Advances in Materials Science and Engineering

The temperature uniformity and thermal deformation of the tool in the autoclave forming process have an important influence on the forming quality of the composite components. In this paper, the prediction methods of the temperature distribution of the tool and the curing deformation of composite components in the autoclave forming process were developed. Using Ansys CFX fluid analysis technology, the temperature field of a large framed tool in the autoclave process was simulated, and the distribution of the surface temperature of the large framed tool was obtained. The calculated temperature field was then applied in the cure-induced deformation simulation of composite components. The thermo-chemical-mechanical coupling analysis was conducted to simulate the curing deformation of the composite components, and the numerical results were verified by practical engineering application.

The crack in the rock is a system that coexists with multiscale and interaction cracks, and it is necessary to evaluate the deformation, stability, and strength of rock mass in many engineering projects and the failure of rock are related to the distribution of cracks in the rock. Cracks of different lengths were set in rock-like materials, and uniaxial loading experiments were carried out under 30 test conditions by changing the length of the rock bridge and the short crack as well as the crack angle. During the experiment, a high-speed camera system was used to record the failure process of the specimens. The following conclusions were obtained: when the crack angle is in the range of 30°to 60° with the loading direction, the shorter cracks are more likely to propagate and coalesce. Most of the specimens initiate cracking from the outer tip of the longer crack and the key point of crack instability is the outer tip of the longer crack. The coalescence mode of the cracks is mainly related to the length of the rock bridge length and the crack angle.

In this study, a series of tribological tests were conducted on a pin-on-disc tester to study the lubrication mechanism of SiO₂ nanoparticles under different surface roughness considering various loads and velocities. For a comprehensive understanding of the mechanism of SiO₂ nanoparticles, base fluid was also employed as a contrast. Results show that the reductions of friction coefficients and wear scar widths increase with the decrease of surface roughness, due to the increase in rolling effect and self-repairing mechanism of SiO₂ nanoparticles. The lubrication mechanism of SiO₂ nanoparticles is the rolling effect when the height-diameter ratio (λ) is less than 6, and the self-repairing mechanism at λ of 6 and 10, whereas, there is no obvious difference by adding nanoparticles when λ is 20. When the height-diameter ratio is less than 6, surface wears show an increasing trend as the load increases due to the high hardness of nanoparticles, while it is the opposite at λ of 10 and 20 because of the self-repairing mechanism.

Alumina body densification using slip casting was investigated with low warpage rates. In order to optimize slurry and sintering, 1600°C has been used. As a starting material, three types of alumina were used. Alumina has been used in conjunction with PMAA, and carboxymethyl cellulose in order to prepare the slurry. It was found that warpage rates were reduced when coarser particles were included in the composition. An acid treatment of the slurry was carried out in order to improve densification of the alumina body and to reduce warpage. This study examines the microstructure of a sintered alumina body. In the investigation, it was found that preparing a dense product reduced porosity and warping rate by 1.1% and 4%, respectively.

Purpose. This study is a comparison of the effects of temporary restorative materials (PRMs) on the color change that occurs due to the use of different mouthwash solutions in two time periods. Material and Methods. One hundred fifty disc-shaped specimens (10 mm × 2 mm) were fabricated with three PRMs chemically polymerized PMMA (Imident-I), chemically polymerized bisacrylic composite resin (Acrytemp-A), and CAD/CAM PMMA-based polymer (TelioCAD-T) according to manufacturers’ instruction and using a CAD/CAM milling system (n = 10). CIE Lab values of specimens were recorded before immersion. Samples were immersed in solutions (Distilled water-DW, Kloroben-CHX, Listerine Advanced White-LAW, Listerine Total Care-TC, and Listerine Zero-TCZ) in two time periods (t₁, t₂). Color measurements of the samples were made with the help of a spectrophotometer before and after they were removed in mouthwashes (VITA Easyshade V). Results. According to the statistical analysis results, significant differences were observed between the results obtained in our study. The highest roughness values in ΔE1 were seen in A-LAW (1.83) and the lowest in T-DW (0.61). In ΔE2, the highest roughness values were observed in I-LAW (2.70), and the lowest in T-DW (1.05). ΔE values of all obtained groups were found within clinically acceptable limits (ΔE < 3.7). Conclusions. The content of temporary restorative materials, the production technique, the type of mouthwash, and the immersion time of the restoration affect the color stability. Mouthwash with a whitening effect caused the most discoloration. Among the temporary restorative materials, it was the CAD/CAM material that best preserved its color stability.

Desulfurized rubber powder and SBS were used as asphalt modifiers to study the rheological properties and performance of desulfurized rubber powder/SBS composite-modified asphalt (DR/SBSCMA). First, the basic performance indicators such as penetration, ductility, softening point, and viscosity were studied. Second, the high-temperature and low-temperature rheological properties of asphalt were evaluated by using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Finally, their high-temperature stability, low-temperature crack resistance, and water stability under the gradation of AC-13 and SMA-13 were evaluated. The results show that DR/SBSCMA had great advantages in terms of ductility and softening point, especially the softening point, which reached 90°C. It also demonstrated excellent high-temperature performance and tensile strength, and penetration was slightly lower than that of SBS-modified asphalt. Moreover, after compound modification, high-temperature and low-temperature rheological properties were effectively improved, and DR/SBSCMA adequately met the requirements of PG82-34. In addition, DR/SBSCMA maintained excellent high-temperature stability in both AC-13 and SMA-13 mixtures, coupled with obvious improvements in rutting deformation. Meanwhile, its low-temperature cracking resistance is slightly lower than that of SBS-modified asphalt, but both adequately meet the specification requirements. Ultimately, the water stability of DR/SBSCMA is comparable to that of SBS-modified asphalt, with both reaching more than 90%, proving its excellent water stability.