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Volume 50 (2012)
- Issue 6 Pages 306-
- Issue 5 Pages 244-
- Issue 4 Pages 170-
- Issue 3 Pages 112-
- Issue 2 Pages 66-
- Issue 1 Pages 4-
Predecessor
Volume 50, Issue 4
Displaying 1-6 of 6 articles from this issue
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Original Paper
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Shinji OKAZAKI2012 Volume 50 Issue 4 Pages 170-176
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSAn evanescent-wave absorption type fiber-optic hydrogen gas sensor for distributed leakage monitoring was developed. A platinum-supported tungsten trioxide (Pt⁄WO3) thin film as hydrogen sensitive material was successfully immobilized on periphery of bismuth based optical fiber by sol-gel method. The optical propagation loss of the device in air atmosphere was about 0. 25dB⁄m and much smaller than that of existing fiber-optic sensor devices which was composed of conventional silica based optical fiber. This improvement would result from high refractive index of bismuth based fiber. It is suggested that the sensor device with detection length in the range of several tens of meters would be realized. The sensing characteristics such as sensitivity and response speed were evaluated. In the presence of hydrogen, sharp sensor response based on the change in evanescent-wave absorption of sensing clad region was observed. Furthermore, reproducibility of the sensor with repeated exposure to hydrogen gas was good. The response speed strongly depended on the hydrogen concentration and first-order reaction kinetics with respect to the concentration was obtained. Finally, multipoint sensing performance was demonstrated. These results indicate that the proposed sensor is promising for a low-cost and distributed leakage monitoring.View full abstractDownload PDF (1758K) -
Runze ZHOU, Ikuo KOJIMA, Hirokazu TSUJI2012 Volume 50 Issue 4 Pages 177-183
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSFitness-for-service (FFS) assessments are quantitative engineering evaluations that perform to demonstrate the structural integrity of an in-service component that may contain a flaw or damage. It can be used to make run-repair-replace decisions to help determine if pressurized equipment containing flaw that have been identified by inspection can continue to operate safely for some period of time.
This paper provides a burst pressure assessment on carbon steel pipe with different local metal loss types based on the Level 3 assessment of API⁄ASME FFS code. The Level 3 assessment is a computational method (e. g. FEM: Finite Element Method) described in ANNEX B in API-579-1⁄ASME FFS-1. As stated therein, evaluations of plastic collapse (B 1. 2) and local failure (B 1. 3) are required to be performed for the assessment of metal loss.
The author calculated the Maximum Allowable Working Pressure (MAWP) inside a cylindrical shell with local metal loss by the criteria of both plastic collapse and local failure. And the results of safety margin are also discussed in this paper.View full abstractDownload PDF (1067K) -
Kotoji ANDO, Koji TAKAHASHI, Kazuya MATSUO, Yoshio URABE2012 Volume 50 Issue 4 Pages 184-193
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSElbow pipes are commonly used in the piping systems of power plants and chemical plants. The stress states at elbow part are complex and quite different from those of the straight pipes. It is well known that the fatigue lives of metals under simple push-pull conditions were successfully predicted by the Manson's universal slope method. However, it have been pointed out by the several researchers that the low cycle fatigue lives of elbows under combined cyclic bending and inner pressure could not be predicted by the Manson's universal slope method. However, the reasons for this are not made clear. In this work, the low cycle fatigue tests and the finite element analysis of elbows under cyclic bending and inner pressures were carried out. It was found that the bi-axial stress ratio, which is a ratio of hoop stress and axial stress, at elbows are quite high. Considering the bi-axial stress ratio, the revised Manson's universal slope method was proposed in this paper. It was shown that the low cycle fatigue lives of elbows under combined cyclic bending and inner pressure were predicted conservatively by the proposed method.View full abstractDownload PDF (1202K) -
Hiroko OSEDO, Koji TAKAHASHI, Kotoji ANDO2012 Volume 50 Issue 4 Pages 194-199
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSThe effects of overload on the fatigue limit and threshold stress intensity factor range (Δkth) of SUS316 were studied. Tensile or compressive overload were applied to the bending fatigue test specimens with a small crack-like surface defect and fatigue tests were carried out to determine the fatigue limit and Δkth. It was found that the Δkth increased by tensile overloading. The increasing rate of Δkth in the CT specimen is larger than that in the bending fatigue test specimen with a small crack-like surface defect. Thus, the crack size effects on the improvement of Δkth after overloading were observed. The results are discussed from the viewpoint of fracture mechanics.View full abstractDownload PDF (358K) -
-Stress of the Corner of Hot Dip Galvanizing Bath at Start-up Operation (2nd Report) -Koji MISAKI, Toru TSUDA, Kouichi KOBAYASHI, Ryo OHTAGAKI, Tadakazu TAN ...2012 Volume 50 Issue 4 Pages 200-209
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSAt start-up operation of hot dip galvanizing baths to galvanize steel products, several leakage accidents of liquid zinc due to the damage in the vicinity of welded parts between side and bottom plates have been reported. Generally, liquid zinc is transferred to a new bath which has been heated adequately. In some of the accidents, however, it was found that transferred liquid zinc solidified in the bath heated inadequately. The purpose of this paper is to obtain stresses of the bath which are generated by thermal expansion of solid zinc inside the bath due to continuous heating in order to investigate the cause of above damages. Basing on the distribution of temperature on various parts of the bath obtained by unsteady thermal conduction analysis, stresses are calculated by elastic-plastic analysis with taking effects of strain rate and temperature for solid zinc into account.View full abstractDownload PDF (1097K) -
-Stress of the Corner of Hot Dip Galvanizing Bath at Start-up Operation (3rd Report) -Koji MISAKI, Toru TSUDA, Kouichi KOBAYASHI, Ryo OHTAGAKI, Tadakazu TAN ...2012 Volume 50 Issue 4 Pages 210-219
Published: July 25, 2012
Released on J-STAGE: August 09, 2012
JOURNAL FREE ACCESSAt start-up operation of hot dip galvanizing baths to galvanize steel products, several leakage accidents of liquid zinc due to the damage in the vicinity of welded parts between side and bottom plates have been reported. Generally, liquid zinc is transferred to a new bath which has been heated adequately. In some of the accidents, however, it was found that transferred liquid zinc solidified in the bath heated inadequately. In other paper, the author reports the stresses of the bath due to the thermal expansion of solid zinc inside the bath based on unsteady thermal conduction analysis and elastic-plastic analysis with taking effects of temperature and strain rate for the solid zinc into account. This paper reports the results of additional analysis to investigate especially the effect of the expansion of solid zinc on generated stresses.View full abstractDownload PDF (1399K)
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