Mechanical Properties of Side-Pressed Laminated Bamboo Lumber Based on Ultrasonic NDT Technology

This study investigates the effect of the curing mode (dual-cure vs. self-cure) of resin cements (four self-adhesive and seven conventional cements) on their flexural strength and flexural modulus of elasticity, alongside their shear bond strength to lithium disilicate ceramics (LDS). The study aims to determine the relationship between the bond strength and LDS, and the flexural strength and flexural modulus of elasticity of resin cements. Twelve conventional or adhesive and self-adhesive resin cements were tested. The manufacturer's recommended pretreating agents were used where indicated. The shear bond strengths to LDS and the flexural strength and flexural modulus of elasticity of the cement were measured immediately after setting, after one day of storage in distilled water at 37 °C, and after 20,000 thermocycles (TC 20k). The relationship between the bond strength to LDS, flexural strength, and flexural modulus of elasticity of resin cements was investigated using a multiple linear regression analysis. For all resin cements, the shear bond strength, flexural strength, and flexural modulus of elasticity were lowest immediately after setting. A clear and significant difference between dual-curing and self-curing modes was observed in all resin cements immediately after setting, except for ResiCem EX. Regardless of the difference of the core-mode condition of all resin cements, flexural strengths were correlated with the LDS surface upon shear bond strengths (R2 = 0.24, n = 69, p < 0.001) and the flexural modulus of elasticity was correlated with them (R2 = 0.14, n = 69, p < 0.001). Multiple linear regression analyses revealed that the shear bond strength was 17.877 + 0.166, the flexural strength was 0.643, and the flexural modulus was (R2 = 0.51, n = 69, p < 0.001). The flexural strength or flexural modulus of elasticity may be used to predict the bond strength of resin cements to LDS.

The influence of magnetic field swept rate on the ultrasonic propagation velocity of magnetorheological fluids

Purpose: The purpose of the research is to establish the relationship between the velocity of ultrasonic waves in Lesnik, Maslav granites, Bukinsky gabbro, and Kateryniv labradorite at temperatures up to 800 degrees. Methods: In this study, samples of natural stone from the following rocks were heated: Maslav granite, Lesnik granite, Kateryniv labradorite, and Bukinsky gabbro. The samples were made in the form of cubes with a side size of 15×15 cm. One side of the sample was polished and the other sides were sawn. Measurements of ultrasonic wave propagation were made on the polished side. The samples were heated to temperatures of 200, 400, 600, and 800 degrees Celsius. Three cubes were taken for each temperature. Before heating, the velocity of ultrasonic waves in the samples of natural stone was measured using a handle with two piezoelectric sensors with a base of 120 mm. The ultrasonic wave was measured using a UK-14PM device. The velocity of ultrasonic wave propagation in the stone samples after heating was also measured. The velocity of ultrasonic wave propagation was calculated from the time it takes the ultrasonic wave to pass between the sensors. Results: In this research, the authors consider the effect of high temperature on the velocity of ultrasonic waves in granites, gabbro, and labradorite. The article provides an overview of the main factors that affect the velocity of ultrasonic wave propagation in natural stone. The results of studies conducted to investigate the effect of high temperature on this velocity in strong rocks are considered. The relationship between the velocity of ultrasonic wave propagation in Lesnik, Maslav granites, Bukinsky gabbro, and Kateryniv labradorite at temperatures up to 800 degrees has been established. Lesnik granite has the least loss of ultrasonic wave velocity upon heating, while Maslav granite has the greatest loss. When comparing labradorite and gabbro, labradorite has the least loss of ultrasonic wave velocity upon heating. Scientific novelty: For the first time, the dependence of the velocity of ultrasonic wave propagation in Lesnik, Maslav granites, Bukinsky gabbro, and Kateryniv labradorite at temperatures up to 800 degrees from the heating temperature has been obtained. Practical significance: Based on the obtained values, it is possible to assess the strength of natural stone after fires using a non-destructive control method. Keywords: high temperature, ultrasonic wave, natural stone, rock-forming minerals, color.

Statement of the Problem Composite resin may be used in different temperatures; it is crucial to determine the effect of temperature on mechanical properties of nanohybrid and silorane-based composite.Purpose This in vitro study compared the flexural strength and modulus of elasticity of nanohybrid and silorane-based resin composite, at 4˚C, room temperature (25˚C), and 45˚C.Materials and Method In this experimental study, 60 specimens were prepared in a metal split mold (2×2×25mm). Two different resin composites, Filtek Z250 XT (3M/ ESPE) and Filtek P90 (3M/ESPE), were evaluated. The material were inserted into split molds at room temperature, 4˚C or 45˚C and cured with LED (1200 mW/cm2) for 20 seconds in four points (n=10). Then, a three-point bending test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min for measuring the flexural strength and flexural modulus of samples. The data were analyzed by the two-way ANOVA and Tukey test (p< 0.05).ResultsThe mean highest flexural strength was observed at 45˚C, showing statistically significant difference with flexural strength at 4˚C (p= 0.0001) and 25˚C (p= 0.003) regardless of the type of resin composite. The flexural modulus at 45˚C was highest, showing the statistically significant difference with flexural modulus at 4˚C (p= 0.0001) and 25˚C (p= 0.002). The flexural modulus was statistically different between nanohybrid and silorane-based resin composite (p= 0.01) in 25˚C and 45˚C, but there were no statistically significant differences between flexural strength of Filtek Z250 XT and Filtek P90 regardless of the temperatures (p= 0.062).ConclusionPreheating the resin composite at 45˚C improves flexural strength and modulus of nanohybrid and silorane-based resin composite. However, flexural strength and modulus of the tested materials were not affected by precooling. The flexural modulus of nanohybrid resin composite was significantly higher than silorane-based resin composite in 25˚C and 45˚C temperatures.

The aim of the study was to test whether the filler composition of resin composites influences their flexural strength and modulus of elasticity. Flexural strength and modulus of elasticity were obtained through a three-point bending test. Twelve bar shaped specimens of 5 commercially available composites--Supreme (3M/ESPE), a universal nanofilled composite; Esthet-X (Dentsply), Z-250 (3M/ESPE), Charisma (Heraeus Kulzer), universal hybrid composites; and Helio Fill (Vigodent), a microfine composite--were confectioned according to the ISO 4049/2000 specifications. The test was performed after a 7-days storage time using a universal test machine with a crosshead speed of 1 mm/min. The filler weight content was determined by the ashing technique. The data obtained on the mechanical properties were submitted to ANOVA and Tukey test (p < 0.05). Pearson's correlation test was used to determine the correlation between the filler content and the mechanical properties. A weak but significant correlation between the mechanical properties evaluated and the filler weight content was observed (p < 0.000). The microfine composite presented the lowest filler weight and the lowest mechanical properties. Statistically different flexural strength and modulus of elasticity results were observed among the universal hybrid composites. The nanofilled composite presented intermediary results. Within the limitations of this in vitro study, it could be concluded that the filler content significantly interfered in the flexural strength and modulus of elasticity of the composites tested.

Aim The purpose of this study was to compare and evaluate the flexural strength and modulus of elasticity of three adhesive luting cements as a function of specimen age, effect of storage media, and effect of curing through porcelain. Materials and Methods Twenty samples fabricated for self-cure resin-modified glass ionomer cement (GIC; RelyX Luting 2, 3M ESPE, United States) were classified as group 1, whereas 40 samples fabricated for two dual-cure resin cements (20 samples each), Universal Resin Cement (Ammdent, Italy) and Maxcem Elite (Kerr Australia Pty. Ltd.), were classified as groups 2 and 3, respectively. The dual-cure cements were photo-activated using light cure unit with an intensity of 550 mW/cm2 in nine overlapping sections for 20 seconds per section on both sides. A total of 60 samples (20 samples in each group) were fabricated and tested using universal testing machine to compare flexural strength and modulus of elasticity of resin-modified GIC with two dual-cure adhesive resin cements, to determine the influence of storage of the specimens in artificial saliva at 37°C for 24 hours and to determine the influence of curing through porcelain disk of 2 mm thickness on these properties. Results The overall mean flexural strength and modulus of elasticity of resin-modified GIC was less than the dual-cure resin cements. The values reduced for resin-modified GIC when the samples were tested after 24 hours of storage in saliva, whereas an increase in the strength was seen for dual-cure cements. The curing through porcelain disk reduced the properties of dual-cure cements. Maxcem Elite showed better overall mean flexural strength and modulus of elasticity in all the parameters. Conclusion When comparing all three cements, both dual-cure cements showed better flexural strength and modulus of elasticity compared to resin-modified GIC, which indicates their use in cementation of fixed restorations.

Resin composite is widely used in the dental field in clinics as a biomaterial. For example, it has been used as a composite material, a type of biomaterial, to repair caries and restore masticatory function, and as a luting agent to adhere the restoration to the tooth substrate. In order to demonstrate its function, we have measured the mechanical strength. From such basic research, we explain the potential of a dental material through the measurement of flexural strength and modulus of elasticity. In this research, we introduce commercial products that are actually used as composite materials suitable for tooth substrate and provide readers with their properties based on flexural strength and modulus of elasticity. In clinical performance, it might be advisable to delay polishing when a composite material is used for a luting material, a filling material and a core build-up material, as the flexural strength and the flexural modulus of elasticity were improved after 1 day of storage, and flexural strength and characteristics are considered as important mechanical properties of oral biomaterials.

In wood structural design, the modulus of elasticity (MOE) and modulus of rupture (MOR) are two key indexes of wood mechanical properties. In this study, Taxodium ascendens. Brongn plantation grown in terrestrial site were selected for the research material to study variation patterns of wood flexural elastic modulus and wood bending strength within-tree and among-trees. The results showed that the flexural modulus of elasticity and flexural strength for Taxodium ascendens increased first in radial direction from pith to bark, then to flatten out. Their longitudinal variation pattern showed increasing pattern first from the base of the trunk upward and then tended to flatten out too. Their average values were 5004 MPa in flexural modulus of elasticity and 65.3 MPa in flexural strength (bending strength or modulus of rupture) respectively. The mean values of flexural modulus of elasticity and flexural strength of Taxodium ascendens varied in the ranges of 4643 MPa to 5523 MPa and 57.0 MPa to 70.4 MPa, respectively. The mean values of flexural modulus and flexural strength were smallest at the base and the highest at breast height, when the age of the specimens within trees was more than 20 years old. The flexural modulus of elasticity and flexural strength of Taxodium ascendens varied significantly among trees. There was a highly significant positive correlation between MOE and MOR. According to the China grading standards of wood physical and mechanical properties, (Wood mechanical grade I is below 7.4 GPa in MOE and grade II is below 54.1 MPa∼88.0 MPa in MOR), the wood bending strength of Taxodium Ascendens is small and weak. Its wood is not suitable for structural material with high strength.

Improvements in the national standard for the unit of the propagation velocity of longitudinal ultrasonic waves in solids are examined. The measurement techniques and standard measures for velocity are described. The composition and metrological characteristics of the new standard are discussed. In accordance with the scientific and technical program "Standards of Russia" and the steps planned for the intro- duction of the national primary standard for the unit of the propagation velocity of longitudinal ultrasonic waves in solids, GET 189-2010 (1), work has been under way at the Far Eastern Branch of the All-Russia Research Institute of Physicotech- nical and Radio Measurements (VNIIFTRI) during 2010-2012 to improve the standard, including the development and intro- duction of two new standards facilities as part of the standard for measuring the propagation velocities of shear and surface ultrasonic waves in solids. Thus, the new national primary standard GET 189-2012 ensures the uniformity of measurements of the propagation velocities of the main types of acoustic waves in solids. This standard is at the top of the national verifi- cation scheme for means of measuring the propagation velocity of ultrasonic waves in solids, which establishes the order of transfer of reproduced units to working standards and means of measurement. The need for measurements of the propagation parameters of ultrasonic waves in solids arises from fundamental, as well as applied research. The propagation parameters of ultrasonic waves are used in fundamental research for calculating the elastic constants and moduli of elasticity - the most important characteristics of solids (2). These parameters are also need- ed for determining the physical and mechanical characteristics, as well as the endurance properties of solids, and are of the greatest importance for creating new materials, and in developing techniques for producing and using these in technology and industry. However, the demand for measurements of the propagation velocity of ultrasonic waves is primarily related to the need to ensure the uniformity of measurements in the area of nondestructive testing of the quality of materials and work pieces using acoustic methods and means of measurement. An analysis of Russian and foreign literature in this area shows that the most promising approach for the develop- ment of original standard means of measurement in solid-state acoustics is the use of contactless methods for generating and receiving ultrasonic waves: optical and capacitive (3-8). Optical methods form the basis of the standard GET 189-2012. The standard laser-interference system for measuring the propagation velocity of longitudinal ultrasonic waves in the standard GET 189-2010 (1) serves as the basis for creating the unified standard facility for reproduction of the units of the prop-

This study analyzed how hole perforation and surface cutting affect ultrasonic wave propagation velocity and resonant frequency in wood. While non-destructive evaluation techniques for wood elasticity are well-established, the specific influence of defects like holes and orthogonal cuts on wave behavior remains underexplored. This study aimed to fill this gap by assessing how these defects influence wave behavior and providing new insights into their impact on wood's mechanical properties. Four softwood species and seven hardwood species were analyzed. In hardwood specimens, ultrasonic propagation velocity and resonant frequency were measured under increasing levels of hole perforation (9, 27, and 45 holes). In contrast, the effects of one and two orthogonal surface cuts were examined in softwood specimens. The results revealed that the ultrasonic propagation velocity decreased noticeably with an increasing number of holes. Meanwhile, resonant frequency exhibited only a slight decrease. In contrast, softwoods displayed minimal changes in ultrasonic velocity but notable reductions in resonant frequency due to surface cutting. This study highlights the differences in continuous wave propagation pathways associated with the two defect types and estimation methods, offering novel insights into wood evaluation techniques.

The flexural strength and elastic modulus of rapidly prototyped denture base materials are affected by numerous factors including reinforcement with nanoparticles (NPs) and post-curing duration (PCD), though the effect of these two factors together has been overlooked. The present study tested the effect of nanodiamonds (NDs) or silicon dioxide nanoparticles (SNPs) with various PCDs on the flexural strength and elastic modulus of rapidly prototyped denture base materials. To measure the flexural strength and elastic modulus, bar-shaped specimens (64 × 10 × 3.3 mm) were designed and rapidly prototyped using ASIGA and NextDent denture base resins. Each resin (N = 150) was divided into five groups (n = 30) according to NP type and concentrations: pure group as a control without additives, 0.25% NDs, 0.5% NDs, 0.25% SNPs, and 0.5% SNPs. Specimens from each group were further divided into three groups (n = 10) and post-cured for 15, 60, or 90 min, followed by thermocycling for 5,000 cycles. After measuring the flexural strength and elastic modulus using a three-point bending test, a scanning electron microscope was used to analyze the fractured surface. The bonds between the NPs and the resin were tested by Fourier-transform infrared spectroscopy. ANOVA and post hoc tests were used for data analysis (α = 0.05). The flexural strength increased with prolonged PCD and the highest values for all tested groups were reported at 90 min (P < 0.001). The flexural strength of both materials increased significantly with the addition of NDs and SNPs in comparison to the pure groups (P < 0.05). K-factor ANOVA analysis of the elastic modulus showed that each factor (NP type, PCD, and material type) had a significant effect on the elastic modulus (P < 0.001). The flexural strength and elastic modulus of rapidly prototyped denture base resin were increased with the addition of NDs or SNPs and when increasing the PCD. Factors including nanoparticle type and concentration, the post-curing duration, and the material type solely or in combination could affect the flexural strength and elastic modulus of prototyped denture base materials.

Ultrasonic measurement method for three-dimensional assembly stress of aero-engine rotors

Many existing reinforced concrete (RC) structures constructed more than 50 years ago now require maintenance. This is especially true in cold, snowy regions where significant frost damage deterioration of RC structures becomes a severe problem. In this study, falling-weight impact tests were performed to investigate the impact resistance behavior of RC beams degraded by frost damage. An RC beam was subjected to approximately 900 freeze-thaw cycles to emulate the frost damage before the execution of the impact test. The surface of the beam was remarkably scaled, and its coarse aggregate was exposed. The degree of deterioration was evaluated by the distribution of ultrasonic propagation velocity. The following conclusions were drawn. (1) The ultrasonic propagation velocity of RC beams was significantly reduced following 872 freeze-thaw cycles. At the upper edge of the RC beam, the ultrasonic wave propagation velocity decreased from 4,000 m/s to 1,500 m/s in some parts. This corresponds to a relative dynamic elastic modulus of approximately 14%. (2) The residual deflection of RC beams with frost damage increased at most by 20% compared with beams without frost damage. The increase in residual deflection was primarily related to the peeling of concrete at the collision site and the opening of multiple bending cracks. (3) According to the existing residual deflection calculation formula, an increase of 20% in the residual deflection corresponds to a decrease of about 17% in the bending capacity of the RC beam. When the relationship between the degree of frost damage deterioration and the impact resistance of RC structures is defined, existing structures subjected to accidental impact force from rockfalls are safer and can be maintained more efficiently.

Acid Effects on the Physical Properties of Different CAD/CAM Ceramic Materials: An in Vitro Analysis.

Aim: the aim of this study was to compare the flexural strength and elastic modulus of three-dimensionally (3D) printed, conventional heat-cured, and high-impact implant-supported overdenture materials specimens. Materials and Methods: Thirty implant-supported overdenture materials specimens (bar-shaped, 65.0 × 10.2 × 5.1 ± 0.2 mm3) with one central hole were fabricated using 3D-printed, heat-cured conventional, and high-impact denture base resins (n = 10/group). Autopolymerizing acrylic resin was used to attach titanium matrix housings to the central holes of the specimens. A three-point bending test was conducted using a universal testing machine and a model analog with a crosshead speed of 5 mm/min. The indicative flexural strength and elastic modulus were recorded. Data were statistically analyzed using analysis of variance (ANOVA) and the Tukey tests at α = 0.05. Results: One-way ANOVA revealed a significant effect of denture base material on the flexural strength (p < 0.001) but not on the elastic modulus (p = 0.451) of the evaluated materials. The flexural strength of the 3D-printed specimens (95.99 ± 9.87 MPa) was significantly higher than the conventional (77.18 ± 9.69 MPa; p < 0.001) and high-impact ones (82.74 ± 7.73 MPa; p = 0.002). Conclusions: The maximum flexural strength was observed in the 3D-printed implant-supported overdenture material specimens, which might indicate their suitability as an alternative to the conventionally fabricated ones. Flexural strength and elastic modulus of conventional and high-impact heat-cured implant-supported overdenture materials specimens were comparable.