• Title/Summary/Keyword: Test Bar

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Analysis of Notched Bar Tensile Tests for Inconel 617 at Room and Elevated Temperatures (Inconel 617 노치시편의 상온 및 고온 인장실험 해석)

  • Oh, Chang-Sik;Ma, Young-Wha;Yoon, Kee-Bong;Kim, Yun-Jae
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1818-1823
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    • 2007
  • In this paper, notched bar tensile tests of Inconel 617 were performed at room ($20^{\circ}C$) and elevated ($800^{\circ}C$) temperature. Finite element analyses are also performed. It is found that, at the room temperature, smooth bar tensile test results could be used to simulate notched bar tensile tests. However, at the elevated temperature, notched bar tensile test results can not be simulated from smooth bar tensile test results. Metallurgical examination reveals that strength weakening results from many cavities over the specimens for smooth bar test at the elevated temperature. "True" tensile properties at the elevated temperature is found using FE simulations. It also suggests that cautious should be taken to determine tensile properties of Inconel 617 at elevated temperatures using smooth bar tests.

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An Investigation into the effect of friction in the split hopkinson pressure bar (SHPB) test by numerical experiments (수치해석을 이용한 SHPB 시험의 마찰영향 분석)

  • Cha, Sung-Hoon;Shin, Myoung-Soo;Shin, Hyun-Ho;Kim, Jong-Bong
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.204-209
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    • 2008
  • The interest in the mechanical behavior of materials at high strain rates has increased in recent years, and by now it is well known that mechanical properties can be strongly influenced by the speed of applied load. The split Hopkinson pressure bar (SHPB) has been widely used to determine mechanical properties of materials at high loading rates. However, to ensure test reliability, measurement error source must be accounted for and eliminated. During experiment, the specimens were located between the incident and the transmit bar. The presence of contact frictions between the test bars and specimen may cause errors. In this work, numerical experiments were carried out to investigate the effect of friction on test results. In SHPB test, the measured stress by the transmitted bar is assumed to be flow stress of the test specimen. Through the numerical experiments, however, it is shown that the measured stress by the transmit bar is axial stress components. When, the contact surface is frictionless, the flow stress and the axial stress of the specimen are about the same. When the contact surface is not frictionless, however, the flow stress and the axial stress are not the same anymore. Therefore, the measured stress by the transmitted bar is not flow stress. The effect of friction on the difference between flow stress and axial stress is investigated.

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The Application of Glass Fiber Reinforced Plastic Bar to Concrete (유리섬유보강 플라스틱바의 콘크리트 적용성에 관한 연구)

  • 김경수;김재욱;문장수;배주성
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.04a
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    • pp.669-675
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    • 1997
  • This paper investigates the performances of GFRP bar and its possibility for using a substitute of steel bar. GFRO bar was made with introducing the glass fiber into GTR added UPE. We carried out the tensile test of GFRP and steel bar and out the three point bend test bond-test and fracture energy measurement on the GFRP bar and steel bar reinforced concrete. The GFRP bar was excellent as comparison with steel bar in the contribution to the energy absorption and the ductility of concrete. But its tensile, bond and bend strengthes were comparatively small. In order to improve these defects, we judged that glass fibers in GFRP bar must be completely adhesive one another by the impregnating glass fibers into UPE.

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New emerging surface treatment of GFRP Hybrid bar for stronger durability of concrete structures

  • Park, Cheolwoo;Park, Younghwan;Kim, Seungwon;Ju, Minkwan
    • Smart Structures and Systems
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    • v.17 no.4
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    • pp.593-610
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    • 2016
  • In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

Calibration of Acceleration Plant and Test Rig Design to Dynamic Fracture (동적 파괴에 대한 가속장치의 보정 및 시험장치 설계)

  • Cho, Jae-Ung;Han, Moon-Sik
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.3
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    • pp.47-52
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    • 2008
  • The force transducer in the acceleration plant due to dynamic fracture is calibrated by dynamically using the stress pulses from a longitudinal bar. The bar is supported by two strings attached to the ceiling. The bar velocities before and after impact are measured and a full bridge at bar and transducer is formed by the four strain gauges. A transient recorder is used to store the stress pulse signals of force transducer and bar. For the first test series, three point bend test specimens can be chosen by means of test rig design and the inspection as sample experiment in this presented paper is sufficient for proving with the numerical simulation of the specimen model.

Evaluation of Tension Behavior in FRP Hybrid Bar Affected by UV Exposure and Freezing/Thawing Tests (UV 폭로 및 동결융해 시험을 거친 FRP Hybrid Bar의 인장거동 평가)

  • Yoon, Yong-Sik;Park, Jae-Sung;Park, Ki-Tae;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.2
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    • pp.130-136
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    • 2017
  • The present work is for an evaluation of tension behavior and surface deterioration of FRP Hybrid Bar due to UV exposure and freezing/thawing(F/T) actions. For the work, FRP Hybrid Bar is subjected to UV exposure test, then F/T test is performed successively to 180 cycles. In FRP Hybrid Bar, no significant surface deterioration is evaluated after UV exposure. Tension hardening performance, a unique engineering advantage of FRP Hybrid Bar, is still maintained after F/T test. The performance in FRP Hybrid Bar exposed to UV is still effective. FRP Hybrid Bar exposed to UV have almost similar tension behavior of FRP Hybrid Bar without UV exposure. Although F/T cycles increase to 180, steel rebar, FRP Hybrid Bar, and FRP Hybrid Bar exposed to UV show no significant changes in tension behavior. In the work, UV exposure and F/T actions are evaluated to have little negative effect on surface deterioration and tensile performance in FRP Hybrid Bar, however spalling of silica coating due to impact should be considered since it affects bonding strength to outer concrete.

Evaluation of Bond Strength in FRP Hybrid Bar Affected by Freezing/thawing Test and UV Rays (동결융해 및 UV 폭로시험을 거친 FRP Hybrid Bar의 인발거동특성 평가)

  • Park, Jae-Sung;Yoon, Yong-Sik;Park, Ki-Tae;Kwon, Sung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.53-58
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    • 2017
  • FRP Hybrid Bar, composed of an embedded steel and the coated composites with epoxy and glass fiber, is an effective construction material with tension-hardening performance and lightweight. The epoxy exposed to UV(Ultra Violet Rays) and FT(Freezing and Thawing) action easily shows a surface deterioration, which can cause degradation of bonding strength between inside-steel and outside-concrete. In the present work, surface inspection for 3 different samples of normal steel, FRP Hybrid Bar before UV, and FRP Hybrid Bar after UV test was performed, then concrete samples with 3 reinforcement types were prepared for accelerated FT test. Through visual inspection on 3 typed reinforcement, no significant deterioration like chalking was evaluated. The results from FT test to 120 and 180 cycles showed FRP Hybrid Bar exposed to UV test has higher bonding strength than normal steel by 106.3% due to enlarged bond area by silica coating. The 3 cases showed a similar bond strength tendency with increasing FT cycles, however a relatively big deviations of bond strength were evaluated in FRP Hybrid Bar after UV test due to loss of silica coating.

A Study on the Relationship between Degree of Rust Condition and Bond Strength in Reinforced Concrete Members (철근의 부식정도와 부착강도에 대한 연구)

  • 유환구;이병덕;김국한;안태송
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04b
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    • pp.621-626
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    • 1998
  • An experimental investigation on the reinforcing bar corrosion and relationshid of reinforcing bar and concrete bond strength has been conducted to establish the allowable limit of rust in the construction field. The reinforcing bars used in this study were rusted before embedding in concrete. The first component of this experiment is to make rust of reinforcing bar rust artificially based on Faraday's theory at certain rates such as 2, 4, 6, 8 and 10% of reinforcing bar weight. For estimation of the amount of rust by weight, Clarke's solution and Shot blasting were adopted and compared. Parameters include 240 and 450kg/㎠ of compressive strengths and diameter of reinforcing bar (16, 19 and 25mm) corresponding development length for pull-ort test. And, pull-out tests were carried. out according to KSF 2441 and ASTMC 234 to investigate the effect of the corrosion rate on reinforcing bar-concrete bond behavior. It is found from the test results that the test techniques for corrosion of bar used in this study is relatively effective and correct test method. Results shows that up to 2% of rust increases the bond strength regardless of concrete strength and diameter of reinforcing bar like the existing data. It might be because of the roughness from rust. As expected, the bond strength increases as compressive strength of concrete increases and the diameter of bar decreases.

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Comparison of Alkali-Silica Reactivity for Mortar Bar and Concrete Prism Specimens Using Crushed Aggregates in Korea (국내 쇄석골재를 사용한 모르타르 봉 및 콘크리트 각주 시험편의 알칼리-실리카 반응성 비교)

  • Kim, Seong-Kwon;Yun, Kyong-Ku;Hur, In
    • International Journal of Highway Engineering
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    • v.14 no.5
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    • pp.93-99
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    • 2012
  • PURPOSES: The purpose of this study is to compare the alkali-silica reactivity for mortar bar and concrete prism specimens using crushed aggregates of 5 types in Korea. And the alkali-silica reactivity for those aggregates are measured by chemical test method. METHODS: The alkali-silica reactivity for those aggregates was measured by chemical test method of KS F 2545, mortar-bar test of KS F 2546, accelerated mortar-bar test method of ASTM C 1260 and concrete prism test method of ASTM C 1293, relatively. RESULTS: The alkali-silica reactivity for those aggregates was verified by chemical test of KS F 2546 and accelerated mortar-bar test of ASTM C 1260. However, it was not by mortar-bar test of KS F 2546 and concrete prism test of ASTM C 1293. CONCLUSIONS: The above results showed that relationship among the four test methods were very low. The results from 3 types of test methods using cement-aggregate combinations appeared to be different. Because the environmental conditions of test methods for measuring the alkali-silica reactivity such as equivalent alkali content(external source), humidity, temperature, and times were different though the aggregates were same. Moreover, alkali-silica reactivity showed the biggest impact when alkalis were supplied form outside and exposed to environmental conditions. The accelerated mortar-bar test method seems to be most appropriate test method for concrete structures exposed to alkali environment.

Pullout Test of Headed Reinforcing Bar in RC or SFRC Members with Side-Face Blowout Failure

  • Lee, Chang-Yong;Kim, Seung-Hun;Lee, Yong-Taeg
    • Architectural research
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    • v.22 no.1
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    • pp.33-39
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    • 2020
  • In this study, side-face blowout failure strength of high strength headed reinforcing bar, which is vertically anchoring between RC or SFRC members, is evaluated throughout pullout test. The major test parameters are content ratio of high strength steel fibers, strength of rebar, length of anchorage, presence of shear reinforcement, and the side concrete cover thickness planned to be 1.3 times of the rebar. In pullout test, tensile force was applied to the headed reinforcing bar with the hinged supports positioned 1.5 and 0.7 times the anchorage length on both sides of the headed reinforcing bar. As a result, the cone-shaped crack occurred where the headed reinforcing bar embedded and finally side-face blowout failure caused by bearing pressure of the headed reinforcing bar. The tensile strength of specimens increased by 13.0 ~26.2% with shear reinforcement. The pullout strength of the specimens increased by 3.6 ~15.4% according to steel fiber reinforcement. Increasing the anchoring length and shear reinforcement were evaluated to reduce the stress bearing ration of the total stress.