• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.458-466
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• 2020

The purpose of this experimental research is to evaluate the compressive and tensile behaviors of high performance hybrid fiber reinforced concrete(HPHFRC) using amorphous steel fiber(ASF) and polyamide fiber(PAF). For this purpose, the HPHFRCs using ASF and PAF were made according to their total volume fraction of 1.0% for target compressive strength of 40MPa and 60MPa, respectively. And then the compressive and tensile behaviors such as the compressive strength, compressive toughness, direct tensile strength, and stress-strain characteristics under compressive and tensile tests were estimated. It was observed from the test results that the compressive strength of HPHFRC was slightly decreased than that of plain concrete, but the compressive toughness, compressive toughness ratio, and direct tensile strength of HPHFRC increased significantly. Also, it was revealed that the plain concrete showed brittle fracture after the maximum stress from the stress-strain curves, but HPHFRC showed strain softening.

• Korean Journal of Materials Research
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• v.7 no.11
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• pp.1007-1011
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• 1997

영활화혁발전소 보일러헤다 재질인 1Cr0.5Mo강의 파형에 따른 저주기 피로특성을 규명하고자 상온(298K) 및 고온(177K)의 삼각파와 사인파형 저주기 피로시험을 수행하였고 소성에너지법을 이용하여 파형에 따른 소성변형에너지와 피로수명과의 +관계를 분석하였다. 저주기 피로시 재료내부의 소성변형에너지를 히스테리시스루프의 면적으로 계산하여 구하였으며 이를통해 저주기 피로수명을 예측하였고 Coffin-Manson법 및 변형률분할법을 이용한 저주기 피로수명 결과와 서로 잘 일치하였다. 또한 상온 및 고온에서 피로반복수의 증가와 함께 재료가 반봅연화됨을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1163-1169
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• 2012

Rubber, a hyperelastic material, is the main material used in tires. During the operation of a car, the tire receives various types of loads. The accumulation of strain energy due to such loads induces tire failure. Generally, because rubber materials used for tires have stress softening characteristics, unlike metals, test methods used for metals cannot be applied to rubber. Therefore, in this study, for the evaluation of the fatigue properties of two types of specimens that have different material components, a tensile test and a fatigue test according to the extended strain range dissimilar to ASTM D4482 are performed, and fatigue life equations are proposed based on the test results.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.41-50
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• 2007

The results from normally consolidated isotropic drained and undrained triaxial compression tests (NCIU and NCID) on sand with high silt content were presented in this paper. The experiments were performed on specimens of Nak-dong River sand with 63% silt content under effective confined pressures, 100 kPa to 400 kPa. From test results, Sandy silt became initially compressive but eventually appeared to provide dilatancy response throughout the entire stress-strain curve The behavior of sandy silt was more difficult to characterize than that of clay and sand due to lower plastic characteristic. Especially, the samples exhibited dilatancy development during shear after failure. The shear behavior and shear strength parameters of sandy silt can be determined as stress-strain behaviors are described by the Mohr-Coulomb failure criterion. The shear behaviors were observed increasing dilatancy volume change tendency with strain-softening tendency after failure. In this paper, the behavior of dilatancy depends on not only sand content but also fine content with low-cohesion during shear in the samples of sandy silt.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.151-161
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• 1994

FCAW has wide application in ship fabrication, maintenance and field erection. It has many advantages over SMAW.SAW and GMAW process. In many applications, the FCAW provides highquality weld metal. This method can reduce weld defects especially porosity and spatter. But the fatigue characteristics of those deposited metal have been rarely investigated. The purpose of this study is to investigate the cyclic stress-strain behavior and fatigue tests by the constant strain control were carried out on the rounded smooth specimen with deposited metal using the metal type flux cored wire. As the results of this study for the deposited metal welded by the metal type flux cored wire, the hardening or softening characteristics under cyclic load were investigated and cyclic stress-strain curve, strain-fatigue life curve, stress-strain function and fatigue life relation which are useful to estimate the fatigue life under the stress concentration condition were obtained.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.33-40
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• 2009

The use of the crumb rubber as an asphalt binder modifier may contribute to road maintenance and repair. The adhesion properties of the crumb rubber modified asphalt (CRMA) sealant have attracted interest due to brittle and adhesion failure of asphalt binders at low temperatures. In this study, the influence of a flexibilizer as a modifier for CRMA at low temperatures was investigated. Their properties were measured using the penetration, the softening point, the tensile and tensile adhesion tests at low temperature. The tensile adhesion strength and the strain of CRMAs were increased with increasing ductile deformation of the CR and the asphalt binder in the flexiblizer modified CRMAs. It was found that the flexibilizer concentration was an important factor for tensile and adhesion properties of CRMAs at low temperatures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.353-367
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• 2003

This paper describes the extension of the numerical model, which was developed to simulate the nonlinear behavior of reinforced concrete (RC) structures subjected to monotonic in plane shear and introduced in the companion paper, to simulate effectively the behavior of RE structures under cyclic loadings. While maintaining all the basic assumptions adopted in defining the constitutive relations of concrete under monotonic loadings, a hysteretic stress strain relation of concrete, which across the tension compression region, is defined. In addition, unlike previous simplified stress strain relations, curved unloading and reloading branches inferred from the stress strain relation of steel considering the Bauschinger effect we used. The modifications of the stress strain relation of steel are also introduced to reflect pinching effect depending on the shear span ratio and an average stress distribution in a cracked RC element. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Tunnel and Underground Space
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• v.8 no.3
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• pp.200-208
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• 1998

This research is intended to investigate the behavior of the jointed rock under various loading conditions: static or dynamic load. The distributed state concept (DSC) is based on the idea that the response of the joint can be related to and expressed as the response of the reference states : relative intact (RI) and fully adjusted (FA) states. In the DSC, an initially RI joint modifies continuously through a process of natural self-adjustment, and a part of it approaches the FA state at randomly disturbed locations in the joint areas. In this study, based on the DSC concept, RI state, FA state, and disturbance function (D) are defined for characterizing the behavior of rock joint. From the results of this research, it can be stated that DSC model is capable of capturing the physical behavior of jointed rock such as softening and hardening and considering the size of joint and roughness of joint surface.

• Geotechnical Engineering
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• v.13 no.4
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• pp.177-198
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• 1997

Since decomposed granite soil shows various characteristics of shear behavior dependent on initial conditions such as weathering degree and grain breakage, it is nacessary to invert ligate stress -strain relationship and changes of shear characteristics for different initial conditions. Associated with abovefnentioned view, direct shear tests, and triaxial compression tutsts(Ef, CD) were carried out in this study for undisturbed and disturbed compacted weathered granite samples obtained from 4 construction work sites with the various weathering degree and components of parent rocks. The deformation behavior of undisturbed samples under small confining stress shows hardening to softening, which is similar to that of over nsolidated clay whereas disturbed weathered granite soils do hardeningfonstant regardless of weathering degree, which is also similar to sedimentary clay. Conventional direct shear-tests for undisturbed samples show a tendency to overestimate cohesion. It is possidle to approximate stress ratio(q/p') and volumetric increment ratio(dv/ds) in the triaxital compression tests by an equation, ($dv/d\varepsilon,=\alpha(M-\eta))$ irrespective of moisture content, weathering degree and disturbance.

• Journal of the Korean Geotechnical Society
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• v.27 no.4
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• pp.51-65
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• 2011

Shear banding, the localization of deformation into thin zones, has a quite practical relevance, as stability and deformation characteristics of earth structures are controlled by the soil behavior within the shear band. In this study, for understanding occurrence and developed pattern of shear band, plane strain compression tests were performed on three soils with different particle-size distribution under various conditions. Digital images were captured during the experiments; then, deformation of a specimen was evaluated by digital image analysis technique. The characteristics of a shear band were evaluated from the state shortly after post-peak occurrence to critical state. Additionally, the statistical procedure was developed to determine the reasonable thickness of a shear band.