Geotubes are the most used technology for coastal recovery due to erosion and, because of the lower price and easier installation, geotextile tube systems can be good alternatives for hydraulic and coastal structures. Geotubes can suffer damage due to cuts in fibers and other components, formation of holes, abrasion originating a reduction in mechanical resistance. On the other hand, when filled in-situ by hydraulic pumping is assumed that tensile stresses act directionally due to the hydraulic pressure and the tensile force in the geosynthetic tube. Therefore, it is important to understand the mechanical behavior as well as to identify the stages during the damage process. A mechanical vital role is sustained by the textile architecture and configuration since stresses will be transferred along the textiles. This paper exhibits the full mechanical characterization of two geotextiles made of polyethilenethereftalate (PET) and polypropylene (PP) respectively, both with different interweave architecture. Results found that textile geometry is crucial for bearing stresses and depend on the acting direction. Acoustic emission technique was employed to identify the mechanism of failure that supported the mechanical characterization findings.

This study aimed to examine the impact of variations in Mg and Cu content within the Al-Mg-Zn-Cu cast alloy on its strength characteristics, utilizing JIS-AC7A as the base material. Two alloys were considered: an Al-Mg-Zn alloy with 3.0 mass% Zn and an Al-Mg-Zn-Cu alloy with added Cu. Tensile and fatigue tests were conducted to assess the alloy’s strength characteristics. The results of the tensile tests revealed a decrease in both yield strength and tensile strength with a decrease in the Mg content. Conversely, the addition of Cu resulted in improved yield and tensile strength. In the fatigue tests, a reduction in Mg content corresponded to an enhancement in fatigue strength, while an increase in Cu content led to a reduction in the fatigue strength ratio. To elucidate the observed strength improvements associated with decreased Mg and increased Cu content, a fracture toughness test was conducted. The Mg3.5-Cu1.0 alloy exhibited the highest stress intensity factor among the tested materials, providing further insights into the mechanism underlying the strength enhancement.

Stress triaxiality is a well-established factor influencing material failure, particularly after elongation. Its significance is evident in its widespread use among damage accumulation models. In this study, we aim to analyze the post-necking behavior of thin metal sheets, specifically A2024-T3 aluminum alloy sheets. Such behavior is explored across a spectrum of stress states, ranging from shear to biaxial conditions. To ensure the robustness of the findings, experiments were conducted on three different lots of the same designated appellation, carefully considering the subtle microstructural variations. The data was meticulously gathered through localized fracture area analysis, employing digital image correlation techniques. Stress triaxiality was directly calculated from the experimental data. Notably, this study offers normalized data using a specific specimen shape, which is particularly valuable in scenarios where conducting an extensive array of experimental tests may be difficult. Based on the results, the overall shape of the fracture locus was effectively confirmed. Moreover, this study provides valuable insight on the influence of microstructure on the fracture locus. Finally, parameters essential for numerical simulations were determined.

Currently, there is no technology that facilitates the nondestructive and contact-free estimation of the peel load of the heat seals of food and other packages in the production line. To address this gap, this study proposed a method using laser photoelasticity. Considering the environmental impact of plastics, biodegradable resin polylactic acid was selected as a sample, and the optical retardations of the sealed section of the specimens were measured by changing the seal temperature in the range of 80–105 ºC. The specimens were then peeled off using a tensile tester, and the loads were recorded. The relationships among the optical retardation, peel load and sealing temperature exhibit dependence on the combination of the machine direction (MD) (direction in which the resin film is stretched during manufacturing) and the direction of the sealing line. This was because the polymer chains were oriented in the MD in advance, and the orientation changed along the sealing line owing to temperature and pressure caused by heat sealing. The MD and sealing temperature at the manufacturing site are known; therefore, it was suggested that it should be possible to obtain a rough estimate of the peel strength using the photoelastic method. However, care would have to be taken, because the estimation accuracy might reduce, further depending on the combination of the MD and seal line.

Coronary stents are thin-walled cellular structures constructed by connecting unit cells in the circumferential and axial directions. The unit cell is subjected to in-plane bending during the expansion process in the diseased artery. As the simple test method to evaluate the in-plane bending and contribute to the design of the stent unit cell shape, the rhombus-shaped specimen having the curved part and the straight part was suggested. The experimental and analytical investigations were performed on the rhombus specimen made of AZ31 magnesium alloy, and the influences of the design parameters on the strain gradient in the curved part and the deformability were investigated. The results proved that the rhombus-shaped specimen was useful to investigate the in-plane bending of the cellular structure. The in-plane strain gradient from tensile to compressive was found to occur in the curved part. Changing the design parameters of the rhombus specimen influences not only the deformability but also the tensile load, namely the force to keep the artery open. It should be emphasized that the addition of the appropriate length of a central straight part was found to be effective in improving the deformability of the cellular structure.

This paper proposes a method for evaluating J-integral from measured displacements based on the finite strain theory. Logarithmic strain components in the material coordinate system are evaluated from displacements measured using digital image correlation. A finite element model is utilized to obtain the logarithmic strains as well as the displacement gradients from measured displacement distributions. Then, the stresses are computed from the logarithmic strains using the incremental strain theory. Finally, the J-integral values are obtained numerically using the domain integration. The effectiveness of the proposed method is demonstrated by applying it to the displacement fields measured by digital image correlation. The J integral values obtained using the proposed method are compared with those obtained based on the small strain theory and with those obtained from the HRR displacement fields. Results show that the J-integral evaluation based on the small strain theory and that from the HRR displacement fields underestimate the J-integral values.

The study focuses on the elongation of reconstructed microparticles in holographic particle measurement. We propose a theoretical formula for particle elongation that requires the determination of the coefficient 𝑚. Previously, the coefficient was set as 2 based on particle size distribution comparisons. However, its suitability computational for other diameters was unclear. We directly compare elongation from particle patterns printed on a glass plate with varying diameters to the theoretical formula. We found that 𝑚 is equal to 1, not 2. This finding is crucial for accurate holographic particle measurement.

This study proposes a method for determining an optimal subset size for digital image correlation. The optimal subset size is defined as that minimizes measurement error. Estimation equation of optimal subset size is proposed based on existing theoretical error model. The estimation equation is a function of 2nd-order displacement gradient (state of deformation), standard deviation of image noise (conservation of intensity values before and after deformation), and mean intensity gradient (speckle pattern quality) as parameters. Measurement errors for various subset sizes are computed in numerical simulations using synthetic speckle images with various measurement condition. For each parameter change, the optimal subset size derived from the measurement error and its estimation equation varies similarly. The analysis of computer-generated speckle images imposed FEM-displacement simulating tensile tests are also conducted and the results indicate the validity of the estimation equation.

The aim of this research is to investigate the decay properties of static pressure fluctuations in grid turbulence, with particular emphasis on the dependence of these properties on low Reynolds numbers in the streamwise direction. Specifically, this investigation addresses variations in the decay exponent of the root mean square (RMS) static pressure fluctuation within the low Reynolds number regime and contrasts this with the behavior of the turbulent kinetic energy. Using direct numerical analysis, the study employs precise methods to maintain the principles of energy and mass conservation. The results indicate that the grid turbulence analysis is accurately reproduced, with the decay exponent showing an increase at lower Reynolds numbers. In addition, a comparative analysis between the decay exponents of turbulent kinetic energy and static pressure fluctuation RMS has been carried out. This comparison shows a more pronounced increase in the decay exponent for static pressure fluctuation RMS. Correlation with a previous study using similar mesh Reynolds numbers and blockage ratios corroborates the observed decay exponent. These results provide important insights into the nature of grid turbulence and its decay phenomena.

The focus of this study is on the microphysical processes of clouds that are essential for improving the accuracy of climate models, particularly the analysis of droplet collisions and coalescence using high-speed imaging and off-the-shelf image processing tools. The temporal dynamics of droplet collision events are captured using the implemented processing package, and the average collision probability and coalescence efficiency for the observed droplet size range are calculated as statistical measures related to droplet collision-coalescence efficiency. By combining publicly available tools, a processing procedure with high reproducibility and implementability is achieved. Furthermore, the collision detection conditions specific to droplet collision extraction are defined, the patterns of false positive samples in the extraction results are classified, and their challenges are identified. The statistical measures calculated from the colliding droplets are consistent with previous studies, confirming the validity of the approach. This study proposes a fundamental analysis method for future observations of droplet collisions in turbulent fields using three-dimensional imaging methods such as inline holography.

A hollow ultrasonic horn can generate microbubbles by breaking down the gas-liquid interface with ultrasonic oscillation in various liquids, including not only water but also highly viscous and corrosive liquids. On the other hand, as the flow rate of the supplied gas increases, the ultrasonic waves do not sufficiently disturb the gas-liquid interface, resulting in the generation of many large bubbles. The purpose of this study is to improve the miniaturization performance of the hollow ultrasonic horn to suppress the generation of large bubbles at high flow rates. Therefore, we evaluated the conventional horn whose ultrasonic oscillation is only longitudinal oscillation and a complex oscillation horn with longitudinal and torsional oscillation. The process of bubble generation, dissolved oxygen concentration, and bubble diameter distribution were investigated. As a result, there was no significant change in the diameter of miniaturized microbubbles in each horn, but the complex oscillation succeeded in suppressing the frequency of generation of large bubbles and increasing the amount of microbubbles generated.

Abstract: The characteristics of liquid flow and mass transfer in a region close to a gas–liquid interface in a radial flow formed through a perforated plate and a wire mesh were experimentally investigated. Visualization of the flow between the wire mesh and the gas–liquid interface showed that eddies always existed near the gas–liquid interface. The radial distribution of the time mean velocity and the fluctuation velocity near gas–liquid interface showed that those were larger at the periphery than at the center. The mass transfer coefficient increased with increasing the mean time and fluctuation velocities. The mass transfer mechanism was considered using the maximum eddy length scale estimated using the normalized energy spectrum function. Consequently, the liquid-phase mass-transfer coefficient was proportional to the square root of the surface renewal rate using the maximum eddy length scale and consistent with that of the surface renewal model.

This paper describes static characteristics of polymer-ceramic PSP (PC-PSP). In the present experiment, the mixture of fluororesin powder (PTFE) with silicone resin is used as the polymer-ceramic of PC-PSP and the PSP dye is Ru(dpp)₃. The static characteristics of pressure and temperature sensitivity were investigated on the combination of polymer-solution and the coating method of PC-PSP. The experimental results showed that the present PC-PSP has equivalent or high pressure sensitivity and substance temperature dependency compared with the other PSPs.

Abstract: In this study, we developed an indentation test device and conducted experiments on gelatin samples with different water contents, assuming normal and degenerated articular cartilage states. From the experimental results, the viscoelastic parameters were quantitatively identified, and the correlation between the water content and viscoelastic parameters was investigated. Consequently, the viscoelastic parameters were noted to be significantly correlated with the water content. A limitation of this study is the lack of experimental data on the actual articular cartilage. However, the experimental method used in this study can be applied to indentation tests of the articular cartilage with some techniques. The degenerative state which caused by the change of water content of the articular cartilage can be quantitatively evaluated using an indentation test.

The LaLaCo Chair is a product that might address the issue of postural deterioration resulting from insufficient exercise. This chair has a mechanism that allows the seat to move up and down to help infants fall asleep, but no studies have investigated its effectiveness in improving posture. In this study, we examined the posture-improvement effect of the LaLaCo Chair by quantitatively measuring and analyzing the posture of 10 participants. Four conditions involving different 2 sitting positions and 2 positions of the hands were used in the experiment. The postural improvement rate of the cervical and thoracic vertebrae was calculated in each vertebrae from angle variation while watching the video. As a result, for the cervical vertebra angle in the anterior-posterior flexion direction, the best improvement rate was “without adjustment of sitting position” at approximately 100%. As for the thoracic vertebra angle, the best improvement rate was “with adjustment” condition at approximately 97% and the posture was restored to the same level as the standard posture. In future studies, we plan to analyze the effect of the LaLaCo Chair on motor function.

In-service pipeline for a long time has accumulated damage, which is leading to water leakage accidents. It is necessary to detect the water leakage phenomena by non-destructive and non-contact method. In this study, we aim to detect the water leakage phenomena based on generated water hammer in service pipeline, which is monitored by non-contact image analysis. The experimental conditions are set to three cases, which is composed of non-leakage, the leakage 0.07 km away from the variable constant flow valve and the leakage 11.6 km away from the variable constant flow valve. In experiments, water pressure and pipe material deformation were monitored in exposed line. The deformation parameters are detected by the Digital Image Correlation (DIC) method, which is applied to lowpass filter. Subsequently, it is evaluated by damping coefficients. As results, the cyclicity in circumferential strain is correlated with the cyclicity due to water hammer. Damping coefficients are determined to increase in the following order: non-leakage, leakage 11.6 km away from the valve, and leakage 0.07 km away from the valve. Thus, the attenuation of circumferential strain is greater with leakage phenomena than non leak condition. This phenomenon can be described by the law of energy conservation within pipeline system.