Materials Science Forum Vol. 1179

Abstract: It is well known that the work hardening process of low-carbon steels is highly dependent on the movement and accumulation of dislocations in the crystal grains, which affect the stress and strain magnitudes and their distribution. The aim of this paper is to explain the importance of dislocation movement and density on the temperature, i.e. stress and strain changes during cold plastic deformation of low-carbon steels. Therefore, tests were carried out in this paper using the methods of static tensile testing, thermography, digital image correlation (DIC) and microstructural analysis. The microstructure analysis was carried out using a light and transmission electron microscope (TEM). The transmission electron microscope analysis was performed in two different modes, the TEM and scanning TEM (STEM). The results of static tensile testing, thermography and digital image correlation (DIC) are related to the microstructural changes that occur during the work hardening process of low-carbon steel. At the moment of maximum work hardening (immediately before fracture), significant grain elongation and high dislocation density of low-carbon steel were observed.

Abstract: Quality control of dental bridges in dentistry is an important area for several key reasons such as meeting high quality standards, identification of imperfections and volume defects (e.g. microcracks, porosity, irregularities), dimensional accuracy, etc. In this paper, tests were performed on additively manufactured 3D-printed and cast Co-Cr dental bridges. Surface comparison of Co-Cr dental bridges (3D-printed and cast) was carried out by checking the possibility of dimensional accuracy determination. Precise analysis of the 3D-printed Co-Cr dental bridge internal structure was performed using industrial computed tomography (iCT). The iCT analyzes were carried out from different observing perspectives of the 3D-printed Co-Cr dental bridges. The results from this study showed different applications of iCT and 3D scanning in quality control of dental bridges. The importance of iCT application in the field of dental bridges quality control was established.

Abstract: The current and significant environmental pollution caused by the use of cement in structural construction highlights the need for more sustainable alternatives. This research evaluates the use of uncalcined scallop shell powder (SP) and recycled glass powder (GP) as partial replacements for cement in conventional concrete mixes with a design strength of f'c = 280 kg/cm². SP and GP were incorporated in a 2:1 ratio at the following replacement levels: 2.5% SP + 5% GP and 5% SP + 10% GP. The analysis conducted on the concrete includes CO₂ emissions associated with its production, workability in its fresh state, and compressive strength in its hardened state. As a result, the mix with the lower replacement percentage proved to be the most optimal, achieving a 1-inch increase in workability and a 2.49% increase in 28-day compressive strength compared to the control mix, along with a 1.08% reduction in CO₂ emissions. This demonstrates the structural and environmental viability of concrete incorporating SP and GP.

Abstract: In Lima, many concrete structures experience accelerated deterioration due to physical and chemical factors, limiting their durability. This study evaluates the effect of recycled glass powder (RGP) and a nanosilica additive (1.5 %) on concrete with f’c = 27.5 MPa (280 kg/cm²), focusing on optimizing its mechanical properties, durability, and economic feasibility. Mixtures with 10 %, 15 %, and 20 % cement replacement by RGP were prepared, assessing compressive, tensile, and flexural strength, as well as permeability and water absorption. The mixture with 10 % RGP (RGP-10) showed the best early age mechanical performance, increasing compressive strength by 39.1 %, tensile strength by 12.7 %, and flexural strength by 26.2 % compared to the concrete control. Mixtures with 15 % and 20 % RGP showed lower initial strength, although future gains are expected due to delayed pozzolanic reactions. Regarding durability, RGP-10 reduced permeability by 9.02 % and water absorption by 6.45 %, while RGP-15 and RGP-20 achieved even greater reductions, with permeability decreasing by 11.48 % and 9.84 %, and water absorption by 8.68 % and 10.56 %, respectively. Although the nanosilica additive increases the initial cost, its combination with RGP produces significant improvements in mechanical properties and durability, contributing to a reduction in maintenance related costs, resulting in a durable, sustainable, and economically viable material.