Low cycle fatigue tests were conducted using elbow specimens of STPT410 with local wall thinning. Local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. The elbow specimens were subjected to cyclic in-plane bending under displacement control without or with internal pressure of 3 MPa. The effects of eroded conditions, such as eroded ratio, eroded angle and position, on the low cycle fatigue behavior were discussed. Seismic assessment for elbow pipe having local wall thinning was also carried out.
Effects of crack-healing on crack propagation behavior in Si_3N_4/SiC were investigated by in-situ observation. The in-situ observation was conducted for two materials which were sintered with different sintering additives and subjected to raising stress at several temperatures, environment (Air, N_2) and loading rate. As a result, it was revealed that suppression of crack propagation and increase of fracture strength were occurred at high temperature in both Air and N,. These effects in N_2 were caused by release of tensile residual stress at high temperature. Moreover, these effects in Air were affected by crack-healing in addition to release of tensile residual stress. These two factors, crack-healing and release of tensile residual stress were dependent on time. So the effect of these factors on increase of fracture strength was higher, as the loading rate was smaller. From these result, it became clear that release of tensile residual stress as well as crack-healing play an important role in suppression of crack propagation and increase of fracture strength.
The graphene nanoribbon (GNR) with a width of 100 nm or less is expected to be applied in semiconductor devices, but measurements of thermophysical properties of suspended GNRs have not yet been realized. In this study, we use the electrical self-heating method to measure the thermal conductivity of suspended GNRs that are directly synthesized by plasma-CVD. The thermal conductivity of suspended 40nm wide GNRs was measured to be less than 1/10 of that of large sized graphene.
Low-cycle fatigue tests for STPT410 elbow pipes were conducted under displacement control with and without an internal pressure of 9 MPa. First, preliminary fatigue tests were conducted under constant displacements of ±15, ±20 and ±30 mm. Next, two-step fatigue tests were carried out in which the elbows were first subjected to cyclic displacements of ±30 or ±20 mm, which correspond to cyclic overload, and then subjected to a second displacement of ±20 or ±15 mm until a fatigue crack penetrated. The total usage factor was 0.8∼1.2. Thus, the remaining fatigue life of a given elbow pipe can be predicted by the cumulative fatigue damage rule.
The thermal conductivity of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition (CAPD) was measured by a time-domain thermoreflactance method. The specific heat and density of the films were measured to be 0.891 J/g·K and 1.70 g/cm3, respectively, as parameters for the estimation of the thermal conductivity. Based on them, the thermal conductivity was estimated to be 2.32 W/m·K. This value is smaller than that of general UNCD/a-C:H films prepared by chemical vapor deposition (CVD). It might be because the CAPD films possesses a huge number of grain boundaries owing to extremely small grains of approximately 2.3 nm as compared with those of CVD films and its structure enhances phonon scattering.
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