• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.347-355
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• 2003

Roughening of metal surfaces frequently enhances the adhesion strength of metals to polymers by mechanical interlocking. When a failure occurs at a roughened metal/polymer interface, the failure prone to be cohesive. In a previous work, an adhesion study on a roughened metal (oxidized copper-based leadframe)/polymer (Epoxy Molding Compound, EMC) interface was carried out, and the correlation between adhesion strength and failure path was investigated. In the present work, an attempt to interpret the failure path was made under the assumption that microvoids are formed in the EMC as well as near the roots of the CuO needles during compression-molding process. A simple adhesion model developed from the theory of fiber reinforcement of composite materials was introduced to explain the adhesion behavior of the oxidized copper-based leadframe/EMC interface and failure path. It is believed that this adhesion model can be used to explain the adhesion behavior of other similarly roughened metal/polymer interfaces.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.199-208
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• 2005

In the calendar and the advertising catalog, the surface Is usually coated by coating polypropylene film. The delamination failure of coating film depends on surface roughness and quality of the substrate paper. In this paper, the mechanisms of delamination failure between the coating film and the paper is investigated by using the root cause analysis as one of techniques of reliability evaluation. The papers used in failure analysis are three kind products made by two domestic and one foreign companies. It found that the main causes of delamination failure between the coating film and the paper were the creation of microvoids caused by shape of filler and their growth caused by contraction of paper.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.233-238
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• 2002

This study presents failure mechanisms for the pull-out strength of headed reinforcement for upper bound solution based on the limit theorem. The failure mechanisms to be presented follow the failure surface pattern of punching shear failure found in the joints of slab with a column. Several failure surfaces of the mechanisms have different characteristics for dissipation works and these mechanisms are able to interpret the role of bar details surrounding headed reinforcement.

• Computers and Concrete
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• v.3 no.1
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• pp.1-15
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• 2006

The seismic safety of reinforced concrete containment building can be evaluated by probabilistic analysis considering randomness of earthquake, which is more rational than deterministic analysis. In the safety assessment of earthquake-resistant structures by the deterministic theory, it is not easy to consider the effects of random variables but the reliability theory and random vibration theory are useful to assess the seismic safety with considering random effects. The reliability assessment of reinforced concrete containment building subjected to earthquake load includes the structural analysis considering random variables such as load, resistance and analysis method, the definition of limit states and the reliability analysis. The reliability analysis procedure requires much time and labor and also needs to get the high confidence in results. In this study, random vibration analysis of containment building is performed with random variables as earthquake load, concrete compressive strength, modal damping ratio. The seismic responses of critical elements of structure are approximated at the most probable failure point by the response surface method. The response surface method helps to figure out the quantitative characteristics of structural response variability. And the limit state is defined as the failure surface of concrete under multi-axial stress, finally the limit state probability of failure can be obtained simply by first-order second moment method. The reliability analysis for the multiaxial strength limit state and the uniaxial strength limit state is performed and the results are compared with each other. This study concludes that the multiaxial failure criterion is a likely limit state to predict concrete failure strength under combined state of stresses and the reliability analysis results are compatible with the fact that the maximum compressive strength of concrete under biaxial compression state increases.

• Proceedings of the Korean Geotechical Society Conference
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• 1988.06c
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• pp.3-67
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• 1988

Model studies on the response of homgeneous earth embankment dams subjected to strike-slip fault movement have been penomed via centrifuge and finite element analysis. The centrifuge model tests have shown that crack development in earth embankment experiences two major patters: shear failure deep inside the embankment and tension failure near the surface. The shear rupture zone develops from the base level and propagates upward continuously in the transverse direction but allows no open leakage chnnel. The open tensile cracks develop near the surface of the embankment, but they disappear deep in the embankment. The functional relationship has been developed based on the results of the centrifuge model tests incorporating tile variables of amount of fault movement, embankment geometry, and crack propagation extent in earth des. This set of information can be used as a guide line to evaluate a "transient" safety of the duaged embankment subjected to strike-slip fault movement. The finite element analysis has supplemented the additional expluations on crack development behavior identified from the results of the centrifuge model tests. The bounding surface time-independent plasticity soil model was employed in the numerical analysis. Due to the assumption of continuum in the current version of the 3-D FEM code, the prediction of the soil structure response beyond the failure condition was not quantitatively accurate. However, the fundamental mechanism of crack development was qualitatively evaluated based on the stress analysis for the deformed soil elements of the damaged earth embankment. The tensile failure zone is identified when the minor principal stress of the deformed soil elements less than zero. The shear failure zone is identified when the stress state of the deformed soil elements is at the point where the critical state line intersects the bounding surface.g surface.

• Journal of the Korean Geotechnical Society
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• v.36 no.4
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• pp.5-15
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• 2020

This paper proposes a revised Modified Cam Clay type failure surface based on the critical state theory. In the plane of the mean effective and von Mises stresses, the original Modified Cam Clay model has an elliptic failure surface which leads the critical-state mean effective stress to be always half of the pre-consolidation mean effective stress without hardening and evolution rules. This feature does not agree with the real mechanical response of clay. In this study, the preconsolidation mean effective stress only reflects the consolidation history of the clay whereas the critical state mean effective stress only relies on the currenct void ratio of clay. Therefore, the proposed failure surface has a distorted elliptic shape without any fixed ratio between the preconsolidation and critical state mean effective stresses. Numerical simulations for various clays using failure surfaces as yield surface provide mechanical responses similar to the experimental data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.1-10
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• 2013

Probabilistic nonlinear first ply failure loads of flat composite panels and nonlinear buckling loads of curved composite panels with cutouts are estimated to provide the more reliable main load carrying structure in the renewable energy industry and offshore structures. The response surface method approximates limit state surface to a second order polynomial form of random variables with the results of deterministic finite element analyses at given sampling design points. Furthermore, the iterative linear interpolation scheme is used to obtain a more accurate approximation of the limit state surface near the most probable failure point (MPFP). The advanced first order second moment method and the Monte Carlo method are performed on an approximated limit state surface to evaluate the probability of failure. Finally, the sensitivity of the reliability index with respect to transformed random variables is investigated to figure out the main random variables that have an effect on failures.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.95-102
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• 2021

Analysis of the fracture surface is one of the most important methods for determining the cause of equipment structural failure. Whether structural failure is caused by impact or fatigue is necessary information in industrial fields. For ferrous and non-ferrous metal materials, two fracture phenomena are generated on the fracture surface: ductile and brittle fractures. In this study, machine learning predicts whether the fracture is based on ductile or brittle when structurural failure is caused by impact. The K-means algorithm calculates this ratio by clustering the brittle and ductile fracture data from a photograph of the impact fracture surface, unlike the existing method, which calculates the fracture surface ratio by comparison with the grid type or the reference fracture surface shape.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.196-202
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• 1998

Because the journal and bearing surface are fully separated by the oil film during the normal operation, fluid film bearings operating in the hydrodynamic lubrication region are expected to have an infinite life. However, there are many parameters that lead to interfere with the normal operation of the bearing and lead to its failure. In this paper, both the causes and countermeasures of the bearing failure are described. Also, the characteristics of wiped bearing surface are investigated through mechanical and chemical test.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.8-13
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• 2010

The shaft surface machining is a popular machine for studying descale machine design and process in automobile industry. In this study, the descale design machine of cutting shaft surface was conducted for the detection of a tool failure in surface process. Induction harden surface is used as analyzing function to detect a sudden change in cutting process level. A preliminary stepped workpiece which had a hard condition was cut by the surface tool and a tool process obtained cutting force machine. At machine failure, the results were suddenly increased and the detailed surfaces were extremely obtained.