• Journal of Chest Surgery
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• v.46 no.6
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• pp.391-401
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• 2013

Mechanical circulatory support (MCS) in the pediatric heart failure population has a limited history especially for infants, and neonates. It has been increasingly recognized that there is a rapidly expanding population of children diagnosed and living with heart failure. This expanding population has resulted in increasing numbers of children with medically resistant end-stage heart failure. The traditional therapy for these children has been heart transplantation. However, children with heart failure unlike adults do not have symptoms until they present with end-stage heart failure and therefore, cannot safely wait for transplantation. Many of these children were bridged to heart transplantation utilizing extracorporeal membranous oxygenation as a bridge to transplant which has yielded poor results. As such, industry, clinicians, and the government have refocused interest in developing increasing numbers of MCS options for children living with heart failure as a bridge to transplantation and as a chronic therapy. In this review, we discuss MCS options for short and long-term support that are currently available for infants and children with end-stage heart failure.

• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.20-28
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• 2005

In this paper, the methodology for the reliability estimation of buried pipeline with longitudinal gouges and dent is presented and the limit state of buried pipeline is formulated by failure assessment diagram(FAD). The reliability of buried pipeline with defects has been estimated by using a theory of failure probability. The failure probability is calculated by using the FORM(first order reliability method) and Monte Carlo simulation. The results out of two procedures have been compared each other. It is found that the FORM and Monte Carlo simulation give similar results for varying boundary conditions and various random variables. Furthermore, it is also recognized that the failure probability increases with increasing of dent depth, gouge depth, gouge length, operating pressure, pipe outside radius and decreasing the wall thickness. And it is found that the analysis by using the failure assessment diagram gives highly conservative results than those by using the theory of failure probability.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.846-854
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• 2024

FEMAXI-ATF is being developed for fuel performance modeling of SiC cladded UO2 fuel with focuses on modeling pellet-cladding mechanical interactions (PCMI). The code considers probability distributions of mechanical strengths of monolithic SiC (mSiC) and SiC fiber reinforced SiC matrix composite (SiC/SiC), while it models pseudo-ductility of SiC/SiC and propagation of cladding failures across the wall thickness direction in deterministic manner without explicitly modeling cracks based on finite element method in one-dimensional geometry. Some hypothetical BWR power ramp conditions were used to test sensitivities of different model parameters on the analyzed PCMI behavior. The results showed that propagation of the cladding failure could be modeled by appropriately reducing modulus of elasticities of the failed wall element, so that the mechanical load of the failed element could be re-distributed to other intact elements. The probability threshold for determination of the wall element failure did not have large influence on the predicted power at failure when the threshold was varied between 25 % and 75 %. The current study is still limited with respect to mechanistic modeling of SiC failure as it only models the propagation of the cladding wall element failure across the homogeneous continuum wall without considering generations and propagations of cracks.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2859-2874
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• 2024

This paper presents the finite element deformation and failure simulation of a typical Korean high-power reactor vessel under a severe accident characterized by large break loss of coolant (LBLOCA) with in-vessel retention of molten corium through external reactor vessel cooling (IVR-ERVC) conditions. Temperature distributions calculated using Modular Accident Analysis Program Version 5 (MAAP5) as thermal boundary conditions were used, and ABAQUS thermal and structural analyses were performed. After full ablation, the temperature of the inner surface in the thinnest section remained high (920 ℃), but the stress remained relatively low (less than 6 MPa). At the outer surface, the stress was as high as 250 MPa; however, the resulting plastic strain was small owing to the low temperature of 200 ℃. Variations in stress, inelastic strain, and temperature with time in the thinnest section suggest that the plastic and creep strains are saturated owing to stress relaxation, resulting in low cumulative damage. Thus, the lower head of the vessel can maintain its structural integrity under LBLOCA with IVR-ERVC conditions. The sensitivity analysis of internal pressure indicates the occurrence of failure in the thinnest section at an internal pressure >9.6 MPa via local necking followed by failure due to high stresses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.1017-1024
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• 2007

This study performed a series of burst tests at ambient temperature using real-scale elbow specimen containing a local wall-thinning defect at it's intrados or extrados and evaluated failure pressure of locally wall-thinned elbows. In the experiment, a 90-degree 100A, Sch. 80 standard elbow was employed, and various wall-thinning geometries, such as length, depth, and circumferential angle, were considered. From the results of experiment, the dependences of failure pressure of wall-thinned elbows on the defect geometries and locations were investigated. In addition, the reliability of existing models was examined by comparing the tests data with the results predicted from existing failure pressure evaluation models for locally wall-thinned elbow.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2096-2101
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• 1999

This paper presents the effect of shape of external corrosion in pipeline on failure prediction by using numerical simulation. The numerical study for the pipeline failure analysis is based on the FEM(Finite Element Method) with an elastic-plastic and large-deformation analysis. The predicted failure stress assessed for the simulated corrosion defects having different corroded shapes along the pipeline axis are compared with those by methods specified in ANSl/ASME B31G code and a modified B31G code.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.346-351
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• 1997

The pin bearing strength is one of the most important design parameters for mechanical joints composed of fiber reinforced composites. Thus the effect of the edge distance and the width of specimen on the pin-bearing strength of unidirectional CFRP composites were experimentally investigated in this paper. As results, the failure modes and the pin bearing strength of mechanical joints turned out to depend on the edge distance and also the width of specimen. The failure of specimen with low ratio of width to hole diameter was caused by the net tension from the hole boundary, on the other hand, the failure of specimen with low ratio of edge distance to hole diameter was caused by the shear-out. The bearing strength in case of the failure by shear-out was quite lower than that in case of failure by net tension.

• Structural Engineering and Mechanics
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• v.4 no.5
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• pp.485-496
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• 1996

This paper describes a numerical and experimental study on the stability and failure behaviour of rectangular symmetric laminated composite plates. The plates are simply supported along the unloaded edges and clamped along the loaded ends, and they are subjected to uniaxial in-plane compression. The finite element method was employed for the theoretical study. The study examines the effect of the plate's stacking sequence and aspect ratio on the stability and failure response of rectangular symmetric laminated carbon fibre reinforced plastics composite plates. The study also includes the effect of the unloaded edge support conditions on the postbuckling response and failure of the plates. Extensive experimental investigation were also carried out to supplement the finite element study. A comprehensive comparison between theory and experimental data are presented and discussed in this contribution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1181-1185
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• 1990

A failure evaluation diagram to evaluate fatigue fracture was developed. The relation between the fatigue limit and the threshold stress intensity factor for the short-cracked specimens of various materials including a piping carbon steel can be rationally predicted by the proposed method. It is shown that the coupled failure evaluation diagram for fatigue and ductile fracture is expecially useful for evaluation of the flaw tolerance as well as the margin of the safety of the pressure vessel and piping. Further, accumulation of fatigue data will be needed to construct an accurate fatigue failure evaluation diagram.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1871-1880
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• 2020

Round robin analyses for vessel failure probabilities due to PTS events are proposed for plant-specific analyses of all types of reactors developed in Korea. Four organizations, that are responsible for regulation, operation, research and design of the nuclear power plant in Korea, participated in the round robin analysis. The vessel failure probabilities from the probabilistic fracture mechanics analyses are calculated to assure the structural integrity of the reactor pressure vessel during transients that are expected to initiate PTS events. The failure probabilities due to various parameters are compared with each other. All results are obtained based on several assumptions about material properties, flaw distribution data, and transient data such as pressure, temperature, and heat transfer coefficient. The realistic input data can be used to obtain more realistic failure probabilities. The various results presented in this study will be helpful not only for benchmark calculations, result comparisons, and verification of PFM codes developed but also as a contribution to knowledge management for the future generation.