• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1575-1588
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• 2019

Fracture near the U-10Mo/cladding material interface impacts fuel service life. In this work, a mesoscale stress model is developed with the fuel foil considered as a porous medium having gas bubbles and bearing bubble pressure and surface tension. The models for the evolution of bubble volume fraction, size and internal pressure are also obtained. For a U-10Mo/Al monolithic fuel plate under location-dependent irradiation, the finite element simulation of the thermo-mechanical coupling behavior is implemented to obtain the bubble distribution and evolution behavior together with their effects on the mesoscale stresses. The numerical simulation results indicate that higher macroscale tensile stresses appear close to the locations with the maximum increments of fuel foil thickness, which is intensively related to irradiation creep deformations. The maximum mesoscale tensile stress is more than 2 times of the macroscale one on the irradiation time of 98 days, which results from the contributions of considerable volume fraction and internal pressure of bubbles. This study lays a foundation for the fracture mechanism analysis and development of a fracture criterion for U-10Mo monolithic fuels.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4647-4658
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• 2023

In this paper, elastic-plastic fracture mechanics analysis is performed to determine the critical crack sizes of the multipurpose canister (MPC) manufactured using austenitic stainless steel under dynamic loading conditions that simulate drop accidents. Firstly, dynamic finite element (FE) analysis is performed using Abaqus v.2018 with the KORAD (Korea Radioactive Waste Agency)-21 model under two drop accident conditions. Through the FE analysis, critical locations and through-thickness stress distributions in the MPC are identified, where the maximum plastic strain occurs during impact loadings. Then, the evaluation using the failure assessment diagram (FAD) is performed by postulating an external surface crack at the critical location to determine the critical crack depth. It is found that, for the drop cases considered in this paper, the principal failure mechanism for the circumferential surface crack is found to be the plastic collapse due to dominant high bending axial stress in the thickness. For axial cracks, the plastic collapse is also the dominant failure mechanism due to high membrane hoop stress, followed by the ductile tearing analysis. When incorporating the strain rate effect on yield strength and fracture toughness, the critical crack depth increases from 10 to 20%.

• Journal of Chest Surgery
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• 제45권4호
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• pp.246-250
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• 2012

Background: Although it is rare for the fracture itself to become a life threatening injury in patients suffering from rib fracture, the lives of these patients are occasionally threatened by other associated injuries. Especially, early discovery of patients with rib fracture and intra-abdominal organ injury is extremely important to the prognosis. This study analyzed the link between rib fracture and intra-abdominal injury to achieve improved treatment. Materials and Methods: Among trauma patients that had visited the hospital emergency room from January 2007 to December 2009, a retrospective study was conducted on 453 patients suffering from rib fracture due to blunt trauma. Rib fracture was classified according to location (left, right, and bilateral), and according to level (upper rib fracture [1-2nd rib], middle rib fracture [3-8th rib], and lower rib fracture [9-12th rib]). The researched data was statistically compared and analyzed to investigate the correlation between the location, level, and number of rib fracture and intra-abdominal organ injury. Results: Motor vehicle injury was found to be the most common mechanism of injury with 208 cases (46%). Associated injuries accompanied with rib fracture were generated in 276 cases (61%). Intra-abdominal organ injury was discovered in 97 cases (21%). Liver injury was the most common intra-abdominal injury associated with rib fracture with 39 cases (40%), followed by spleen injury, with 23 cases (23%). Intra-abdominal injury according to level of rib fracture was presented as upper rib fracture in 11 cases (11%), middle rib fracture in 31 cases (32%), and lower rib fracture in 55 cases (57%), thus verifying that intra-abdominal injuries were commonly accompanied in lower rib fractures (p=0.03). In particular, significant increase of intra-abdominal injury was presented in fractures below the 8th rib (p=0.03). The number of intra-abdominal injuries requiring emergency operations was significantly higher in patients with more than 6 rib fractures (p=0.04). Conclusion: Intra-abdominal organ injury is more common in patients with lower rib fracture, especially fractures below the 8th rib. Intra-abdominal organ injuries generated in multiple rib fracture patients with more than 6 fractures significantly higher severity. These cases must be thoroughly inspected and carefully observed as there is possibility of emergency operation.

• Carbon letters
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• 제15권2호
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• pp.125-128
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• 2014

In this study, the effect of stacking sequence on the flexural and fracture properties of carbon/basalt/epoxy hybrid composites was investigated. Two types of carbon/basalt/epoxy hybrid composites with a sandwich form were fabricated: basalt skin-carbon core (BSCC) composites and carbon skin-basalt core (CSBC) composites. Fracture tests were conducted and the fracture surfaces of the carbon/basalt/epoxy hybrid composites were then examined using scanning electron microscopy (SEM). The results showed that the flexural strength and flexural modulus of the CSBC specimen respectively were ~32% and ~245% greater than those of the BSCC specimen. However, the interlaminar fracture toughness of the CSBC specimen was ~10% smaller than that of the BSCC specimen. SEM results on the fracture surface showed that matrix cracking is a dominant fracture mechanism for the CSBC specimen while interfacial debonding between fibers and epoxy resin is a dominant fracture process for the BSCC specimen.

• 대한기계학회논문집
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• 제17권11호
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• pp.2752-2761
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• 1993

The purpose of this study is to confirm the decreasing problems of residual bending strength, and the fracture machanism experimentally when CFRP composite laminates are subjected to Foreign Object Damage. Composite laminates used for this experiment are CFRP orthotropy laminated plates, which have two-interfaces [O/sub 6//sup o//90/sub 6//sup o/]sub sym/ and four-interfaces [O/sub 3//sup o//90/sub 6//sup o//O/sub 3//sup o]/sub sym/. When the specimen is subjected to transverse impact by a steel ball, the delamination area generated by impact damage is observed by using SAM(Scanning Acoustic Microscope). also, Thefracture surfaces obtained by three-point bending test were observed by using SEM (Scanning Electron Microscope). Then, fracture mechanism was investigated based on the observed delamination area and fracture surface. The results were summarized as follows; (1) It is found that for the specimen with more interface, the critical delamination energy is increased while delamination-development energy is decreased. (2) Residual bending strength of specimen A is greater than that of Specimen B within the impact range of impact energy 1. 65J (impacted-side compression) and 1. 45J (impacted-side tension). On the other hand, when the impact energy is beyond the above ranges, residual bending strength of specimen A is smaller than that of specimen B. (3) In specimen A and B, residual strength of CFRP plates subjected to impact damage is lower in the impacted-side compression than in the impacted-side tension. (4) In the case of impacted-side compression, fracture is propagated from the transverse crack generat-ed near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension.

• Structural Engineering and Mechanics
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• 제81권1호
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• pp.81-91
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• 2022

The effects of interaction between concrete-gypsum interface and edge crack on the failure behavior of the specimens in senicircular bend (SCB) test were studied in the laboratory and also simulated numerically using the discrete element method. Some quarter circular specimens of gypsum and concrete with 5 cm radii and hieghts were separately prepared. Then the semicircular testing specimens were made by attaching one gypsum and one concrete sample to one another using a special glue and one edge crack is produced (in the interface) by do not using the glue in that part of the interface. The tensile strengths of concrete and gypsum samples were separately measured as 2.2 MPa and 1.3 MPa, respectively. during all testing performances a constant loading rate of 0.005 mm/s were stablished. The proposed testing method showed that the mechanism of failure and fracture in the brittle materials were mostly governed by the dimensions and number of discontinuities. The fracture toughnesses of the SCB samples were related to the fracture patterns during the failure processes of these specimens. The tensile behaviour of edge notch was related to the number of induced tensile cracks which were increased by decreasing the joint length. The fracture toughness of samples was constant by increasing the joint length. The failure process and fracture pattern in the notched semi-circular bending specimens were similar for both methods used in this study (i.e., the laboratory tests and the simulation procedure using the particle flow code (PFC2D)).

• Composites Research
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• 제17권4호
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• pp.53-60
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• 2004

본 연구에서는 1차원 파동방정식을 적용한 낙추충격시험 시스템을 제작하여 CFRP 적층판의 충격흡수특성 및 충격 강도평가를 하였으며 그 결과가 유효함을 보였다. 충격흡수에너지에 대해서는 충격에너지가 대략 6.8J이상에서는 동일한 T300 섬유와 적층배향으로 구성된 직교이방성 시험편이 의사등방성(quasi-isotropic)보다 높게 나타났으나 T700 섬유의 경우에는 크게 차이가 나타나지 않았다. 또한 동일한 T300 섬유와 적층수로 구성된 시험편이 T700섬유로 된 시험편보다 높게 나타났으나 T700 섬유의 의사등방성 시험편의 경우에는 크게 차이가 나타나지 않았다. 초음파 C-스캐너를 이용하여 내부손상영역을 관찰하여 시험편의 손상면적과 흡수에너지의 상관관계를 평가하였다. 또한 저속충격손상으로 인한 파면을 파괴메카니즘을 규명하기 위해 주사전자현미경으로 관찰하였다.

• 척추신경추나의학회지
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• 제10권2호
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• pp.51-60
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• 2015

Objectives: The purpose of this study is to investigate the safety, injury mechanism, complication and adverse reactions associated with Chuna manual theraphy(CMT), to report one case of adverse reaction with Thai Massage(TM). Methods: A 76-year-old woman presented with chest pain and dorsalgia. The patient undertook a TM. The patient's chest pain didn't improve by Korean medecine. In MRI study, sternal fracture was diagnosed. Results and Conclusions : It is supposed that this patient suffered chest pain and dorsalgia due to a TM. From this case, we can understand the etiology of sternal fracture to some extent and consider the complication of Chuna manual theraphy through TM. In addition, This study raises the awareness of the possibility of a sternal fracture caused by a low-energy CMT technique.

• 한국정밀공학회지
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• 제19권2호
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• pp.65-71
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• 2002

Turbine blade is subject to cyclic bending force by steam pressure. Stress analysis by fractography is already established technology as means far seeking cause of fracture and has been widely employed. In the X-ray frctography, plastic deformation and residual stress near the fracture surface can be determined and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear power plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined and then the stress intensity factor to actual broken turbine blade was predicted.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.279-284
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• 1994

Fracture mechanics does work for concrete, provided that one used a proper, nonlinear form of fracture mechanics in which a finite nonlinear zone at fracture front is being considered. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to the toughness induced by the microcracking, so that the bridging is the dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrck with stresses transmitted by aggregates in concrete, is modelled by a Dugdale-Barenblatt type model with lenear tension-softening curve for the analyses of crack growth in concrete Finite element technique is shown for inplementation of the model.