Aboma Wagari Gebisa | University of Stavanger (original) (raw)

Papers by Aboma Wagari Gebisa

Fused deposition modeling (FDM), one of the additive manufacturing (AM) technologies, is a promis... more Fused deposition modeling (FDM), one of the additive manufacturing (AM) technologies, is a promising digital manufacturing technique that produces parts, layer by layer, by heating, extruding and depositing filaments of thermoplastic polymers. The properties of FDM-produced parts apparently depend on the processing parameters. These processing parameters have conflicting advantages that need to be investigated. This paper investigates the effect of process parameters on the compressive properties of parts produced by the FDM process. The study is carried out on a high performance polymeric material called ULTEM 9085. Full factorial design of experiment is used to analyze the effects of process parameters on the compressive properties of the material. Five parameters: namely, air gap, raster width, raster angle, contour number and contour width, of the FDM machine are considered in the current study. The results show that, with the exception of the raster width, all other considered parameters have significant interaction effect on the compressive strength. For the compressive strain, air gap, contour number and contour width showed substantial interaction effects.

Polymer Testing, Dec 1, 2018

IOP conference series, Nov 25, 2019

Additive manufacturing (AM) process is a promising manufacturing method that can replace conventi... more Additive manufacturing (AM) process is a promising manufacturing method that can replace conventional manufacturing methods, particularly for parts with complex geometry. It is the process of joining materials layer by layer to make object directly from 3D model data. Due to the inherent manufacturing process characteristics, such products experience material anisotropy with mechanical properties not easy to calculate analytically. On the other hand, numerical simulation is becoming increasingly important to solve complex problems such as in composite materials. However, no significant work of numerical simulation is reported for additive manufactured parts. This paper reports an approach to numerical simulation of additive manufactured parts by adopting methodologies developed for composite materials. To fill the existing gap in this area, the mechanical properties of FDM parts are experimentally studied. The experimental samples are produced from ULTEM9085 material with different printing parameters. The mechanical properties of the samples are then analyzed and numerical simulation using finite element method is done to compare the results with experimental results and verify the simulation model. The main aim of the study is to devise a numerical simulation method for additive manufactured parts by adopting existing methods for composite materials

Additive manufacturing technology is a process of joining materials to make objects from 3D model... more Additive manufacturing technology is a process of joining materials to make objects from 3D model data, usually layer upon layer, contrary to conventional manufacturing technologies, which mostly use subtractive process. The technology has developed from the earlier days of rapid prototyping to sophisticated rapid manufacturing in the last 20 years and can create parts directly from CAD model without the use of tooling. This technology is predicted to revolutionize many sectors of manufacturing by reducing component lead-time, material waste, energy usage, etc. Though there is significant progress in the field, there are still a number of challenges including characterization of mechanical properties. This paper presents a study conducted to characterize the mechanical properties of ABS-M30 materials whose specimens are fabricated using different printing parameters. To understand the mechanical properties, it is vital to study the effects of the printing parameters on 3D printed parts. For this purpose, Design of Experiment (DOE) is used. The printing parameters of the machine (Fortus 450mc Fused Deposition Modeling (FDM) machine) such as raster orientation, air gap, and raster width, were examined to test Tensile strengths and 3-point bend strength of the tested specimens. The study shows that, raster orientation and air gap has more effect on mechanical properties of ABS-M30 products where raster width has less effect.

Volume 2: Advanced Manufacturing

Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, 2017

IOP Conference Series: Materials Science and Engineering, 2019

Procedia Manufacturing, 2019

IOP Conference Series: Materials Science and Engineering, 2017

International Journal of Nanotechnology, 2017

The simple graphite pencil electrode (GPE) tip was etched by burning it using match stick. A dark... more The simple graphite pencil electrode (GPE) tip was etched by burning it using match stick. A dark black coloured deposition was observed in the etched portion. This etched portion of GPE was subjected to characterisation by X-ray diffraction (XRD), and Scanning Electron Microscopy. Further this etched electrode was used for simultaneous investigation of dopamine and ascorbic acid in 0.2 M phosphate buffer of pH 7.4. The modified GPE was stable and reproducible towards detection of dopamine. The stability of this flame etched electrode towards dopamine was characterised by applying multiple cycles. The effect of scan rate was found to be adsorption-controlled electrode process. The detection limit was found to be 3.4708 × 10-7 M and quantification limit was found to be 11.5693 × 10-7 M. The flame etched electrode applied for the detection of dopamine in presence of ascorbic acid and uric acid. The electrode showed excellent selectivity for the resolution of dopamine, ascorbic acid and uric acid with respective oxidation and reduction peak potentials. The effect of interference was examined by varying the concentration of one species while other two were kept constant by using differential pulse voltammetric technique.

International Journal of Nanotechnology, 2017

The Co 3 O 4 /CuO composite nanopowder (NP) modified carbon paste electrode (MCPE) was prepared a... more The Co 3 O 4 /CuO composite nanopowder (NP) modified carbon paste electrode (MCPE) was prepared and immobilised by sodium dodecyl sulphate (SDS). The electrochemical performance of dopamine (DA) in 0.2 M phosphate buffer solution (PBS) of pH 7.4 at Co 3 O 4 /CuO NP MCPE immobilised with SDS (Co 3 O 4 /CuO/SDS MCPE) was investigated by cyclic voltammetric technique as well as compared with bare carbon paste electrode (BCPE) and SDS immobilised bare CPE (CPE/SDS). In addition the electrochemical responses of ascorbic acid (AA) and uric acid (UA) were tested separately and simultaneously. The effect of concentration, quantity and immobilisation time of SDS on the Co 3 O 4 /CuO NP MCPE for the detection of dopamine was examined and optimum condition was attained for

Procedia Manufacturing, 2017

Under the concept of "Industry 4.0", production processes will be pushed to be increasingly inter... more Under the concept of "Industry 4.0", production processes will be pushed to be increasingly interconnected, information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization goes beyond the traditional aim of capacity maximization, contributing also for organization's profitability and value. Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management based on different costing models (ABC and TDABC). A generic model has been developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization's value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity optimization might hide operational inefficiency.

Volume 6: Ceramics; Controls, Diagnostics, and Instrumentation; Education; Manufacturing Materials and Metallurgy

Additive manufacturing (AM) is an emerging rapid manufacturing technique that builds parts by tra... more Additive manufacturing (AM) is an emerging rapid manufacturing technique that builds parts by tracing their cross section, layer upon layer. This technology has many unique capabilities that are not found in conventional manufacturing techniques. One of these is its ability to produce very complex part geometries without the need for any tooling. This unique potential makes it the future manufacturing technique for very complex and intricate geometries such as gas turbine components. The current review investigates the available metal additive manufacturing techniques and materials, in respect of their applicability for gas turbine engine components. From the investigation, it is clear that AM is in a promising progress for the manufacture of aircraft gas turbine components. The current limitations of AM techniques for the production of gas turbine engine components are also covered. The future perspective of this technology in this regard has also been discussed.

Polymer Testing, Dec 1, 2018

IOP conference series, Nov 25, 2019

Volume 2: Advanced Manufacturing

Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, 2017

IOP Conference Series: Materials Science and Engineering, 2019

Procedia Manufacturing, 2019

IOP Conference Series: Materials Science and Engineering, 2017

International Journal of Nanotechnology, 2017

Procedia Manufacturing, 2017

Volume 6: Ceramics; Controls, Diagnostics, and Instrumentation; Education; Manufacturing Materials and Metallurgy