• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.2
• /
• pp.62-67
• /
• 2011

Launching tube is a kind of case to protect the guided weapons from external environments and conducted as a guide when they are fired. The guided weapons have been firmly kept at the launching tube and transferred, and would be separated at the required time when they are fired To meet the aim, it has been used explosive bolts which are reliable and efficient mechanical fastening devices having the special feature of a built-in release. The disadvantage of explosive bolt lies in that it is based on the high explosive effect of a pyrotechnic charge. When the explosive bolt is ignited, there are some bad effects; a flame, fragments and pyro-shock. Because of these bad effects there are many restriction to use bolt as joining devices to precision guided weapons. To solve these problems, the aim of the present work is to invent the ball-type separation bolt which is a pyrotechnically releasable mechanical linking device for two mechanical elements that does not suffer from such drawbacks. A standard pressure cartridge can moreover be easily integrated inside the device according to the present work and this with no modification to its structure. The present work was represented quantitatively the margin of separation safety and analysed separation mechanism in ball type separating bolt to perform the dynamic separation test.

• Analytical Science and Technology
• /
• v.23 no.5
• /
• pp.465-476
• /
• 2010

In this study, a number of volatile organic compounds (VOCs) including benzene, toluene, p-xylene, styrene, and methyl ethyl ketone were analyzed from samples collected in ambient air and under the field conditions. These samples were analyzed independently by two different set-ups for VOC analyses, i.e., between [1] gas chromatography/flame ionization detector with tube sampling - (F-T system) and [2] gas chromatography/mass spectrometer with bag sampling (M-B system). The analytical results derived by both systems showed fairly similar patterns in relative sense but with moderately large differences in absolute sense. The results of M-B system were high relative to F-T system with the F-T/M-B ratio below 1. If the relative biases of the two measurement techniques are derived in terms of percent difference (PD) in concentration values, the results were generally above 35% on average. A student t-test was applied to investigate the statistical significance of those differences between the systems. The results of both analytical systems were different at 95% confidence level for toluene, p-xylene, styrene, and methyl ethyl ketone (P < 0.043). However, F-T and M-B systems showed strong correlations for toluene and p-xylene. The observed bias is explained in large part by such factors as the differences in standard phases used for each system and the chemical loss inside the bag sampler.

• Fire Science and Engineering
• /
• v.24 no.3
• /
• pp.52-57
• /
• 2010

Fire protection countermeasure were considered on the straw thatched roof and wooden structure. For the fire resistant treatment, rice straw was soaked in the fire resistant liquid with different soaking time. After treatment, some rice straw sample was washed with water then the rice straws were tested to check the fire resistance performance. And the wood was soaked in the fire resistant liquid at an atmospheric pressure, vacuum-pressure condition and painted with brush on the surface. To analyse the fire resistant performance of rice straw, ignition delay time was measured under the radiant heat flux of cone heater. And the fire resistant performance of wood samples were tested with 45 degree fire resistant test apparatus and cone heater. Based on the cone heater test, the rice straw which most easily ignitable material shows the longer ignition delay time than not treated ones and even in the water washed straw show a longer ignition delay time than not treated ones. And fire resistant treated woods of vacuum-pressure treated sample showed the most excellent performance on fire resistance. And the fire resistant treated by brush and soaking showed a longer ignition delay time than not treated ones. From this experiment, it was found that a fire resistant treatment of rice straw and wood of the house can be protected from the fire spread.

• Fire Science and Engineering
• /
• v.33 no.4
• /
• pp.28-34
• /
• 2019

Regardless of the ignition source, the main factors affecting the spread of flames to the human body are combustibles. The sound absorption material, which is the finishing material used in music institutes and karaoke rooms, consists of polyurethane that generates a large amount of toxic gas with a high amount of combustion gases during a fire. Still, the current law does not require the use of impregnated finishing materials for tutoring services with less than 100 users. In this study, the rate of flame diffusion was measured using the MultiRaelite composite gas measuring instrument (target substance VOC, HCHO, SO₂, CO₂, CO, HCN, and NO₂) for the collection of sound-absorbing materials installed in the actual music academy. The results showed that the toxic gas found in this experiment exceeded the allowable concentration of TWA (Time Weighted Average) and STEL (Short Term Exposure Limit). In addition, a comparative combustion test of the general sound absorber and non-combustion sound absorbing materials on the market showed wide differences in ignition and diffusion. Therefore, based on the results of the experiment, private institutes with less than 100 users should be mandated to use non-combustion sound absorbing materials.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.1
• /
• pp.74-82
• /
• 2014

For this research, prepared ammonium dihydrogen phosphate aqueous solution and polyurethane dispersion. Use these resin, this article has been analyzed about change of mechanical properties by increasing amount of ammonium dihydrogen phosphate aqueous solution in polyurethan resin on coated leather and dried film. According to measure data for solvent resistance, DPU(polyurethane dispersion) resin and DPU-AD1, D2, D3(samples of polyurethaneresin with ammonium dihydrogen phosphate aqueous solution) had good property. As known in the results, increase of ammonium dihydrogen phosphate constant did not influence to big change of polyurethane resin properties. As test of tensile strength, DPU had highest tensile characteristic($3.114kg_f/mm^2$) and DPU-AD3 had lowest tensile characteristic($2.510kg_f/mm^2$). As same as tensile characteristic, abrasion test determined DPU(50.5 mg.loss) had highest properties. In elongation case, DPU had best properties(602 %) in this experiment.

• Fire Science and Engineering
• /
• v.28 no.5
• /
• pp.71-79
• /
• 2014

This study was performed to test the combustive properties of Medium Density Fibreboards (MDFs) treated with chemicals of the bis-(dimethylaminomethyl) phosphinic acid (DMDAP), N,N-dimethylethylenediaminomethyl-bis-phosphonic acid (DMDEDAP), piperazinomethyl-bis-phosphonic acid (PIPEABP), and methylpiperazinomethyl-bis-phosphonic acid (MPIPEABP). MDFs were painted in three times with 15 wt% solution of the bis-(dimethylaminomethyl) phosphinic acid and alkylenediaminoalkyl-bis-phosphonic acids at the room temperature, respectively. After drying MDF treated with chemicals, combustive properties and volatile organic compounds (VOCs) contents were examined by the cone calorimeter (ISO 5660-1), test for flame retardant (NEMA Notice No. 2012034), and gas chromatography (KS M ISO 11890-2), respectively. It was indicated that the MDFs treated with chemicals showed the longer time to combustion time (CT) = (442~492) s than that of virgin plate by reducing the burning rate except for CT treated with DMDAP. In adition, the MDFs treated with chemicals showed both of the higher char area (44.33~61.33) kg/kg and char length (10.33~11.67) cm than those of virgin plate. Especially, the MDFs treated with chemicals showed the higher mean volatile organic compounds (VOCs) (0.188~0.333) g/L than that of virgin plate within the prescribed limits. Thus, It is supposed that the combustion- retardation properties were improved by the partial due to the treated chemicals in the virgin MDF.

• Journal of the Society of Disaster Information
• /
• v.17 no.3
• /
• pp.617-626
• /
• 2021

Purpose: The purpose of this study is to evaluate the fire srpead risk of building exterior and roofing materials due to the firebrand of forest fire occurring in the urban areas. Method: In order to achieve this research purpose, by selecting building materials used for exterior and roofing materials of buildings, the time to ignition, total heat release, and heat release rate were investigated, and a forest fire firebrand system was established to the possibility of fire spread was confirmed. Result: As a result of the cone calorimeter test, the roofing material had a similar or faster ignition time due to radiant heat compared to the exterior material with the steel plate exposed to the outside, and showed a higher heat release rate and total heat release than the exterior material. Although it was affected by the flammable material, it was confirmed that it did not spread easily due to the limited amount of combustible material, and carbonization marks appeared inside. Conclusion: The cone calorimeter test method has been shown to be useful in understanding the combustion characteristics of building materials by radiant heat, but the fire spread due to a firebrand in a forest fire is directly affected by the flame due to the ignition of surrounding combustibles, so finding a direct correlation with the cone calorimeter method is difficult. It is judged that the roof material may be more vulnerable to the spread of fire due to the fire than the exterior material.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.1
• /
• pp.1-8
• /
• 2023

At construction sites, interest in the production of precast materials is increasing due to off-site conditions due to changes in construction site conditions due to increased labor costs and the Act on the Punishment of Serious Accidents. In particular, the precast prestressed hollow slab has a hollow shape in the cross section, so structural performance is secured by reducing weight and controlling deflection through stranded wires. With the application of structural standards, the urgency of securing fire resistance performance is emerging. In this study, a fire-resistance cross section was developed by reducing the concrete filling rate in the cross section and improving the upper and lower flange shapes by optimizing the hollow shape in the cross section of the slab to have the same or better structural performance and economic efficiency compared to the existing hollow slab. The PC hollow slab to which this was applied was subjected to a two-hour fire resistance test using the cross-sectional thickness as a variable, and as a result of the test, fire resistance performance (load bearing capacity, heat shielding property, flame retardance property) was secured. Based on the experimental results, it is determined that fire resistance modeling can be established through numerical analysis simulation, and prediction of fire resistance analysis is possible according to the change of the cross-sectional shape in the future.

• Elastomers and Composites
• /
• v.46 no.2
• /
• pp.164-170
• /
• 2011

In this study, silicone rubber filled with environmentally-friendly perlite was prepared by mechanical mixing in order to improve thermal properties, such as heat and fire resistances. We found that the properties of silicone rubber composites depended on perlite concentration by various characterization methods. Thermogravimetric analysis(TGA) indicated that the initial degradation temperature of silicone/perlite composite was higher than that of pristine silicone rubber. The gas torch test showed that the opposite side temperature of composite materials was remarkably low as compared to that of pristine silicone rubber. In addition, the composites containing 5 wt% and 10 wt% of perlite showed remarkable thermal stability at elevated temperatures according to the results of both fireproof furnace tests under the RABT condition and carbonization furnace tests. The images from a scanning electron microscope(SEM) showed the degree of dispersion of perlite in silicone rubber. Finally, it was confirmed that limited oxygen index(LOI) was increased with perlite concentration.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.5
• /
• pp.9-15
• /
• 2010

Recently, the high-compressive strength concrete where the use is extending was weak in fire because of spalling that was occurring with rise of internal vapor pressure by high temperature. For preventing spalling of high-strength concrete in fire, Organic fibers have been using in concrete generally. By melting of organic fibers in concrete in fire, the internal moistures of concrete moves quickly to the outside, and so, preventing of spalling of high-strength concrete. But this method will be able to prevent the spalling of high-strength concrete, but makes the decrease of the concrete strength after fire. This study make a comparison between properties of preventing of spalling and remaining compressive strength of concrete using intumescence Alkali-Silicates fire-resistant material and that of concrete with organic fibers. Using organic fibers for preventing of spalling of concrete are P.P and Nylon fibers, and anti-fire intumescence material for protection of concrete surface is alkali-silicate materials. Fire resistance test executed as long as 3 hr under the flame temperature $1,200^{\circ}C$ over. In the case of concrete with P.P fibers, don't occurred the spalling, but the remaining compressive strength will not be able to measure, the concrete using intumescence Alkali-Silicates system fire-resistant material is not only preventing of the spalling but also the remaining compressive strength maintained until the maximum 96%.