Soft sedimentary rocks, especially mudstones, disintegrate subjected to cyclic drying and wetting, known as slaking, which was the cause of severe slope failures/ground settlement. In this study, a conventional oedometer was modified to make a drying/wetting cycle with temperature variation to examine the effects of slaking for four materials. Further, Hamamatsu mudstone, for evaluating the vertical stress influences, was experimented with under three loading conditions. The particle breakage was also measured along the drying/wetting cycles. It showed that particle breakage in the first cycle and consecutive cycles are governed by stress conditions and the void ratio of the specimen respectively.
This paper presents experimental data of Standard Penetration Test (SPT) and shear wave velocity Vs measurements using a pressurized chamber. The influences of soil density and soil fabric were focused because they have been found to be the major factors to liquefaction resistance under similar stress states. Two sand specimens were prepared and consolidated to a mean effective stress of around 30 kPa. The specimens’ relative density was of about 80 %, and theVs values measured were between 175 and 190 m/s, such that the small-strain stiffnessG0 differed by 16 %. SPT was performed in constant stress conditions, and almost equal blow counts (N-value) were recorded in the two specimens. The results demonstrated that N-value could not reflect the discrepancy in soil fabric as indicated by the differentVs(G0) values at the given density.
This paper reports on the quality evaluation of soil samples taken by small-scale freeze sampling technique. The quality of samples from model ground was evaluated by using a pressure chamber and Vs measurement, focusing on the changes inDr and G0 at the given confining pressure. The changes in Dr and G0 were 2.7% and 4.3% for the hollow cylindrical specimen trimmed from freezing sample taken from dense model ground. Therefore, there is a high possibility that small-scale freezing sampling can be used to obtain hollow cylindrical specimens which remain the in-situ density and soil structure.
In this paper, we have examined the applicability of the log piling method, a liquefaction countermeasure, to shallow soil improvement. Three improvement cases with different liquefiable layer thicknesses all with the same improvement depth ratio of 0.58, and two unimproved cases with varying liquefiable layer thicknesses were tested using 1G shaking table in a laminar soil box. Excess pore water pressure ratios, settlement of structure model, and pile deformation after the tests were measured. Results show that even with the same improvement depth ratio, greater liquefiable layer thickness leads to smaller settlement and pile deformatoion.
The behavior of large strain region during liquefaction was analyzed by focusing on the relationship between the normalized cumulative dissipated energy ΣΔW/σ’c and φ/φf, which is the internal friction angle φ at each loading stage divided by the peak internal friction angleφf. The results showed that φ/φf tends to decrease after ΣΔW/σ’c peaks, and this trend depended on the relative density. The tendency of φ/φf to decrease was formulated, and a one-element simulation was performed using an effective stress analysis method based on finite deformation theory that incorporates the formulated relationship. As a result, the improved effective stress analysis method was able to simulate the behavior up to the large strain region with a certain degree of accuracy. However, the simulation using the specimen model caused divergence in the middle of the analysis. We plan to improve the method, including stability improvements.
The Hokkaido Eastern Iburi Earthquake caused over 3300 landslides in volcanic deposits of Atsuma and Abira including Spfa and En-a, influenced by substantial rain from three weeks prior to the earthquake. A series of one-dimensional particle crushing tests were performed to investigate the effect of soaking time on the reduction of peak shear stress. Intra-particle saturation ratio of En-a and Spfa pumice has a good correlation with the Logarithmic value of soaking time. Intra intraparticle saturation ratio of the En-a particle is higher than the Spfa. The median crushing strength (σf)50 of Spfa and En-a reduced consecutively by 56%, and 57% when the soaking time increased from 0 to 504 hours.
In this research, we investigate scattering of ultrasonic Lamb waves at impact damage in quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates. Based on the Mindlin-Reissner plate theory, we extended the calculation method in isotropic materials to that in quasi-isotropic materials. The calculation results of angular distribution of scattering amplitude agreed with the simulation results, showing the accuracy of this method. The amplitude of scattering waves achieves resonance peaks when the wavelength is close to the radius of damaged area. The findings will be useful for establishing a scattering-based damage detection method in quasi-isotropic CFRP laminates.
The authors propose a new fixed abrasive tool with a deformable abrasive layer for mirror-polishing of rough surface glass in a single process. During the polishing, the deformation of the binder in the abrasive layer smoothes the protrusion of abrasive grains. The layer include diamond grains of ϕ4-6μm for truncating the pearskin surface of the glass, and ceria grains of ϕ2μm for promoting a chemical reaction to improve the surface roughness. Through polishing experiments, it was confirmed that our new tool achieved a finished surface with a surface roughness Ra of 4nm in a single process.
Mg alloy (ZM21) tubes were drawn using a die after die-less mandrel drawing, and dimensions and surface roughness were measured to fabricate the Mg alloy tubes for a bioabsorbable stent. As a result, the larger the speed ratio in die-less mandrel drawing, the greater the amount of wall thickness reduction from the original tubes. Furthermore, the die reduction where the outer surface roughness was minimum decreased as the speed ratio increased. Under above optimal conditions, Mg alloy tubes with an outer diameter of 3 mm and a wall thickness of 0.3 mm were fabricated.
The demand for high precision products with functional surfaces has increased in recent years. This report describes new milling systems with a tool spindle that can realize fine radial or axial motion. A tool spindle developed has voice coil motor-driven units for exciting a spindle head based on NRRO sensor signals to reduce error motion in the radial directions. Another developed spindle has a giant magnetostrictive element inside a tool shank to drive an end mill tool axially during rotation. The developed spindle systems realized high precision and micro-milling processes.
A surface fine-structured metal plate can be directly joined with an injection-molded polymer part during the molding. Many research groups have been trying to improve the performance of the direct joining by investigating fine-structuring methods and/or injection molding. In this paper, we present one of the improving methods, the addition of fluidity modifiers to polymer materials. We expected that the modifier does not quite change the basic characteristics of the polymer material at the solid state, such as strength, but improves fluidity of the melt polymer; the higher fluidity achieves the higher infiltration into the metal fine structure. To confirm the modifier effect, we performed various kinds of surface/interface analyses and discussed the joining mechanism.
It has been reported that the in-mold filling behavior of injection-molded products up to 18 mm in thickness is not affected by gravity. In this study, the thickness of the molded product was increased to 30 mm, the mold temperature was increased to 90°C, and the visualization analysis of the effect of gravity was performed when the gate position was changed upward, downward, and laterally. When the thickness of the molded product was 25mm or more, the sagging phenomenon occurred at the upper gate, and the slanting filling at the front became apparent at the side gate. It was clarified that the initial filling was stabilized at the lower and side gates, while the upper gate was unstable in the high temperature mold.
Distributed energy resources (DERs), such as electric vehicles and batteries have been focused for new flexibility resources to realize massive integration of photovoltaic power and wind power. DERs are expected to be controlled via the Internet, etc., but there are few simple models that can discuss complex behavior of both the communication process and DER itself. In this study, we constructed Model 0 as a rudimentary reference model that describes the structure of such complex behavior with delays. This paper explains an overview of Model 0 and examples of describing DERs with local connection and with cloud connection.