Abstract: In order to investigate fatigue characteristics of vulcanized natural rubber (NR), fatigue
tests are carried out under various stress ratios R (R = minimum stress / maximum stress). It was
considered that the fatigue cracks were initiated from flaws in very early stage of total life. The
fatigue damage process was almost the fatigue crack propagation process and it is independent of R.
The crack growth rate was proportional to the crack length to about the first power, when the crack
length was defined as the length of the direction perpendicular to the loading direction. Miner’s rule
was examined to observe the fatigue crack behavior and checked by using two-step loading fatigue
tests experimentally. It seems Miner’s rule has a possibility to predict fatigue lives.
Abstract: This paper describes the state of the art in design codes and guidance using fracture
mechanics. In Germany, a railroad accident occurred in June, 1998, which resulted in about 100
passenger deaths due to a wheel fracture. In September, 1999, a water leak accident due to a crack in
a pipe happened at the Tsuruga nuclear plant in Japan. Such serious accidents are the result of
fracture events. Fracture mechanics is thought to be a tool to avoid such catastrophic fracture
accidents. The state of the art in designing mechanical components or structures applying fracture
mechanics was reviewed. The American Society of Mechanical Engineer, the Japanese Society of
Mechanical Engineers, the Japanese Welding Society, and the Japanese Industrial Standard were
mainly surveyed. This report suggests that a more consideration of fracture mechanics in the design
codes and guidance is needed for avoiding fracture accidents in components or structures.
Abstract: A fuel channel, which is the major structure of a nuclear reactor, is excited by the flow of
cooling water during the operation of the nuclear reactor. This flow of cooling water can cause
excessive vibration of the structure by the resonance. So, in the design process of a nuclear structure,
the exact evaluation of the effect of water to modal characteristics and stiffness characteristics is very
important to generate an exact analysis model. In this study, the effect of water height for modal
characterisics of the fuel channel is investigated and the stiffness evaluation of that is conducted using
the modal test results.
Abstract: The law of low-cycle fatigue with hold time at elevated temperature is investigated in this
paper. A new life prediction model for the situation of fatigue and creep interaction is developed,
based on the damage due to fatigue and creep. In order to verify the prediction model,
strain-controlled low-cycle fatigue tests at temperature 693K, 823K and 873K and fatigue tests with
various hold time at temperature 823K and 873K for 316L austenitic stainless steel were carried out.
Good agreement is found between the predictions and experimental results.
Abstract: A fatigue analysis method was developed to predict the fatigue behavior of the
T300/QY8911 multidirectional laminated composites. The finite element analysis of the
interlaminar stresses and the average of them localized to the free edges of the specimens were
made for predicting the delamination onsets and lives. The residual lives to failure after
delamination was estimated afterwards. The predicted fatigue lives agree well with the test results.
Abstract: Laser shot peen-forming of sheet metal(or LasershotSM Peening) is a new plastic forming
technique for metallic materials, which uses high-power pulsed laser replacing the tiny balls to peen
the surface of sheet metal. When the pressure of shock waves induced by laser impresses an
inhomogeneous residual stresses distribution in a given depth on the surface of sheet, it responds to
the stress by elongating at the peened surface and effectively bending the sheet. In order to
investigate the mechanism of laser shot peen-forming, the narrow strip peen-forming experimental
of aluminum alloy 6061-T6 was carried out by using a pulsed Nd:glass laser with 0.5Hz
repetition-rate. Here, under some given laser energy, laser pulse width, laser beam diameter and
pulse repetition frequency and so on, the influence of shot strip interval and shot times on surface
residual stresses and the deformation of the sheet is analyzed. The results show that the bending
forming of the sheet metal can be found, and the peened surface of sheet metal becomes convex.
That the bending increases with shot strip interval increase is not obvious, but it increases with the
shot times increase in a proper range of shot times. Besides, because laser shot peen-forming
generates compressive residual stresses on the surface, it offers many desirable characteristics in
shaped metals and is a valuable technique for producing components for a range of industries.
Abstract: The isothermal low cycle fatigue (LCF) behaviors of a directionally solidified (DS) nickel
base superalloy, coated with a NiCrAlYSi coating were studied. The study concerned NiCrAlYSi
coating formed by an arc-discharged physical vapor deposition (PVD) process for protection against
high-temperature corrosion and oxidation of gas turbine blades. The effect of protective coating on
LCF life of coating/substrate system was investigated at high temperatures and compared with
uncoated alloy. The test results show that coating has no or less effect on LCF life under high strain
range and the LCF life is governed by the fatigue behavior of substrate at different temperatures.
However, when strain range is smaller, crack initiation and propagation are observably affected by
temperature, which leads to a shorter LCF life of coating/substrate system at 500°C and a longer LCF
life at 760°C or 980°C.
Abstract: We applied the fracture mechanics approach and the nonlinear finite element method to
the analysis of interfacial failure in cylinder rubber bush bonded on their outer and inner curves
surfaces to rigid metal cylinders. The fracture parameter, tearing energy for rubber bushes was
calculated using global energy change. The contact of interfacial crack during deformation was
considered. The analyses for initially small cracks and relatively large cracks growing downwards
disagree with the previous linear solutions. The variation tearing energy for cracks growing
upwards is consistent with the existed results except a small range of crack length at the bottom end,
where negative tearing energies exist which indicates a small crack is unexpected to initiate.
Abstract: In order to clarify the effects of the hybrid surface modification process; a combination of
Fine Particle Bombardment (FPB) treatment and nitriding, on the fatigue properties of AISI 4135
steel (stress concentration factor: α=2.36), high cycle fatigue tests were carried out with a rotational
bending machine at room temperature. Observations of fracture surfaces and measurements of
hardness and residual stress distributions were carried out to investigate the fracture mechanism and
fatigue strength. It was revealed that treating process sequence did affect residual stress distributions.
Compressive residual stress generated at the surface of FPB treated specimen after nitriding was
higher than that of the one FPB treated before nitriding. It was clarified that the higher the specimen
hardness was, the higher compressive residual stress was generated at the surface. Therefore, FPB
treatment after nitriding increased the fatigue strength of steel.