Browsing by Author "Soares, Delfim"
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- CFD analysis of multi-layer cooling channels in three-dimensionally structured grinding wheelsPublication . Costa, Sharlane; Capela, Paulina; Hassui, Amauri; Ribeiro, J.E.; Pereira, Mário; Soares, DelfimMinimizing heat damage and surface integrity loss in grinding depends on effective cooling. Conventional techniques, however, suffer with low efficiency because of the fast air barrier restricting fluid access. Grinding wheels with internal cooling channels have been suggested to solve this; nonetheless, the impact of channel geometry and multi-layer topologies is yet unknown. This work investigates their effects on coolant flow pattern and thermal performance by means of computational fluid dynamics (CFD) simulations, experimental validation, and statistical optimization combined. The ideal arrangement was found by the Taguchi- Grey study to be 30 channels, 78 degrees inclination, 1.7 mm diameter and 2 mm interlayer distance. ANOVA determined that diameter (59.7 %) and number of channels (21.8 %) are the most influential parameters. CFD results showed that multilayer structures significantly increase fluid dispersion in the workpiece. The three-layer design stood out for providing the most uniform and dynamic fluid distribution, reducing cooling inconsistencies. Grinding tests confirmed that this configuration achieved the lowest temperatures for all different depths of cut. These findings highlight that increasing the number of flutes alone is insufficient; a three-dimensional flute structure with optimized geometry is essential to ensure efficient cooling. By integrating numerical modeling, statistical optimization, and experimental validation, this study provides a framework for designing grinding wheels with internal cooling channels, improving fluid distribution and thermal control.
- Control of the dimensional variation adjusting the thermal drying cycle of abrasive composites with incorporated PLAPublication . Costa, Sharlane; Marques, F.D.P.; Pereira, Mário J.; Ribeiro, J.E.; Soares, DelfimIn composite production, during the thermal drying cycle (T<100ºC), size variation of the composite material occurs due to thermal expansion and water elimination. However, when incorporating PLA components, produced by additive manufacturing, into the abrasive composite, the dimensional variation of the set is very large due to the higher polymer thermal expansion. During this stage, this composite, still in the green state, could not have the sufficient mechanical strength to withstand dimensional variations. These can result in crack formation. Therefore, the proper thermal cycle is a critical step. To define the convenient heating rate during the drying of composites with a PLA piece, thermomechanical analyzes were conducted. Three different heating ramps were tested, 0.1, 0.5, and 2.0 ºC/min in the most critical phase of dimensional change (up to 60 ºC), after this temperature the heating continues at 2 ºC/min. The results indicate that the slower the heating rate, the higher the absorption of the polymer's expansion by the composite. In the slower heating rate (0.1 ºC/min) it was possible to minimize the dimensional variation of the samples by more than 94%.
- Mechanical and optical properties assessment of an innovative PDMS/beeswax composite for a wide range of applicationsPublication . Ariati, Ronaldo; Souza, Andrews; Souza, Maria S.; Zille, Andrea; Soares, Delfim; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is an elastomer that has received primary attention from researchers due to its excellent physical, chemical, and thermal properties, together with biocompatibility and high flexibility properties. Another material that has been receiving attention is beeswax because it is a natural raw material, extremely ductile, and biodegradable, with peculiar hydrophobic properties. These materials are applied in hydrophobic coatings, clear films for foods, and films with controllable transparency. However, there is no study with a wide range of mechanical, optical, and wettability tests, and with various proportions of beeswax reported to date. Thus, we report an experimental study of these properties of pure PDMS with the addition of beeswax and manufactured in a multifunctional vacuum chamber. In this study, we report in a tensile test a 37% increase in deformation of a sample containing 1% beeswax (BW1%) when compared to pure PDMS (BW0%). The Shore A hardness test revealed a 27% increase in the BW8% sample compared to BW0%. In the optical test, the samples were subjected to a temperature of 80 ◦C and the BW1% sample increased 30% in transmittance when compared to room temperature making it as transparent as BW0% in the visible region. The thermogravimetric analysis showed thermal stability of the BW8% composite up to a temperature of 200 ◦C. The dynamic mechanical analysis test revealed a 100% increase in the storage modulus of the BW8% composite. Finally, in the wettability test, the composite BW8% presented a contact angle with water of 145◦. As a result of this wide range of tests, it is possible to increase the hydrophobic properties of PDMS with beeswax and the composite has great potential for application in smart devices, food and medicines packaging films, and films with controllable transparency, water-repellent surfaces, and anti-corrosive coatings.
- A New Grinding Wheel Design with a 3D Internal Cooling Structure SystemPublication . Costa, Sharlane; Capela, Paulina; Souza, Maria S.; Gomes, José R.; Carvalho, Luís; Pereira, Mário J.; Soares, DelfimThis work discusses challenges in conventional grinding wheels: heat-induced tool wear and workpiece thermal damage. While textured abrasive wheels improve heat dissipation, the current surface-only methods, such as those based on laser and machining, have high renewal costs. The proposed manufacturing technology introduces an innovative 3D cooling channel structure throughout the wheel, enabling various channel geometries for specific abrasive wheel applications. The production steps were designed to accommodate the conventional pressing and sintering phases. During pressing, a 3D organic structure was included in the green body. A drying cycle eliminated all present fluids, and a sintering one burnt away the structure, revealing channels in the final product. Key parameters, such as binder type/content and heating rate, were optimized for reproducibility and scalability. Wear tests showed a huge efficiency increase (>100%) in performance and durability compared of this system to conventional wheels. Hexagonal channel structures decreased the wear rates by 64%, displaying superior wear resistance. Comprehensive CFD simulations evaluated the coolant flow through the cooling channels. This new design methodology for three-dimensionally structured grinding wheels innovates the operation configuration by delivering the coolant directly where it is needed. It allows for increasing the overall efficiency by optimizing cooling, reducing tool wear, and enhancing manufacturing precision. This 3D channel structure eliminates the need for reconditioning, thus lowering the operation costs.
- Performance of 3D-structured grinding wheels with multi-layer internal cooling channelsPublication . Costa, Sharlane; Capela, Paulina; Hassui, Amauri; Ribeiro, J.E.; Pereira, Mário; Soares, DelfimGrinding is a key machining process in industries that demand high precision and surface quality. However, the conventional flood cooling method is often ineffective due to the air barrier formed by the rotating wheel, which restricts fluid access to the contact zone. This causes thermal instability, high coolant use, and environmental impact. To overcome these limitations, this study investigates alumina grinding wheels with internal cooling systems, fabricated by a novel additive route. Sacrificial 3D-printed polymer inserts were embedded during pressing and eliminated during sintering, enabling multilayered channels within a monolithic abrasive matrix. This represents the first practical application, with detailed method of production, of a fully embedded cooling system in vitrified grinding wheels. Two configurations, with one and three internal channel layers, were compared to a conventional wheel under external cooling. Controlled grinding tests on AISI 1045 steel were performed at varying depths of cut, and key variables such as cutting forces, force ratio, specific energy, and temperature variation (Delta T) were analyzed. The three-layer wheel showed the best performance, reducing tangential force by up to 49.3 %, force ratio by 21.3 %, specific energy by 50 %, and Delta T by 58.6 % compared to the conventional system. A detailed thermal profile enabled segmentation into cut-in, steady-state, and cut-out zones. The greatest benefit from internal cooling occurred in the steady-state region, with heating rates reduced by up to 78 %. These results confirm that the proposed additive manufacturing approach offers a scalable route to produce structured wheels with embedded channels, improving coolant application, process stability, and sustainability in high-performance grinding.
- Rheology of F620 solder paste and fluxPublication . Barbosa, Flavia V.; Teixeira, José C.F.; Teixeira, Senhorinha F.C.F.; Lima, Rui A.; Soares, Delfim; Pinho, DianaThe aim of this paper is to characterize the rheological properties of the flux media exposed to different levels of solicitation and to determine its influence on the rheology of the solder paste. The data obtained experimentally are fundamental for the development of numerical models that allow the simulation of the printing process of printed circuit boards (PCB). Design/methodology/approach – Rheological tests were performed using the Malvern rheometer Bohlin CVO. These experiments consist of the analysis of the viscosity, yield stress, thixotropy, elastic and viscous properties through oscillatory tests and the capacity to recover using a creeprecovery experiment. The results obtained from this rheological analysis are compared with the rheological properties of the solder paste F620. Findings – The results have shown that the flux is viscoelastic in nature and shear thinning. The viscosity does not decrease with increasing solicitations, except in the case where the flow is withdrawn directly from the bottle. Even if the solder paste shows a thixotropic behavior, this is not the case of the flux, meaning that this property is given by the metal particles. Furthermore, the oscillatory tests proved that the flux presents a dominant solid-like behavior, higher than the solder paste, meaning that the cohesive/tacky behavior of the solder paste is given by the flux. Research limitations/implications – To complement this work, printing tests are required. Originality/value – This work demonstrates the importance of the rheological characterization of the flux in order to understand its influence in the solder paste performance during the stencil printing process.
- Texturing methods of abrasive grinding wheels: a systematic reviewPublication . Costa, Sharlane; Pereira, Mário J.; Ribeiro, J.E.; Soares, DelfimCreating textures on abrasive wheels is a strategy that allows a significant improvement in grinding operations. The reduction of the internal stresses in the workpiece and the temperature during the grinding operation generates an increase in the dimensional accuracy of the workpiece and a longer tool life. Textured abrasive wheels can be produced in many different ways. Depending on the processing method, the dimensional accuracy of the tool and its applicability is changed. Some methods can produce tools with three-dimensional grooves; there are also methods that are employed for the re-texturing of grooves after the grooved zone wears out. In the literature, the benefits of textured grinding wheels over traditional wheels have been extensively discussed. However, information on the particularities of texturing methods is still lacking. To clarify the advantages, limitations, and main advances regarding each of the groove production methods, the authors of this article carried out a systematic review. The objective of this work is to establish the factors that are affected by groove production methods and the technological advances in this area. The benefits and drawbacks of various grooving techniques are then reviewed, and potential study areas are indicated.