Burst Test on the Steam Generator Tube With Multiple Part-Through-Wall Flaws

2015 ◽  
Author(s):  
Jin Weon Kim ◽  
Ki Hyeon Eom
Keyword(s):  
Steam Generator ◽  
Interaction Effect ◽  
Room Temperature ◽  
Ligament Length ◽  
Outer Diameter ◽  
Constant Depth ◽  
Positive Interaction ◽  
Failure Pressure ◽  
Electro Discharge Machining ◽  
Axial Part

This study carried out burst tests on steam generator (SG) tube specimens containing multiple axial part-through-wall (PTW) flaws at room temperature (RT). The specimens were machined from SG tube of Alloy 690TT with an outer diameter of 19.05mm and a thickness of 1.067mm. The flaws were made by electro-discharge machining (EDM) method on the outer surface of specimen. In the experiment, six types of multiple PTW flaws with a constant depth of 50% of wall thickness and single flaw with four different lengths were considered. The results showed that the interaction effect for collinear axial PTW flaws diminished with increasing ligament length between flaws. The ligament length had less influence on the interaction effect for longer flaws than shorter flaws. For non-aligned axial PTW flaws, however, the interaction effect was increased and remained with increase in circumferential ligament length. For parallel axial PTW flaws, the positive interaction effect appeared when the ligament between flaws was less than 2mm. However, the failure pressure decreased with increasing circumferential ligament length between flaws and reached the minimum when they were separated by about 90-degree in circumferential direction. Interaction effect was enhanced as number of flaws for collinear and non-aligned axial PTW flaws increased. Regardless of flaw configurations and ligament lengths, multiple PTW flaws of shorter length were failed by rupture at bottom of flaws followed by coalescence and unstable tearing. But, the flaws of length longer than 25.4mm were failed by rupture at bottom of one of multiple axial flaws.

Failure Behavior of Multiple-Axial Part-Through-Wall Flaws in Alloy 690TT Steam Generator Tubes

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Ki Hyeon Eom ◽  
Jin Weon Kim ◽  
Yun Jae Kim ◽  
Jong Sung Kim
Keyword(s):  
Experimental Data ◽  
Failure Mode ◽  
Steam Generator ◽  
Interaction Effect ◽  
Room Temperature ◽  
Failure Behavior ◽  
Constant Depth ◽  
Failure Pressure ◽  
Axial Part ◽  
Steam Generator Tubes

This study investigates the interaction effect of multiple-axial part-through-wall (PTW) flaws on the failure behavior of Alloy 690TT steam generator (SG) tubes. Burst tests of tubes with single and multiple flaws were conducted at room temperature (RT). The flaws were made by the electrodischarge machining (EDM) method on the outer surface of the specimens. Six different configurations of multiple flaws were considered to see the interaction effect; two and three collinear, two and three parallel, and two and three nonaligned flaws. In all cases, an axial flaw with a constant depth of 50% wall-thickness was considered, and the following variables were systematically varied; the axial and/or circumferential separating ligament lengths between flaws, the flaw length, and the number of flaws. Effects of these variables on the failure pressure and failure mode were investigated based on experimental data. The effects of separating ligament lengths and flaw lengths on the failure pressure were dependent on the type of flaw configuration. For collinear and nonaligned flaws, the decrease in failure pressure by the interaction of multiple flaws became significant as the number of flaws increased. The failure mode of multiple flaws was strongly dependent on the length of the flaws.

Corporate cash holdings and their implications on firm value in family and founder firms

2012 ◽  
Vol 9 (2) ◽  
pp. 257-273 ◽  
Author(s):  
James Lau ◽  
Joern H. Block
Keyword(s):  
Adverse Selection ◽  
Interaction Effect ◽  
Firm Value ◽  
Family Firms ◽  
Cash Holdings ◽  
Agency Cost ◽  
Economic Incentives ◽  
Positive Interaction ◽  
Superior Knowledge ◽  
Corporate Cash Holdings

This research investigates whether the presence of controlling founders and families has significant impact on the level of cash holdings, and their implications on firm value. The agency cost of cash holdings in founder firms is arguably less severe than family firms, due to founders’ economic incentives, strong psychological commitment and superior knowledge, whereas family firms are exposed to adverse selection and moral hazard as a result of altruism. Results indicate that founder firms hold a significantly higher level of cash holdings than family firms. In addition, there is a positive interaction effect between founder management and cash holdings on firm value, suggesting the presence of founders as managers helps to mitigate the agency costs of cash holdings.

scholarly journals Fatigue Variability of Alloy 625 Thin-Tube Brazed Specimens

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1162
Author(s):  
Seulbi Lee ◽  
Hanjong Kim ◽  
Seonghun Park ◽  
Yoon Suk Choi
Keyword(s):  
Fatigue Life ◽  
Heat Exchanger ◽  
Room Temperature ◽  
Metal Layer ◽  
Outer Diameter ◽  
Multiple Crack ◽  
Joint Failure ◽  
Alloy 625 ◽  
Thin Tube ◽  
Brazed Joint

As an advanced heat exchanger for aero-turbine applications, a tubular-type heat exchanger was developed. To ensure the optimum performance of the heat exchanger, it is necessary to assess the structural integrity of the tubes, considering the assembly processes such as brazing. In this study, fatigue tests at room temperature and 1000 K were performed for 0.135 mm-thick alloy 625 tubes (outer diameter of 1.5 mm), which were brazed to the grip of the fatigue specimen. The variability in fatigue life was investigated by analyzing the locations of the fatigue failure, fracture surfaces, and microstructures of the brazed joint and tube. At room temperature, the specimens failed near the brazed joint for high σmax values, while both brazed joint failure and tube side failure were observed for low σmax values. The largest variability in fatigue life under the same test conditions was found when one specimen failed in the brazed joint, while the other specimen failed in the middle of the tube. The specimen with brazed joint failure showed multiple crack initiations circumferentially near the surface of the filler metal layer and growth of cracks in the tube, resulting in a short fatigue life. At 1000 K, all the specimens exhibited failure in the middle of the tube. In this case, the short-life specimen showed crack initiation and growth along the grains with large through thickness in addition to multiple crack initiations at the carbides inside the tube. The results suggest that the variability in the fatigue life of the alloy 625 thin-tube brazed specimen is affected by the presence of the brazed joint, as well as the spatial distribution of the grain size and carbides.

Evaluation of the Creep Rupture Behavior of Alloy 690 Steam Generator Tubes Considering the Pressure Ramp Rate

2021 ◽  
Author(s):  
Jongmin Kim ◽  
Min-Chul Kim ◽  
Joonyeop Kwon
Keyword(s):  
Steam Generator ◽  
Creep Rupture ◽  
Parameter Method ◽  
Alloy 600 ◽  
Steam Generator Tube ◽  
Failure Pressure ◽  
Alloy 690 ◽  
Rupture Model ◽  
Temperature And Pressure ◽  
Steam Generator Tubes

Abstract The materials used previously for steam generator tubes around the world have been replaced and will be replaced by Alloy 690 given its improved corrosion resistance relative to that of Alloy 600. However, studies of the high- temperature creep and creep-rupture characteristics of steam generator tubes made of Alloy 690 are insufficient compared to those focusing on Alloy 600. In this study, several creep tests were conducted using half tube shape specimens of the Alloy 690 material at temperatures ranging from 650 to 850C and stresses in the range of 30 to 350 MPa, with failure times to creep rupture ranging from 3 to 870 hours. Based on the creep test results, creep life predictions were then made using the well-known Larson Miller Parameter method. Steam generator tube rupture tests were also conducted under the conditions of a constant temperature and pressure ramp using steam generator tube specimens. The rupture test equipment was designed and manufactured to simulate the transient state (rapid temperature and pressure changes) in the event of a severe accident condition. After the rupture test, the damage to the steam generator tubes was predicted using a creep rupture model and a flow stress model. A modified creep rupture model for Alloy 690 steam generator tube material is proposed based on the experimental results. A correction factor of 1.7 in the modified creep rupture model was derived for the Alloy 690 material. The predicted failure pressure was in good agreement with the experimental failure pressure.

scholarly journals Laboratorial technique for fabrication of outer diameter stress corrosion cracking on steam generator tubing

2014 ◽  
Vol 13 (3) ◽  
pp. 112-119
Author(s):  
Jae-Min Lee ◽  
Sung-Woo Kim ◽  
Seong-Sik Hwang ◽  
Hong-Pyo Kim ◽  
Hong-Deok Kim
Keyword(s):  
Stress Corrosion ◽  
Steam Generator ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Outer Diameter ◽  
Steam Generator Tubing

Evaluation of Interaction Effects on Part-Through Cracks in Steam Generator Tubes

2013 ◽  
Author(s):  
Yong-Seok Kang ◽  
Hong-Deok Kim ◽  
Kuk-Hee Lee ◽  
Jai-Hak Park
Keyword(s):  
Steam Generator ◽  
Interaction Effect ◽  
Structural Integrity ◽  
Structural Parameters ◽  
Interaction Effects ◽  
Multiple Cracks ◽  
Performance Limit ◽  
Steam Generator Tubing ◽  
Steam Generator Tubes

Degraded steam generator tubing can affect its safety functions. Therefore, its integrity should be maintained for each degradation form and all detected degradation must be assessed to verify that if adequate integrity is retained. Determination of tube integrity limits includes identifying acceptable structural parameters such as flaw length, depth, and amplitude of signals. If we consider just single-cracked tubes, short and deep flaws are not likely to threaten structural integrity of tubes. But if it has multiple-cracks, we have to consider interaction effects of multiple adjacent cracks on its burst pressure. Because adjacent multiple cracks can be merged due to the crack growth then it can challenge against the structural performance limit. There are some studies on the interaction effects of adjacent cracks. However, existing works on the interaction effect consider only through-wall cracks. No study has been carried out on the interaction effects of part-through cracks. Most cracks existing in real steam generator tubing are not through-wall cracks but part-through cracks. Hence, integrity of part-through cracks is more practical issue than that of through-wall cracks. This paper presents experimental burst test results with steam generator tubing for evaluation of interaction effects with axial oriented two collinear and parallel part-through cracks. The interaction effect between two adjacent cracks disappeared when the distance exceeds about 2 mm.

Coalescence Pressure Evaluation of Multiple Through-Wall Cracks in Steam Generator Tube Using Elastic-Plastic Finite Element Analyses

2015 ◽  
Author(s):  
Jin-Won Hong ◽  
Jae-Boong Choi ◽  
Nam-Su Huh
Keyword(s):  
Finite Element ◽  
Steam Generator ◽  
Interaction Effect ◽  
Evaluation Model ◽  
Multiple Cracks ◽  
Crack Interaction ◽  
Collinear Cracks ◽  
Elastic Plastic ◽  
Parallel Cracks ◽  
Steam Generator Tubes

During an in-service inspection, if multiple cracks have been found in a nuclear component, the crack interaction effect due to adjacent cracks should be taken into account to characterize the detected multiple cracks into equivalent single combined crack or independent single crack. However, there must be many factors to be considered to quantify crack interaction effect, many experimental and numerical works should be made to propose robust guidelines on crack interaction effect depending on material characteristics of interest. Although many works have been made during the past few years to evaluate crack interaction effect of steam generator tubes with multiple cracks, the robust guidelines are still lacking. In this study, systematic 3-dimensional (3D) elastic-plastic finite element (FE) analyses are performed for steam generator tubes with multiple through-wall cracks. As for geometries of multiple through-wall cracks, four different cases are considered; axial collinear cracks, axial parallel cracks, circumferential collinear cracks, and circumferential parallel cracks. The geometric variables affecting the Pc (coalescence pressure), i.e. crack length and distance between multiple cracks, are systematically varied in the present study. Based on the coalescence pressure evaluation model proposed by authors in the previous study and the present FE results, the Pc of steam generator tubes with multiple cracks are investigated.

Green hotel adoption: a personal choice or social pressure?

2019 ◽  
Vol 31 (8) ◽  
pp. 3287-3305 ◽  
Author(s):  
M.S. Balaji ◽  
Yangyang Jiang ◽  
Subhash Jha
Keyword(s):  
Willingness To Pay ◽  
Social Norms ◽  
Interaction Effect ◽  
Least Squares Method ◽  
Positive Interaction ◽  
Intention To Stay ◽  
Content Type ◽  
Personal Norms ◽  
Green Hotel ◽  
Green Hotels

Purpose This study aims to examine the potential guest perception of green hotel attributes (GHAs) and the underlying mechanism through which GHA perception influences attitude toward green hotels, intention to stay at green hotels and willingness to pay a premium. It also investigates the moderating roles of personal norms and social norms in the influence of GHA perception on identification and trust toward green hotels. Design/methodology/approach A two-stage survey was used to collect data via Prolific Academic. The authors tested the hypotheses on 521 valid responses using the partial least squares method. Findings The results show that identification and trust mediate the effect of GHA perception on attitude, intention to stay and willingness to pay a premium for green hotels. The authors found a positive interaction effect between GHA perception and personal norms on identification and trust and a negative interaction effect between social norms and GHA perception on trust. The interaction effect of GHA perception and social norms on identification is not significant. Originality/value This study presents an integrated framework for green hotel adoption by examining the potential guest perception of GHAs and explores how it fosters positive guest responses. Findings show that GHA perception positively influences potential guest responses through identification (the personal route) and trust (the social route). This study also simultaneously considers personal norms and social norms, together with the effects of their interactions with GHA perception on identification and trust.

scholarly journals GENOTYPE-LOCATION INTERACTION OF INDICA RICE USING AMMI MODEL

2011 ◽  
Vol 24 (2) ◽  
pp. 09-18
Author(s):  
M. J. Hasan ◽  
M. U. Kulsum ◽  
M. S. Hossain ◽  
M. M. Billah ◽  
A Ansary
Keyword(s):  
Interaction Effect ◽  
Indica Rice ◽  
Average Yield ◽  
Phenotypic Stability ◽  
Positive Interaction ◽  
G X E Interaction ◽  
Main Effect ◽  
Days To Maturity ◽  
Ammi Model ◽  
Rice Genotypes

Phenotypic stability of 12 rice genotypes for plant height, days to maturity and yield were assessed at five different locations through regression and deviation from regression using Additive Main Effect and Multiplicative Interaction (AMMI) model. The result showed highly significant genotypic and G x E interaction. The G x E interaction influenced the relative ranking of the genotypes tested, BR1A/BR827R, Teea, BRRI dhan33 and Mayna showed low interaction effect with score nearest to zero with above average yield. While two genotypes BRRI hybrid dhan4 and Heera995 exhibited high positive interaction effect, gave mean grain yield around 5 ton/ha and was better suited to favorable environments. Similarly AMMI characterized the environments and identified Satkhira as a favorable environment for the better expression of the trait studied.DOI: http://dx.doi.org/10.3329/bjpbg.v24i2.17001

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