• Journal of the Korean Society for Heat Treatment
• /
• v.30 no.3
• /
• pp.117-126
• /
• 2017

The variation in microstructure and mechanical properties during heat treatment was examined in a series of 0.27% C-1.5% Mn-1.0% Cr steels with silicon contents in the range of 0 to 1.0 wt%. It was found that addition of 0.5%~1.0% silicon increased both tensile strength and impact toughness through solid solution strengthening and microstructural refinement. 0.27% C-1.0% Si-1.5% Mn-1.0% Cr steel showed tensile strength of 1,700 MPa in the as-quenched condition and the steel revealed a full martensitic structure even after air cooling from $900^{\circ}C$ to room temperature, showing air hardening characteristics. Tempering at $150^{\circ}C$ which corresponds to the typical paint-baking temperature after painting of body in white, slightly decreased the tensile strength and increased elongation, but substantially increased the impact toughness compared to the as-quenched steel.

• Journal of the Korean Society for Heat Treatment
• /
• v.6 no.2
• /
• pp.59-69
• /
• 1993

Bending fracture strength test and impact strength test were made for VC coated die steels treated by immersing in molten borax bath and for hardened steels which were quenched and tempered, in order to clarify the effect of VC coating at $1000^{\circ}C$. The material used in this investigation was representative cold and hot work die steels STD11, STD61. The results obtained are as follows. 1) The bending fracture strength of VC coated die steel (STD11, STD61) was lessened with increasing the thickness of the VC coated layer. 2) With increasing the immersing time (imcreasing the thickness of the VC coated layer) the maximum hardness was obtained at 480 minutes holding, after that holding time hardness was decreased. 3) The impact strength of the VC coated die steel was not decreased. In the casse of STD11, it was higher than that of the quenched condition especially at low tempering temperature, and vice versa at high tempering temperature. However in the case of STD61 shows the result to the contrary.

• Journal of the Society of Disaster Information
• /
• v.12 no.4
• /
• pp.373-380
• /
• 2016

In order to develop composite fiber panels that can maximize the protection and blast resistance of the existing structures by improving lightweight, high-strength and fireproof performances of the single layer material of precast panels, the basic properties of the inner and outer covers that are mixed with aramid fibers (AF) and polyester fibers (PF) were evaluated in this study. Also, a basic study was performed on the performance of composite fiber panels by testing Nano-sized composite materials that are lightweight and excellent in fire resistance for their compressive strength, bending strength and tensile strength.

• The Journal of Engineering Geology
• /
• v.34 no.1
• /
• pp.67-105
• /
• 2024

This study compares the quartzites of four quartzite units: The Fagfog Quartzite, Dunga Quartzite (member of the Robang Formation), Pandrang Quartzite (member of the Kalitar Formation) and the Chisapani Quartzite. The analysis shows variations in flakiness and elongation, as the Fagfog Quartzite displays low flakiness whereas the Pandrang and the Chisapani have moderate and the Dunga Quartzite has shown variations. The density values of the four quartzite units remain consistent, indicating uniform physical properties and porosity levels. However, bulk density values differ among the quartzites, suggesting variations in particle arrangement, porosity, and density. Regarding strength measures, the Pandrang and the Chisapani Quartzite have higher strength characteristics as compared to the Fagfog and the Dunga Quartzites. The Pandrang Quartzite has the highest average point load strength index, classifying it as "Extremely Strong". The resistance to impact and crushing forces varies among the quartzites, with lower Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) indicating higher strength and durability. Durability tests show that the Fagfog Quartzite has high durability against slaking, with a slight decrease observed after the fifth cycle. The Dunga Quartzite shows varying degrees of weathering, while the Pandrang and the Chisapani Quartzite have minimal weight changes, indicating strong resistance to weathering. Magnesium sulfate soundness tests indicate high durability and resistance to degradation for all four units. The Los Angeles abrasion value (LAAV) tests indicate favorable resistance to abrasion for the majority of the Fagfog, Dunga, and the Pandrang Quartzites samples, while Chisapani Quartzite shows more variability in LAAV values. The Pandrang Quartzite shows a higher proportion of elongated particles but lower flakiness index values as compared to Fagfog and Dunga Quartzites while Chisapani Quartzite stands out with a significantly higher presence of flaky particles and lower elongation index values. Mechanically, the Fagfog and Dunga Quartzite show higher strength and better resistance to abrasion and freeze and thaw. The Pandrang Quartzite shows moderate resistance to crushing and sudden effect, while the Chisapani Quartzite has variable resistance to effect. This comparative study emphasizes the diversity and complexity of quartzite rock types, showing the need for comprehensive characterization and assessment to determine their suitability for specific applications.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.4 no.2
• /
• pp.25-30
• /
• 2013

In this study a hybrid safety barrier system consisting of steel rail and carbon fiber reinforced polymer (CFRP) post is considered. W hile CFRP post is selected for impact energy reflection due to its high strength, steel rail is selected for impact energy absorption due to its high ductility. A numerical model considering the elastoplastic behavior of steel is formulated to simulate the dynamic responses of the hybrid system subject to an impact load. A hybrid roadside guard rail system of steel rail and CFRP post is proposed and analyzed with a case study. The numerical model for the hybrid roadside guard rail system is used to find optimized design of the proposed hybrid system.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.11a
• /
• pp.30-31
• /
• 2014

Since consists of regression equation by penetration depth prediction calculated by existing NDRC formula mainly considers properties of projectile, impact velocity, compressive strength as parameter, it is difficult to apply it to fire reinforced concrete. In this study, scabbing limit thickness was predict considering fiber reinforcement effect by local fracture of concrete was evaluated through high-velocity impact test. As a result of applying fracture reduction coefficient to NDRC, it was possible to predict scabbing limit thickness of fiber reinforced concrete similarly with actual measurement.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.2
• /
• pp.98-102
• /
• 2012

Increasing the fuel economy has been an inevitable issue for the development of new cars, and one of the important measures to improve the fuel economy is to decrease the vehicle weight. In order to obtain this goal, the researches about lighter, stronger and the well impact absorbing bumper impact beam have been studied without sacrificing bumper safety. In this study, the overall weight reduction possibility of rear bumper impact beam could be examined based on the variation of frontal, offset and corner impact crash capability by substituting a ultra high strength steel material (boron steel ) having tensile strength of 1.5 GPa grade instead of conventional steels. In addition, the section variations (open section, closed section, open section with 5 stays) of the bumper impact beam structure were examined carefully. It could be reached that this analysis could be well established and be contributed for design guide and the optimum design conditions of the automotive rear bumper impact beam development.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.220-225
• /
• 2007

The mechanical characteristics of AC4C Aluminum Casting Alloy were investigated by tensile test and impact test. Based on the tensile test' s result, we found that the yield strength of a high speed was about 10% higher than that of a low speed test and the maximum rupture strain mostly occurred in low speed tensile test. The impact energy of curved surface specimen was higher than that of plane surface specimen that can be measured in impact test.

• Journal of the Korean Society of Safety
• /
• v.10 no.4
• /
• pp.68-74
• /
• 1995

This paper analyzes the behaviors of the membrane under drop impact loadings using the acoustic emission technique. The analysis is useful for evaluating the strength of the membrane as well as for studying its damping characterisics due to the corrugation and the ring knot. The membrane for LNG storage tank is basically composed linear and circular elements. Two membrane specimens have approximately same drop impact mass and same drop speed. Locan 320 system with piezoelectric sensor is used in the experimental measurement. Experimental results for the membranes indicated that AE siganls having higher energies were generated with increasing drop impact loadings. It was confirmed that the ring knot. membrane has high absorption of drop impact loadings in comparison with the flat membrane. These results are very important to reliable design and to improve the safey of the membrane components.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.136-142
• /
• 2018

Additive manufacturing process technology, known as the 3D printing process, is expanding its utilization from simple model realization to commercialized part production based on continuous material development. Recently, research and development have been actively carried out to fabricate lightweight and high-strength parts using polymers, such as polyamide (polyamide), which is a high-strength engineering plastic material. In this study, the Izod impact characteristics were analyzed for polyamide 12 (PA12) materials. For the specimen production, selective laser sintering process technology, which has excellent mechanical properties of finished products, was applied. In addition, PA12 and glass bead reinforced PA12 materials were produced. The specimens were classified according to the production direction on the production platform, and each specimen was subjected to an Izod test at test temperatures of $-25^{\circ}C$, $25^{\circ}C$, and $60^{\circ}C$. As a result, the impact strength of PA12 and glass bead-reinforced PA12 of vertical direction specimens were 48.8% and 16.3% lower than those of the parallel specimens at a $25^{\circ}C$ test temperature and the impact strength of parallel specimens was improved by 46.5% and 20.4% at a test temperature of $60^{\circ}C$ compared to that at $-25^{\circ}C$.