• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.857-860
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• 2006

In the present study, the method and procedure for analysis of impact damage behavior for concrete under penetration and perforation of projectile is investigated. Conservation law, equation of motion, initial and boundary conditions, and FEM formulation are introduced and derived respectively. Specially, the constitutive equation which rate-dependent damage combined with rate-dependent plasticity within the appropriate framework of theory of thermodynamics is examined. This paper aimed at the review with respect to impact damage models for concrete to develop that model. This paper is a basis research for the development of impact damage model for concrete.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.293-299
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• 2015

We analyzed the damage effect on Glass Fibre Reinforced Plastics(GFRP) under air flow by irradiation of continuous wave near-IR laser. Damage process and temporal temperature distribution were demonstrated and material characteristics were observed with laser intensity, surface flow speed and angle. Surface temperature on GFRP rapidly increased with laser intensity, and the damaged pattern was different with flow characteristics. In case of no flow, penetration on GFRP by burning and flame generation after laser irradiation was appeared at once. GFRP was penetrated by the heat generated from resin ignition. In case of laser irradiation under flow, a flame generated after burning extinguished at once by flow and penetration pattern on GFRP were differently shown with flow angle. From the results, we presented the damage process and its mechanism.

• Journal of the Korean Society of Costume
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• v.56 no.4 s.103
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• pp.124-133
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• 2006

Human hair could be damaged by various physicochemical conditions and treatment. Permanent and decoloring treatment were the most serious factor on hair damage. The new permanent wave lotion containing Permeation enhancers such as Cremophor EL, Transcutol and propylene glycol based on cysteine permanent wave lotion were prepared. Efficiency of permanent wave and hair damage following pH of permanent wave lotion and addition of permeation enhancer were investigated. PH of solution, wave efficiency, loss of protein from hair, morphology of hair by SEM and solubility of alkaline solution were evaluated. The addition of Cremophor EL and Transcutol with ethanol increased permanent wave efficacy and decreased hair damage effectively. They diminished permanent wave lotion's pH and augmented permanent wave lotion's penetration compare to cysteine permanent wave lotion. new permanent wave lotion containing permeation enhancers such as Cremophor EL could be a good candidate for a new permanent wave lotion.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.141-148
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• 2009

The purpose of this paper is to propose a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. Green roof system is considered to be an important subject in construction industry for green growth project. At the same time, we have to consider the counterplan for protection the damage of waterproofing layer and concrete substrate from the penetration of plant root. But many kinds of materials for protection from root penetration are using in construction field. But the performance of those materials is not clear, and there is not test methods for the evaluation of performance. So in this paper, based on the research results of 4 institutes during four years and foreign cases, we made a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. This test method deals with about environmental condition of laboratory, experimental facilities, kinds of plant, specimen of test, management methods, evaluation duration and documents, etc.

• Computers and Concrete
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• v.7 no.2
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• pp.103-118
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• 2010

Penetration of a fragment-like projectile into Fiber Reinforced Concrete (FRC) was simulated using finite element (FE) and particle formulations. Extreme deformations and failure of the material during the penetration event were modeled with multiple approaches to evaluate how well each represented the actual physics of the penetration process and compared to experimental data. A Fragment Simulating Projectile(FSP) normally impacting a flat, square plate of FRC was modeled using two target thicknesses to examine the different levels of damage. The thinner plate was perforated by the FSP, while the thicker plate captured the FSP and only allowed penetration part way through the thickness. Full three dimensional simulations were performed, so the capability was present for non-symmetric FRC behavior and possible projectile rotation in all directions. These calculations assessed the ability of the finite element and particle formulations to calculate penetration response while assessing criteria necessary to perform the computations. The numerical code EPIC contains the element and particle formulations, as well as the explicit methodology and constitutive models, needed to perform these simulations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.311-321
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• 2011

To analysis the effect of reinforcement ratio and impact velocity on local damage, a series of impact analyses are performed to predict local effects. According to these results, the reinforcement ratio has no effect on the penetration depth and perforation thickness, but notable change to the scabbing area were observed. The higher the missile velocity becomes, the greater the degree of local damage to the reinforced concrete slabs is. Analysis results will be useful in the impact-resistance design of containment buildings and structures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.329-331
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• 2013

The salt damage resistance of waterproofing membrane was evaluated on the cracked mortar substrate. The types of specimens are urethane, acrylic waterproofing membrane, and no coating mortar substrate. After these specimens were cured by water curing for 4 weeks, they were cured by atmospheric curing at 20±2Co for 8 weeks. The salt water immersion test was carried out by following KS F 2737, and the penetration depth of chloride ion into substrate was measured in 1, 4, 8, and 13 weeks. As a result, in the case of non coating specimen, the chloride ion penetrated within one week. In the coated specimens, a regardless of the membrane type, the chloride ion did not penetrate during 13 weeks-tests on condition that the cracked width of substrate is less than 0.3mm. Also, the penetration speeds of the coated specimens were lower than that of non coating specimen. Therefore, our results reached a conclusion that waterproofing membrane has high salt damage resistance.

• Geomechanics and Engineering
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• v.34 no.1
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• pp.103-113
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• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.467-472
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• 2000

It is known that chloride ion in concrete destroys the passive film of reinforcement inside concrete and accelerates corrosion which is the most influencing factor to durability of concrete structures. In this thesis, a chloride ion diffusion model for blast furnace slag(BFS) concrete, which has better resistance to both damage due to salt and chloride ion penetration than ordinary portland cement concrete, is proposed by modifying existing model of normal concrete. Proposed model is verified by comparing diffusion analysis results with both results by indoor chloride penetration test for specimens and field test results for actual RC bridge pier. Also, the optimum resistance condition to chloride penetration is obtained according to degrees of fineness and replacement ratios of BFS concrete. As a result, resistance to chloride ion penetration for BFS concrete is more affected by replacement ratio than degree of fineness.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.125-128
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• 2004

This study concerns the new estimated strength equation of concrete by penetration test. There are not only few estimate strength equations of concrete, but also many problems to apply them because of time, cost, easiness, structural damage, reliability and so on. In this study, there performed a series of penetration test with in 730days' concrete structures and proposed equations as follows; $$Linear\;:\;f_{ck}=2.95d-80.0(r^2= 69.8\%)$$ $$Quadratic\;:\;f_{ck}=0.204d^2-12.15d+193.2(r^2=83.6\%)$$ here, fck : Estimated compressive strength of concrete by MPa d: exposed probe length by mm.