Abstract: The locally wall thinned phenomenon of pipes is simulated as metal loss due to
erosion/corrosion. Therefore, fracture behaviors of pipes with local wall thinning are very important
for the integrity of nuclear power plant. In this study, monotonic bending tests without internal
pressure are conducted on 1.91-inch diameter Schedule 80 STS370 full-scale carbon steel pipe
specimens. We investigated fracture strengths and failure modes of locally wall thinned pipes that
welded and unwelded by four point bending test. From test results, we could be divided three types
of failure modes.
Abstract: Mechanical properties of the pre-strained material are different with those of virgin
material without pre-strain. Buried pipelines for natural gas transmission may be deformed by
outside force such as ground subsidence, ground liquefaction, cold bending and mechanical
damage. Plastic deformation affects the tensile properties and fracture toughness. The effects of prestrain
on the mechanical properties of API 5L X65 pipe were diversely investigated through the
tensile test, crack tip opening displacement test and Charpy impact test. Axial tensile pre-strain of
1.5, 5 and 10% was applied to plate-type tensile specimens cut from the pipe body prior to
mechanical testing. Tensile test revealed that yield strength and tensile strength were increased with
increasing tensile pre-strain. However, Fracture toughness for crack initiation decreased with
increasing tensile pre-strain. Structural integrity evaluation of the API 5L X65 pipe with crack-like
flaws was assessed by using the level 2 in the API 579 code.
Abstract: Steam generator in a nuclear power plant is huge heat exchanger that transfers heat from
reactor to make steam to drive turbine-generator. Failure of the steam generator tubes can result in the
release of fission products to the secondary side. Therefore, accurate integrity assessment of the
cracked steam generator tubes is of great importance for maintaining the safety of the nuclear power
plant. This paper provides limit loads for circumferential through-wall cracks in steam generator
tubes under combined internal pressure and bending loads. Such limit loads are developed on the
basis of three dimensional finite element analyses assuming elastic-perfectly plastic material
behavior. As for the crack location, both the top of the tubesheet and U-bend regions are considered.
The analysis results can be directly applied to the practical integrity assessment of cracked steam
generator tubes, because the comparison between experimental data and FE results shows a very good
Abstract: The present work deals with an applicability of the local approach to assess in-plane size
effects among different sized compact tension (CT) specimens. To characterize ductile crack growth
of typical nuclear materials, SA515 Gr.60 and SA516 Gr.70 carbon steels, finite element analyses
employing modified GTN and Rousselier models as well as fracture toughness tests were carried out.
Material damage parameters were calibrated using standard CT specimens and reflected to predict
fracture resistance (J-R) curves of larger CT specimens. Since comparison results between
numerically estimated J-R curves and experimentally determined ones corresponded well, it is
anticipated that the local approach might be used as a promising tool for ductile fracture evaluation
incorporating the in-plane size effect.
Abstract: An effort has been made in the present investigation to evaluate the wear resistance of
nuclear fuel rods with a variation of the supporting spring shapes and their stiffness by conducting
fretting wear tests in room temperature air and water. With increasing slip amplitude, the wear
volume and maximum wear depth are increased with increasing slip amplitude. However, these are
not linearly increased with increasing spring stiffness. After the wear test, the worn surfaces were
observed to investigate the debris behavior and wear mechanism by using an optical microscope
(OM). The results indicated that almost all of the wear debris remained between the contacting
surfaces and the wear debris layers were well developed in room temperature air. Besides, some of
the debris also remained on the worn surface in room temperature water. This result shows that the
remaining debris effect on the worn surface was more dominant than the spring stiffness one. So, in
order to improve the fretting wear resistance of a nuclear fuel rod, it is necessary to consider the
debris behavior between contacting surfaces even though the supporting spring shape was
optimized by considering the contact mechanics, material compatibility, etc. From the experimental
results, the fretting wear mechanisms and the effect of spring properties were discussed.
Abstract: The performance of bogie decreases according as traveling distance increases. Its causes were
expected to be fatigue, wear, and deterioration. Especially, maintenance coat needs about triple than
manufacture cost during required life in case of container and uncovered freight car. Freight car doesn’t
adapt corrective maintenance which repairs a poor part after a trouble but use preventive maintenance which
fixes a bad part before a trouble. There were a few researches on preventive maintenance such as inspect
affairs and facilities management. They couldn’t estimate the operation reliability on railroad vehicle.
Therefore, this study proposes the preventive maintenance procedure that predict repair period of end
beam for uncovered freight car using reliability function and instantaneous failure rate on the basis of fatigue
test and load history data.
Abstract: In the present work, the mechanical properties of 321 stainless steel pressure equipments
exposed to an accident fire in a chemical unit were investigated. The performance and
microstructure of this material were described by chemical compositions analysis, tensile test,
scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and
X-ray diffraction (XRD). The experiment results showed that the mechanical properties of the
material were degraded. The grains on the external surface of the fracture became coarse. These
results indicated that serious damage to 321 stainless steel had been induced by extreme heat of the
fire and this pressure vessel could not be used anymore.
Abstract: The present work presents plastic limit load solutions for branch junctions under internal
pressure and in-plane bending, based on detailed three-dimensional (3-D) FE limit analyses using
elastic-perfectly plastic materials. The proposed solutions are valid for a wide range of branch
junction geometries; ratios of the branch-to-run pipe radius and thickness from 0.0 to 1.0, and the
mean radius-to-thickness ratio of the run pipe from 5.0 to 20.0.
Abstract: Wiper blade is one of inexpensive automotive components, but the component is very
important part considering car safety for securing automotive visual field. Therefore study for
securing longer endurance of wiper blade was proceeding, that is about variables effecting on
endurance. In this paper, it was proved that the effect to extend endurance could be acquired by
securing proper friction coefficient. Be compared endurance in Weibull distribution that is reliability
technique and seized effect about blade pressure distribution, contact pressure, blade rubber surface
treatment etc. for securing proper friction coefficient. Relation between these variables was cleared
through test. Also, designed and proposed tester for measuring friction coefficient of wiper blade.
Abstract: his study was prosecuted to analyze a structural resistance degradation model for the
existing column in the 3-story building to be remodeled. The probabilistic random variables in this
study were dealt with an initial member strength, current maximum crack width, current density and
diameter of reinforcement with elapsed time and corrosion initiation time, TDRA has been performed
to calculate the reliability index, the failure probability, the degradation level according to the member
strength loss in reinforced concrete columns due to corrosion of steel reinforcement.