The structural system of prestressed concrete (PC) voided slab deck is intermediate between plate and girder. Therefore, the conventional design method is based on the assumption that the system is similar to the plate system or to the grid system. In this paper, the structural behavior of a continuous PC voided slab deck with three spans was analyzed by using the three dimensional solid finite element method (FEM). The analytical results were compared with those obtained from the conventional beam, plate and grid theories. In addition, the effect of parameters on the stress at the intermediate support was discussed; and the suitability of negative bending moment reduction at the intermediate support described in the specification for continuous roadway bridges was investigated.
Stress sensitivity of damage evolution equation and related mesh dependence in local approach to creep crack growth analysis were investigated. According to the numerical results for a plate subjected to uniform tension, the damage localization was observed under the conditions of vanishing pre-existed stress or strain concentrations. The reason for this damage localization was attributed mainly to the stress sensitivity of the damage evolution equation. Finally, several regularization methods in local approach were discussed and compared with each other by analyzing axisymmetric problems.
Hydrogen embrittlement (HE) of SUS304 stainless steel single crystals deformed at 293K or 196K was investigated under constant-loading conditions with cathodic charging. The specimens oriented for , , ,  and 0.50 in Schmid factor were prepared, and their susceptibility to hydrogen embrittlement was evaluated from the threshold stress to fracture. When the specimens were prestrained at 273K, no specimen was fractured except the -oriented specimen having the 45% prestrain. However, all the specimens having the>20% prestrain at 196K have the threshold stresses and each value corresponds to about 30% of the yield strength (0.2% off-set). These results imply that the hydrogen embrittlement under constant-loading test occurred only on the specimens with a large amount of martensite induced by low temperature deformation.
This paper is concerned with the temperature dependence of flexural static strength of pitch/PAN hybrid unidirectional CFRP laminates. These laminates were constructed by laminating the PAN based CFRP layers on the compression side of the pitch based CFRP layers. Three point bending tests were performed at a wide range of temperature below and above the glass transition temperature of the matrix resin. It was found that the existence of a few PAN based CFRP layers in the compression side of the specimen remarkably increased the flexural strength of hybrid CFRP laminates at temperature below the glass transition temperature without decreasing the flexural modulus.
This study dealt with the tensile strength and fracture mechanism of quasi-isotropic carbon/epoxy laminates with different stacking sequence. The stacking sequences employed in this study were [0/±45/90]s, [0/+45/90/-45]s, [0/90/±45]s, [±45/0/90]s, [±45/90/0]s, [90/0/±45]s and [90/±45/0]s. The maximum load of each quasi-isotropic laminate showed a higher value than that of  laminate. Splitting failure in 0° layer, shear fracture in 45° layer and delamination initiated from the cracks in 90° layer were dominant fracture patterns in quasi-isotropic carbon/epoxy laminates, and their control was important to improve the laminate strength. Especially the suppression of the splitting failure in 0° layer was most important for the improvement of laminate strength because the load bearing capacity of 0° layer was the highest among all layers. The laminates with 0° layer placed at the inner layer showed higher strength because the splitting failure in 0° layer was suppressed sufficiently. The shear fracture in 45° layer initiated from the cracks in 90° layer also affected the laminate strength. The [90/±45/0]s laminate showed the highest strength among the laminates employed in this study, since the suppression of the fracture in 0° layer and of the fracture progress from the cracks in 90° layer is realized well. From the viewpoint of the suppression of fracture, it was verified that the application of interleaf was effective for the improvement of laminate strength of quasi-isotropic carbon/epoxy laminates.
In order to investigate the strength reliability and durability of ceramic parts under gas turbine environments, the effect of oxide layer on the damage behavior caused by a particle impact in silicon carbide (SiC), which was oxidized at 1673K or at 1523K for 200 hours in the atmosphere, was examined. The long-term oxidation produced a slight increase in the static fracture strength of SiC. Particle impact caused a spalling of the oxide layer and some cracks in the substrate. The spalling patterns and the extent of the damage induced were dependent upon both the property and the velocity of the particle. An explanation of the spalling behavior based on the mechanism of lateral crack formation in ceramic materials could be shown. In the low velocity region, the oxidized SiC showed a slight increase in residual strength after particle impact, as compared with the as-received SiC.
It has been reported that the mechanical properties of spider threads are almost comparable to the best man-made fibers such as aramid fibers. In this paper, the effects of ultraviolet ray (UV) and quasi-acid rain on the mechanical properties of spider silk produced by Nephila clavata, so called Jorougumo, were investigated to elucidate the environmental effect on the fibers. It was shown that (1) acid rain lower than pH 4, which is often the case at present, did not reduce the tensile strength of the drag line much and (2) UV irradiation induced the degradation of the spider thread. These results may be of value in the assessment of the environment of spider inhabitant.
Biaxial low cycle fatigue tests under pure and combined axial and torsional loading were conducted on type 316L stainless steel at room temperature, 550°C and 650°C. In the axial and combined axial-torsional loading tests, cracks propagated almost along the principal strain plane at all temperatures. But in the pure torsion test, the crack growth direction transfered from the principal strain plane to the maximum shear plane with increasing temperature. Cracks became zigzag shape at high temperature or under pure torsional loading. These differences were discussed in relation to the increase of microstructual damaged zone, such as slip band, at high temperature and the normal strain acting on crack surface. The crack length was correlated to life fraction. The crack growth behaviour varied with temperature or principal strain ratio and scattering of the data became large at an early stage of life. But this scattering became small in a latter stage of life. This suggests that microstructure of material affects the microcrack growth behaviour.
This paper describes the vibrating reed machine developed for measuring Young's modulus of thin films. The developed machine measures a resonance frequency with 0.001Hz resolution for determining Young's modulus of thin films in vibrating reed method. Young's modulus of sputtered Cr films, of which thickness was ranged from 0.2μm to 6μm, were measured. The Young's modulus of Cr thin films of 3-6μm in thickness agreed with the bulk Young's modulus of pure Cr, while the Young's modulus of 0.2-0.3μm thin films was about twice larger than that of the bulk material. The Young's modulus of Cr thin films measured in vibrating reed method agreed well with that measured in the 3-points bending method. The increase in Young's modulus with decreasing film thickness was discussed by the microstructure observed by SEM and X-ray diffraction.
Neutron diffraction measurements of lattice spacings provide the spatial map of residual stress near welds in ferritic steel socket joints. The high tensile stress greater than 200MPa was found in the fusion and heat-affected zones in the hoop direction. However, the highest tensile stress in the axial direction at the weld root was about 110MPa relatively lower than the expected value from the fatigue test results. The balancing compressive stress was found near the surface of the socket weld fusion zone. Heat treatment at 625°C for 2 hours was sufficient for the relief of residual stress in socket welds.
During excavation for an underground construction such as subway and subsurface structure of building ground water would infiltrate and may be flooded if a part of the retaining wall is not perfect. The objective of this study is to measure impedance by installing multiple electrode in the retaining wall and to check the leakage of water caused by imperfections in the retaining wall. The results of laboratory tests indicate that the measurement of impedance is useful to estimate the amount of seepage water and seepage area.