• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.712-719
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• 2012

Penetrator with enhanced lateral effect(PELE) is a newconcept projectile, without dynamite and fuze. It consists of high-density jacket, closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE, by AUTODYN-3D code, the calculation models of projectile body and bullet target are established and the process of penetrating aluminum-2024 alloy target of PELE is simulated, and the scattering characteristics after penetrating aluminum-2024 alloy target of PELE are studied by different initial velocity. The explicit finite element analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. As expansion of filling, the fragments were obtained velocities and dispersed laterally and further more enhancing the damage area largely. The number and shape of the PELE fragments were different depend on impact velocity and incidence angle of filling which fragment generated during penetration and lateral dispersion process.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.499-507
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• 2018

In this paper splitting failure on rock pillars among the underground caverns has been studied. The damaged structure is considered to be thin plates and then the failure mechanism of rock pillars has been studied consequently. The critical load of buckling failure of the rock plate has also been obtained. Furthermore, with a combination of the basic energy dissipation principle, generalized formulas in estimating the number of splitting cracks and in predicting the maximum deflection of thin plate have been proposed. The splitting criterion and the mechanical model proposed in this paper are finally verified with numerical calculations in FLAC 3D.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.3
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• pp.248-254
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• 2015

The strength and fatigue life of Satin and Twill-woven CF/epoxy composite(CFRP) have been investigated. Damage mechanism fatigue method has been used to assess fatigue damage accumulation. It is based on measured residual stiffness and residual strength of carbon-fiber reinforced plastic(CFRP) laminates under cyclic loading. Fatigue damage evolution in composite laminates and predict fatigue life of the laminates were simulated by finite element analysis(FEA) method. The stress analysis was carried out in MSC patran/Nastran. A modified Hashin's failure criterion di rmfjapplied to predict the failure of the experimental data of fatigue life but a Ye-delamination criterion was ignored because of 2D modeling. Almost linear stiffness and strength degradation were observed during most of the fatigue process. These stress distribution data were adopted in the simulation to simulate fatigue behavior and estimate life of the laminates. From the results, the predicted fatigue life is more conservatively estimated than the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.193-200
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• 2008

Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

• Journal of Applied Reliability
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• v.9 no.3
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• pp.259-274
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• 2009

Printed circuit boards for RAM are widely used in modern electronics such as computers, artificial satellites and consumer durables. They are exposed to a very diverse environment and consists of many complicated components and therefore needs careful approach to the enhancement and assessment of reliability of the item. In this article reliability standards for PCBs for RAM are established in terms of quality certification tests and failure rate tests.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.111-114
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• 1999

SFRC(Steel Fiber Reinforced Concrete) has advantage of crack resistance and ductility failure behavior. But the study which investigated about effect of steel fiber under bearing stress is not to be enough, and it does not be sure of criterion of SFRC for allowable bearing stress formula in internal specification. The purpose of this study is to clear the influence of SFRC on the bearing capacity and ductility of material through static loading test. additionally, arrive an allowable bearing stress formula for SFRC and examine mechanical behaviro by the 3-D finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.163-168
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• 2000

Once the chip has developed a mixed mode of side-curl and up-curl, it would generally curl to strike the tool flank. The development of the bending stresses and sheat in the chip would ultimately lead to chip failure. This paper approach this problem from a mechanics-based approach, by treating the chip as a 3-D elastic curved beam, and applying appropriate constraints and forces. The expressions for bending, shear and direct stresses are developed through an energy-based criterion. The location of the maximum stresses is also identified and explained for simulated test conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.730-734
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• 2000

Once the Chip has developed a mixed mode of side-curl and up-curl, it would generally curl to strike the too] flank. The development of the bending stresses and shear in the chip would ultimately lead to chip failure. This paper attacks this problem from a mechanics-based approach. by treating the chip as a 3-D elastic curved beam, and applying appropriate constraints and forces. The expressions for bending. shear and direct stresses are developed through an energy-based criterion. The location of the maximum stresses is also identified and explained for simulated test conditions.

• Structural Engineering and Mechanics
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• v.38 no.6
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• pp.803-823
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• 2011

In this paper, the three dimensional Parallel Realistic Failure Process Analysis ($RFPA^{3D}$-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1117-1124
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• 2008

In This paper, load-settlement curves that obtained from 11 sites were analyzed. At all tests, the load is applied until apparent failure is observed. The validity of the ultimate and yield load estimation method and load calculated from the settlement criterion was investigated through comparison with the measured data. The result indicated that B. Hansen 80% criterion and Stability Plot in ultimate loading decision law almost have been regared as same by comparing measured date and ultimate bearing capacity decided in depending yield loading decision law from 13% to 46% difference have taeyaeen came out when measured data and Davisson was compared, and S-log t from 5% to 41% log P-log S from 14% to 50% difference have been came out. When Settlement standard and measured data was compared difference had been came out about 3% in total settlement 0.1D criterion and from 12% to 35% difference had been came out in net settlement.