multi-material samples were extensively compared with the homogenous samples of the same base material with a shear test to assess their mechanical performance. Strain variations on the samples were analyzed and post-processed with DIC software as different material combinations were explored. Additionally, statistical analysis was performed to validate the results and assess the feasibility of the methodology.Item Open Access Effect of Printing Parameters on the Structure and Properties of 316l Stainless Steel(2022-03-03) Hukpati, Kenneth Sesi; Boakye-Yiadom, SolomonThe emergence of 3D-printing provides the flexibility of 316L stainless steel alloy parts for various structural applications. Although several studies have been done on the effect of parameters on structure and properties, little attention has been paid to the high-strain rate deformation behaviour of this material. Therefore, in the current studies, the effect of printing parameters and the build orientation on the microstructure and high strain rate properties of 3D-printed 316L stainless steel alloy was investigated. In this study, the effect of the individual printing parameters on the boundaries as well as the spatial distribution of sub grains structures were established. There was anisotropy with the high strain rate behaviour, the perpendicular surface exhibited high maximum flow stress with a low strain whereas the parallel surface had lower maximum flow stress with a high strain. For the individual printing parameters, any combination of parameters that gives a finer microstructure showed higher flow stress with a low strain. Also, printing parameter sets that resulted in a coarse structure exhibited lower maximum flow stress and a higher strain. The observations from this study show that the orientation of the process induced pores affect the high strain compressive load of additively manufactured 316L stainless steel.Item Open Access Topology and Printing Orientation Optimization of Orthotropic Material for Additive Manufacturing(2021-11-15) Moter, Ahmed Elsayed Bayoumy Elsayed; Czekanski, AlexMechanical properties of 3d printed polymers have witnessed remarkable improvements as a result of optimization in topology and raster orientation. This study proposes and evaluates a strategy to deal with stiffness maximization of structures in elastic region subjected to global volume and compliance constraints. This work also presents a unique approach to dealing with local constraints, specifically stresses along and perpendicular to the fibers of the printed structures (principal material axes). A modified SIMP (modified solid isotropic material with penalization) method is used with the method of moving asymptotes (MMA) as the optimizer. A detailed description of the formulation and sensitivity analysis are discussed. 2D structures are then analyzed in the numerical examples section. The method can also be used for 3D structures, as the formulation derivation is general. Results show that this method is effective for producing manufacturable 3D printed structures that avoid stress concentrations.