Abstract Despite extensive research on porcelain tile finishing, no combined kinematic-phenomenological criterion based on cumulative abrasive contacts exists to optimize the transition between grit sizes. This study proposes a transition criterion (t2) derived from the exponential gloss evolution model. We conducted experiments on a commercial porcelain stoneware tile (ISO 13006 Group BIa, water absorption <0.5%) with nominal composition: 68% SiO2, 18% Al2O3, 8% feldspar, fired at 1200 °C. Using #600 to #1500 SiC fickerts under 70 N normal load (contact pressure 12.5 MPa), the t2 criterion reduced abrasive contacts from 11,275 to 2,255 (80%) while retaining 96% of the saturation gloss (69.4 GU vs. 66.7 GU; ±1.2 GU, n=5). Roughness asymmetry (Rsk) identified the ductile-brittle transition. The framework extends to industrial-scale validation and real-time kinematic simulation of polishing lines, reducing tool waste and energy consumption.
Abstract This study presents an integrated thermomechanical characterization of extruded, pressed, and fired clay bricks (BCEPQ), focusing on thermal conductivity, thermal effusivity, thermogravimetric behavior (TG/DTG), and compressive strength. The objective was to evaluate how the densification promoted by pressing influences the thermal and mechanical performance of the material. Experimental tests were conducted on 20 representative specimens under controlled laboratory conditions. The results showed an average thermal conductivity of 0.5188 W/m·K and thermal effusivity of 898.295 W·s¹/²/m²·K, indicating intermediate thermal behavior compared with conventional clay masonry units. Thermogravimetric analysis revealed high thermal stability up to 1000 °C, with negligible mass loss (<0.01%). The average compressive strength reached 8.30 MPa, exceeding the minimum requirements for ceramic masonry applications. The findings demonstrate that the extrusion-pressing manufacturing process produces a balanced combination of thermal performance, thermal stability, and mechanical resistance. This balance positions BCEPQ bricks as a promising alternative for masonry systems requiring both structural reliability and moderate thermal insulation, although full-scale system validation remains necessary.
Abstract The concentrations of stress and strain along the edges caused by the presence of geometric discontinuities in solids, such as circular, elliptical, and square shapes, have attracted the attention of the scientific community for more than a century due to their wide applicability in engineering. In this context, this research conducts a computational simulation using COMSOL Multiphysics software based on the Finite Element Method (FEM), performing a parametric study varying the dimensions of a perforated plate with a circular hole in seventy-two combinations. The plate has a constant thickness, and the combinations were obtained by varying the width (L), length (a), hole position, and radius (⌀). For a better analysis, the seventy-two combinations were divided into two groups of thirty-six, in which the influence of width (L) variation on the stress concentration factor (k) was evaluated. The results show that varying the plate width from 0.3a to 0.7a does not significantly affect the values of k. Finally, among the analyzed combinations and for the established parameters, the stress-strain curves demonstrated that the regions near the hole edge enter the plastic zone more rapidly, emphasizing the importance of analyzing strain distribution and stress concentration in structural design.
Abstract This study presents an experimental and numerical investigation of the structural performance of masonry built with Extruded, Pressed, and Fired Ceramic Blocks (BCEPQ), an emerging class of units for structural masonry systems. Despite their potential advantages, the mechanical behavior of BCEPQ units assembled through dry interlocking remains largely unexplored. An extensive experimental program was conducted, including physical and mechanical characterization of the blocks, compressive testing of prisms and small walls, and full-field deformation measurements using Digital Image Correlation (DIC). The blocks exhibited a characteristic compressive strength of 4.86 MPa and water absorption of 22.83%, while prisms and small walls reached average compressive strengths of 1.66 MPa and 0.98 MPa, respectively, with brittle failure modes governed by stress concentration and interface effects. A three-dimensional finite element model was developed in ANSYS 2024 R1 using experimentally obtained properties and linear elastic assumptions. Numerical results reproduced the main trends observed experimentally, with an average discrepancy of approximately 20%, confirming the exploratory nature of the model. The study provides unprecedented experimental data on BCEPQ masonry, highlights structural limitations associated with mortarless assembly, and offers technical insights to support future improvements in block geometry, manufacturing processes, and computational modeling of ceramic masonry systems.
Abstract This work presents the synthesis and characterization of niobium pentoxide (Nb₂O₅) obtained by combustion reaction, as well as its application as a heterogeneous catalyst in the production of biodiesel via simultaneous transesterification and esterification reaction (TES). The choice of Nb2O5 is justified by the fact that it is a material with wide applications, as a catalyst for biodiesel production; few reports in the literature can be explored. The vast majority of natural Nb2O5 is extracted in Brazil, in the city of Araxá in Minas Gerais (MG) by the Brazilian Metallurgy and Mining Company (CBMM), as it holds 98.2% of the world’s reserves. The synthesis of Nb2O5 was carried out on a laboratory scale using urea as fuel and niobium ammonium oxalate as precursor. The material obtained was characterized by XRD, FTIR, DG, BET, and SEM, showing a polyphasic structure (T-orthorhombic and TT-pseudohexagonal), polydisperse particle size distribution, surface area of 14.59 m2·g, and predominance of mesopores with a mean diameter of 7.16 nm. Subsequently, Nb2O5 was applied as a catalyst in the production of biodiesel from soybean vegetable oil and residual frying oil, using ethanol and methanol. The conversions into ethyl and methyl esters, densities, and acidity values were analyzed and compared with the standards of the National Petroleum Agency (ANP). The highest conversions were observed for soybean oil using methanol (34.74±0.79%) and residual frying oil using methanol (42.54±1.09%). Although the parameters obtained were below regulatory requirements, the results demonstrated the potential of Nb2O5 as an efficient and low-cost catalyst. The production of biodiesel using alternative and renewable materials highlights the feasibility of applying Nb2O5 in sustainable processes, with the possibility of future optimizations in synthetic routes and reaction conditions.
