http://bura.brunel.ac.uk/handle/2438/231 Fri, 17 Apr 2026 08:17:26 GMT 2026-04-17T08:17:26Z http://bura.brunel.ac.uk/handle/2438/26318 Title: Multi-Response Optimization of Ti6Al4V Support Structures for Laser Powder Bed Fusion Systems Authors: Dimopoulos, A; Zournatzis, I; Gan, T-H; Chatzakos, P Abstract: Copyright © 2023 by the authors. Laser Powder Bed Fusion (LPBF) is one of the most commonly used and rapidly developing metal Additive Manufacturing (AM) technologies for producing optimized geometries, complex features, and lightweight components, in contrast to traditional manufacturing, which limits those characteristics. However, this technology faces difficulties with regard to the construction of overhang structures and warping deformation caused by thermal stresses. Producing overhangs without support structures results in collapsed parts, while adding unnecessary supports increases the material required and post-processing. The purpose of this study was to evaluate the various support and process parameters for metal LPBF, and propose optimized support structures to minimize Support Volume, Support Removal Effort, and Warping Deformation. The optimization approach was based on the Design of Experiments (DOE) methodology and multi-response optimization, by 3D printing and studying overhang geometries from 0° to 45°. For this purpose, EOS Titanium Ti64 Grade 5 powder was used, a Ti6Al4V alloy commonly employed in LPBF. For 0° overhangs, the optimum solution was characterized by an average Tooth Height, large Tooth Top Length, low X, Y Hatching, and high Laser Speed, while for 22.5° and 45° overhangs, it was characterized by large Tooth Height, low Tooth Top Length, high X, Y Hatching, and high Laser Speed. Description: Data Availability Statement: All data analyzed or generated during the study are included in this article. Fri, 13 Jan 2023 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/26318 2023-01-13T00:00:00Z http://bura.brunel.ac.uk/handle/2438/26317 Title: Correction: Dimopoulos et al. Multi-Response Optimization of Ti6Al4V Support Structures for Laser Powder Bed Fusion Systems. J. Manuf. Mater. Process. 2023, 7, 22 Authors: Dimopoulos, A; Zournatzis, I; Gan, TH; Chatzakos, P Abstract: Error in Table: In the original publication [1], there is an error in Table 9. The Lower Limit of Laser Speed should be 1000 mm/s, not 100 mm/s. Error in Figure: In the original publication [1], there was a mistake in “Figure 12” as published. The value “1.13” in the warping deformation chart should be replaced with the value “0.13”. The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated. Description: Reference of original article: Dimopoulos, A. et al. (2023) 'Multi-Response Optimization of Ti6Al4V Support Structures for Laser Powder Bed Fusion Systems',.Journal of Materials Processing and Manufacturing Science, 7 (1), 22, pp. 1 - x. doi: 10.3390/jmmp7010022. Wed, 26 Apr 2023 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/26317 2023-04-26T00:00:00Z http://bura.brunel.ac.uk/handle/2438/24844 Title: Evaluation of eco-friendly concrete having waste PET as fine aggregates Authors: Bamigboye, GO; Tarverdi, K; Umoren, A; Bassey, DE; Okorie, U; Adediran, J Abstract: This study assesses the impacts of recycling waste polyethylene terephthalate (PET) plastic bottles as a partial substitute for fine natural aggregates on the workability, mechanical, microstructural, economic, and thermal properties of concrete. The mix design adopts a concrete mix ratio of 1:2:4 for grade M25, 0.55 water/cement ratio, ordinary Portland cement (OPC) as the binder, varying proportions of heat-processed waste PET and river sand as fine aggregates, and granite as coarse aggregate. Results indicate that workability increased with increasing percentages of waste PET plastics until the 40%PET level, beyond which workability reduces. Compressive and split tensile strength decreased with increasing percentages of waste PET plastics. However, 10% to 40%-PET-modified mixes achieved the recommended strength for M20 concrete. Microstructural analysis on the 30%PET indicates higher quantities of O and Ca, and trivial percentages of Mg, Si, C, Al, and Au. Whereas 100%PET indicates the presence of only C, O, and Au. 100%PET endures three transition stages during heat flow. A glass transition, an exothermic peak below decomposition temperature during cooling at a temperature of 199.88 °C from PET crystallization, and a baseline shift after the endothermic peak at 243.22°C. Thermogravimetry revealed that 100%PET suffers a dual-stage decomposition, an initial stage accounting for an 87.41% reduction in sample mass and a second stage accounting for a further mass loss of 12.79%. Highly significant statistical correlations and regressions developed variations between PET% and the workability and mechanical parameters. The study shows that heat-processed PET-modified concrete is appropriate for structural applications due to its suitable fresh, mechanical, microstructural, and thermal properties. Besides, this practice is eco-friendly and sustainable as it conserves natural resources. Mon, 15 Nov 2021 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/24844 2021-11-15T00:00:00Z http://bura.brunel.ac.uk/handle/2438/20936 Title: µECM process investigation and sustainability assessment Authors: Mortazavi Nasiri, Mina Abstract: Micro electro chemical machining (µECM) as an alternative machining process gains more attraction in micro and nano industries and gradually finds its place among other non-conventional manufacturing methods. µECM same as ECM aimed at electrically conductive materials; µECM process is based on anodic dissolution of the materials at atomic level. Current progress in µECM has presented valuable improvement in the process control and monitoring, shaping accuracy, simplifying the tool design and the process stability. This makes the µECM an outstanding alternative technology to produce accurate and complex 3-dimensional micro components. However, there is still a gap in application of µECM at research level and industrial level; development and commercialisation of the µECM require huge industrial investment which still needs justification to be attractive for investors. Despite worldwide attempts to investigate and demonstrate the µECM process in full details and develop the µECM technology for the industrial applications, there is still a need for further investigation and research due to the complex and multidisciplinary nature of this process. Currently, this process is very much dependent on operator experience and trial and error approach. The lack of trained knowledgeable operators in addition to the lack of a comprehensive database (combination of materials, electrolytes and machining parameters) have increased the time and the cost of the commercialised development of this technology. A comprehensive analytical literature review highlighted three areas of knowledge gap which can be further investigated and developed. One of the main challenges in current state of this technology is initial set up for machining parameters. Current records show that the initial parameters have been set up using trial and error approach or simulation data; and there is still ongoing effort to find a better solution to set up the initial parameters. The electrode-electrolyte interface was recognised as one of the main effective parameters on µECM machining performance. The complex nature of the reaction which happens at this interface, in addition to the electrode-electrolyte structure need further investigation and analysis in order to improve the µECM machining performance. Finally, the ever increasing demand to optimise all manufacturing processes and products, has increased the need to assess the sustainability of the machining process including new developed technologies; but there is very little information available in the area of micro and nano machining sustainability assessment including µECM. Therefore, in this research it has been tried to address these three knowledge gaps and to suggest new methodologies to overcome them using a new practice consisting of laboratory experiments, mathematical analysis and simulation to investigate the initial machining parameters’ values, explore the electrode-electrolyte interface structure for stainless steel workpiece and tungsten and nickel tool electrodes. Also, to introduce a series of indicators and measures to assess the sustainability of the µECM process to justify its initial high cost in comparison with any other machining process. Laboratory experiments carried out using potentiostat (iviumstat) and mathematical analysis and simulation took place using Matlab and Simulink; and a few experiments carried out using in house built µECM machine to examine the obtained results through the laboratory and simulation works. The results suggested that combination of 6.5 to 7.5 volts, electrolyte concentration between 0.4 and 0.7 mole/L and inter-electrode gap between 22 and 27 µm generates optimum process results. Additionally, electrode-electrolyte interface structure is a useful parameter to set up the pulse on time. Finally, introduced sustainability assessment indicators and measures provides the opportunity to assess the µECM process for further optimisation. As a result, µECM is a valuable process and in claim for current manufacturing industries especially in micro and nano products which demand higher accuracy and quality, better production life cycle and lower cost. So, it is very worthy to invest for further development to bring this technology to the industrial level. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2020 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/20936 2020-01-01T00:00:00Z