Abstract: Fatigue crack propagation behavior under cyclic tensile or torsional loading with biaxial static
loads has been investigated. Two different biaxial loading systems, i.e. cyclic tensile loading with static
torsional load and cyclic torsional loading with static tensile load, were employed to thin-walled tubular
specimens. The crack propagation was measured by two crack gages mounted near the notch and crack
opening level was measured by unloading compliance method. The directions of the fatigue crack
propagated under respective biaxial loading conditions were examined and the growth rates were
evaluated by using several cyclic parameters, including equivalent stress intensity factor range, Keff,
crack tip opening displacement range, CTD, minimum strain energy density factor range, Smin.
Furthermore, the growth rates were evaluated by effective cyclic parameters considering crack closure. It
was found that the biaxial static stress superimposed on the cyclic tensile or torsional loading tests has no
influence on the propagation directions of the cracks. Furthermore, it was shown that the fatigue crack
growth rates under biaixial faigue loading were well expressed by using the cyclic fatigue parameters,
Keq,eff, CTDeff, Smin,eff considering crack closure effect.
Abstract: The present paper provides plastic limit load solutions for axial and circumferential
through-wall cracked pipes based on detailed three-dimensional (3-D) finite element (FE) limit analysis
using elastic-perfectly plastic behavior. As a loading condition, both single and combined loadings are
considered. Being based on detailed 3-D FE limit analysis, the present solutions are believed to be
valuable information for structural integrity assessment of cracked pipes.
Abstract: The effect of hydrolysis of polycarbonate on tensile behavior were investigated.
The specimens were exposed in a chamber at constant room temperature and water for 300 hours,
and measurements were made on the variation of weight and tensile properties. In addition,
the increase and decrease of the carbonate part was measured with an ultraviolet spectroscopy.
The results are as follows: It was confirmed that it was effective to the examination of the influence of
the diffusion of water with an overlay castfilm. It has been understood to the diffusion of water from
the surface layer has diffused at the same time by about 6μm, and it has diffused gradually
when it is deeper than 6μm. The change in the tensile behavior by the hydrolysis
was able to be confirmed by observing the carbonate part of the polycarbonate. It became clear,
the break strain has decreased because the carbonate part is taken apart by the hydrolysis.
Afterwards, the break strain steadies by constructing a bridge, and the yield stress increases.
Abstract: The strain energy density factor approach under mixed-mode condition is used for the
prediction of crack propagation in the orthotropic steel deck specimen, which is similar to that of
existing suspension bridges. Stress intensity factor approach is used to compare with strain energy
density factor approach for the fatigue crack growth analysis. The stress intensity factors are
computed by numerical extrapolation using cracked models for the different crack length. The study
shows that the fatigue crack propagation under mixed-mode condition is slower than that under
mode I only. Parametric studies on the initial crack length, critical crack length and parameters
related to crack growth equations are performed to show the influence of these parameters on the
Abstract: Damages in nuclear facilities during the operation of the Reactor Coolant System (RCS)
are caused by cyclic loadings due to mechanical or thermal fatigue. Therefore, the development of
an integrated technology including fabrication of standard specimens and their practical usage is
needed to enhance the reliability of nondestructive testing for surge lines or main feed water lines.
In this study, thermal fatigue cracks on STS 304 plates (t = 6mm) and tubes (O.D = 89.7mm. t =
7.7mm) for performance demonstration inspection were fabricated for the Reactor Coolant System
(RCS) in nuclear power plants. In case of plates, cyclic thermal changes, from 20 to 450, were
loaded on the V-notched specimens under tensile stressed conditions. The applied tensile stress was
1,700MPa at the notch portion. In the case of tubes, cyclic thermal changes, from 35 to 355,
were applied on the V-notched specimens under compressive stressed conditions. In the case of
plates, the initial crack was generated at 17,000 cycles and the depth of crack was 2.54mm at
22,000 cycles. Unlike the plates, in the case of tubes, the initial crack formed at 14,000 cycles and
the crack penetrated the tube at 25,000 cycles. In this paper, shapes and fractographies of fabricated
thermal fatigue cracks, and the used cyclic thermal loads are presented.
Abstract: In carbon steel pipes of nuclear power plants, local wall thinning may result from
erosion-corrosion or flow-accelerated corrosion(FAC) damage. Local wall thinning is one of the
major causes for the structural fracture of these pipes. Therefore, assessment of local wall thinning
due to corrosion is an important issue in nondestructive evaluation for the integrity of nuclear power
plants. In this study, laser-generated ultrasound technique was employed to evaluate local wall
thinning due to corrosion. Guided waves were generated in the thermoelastic regime using a
Q-switched pulsed Nd:YAG laser with a linear slit array. . In this paper, time-frequency analysis of
ultrasonic waveforms using wavelet transform allowed the identification of generated guided wave
modes by comparison with the theoretical dispersion curves. Modes conversion and group velocity
were employed to detect thickness reduction.
Abstract: Pipelines of nuclear power plants undergo high pressure and temperature. Thermal
stratification typically occurs in the surge line and the main feed water lines by flow and this
stratification will initiate and propagate thermal fatigue cracks. This may cause rupture and leakage
and it is a serious problem to nuclear power plants operation. Therefore it is very important to detect
and measure thermal fatigue cracks. In this study, thermal fatigue cracks were generated in
austenitic stainless steel specimens by a thermal cycle in notched pipes and weld jointed pipes.
Ultrasonic techniques were used to evaluate the thermal fatigue crack depth. When ultrasonic waves
propagate from an angle beam probe to thermal fatigue cracks, waves are reflected and diffracted.
Crack depth was evaluated by the reflected signals from back wall and diffracted signals from the
crack tip, but diffracted signals were too weak to detect so the reflected signals were more useful.
The TOFD and dB drop methods were used in this study. The TOFD method is uses a time delay of
diffracted signal from the crack tip. The dB drop method is an application of an amplitude
decreasing rate by a probe moving distance.
Abstract: A uniform model, in which the crack, V-notch, U-notch and arc are described as breach
uniformly, is put forward in this paper. The tip radius, depth and field angle of breach are regarded as
the parameter of annularly breached bar. The stress field and displacement field near the tip of the
annularly breached bar under bending, in which takes fα(a/b) as its descriptive parameter, was given.
All forms of breaches according to the change of tip radius, depth and field angle were discussed. The
effects of parameters on fα(a/b) in bending were analyzed. The criteria for the safety design and
fracture design both of which on fα(a/b) were obtained. The results not only can be applied widely to
anti-fracture design but also be used for reference in anti-fatigued design in product lifecycle
Abstract: The anti-fatigued design is an important field in product lifecycle management. A uniform
criterion of annularly breached spindle was put forward in this paper. The crack, V-notch, U-notch
and arc were described as breach uniformly according to the tip radius, depth and field angle of breach
in the method. The connection between sharp V-notch and crack, between V-notch and U-notch has
been set up. We fuse the fatigue fracture theory and life prediction techniques together on the design
technology of lifecycle safety guarantee of mechanical structures. The relationship between life and
detectability of the breached spindle system was discussed to provide useful guidance for practical
applications. The criterion for the safety design and fracture design both of which on fα was obtained.
The criterion of annular breached spindle under torsion was obtained at first and then the effects of
bending to lifecycle of spindle were analyzed.
Abstract: Structural Health Monitoring (SHM) of aircrafts is of great relevance in the present age
aircraft industry. The present study demonstrates three techniques that have the potential for the
SHM of multi-layered composite structures. The first technique is based on multi-transmitter-multireceiver
(MTMR) technique with tomographic methods used for data reconstruction. In the MTMR,
the possibility of SHM using algebraic reconstruction techniques (ART) for tomographic imaging
with Lamb wave data measured in realistic materials is examined. Defects (through holes and low
velocity impact delaminations) were synthetic and have been chosen to simulate impact damage in
composite plates. The second technique is a single-transmitter-multi-receiver (STMR) technique
that is more compact and uses reconstruction techniques that are analogous to synthetic aperture
techniques. The reconstruction algorithm uses summation of the phase shifted signals to image the
location of defects, portions of the plate edges, and any reflectors from inherent structural features
of the component. The third technique involves a linear array of sensors across a stiffener for the
detection of disbanded regions.