• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.261-262
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• 2008

Failure Mode Effects and Criticality Analysis (FMECA) evaluates criticality and severity of each failure mode. Generally, those indices are determined subjectively by experts and operators. However, this process has no choice but to include uncertainty. In this paper, a method for eliciting expert opinions considering its uncertainty is proposed to evaluate the criticality and severity. In addition, a fuzzy expert system is constructed to determine the crisp value of risk level for each failure mode. The results are worth considering while deciding the proper policies for each component of the system.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.173-176
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• 2006

The one of the commonly reported failure mode of the RC beam strengthened with FRP was caused by the separation of the concrete cover, so called delamination. Therefore, ACI440 recommended that concrete cover delamination can be prevented in strengthened beams if bond length of FRP composite be exteneded over a point of cracking moment. In this study, the failure mode and the flexural performance of RC beam with different bond length of FRP are estimated. Each bonded length is calculated based on the point of cracking moment with addition or subtraction of specific length(=150mm). The results of this study show that mid-span debonding occurs in the specimen strengthened with CFRP strips which are bonded over the point of cracking moment, while concrete cover deliamination occurs at the termination point of CFRP in the specimen with less bonded length than the point of cracking moment region.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.144-149
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• 2015

This study aims to quantitatively evaluate failure pressure of wall-thinned elbow under combined load along with internal pressure, by conducting real-scale burst test and finite element analysis together. For quantitative evaluation, failure pressure data was extracted from the real-scale burst test first, and then finite element analysis was carried out to compare with the test result. For the test, the wall-thinning defect of the extrados or intrados inside the center of 90-degree elbow was considered and the loading modes to open or close the specimen maintaining a certain load or displacement were applied. Internal pressure was applied until failure occurred. As a result, when the bending load was applied under the load control condition, the intrados of the defect was more affected by failure pressure than the extrados, and the opening mode was more vulnerable to failure pressure than the closing mode. When the bending load was applied under the displacement control, it was hardly affected by failure pressure though it was slightly different from the defect position. The result of the finite element analysis showed a similar aspect with the test. Moreover, when major factors such as material properties and pipeline thickness were calibrated to accurate values, the analytical results was more similar to the test results.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.1
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• pp.46-57
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• 2022

In this paper, we proposed the DFMEA Implementation Method for safety design of Weapon System. First, we presented the process for DFMEA. And then, the case analysis of OOO missile was performed in accordance with the process presented. After defining the system requirements of OOO missile, failure definition scoring criteria was set. In order to clarify the definition of failure, the failure was classified into safety, reliability, maintainability and others. After performing the function analysis, the relationship matrix analysis was performed to identify the failure mode according to the function without omission. After clarifying the failure classification, mode of failure, cause of failure and effect were analyzed to calculate the severity, occurrence and detection values. After the action priority was judged, the recommended action according to the failure classification was identified for the determined action priority. The results of this study can be used as a relevant basis for the design reflection and resource re-allocation of stakeholders.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.400-412
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• 2013

For the composite behavior of steel tube and inner concrete, the shear connectors should be applied to the CFT structures. However, the present design codes don't provide the design criteria that can be applied on shear connectors in the CFT structures typically filled with plain concrete. This study has been carried out to propose design criteria (shear strength and resistance factor) for the stud shear connectors in CFT structures. Experimental tests using the push-out specimens with the plain concrete blocks and finite element analysis were conducted for the purpose of verifying the main failure mode to propose the shear strength of studs in CFT structures. From the results of this study, the main failure mode of studs in CFT structures is splitting crack of concrete and this failure mode reduces shear strength of studs in CFT structures relatively to those embedded in RC blocks.

• The Journal of Advanced Prosthodontics
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• v.8 no.6
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• pp.489-493
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• 2016

PURPOSE. This in-vitro study aimed to evaluate the fracture resistances and failure modes of endodontically treated mandibular premolars restored with endocrowns and conventional post-core retained crowns. MATERIALS AND METHODS. Thirty mandibular premolars were assigned into three groups (n=10): GI, intact teeth; GE, teeth with endocrowns; GC, teeth with conventional post-core supported crowns. Except for the teeth in group GI, all specimens were cut to 1.5 mm above the cementoenamel junction and endodontically treated. Both endocrowns and conventional crowns were fabricated from lithium-disilicate blocks using a CEREC 3D CAD/CAM unit. All specimens were subjected to thermocycling and then to $45^{\circ}$ oblique compressive load until fracture occurred. The fracture resistance and failure mode of each specimen were recorded. Data were analyzed with one-way ANOVA and LSD Post Hoc Test (${\alpha}=.05$). RESULTS. The fracture resistances of GE and GC were significantly lower than that of GI (P<.01), while no significant difference was found between GE and GC (P=.702). As of the failure mode, most of the specimens in GE and GC were unfavorable while a higher occurrence of favorable failure mode was presented in GI. CONCLUSION. For the restoration of mandibular premolar, endocrown shows no advantage in fracture resistance when compared with the conventional method. Both of the two methods cannot rehabilitate endodontically treated teeth with the same fracture resistances that intact mandibular premolars have.

• Geomechanics and Engineering
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• v.36 no.5
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• pp.417-426
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• 2024

Shield tunneling method is widely used to build tunnels in complex geological environment. Stability control of tunnel face is the key to the safety of projects. To improve the excavation efficiency or perform equipment maintenance, the excavation chamber sometimes is not fully filled with support medium, which can reduce the load and increase tunneling speed while easily lead to ground collapse. Due to the high risk of the face failure under non-fully support mode, the tunnel face stability should be carefully evaluated. Whether compressive air is required for compensation and how much air pressure should be provided need to be determined accurately. Based on the upper bound theorem of limit analysis, a non-fully support rotational failure model is developed in this study. The failure mechanism of the model is verified by numerical simulation. It shows that increasing the density of supporting medium could significantly improve the stability of tunnel face while the increase of tunnel diameter would be unfavorable for the face stability. The critical support ratio is used to evaluate the face failure under the nonfully support mode, which could be an important index to determine whether the specific unsupported height could be allowed during shield tunneling. To avoid of face failure under the non-fully support mode, several charts are provided for the assessment of compressed air pressure, which could help engineers to determine the required air pressure for face stability.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.162-172
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• 2005

The objective of this research works is to investigate into characteristics of bending stiffness and failure for the ISB ultra-lightweight panel with internally structured material. The expanded metal with a crimped pyramid shape and woven metal are employed as an internally structured material. Through three-points bending test, the force-displacement curve and failure shape are obtained to examine the deformation pattern, characteristic data, such as maximum load, displacement at maximum load, etc, and failure pattern of the ISB panel. In addition, the influence of design parameters fur ISB panel on the specific stiffness, the specific stiffness per unit width, failure mode and failure map has been found. Finally, it has been shown that ISB containing expand metal with the crimped pyramidal shape is prefer to that containing woven metal from the view point of optimal design for ISB panel.

• Journal of Korean Society of Disaster and Security
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• v.7 no.1
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• pp.43-50
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• 2014

Based on the reliability theory, the risk assessment of steel beams is performed by the determination of failure probability. In the calculation, bending, shearing and combined (bending + shearing) modes are examined. The resistance and the loads on the beam are assumed to be normal distribution. To investigate the failure probability changes, total load applied at the mid span of beam is divided into 1 to 1 and 1 to 2 ratio and then these divided loads are placed on the trisected points on beam. The change of boundary conditions at beam ends are also included in the investigation. It shows that failure is governed by the combined mode for the present beams and the second order bound analysis of failure probability is not crucial. On the whole failure probability decreases with increasing end restraints at the beam ends with some exception.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.143-152
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• 2015

In the present study, the fiber and matrix failure of composite laminates under arbitrary biaxial stresses were evaluated based on separate mode criteria such as Hasnin and Puck theories. There is a limitation to predict the fiber-dominant and/or matrix-dominant failures under arbitrary stress states using limit criteria (maximum stress and maximum strain theories) and interactive criteria (Tsai-Hill and Tsai-Wu theories). There is little literature for failure analysis of ships and offshore composite structures considering advanced failure theories such as Hashin and Puck theories. Furthermore, there is not enough practical commercial finite element analysis (FEA) code which is basically adopted the separate mode criteria. Hence, in the present study, the user-defined subroutine of commercial FEA code ABAQUS for evaluation of fiber and matrix failures of composite structures was developed based on Hashin and Puck failure criteria. And then, the proposed subroutine was validated by comparing with a series of experimental results of carbon- and glass-implemented composite laminates to guarantee the reliability and usefulness of the developed method.