• Journal of Power System Engineering
• /
• v.9 no.3
• /
• pp.71-78
• /
• 2005

A high-pressure hose includes rebar layers of the synthetic fiber such as nylon or a steel wire to control internal pressure. The hose assembly is manufactured through the swaging process to clamp the hose into the metal fittings. Usually, the hose behavior is affected by the resultant of the longitudinal and circumferential forces produced by the internal pressure. The rebar layers can appear the most ideal rebar effect when they are arranged to the same direction as the resultant force. The braid angle applied in the rebar layers is an important factor in determining ultimate burst pressure and overall hose life. Failure can occur on the contacted parts of a hose with the metal fittings under severe operating conditions such as high pressure and temperature of the inner fluid. In this paper, the mechanical behavior between the hose and the metal fittings during the swaging process and the stress variation characteristics of a high-pressure hose under a constant applied pressure are analyzed with respect to the braid angle of steel wire using the finite element method.

• Journal of Energy Engineering
• /
• v.22 no.2
• /
• pp.148-155
• /
• 2013

The steam generators of OPR-1000 plants have Alloy 600 and Alloy 690 as the tube material and its tube expansion method is the explosive expansion method. According to the experience of these plants, circumferential cracks were largely occurred in steam generator tubes expanded by the explosive expansion method and their locations were the outer surface of tube expansion transition region surrounding with piled-up sludge. But even though tubes have the same conditions, tubes with the hydraulic expansion method shows the prevail trend of axial cracks compared to circumferential cracks. Therefore in this study, in order to identify the difference of such phenomena as above, configurations of tube and tubesheet were modeled and at operating conditions, stress values applied in the tube expansion transition area in accordance with tube expansion methods were calculated by using computational program and the direction and the predominance of cracks were evaluated.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.849-855
• /
• 2000

This study evaluated the effect of restraint of pressure induced bending(PIB) on crack mouth opening displacement(CMOD) for circumferential through-wall crack in pipe by using both elastic and elastic-plastic finite element analyses. The analyses results showed the restraint of PIB was decreased crack opening for a given crack length and tensile stress, and the effect was considerable for large crack and short restraint length. Also, the restraint effect on CMOD was independent on the variation in pipe diameter and decreased with increasing pipe thickness, and it depended on not total restraint length but short restraint length for non-symmetrically restrained. Additionally, the effect of restraint of PIB was more significant in the elastic-plastic analysis results compared with in the elastic analysis results.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.12
• /
• pp.1123-1131
• /
• 2008

This paper provides V-factor estimation under combined mechanical and thermal load for circumferential cracks. Results are based on finite element analyses and effect of types and magnitudes of the thermal stress, crack geometry, the loading mode and plastic strain hardening on variations of the V-factor are investigated. The results of finite element analyses are compared with R6 values. As a result, it is shown that R6 gives generally conservative results. The conservatism is especially increased for the combination of large mechanical and thermal load. As a result, new estimation method which uses failure assessment line in R6 is proposed for V-factor and gives less conservative results.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.274-277
• /
• 2004

The most important mode of subcritical crack growth is primary water stress corrosion crack, which was the reported mechanism from the root cause analysis of the crack in the bimetallic welds. Stress corrosion crack growth evaluations was carried out for several flaw shapes of both axial and circumferential flaws, using the steady-state stresses including residual stresses. This evaluation considered the possibility of additional flaws in the primary loops of nuclear power plant, even though no such flaws have been identified by Ultrasonic Test. Consequently, Results show that the predicted flaw sizes will determine acceptability for continued service and maintenance.

• Journal of Mechanical Science and Technology
• /
• v.18 no.5
• /
• pp.808-813
• /
• 2004

The stress analysis on orthotropic composite cylindrical shells with one circular or one elliptical cutout subjected to an axial force is carried out by using an analytical and experimental method. The composite cylindrical shell governing equation of the Donnell's type is applied to this study and all results are presented by the stress concentration factor. The stress concentration factor is defined as the ratio of the stress on the region around a cutout to the nominal stress of the shell. The stress concentration factor is classified into the circumferential stress concentration factors and the radial stress concentration factors due to the cylindrical coordinate of which the origin is the center of a cutout. The considered loading condition is only axial tension loading condition. In this study, thus, the maximum stress is induced on perpendicular region against axial direction, on the coordinate. Various cutout sizes are expressed using the radius ratio, (equation omitted), which is the radius of a cutout over one of the cylindrical shell. Experimental results are obtained using strain gages, which are attached around a cutout of the cylindrical shell. As the result from this study, the stress concentration around a cutout can be predicted by using the analytical method for an orthotropic composite cylindrical shell having a circular or an elliptical cutout.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.04a
• /
• pp.171-178
• /
• 2000

In order to evaluate the tensile behaviors of hoop direction for the nuclear fuel cladding tubes the shapes of specimen and jig fixtures for the ring test are decided with various conditions under the elastic-large plastic deformations. The axial displacement of the jig cylinders is converted to the circumferential direction elongations of specimen. The stress distributions on specimen are depended on the radii and locations of specimen and jig size and central angle. Therefore we calculated the stress distributions and decided the optimum shapes to get the uniform stress in the area of specimen gage length. Form the analysis the stress distributions in gate area are reviewed with the radii and location of specimen notch and the central angle of jig cylinder,. The optimum shapes of specimen and jig are proposed to the clad tube having 10.62 mm in diameter and 0.63mm in thickness for 16x16 PWR nuclear fuel assembly.

• Structural Engineering and Mechanics
• /
• v.57 no.5
• /
• pp.823-835
• /
• 2016

Using the Complementary Functions Method (CFM), a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material (FGM) is presented. The mechanical properties are assumed to obey the exponential variations in the radial direction, and the Poisson's ratio is assumed to be constant, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. In the present paper, a semi-analytical iterative technique, one of the most efficient unified method, is employed to solve the heat conduction equation and the Navier equation. For different values of inhomogeneity constant, distributions of radial displacement, radial stress, circumferential stress, and effective stress, as a function of radial direction, are obtained. Various material models from the literature are used and corresponding temperature distributions and stress distributions are computed. Verification of the proposed method is done using benchmark solutions available in the literature for some special cases and virtually exact results are obtained.

• Nuclear Engineering and Technology
• /
• v.53 no.11
• /
• pp.3852-3859
• /
• 2021

This paper presents experimental and numerical analysis results regarding the effects of an incomplete penetration defect on the fatigue lives of socket welded pipes. For the experiment, four-point bending fatigue tests with various defect geometries (defect depth and circumferential length) were performed, and test results are presented in terms of stress-life data. The results showed that for circumferentially short defects, the fatigue life tends to increase with increasing crack depth, but for longer defects, the trend becomes the opposite. Finite element analysis showed that for short defects, the maximum principal stress decreases with increases in crack depth. For a longer defect, the opposite trend was found. Furthermore, the maximum principal stress tends to increase with an increase in defect length regardless of the defect depth.

• Restorative Dentistry and Endodontics
• /
• v.33 no.5
• /
• pp.457-462
• /
• 2008

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior. these two factors should be considered. In this experiment. I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups. one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme. Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress $({\sigma}{\theta})$ was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components. Filtek Supreme groups showed higher residual stress.