The objectives of this study are to clarify the wood properties of Sanbu-sugi cultivar of sugi (Cryptomeria japonica D. Don) planted in Chiba prefecture, Japan. Stress-wave velocity (SWV) of stem, dynamic Young’s modulus (DMOE) of logs, wood properties (basic density, latewood tracheid length, microfibril angle of S2 layer in latewood tracheid, and static bending properties), and bending properties of 2 by 4’s were investigated for Sanbu-sugi cultivar with different 5 stand ages (11, 19, 30, 48, and 70-years-old). From obtained results, changes of wood properties due to changes of stand age were also discussed. Based on the radial variation of wood properties, juvenile wood of Sanbu-sugi existed from pith to 15th or 20th annual ring from pith. SWV of stem and DMOE of logs increased with increase of stand age up to 30 years, and then it slightly decreased. Thus, SWV of stem and DMOE of logs became stable from about 30-years-old due to increase of mature wood volume. Mean values of modulus of elasticity and modulus of rupture in 2 by 4’s were 8.54 GPa and 56.2 MPa, respectively. Modulus of elasticity of 2 by 4’s in mature wood was almost the same for that obtained from trees with different stand age.
Stiffness of carbon fiber reinforced polymer composites (CFRP) under the cyclic loading of bending deformation has been measured at various temperatures and deformation amplitudes. The stiffness of specimens decreases gradually with the number of loading cycles. The stiffness reduction correlates with the decrease in bending strength and the increase in viscoelastic loss, which suggests the stiffness reduction process corresponds to the damage accumulation process under the cyclic loading. The stiffness reduction process whose rates increase with increasing temperature and deformation amplitude, has been proved to be the thermally activated process depending on load stress (deformation amplitude). Analyzing the stiffness reduction curves at various temperatures and loads by means of reduced variable methods, a master curve that can be used to estimate a fatigue life has been composed, and an activation energy and an activation volume are estimated to be 26±3kcal/mole and 1.1×10-28m3 respectively. A molecular process for the stiffness reduction is discussed on the basis of the rate process theory.
This paper studies the stress waveform effect on low cycle fatigue life for three kinds of notched specimens at elevated temperature. Low cycle fatigue tests were carried out using circumferential notched specimens of SUS316FR stainless steel using fast-fast, slow-fast and hold-time stress waveforms at 923K. Neuber’s rule recommended in ASME Code Case was applied to estimate failure and crack initiation lives. Failure lives were underestimated by Neuber’s rule in ASME Code Case NH. Crack initiation lives under the fast-fast, slow-fast and hold-time stress waveforms were correlated within a factor of 4 scatter band by using modified Neuber’s equation in which the exponent of Kt was changed from 2 to 1.2 in the combination with frequency modified fatigue life equation.
Shot peening, which imparts compressive residual stress, is a very effective means for improving the fatigue strength and is widely used for springs. The relationship between fatigue strength and compressive residual stress by shot peening is well known and is a subject of many previous studies. Residual stress caused by shot peening is generally evaluated using X-ray stress measurement method, and it give rise to compressive residual stress macroscopically when the X-ray irradiation area is not small. On the other hand, in order to investigate the microscopic stress distribution of dents around the vicinity, there are research and experiments with big steel ball simulating a shot, and studies using FEM method confirms that tensile residual stress is generated locally, such as the center of a dent. However, identifying the residual stress generation mechanism by shot peening using calculation alone is a very difficult task because there are many factors involved. In this study, with the aim of clarifying experimentally the microscopic residual stress distribution of peening surface with CCW(conditioned cut wire), which is widely used for the production of spring, we have developed an X-ray diffractometer which makes it possible to measure the microscopic stress distribution. We prepared as specimen SUP9 (JIS G 4801: spring steels), shot peened at coverage of 10%, 60% and 300%. The microscopic residual stress distribution is measured in an area of 0.8mm x 0.8mm with 0.1mm step on each specimen surface. Obtained results are summarized as follows: Shot peened surface has average compressive residual stress present in large irradiation areas, but the tensile stress and compressive stress of the yield stress order has been distributed in local areas of 100μm or less. It became clear that, even if the coverage of the shot peening is increased, there is not much difference of macroscopic residual stress, and an overall uniform compressive stress distribution is not obtained; but there is a large residual tensile stress in the local area. There is no correlation between surface shape and residual stress distribution due to shot peening. In the stress distribution around the dent by single shot, unlike previous research results using shot peening of the sphere, it clearly indicates a residual stress distribution with no regularity.
To apply a transformation-induced plasticity (TRIP)-aided steel consisting of bainitic ferrite structure matrix and metastable retained austenite of 10 vol% (TBF steel) to some precision gears, the effects of fine particle peening on the Vickers hardness and residual stress in a surface layer of the TBF steel were investigated. The peened surface layer showed much higher Vickers hardness and compressive residual stress than those of a quenched and tempered SNCM420 steel. The increased Vickers hardness was mainly caused by an increase in the strain-induced transformed martensite fraction. The compressive residual stress was increased by the increases in size and gravity of shot material and arc-height. The higher compressive residual stress was principally associated with (1) plastic strain due to severe plastic deformation and (2) expansion strain due to the strain-induced transformation of metastable retained austenite. Contribution of the (2) was approximately 30% of total residual stress.
Precipitates in a Mg-2Gd-1Zn (at%) alloy, aged at 573 K for 100 h after forging, have been characterized using transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). TEM observation reveals that the precipitates have thin plate morphology. The energy dispersive X-ray spectrometry (EDX) and selected area electron diffraction (SAED) pattern have indicated that the plate-shaped precipitate has an fcc structure and a lattice parameter of approximately 2.23 nm, which is identical to β-Mg5Gd. It is suggested that the most probable dominant orientation relationship between the β-Mg5Gd precipitate and α-Mg matrix is (1120)α // (001)β and α // β based on the crystal orientation analysis using EBSD. It is speculated that the strengthening in the Mg-Gd-Zn alloy is attributable to the plate-shaped β-Mg5Gd precipitates. The precipitates which are formed on prismatic planes of α-Mg matrix during the heat treatment can provide the most effective obstacles to basal dislocation slip.
It has been revealed that hydrothermal oxidation of persistent organochlorine substances is dramatically facilitated with the aid of Cu-based catalysts such as Cu-supported WO3, because the Fenton-type reaction catalyzed by Cu ions undergoes substantial acceleration under subcritical conditions of water at around 200~300℃, leading to the increased formation of hydroxyl radicals which possess a strong oxidative power. In this study, the catalytic hydrothermal oxidation of 4-chlorophenol with CuO or Cu2O has been examined using the slurry flow and catalyst packed-bed reactor systems. It is found that Cu2O has a remarkable catalytic activity for the hydrothermal oxidation of 4-chlorophenol compared with those of CuO and Cu-supported TiO2. The conversion of 4-chlorophenol reached nearly 100% at reaction temperatures around 130℃ when Cu2O was used as catalyst, indicating that it is possible to substantially reduce the reaction condition required for the complete decomposition of persistent organochlorine substances by the hydrothermal oxidation. The continuous treatment of 4-chlorophenol has been also conducted using the packed-bed reactor system with Cu2O. The results demonstrated that 4-chlorophenol could be degraded for up to 22 hours without significant loss of the catalytic activity.
Pressure effect on the conformational equilibrium of 1-butyl-3-methylimidazolium cation ([bmim]+) in the [bmim]-based ionic liquids (ILs) with three different anionic species (I, BF4, and PF6) have been studied using Raman spectroscopy. The gauche conformer for the NCCC angle of [bmim]+ increases with increasing pressure at all cases, and the trans conformer decreases. From the pressure dependence of the Raman intensity, we determined the difference in the partial molar volume (ΔVtrans→gauche) between the conformers of [bmim][X](X= I, BF4, and PF6). The negative ΔVtrans→gauche is due to the molecular volume difference (ΔVM) which consists of the van der Waals volume and void volume differences. This means that the pressure-induced [bmim]+ conformational preference of [bmim]-based ILs is dependent of the configuration of [bmim]+ against each anionic species. Thus, we proposed that the increment of the gauche conformer of [bmim]+ on the pressure-induced phase transitions is related to the change in the initial configuration of [bmim]+ against anion by compression.