• 한국방재학회 논문집
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• 제8권2호
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• pp.97-103
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• 2008

Determination of stress-strain relationship in torsional tests is complicated due to nonuniform stress-strain variation occurring linearly with the radius in a soil specimen in torsion. The equivalent radius approach is adequate when calculating strain at low to intermediate strains, however, the approach is less accurate when performing the test at higher strain levels. The modified equivalent radius approach was developed to account for the problem more precisely. This approach was extended to generate the plots of equivalent radius ratio versus strain using modified hyperbolic and Ramberg-Osgood models. Results showed the effects of soil nonlinearity on the equivalent radius ratio curves were observed. Curve fitting was also performed to find the stress-strain relationship by fitting the theoretical torque-rotation relationship to measured torque-rotation relationship.

• Geomechanics and Engineering
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• 제6권3호
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• pp.277-292
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• 2014

Soil nailing, as an effective stabilizing method for slopes and excavations, has been widely used worldwide. However, the interaction mechanism of a soil nail and the surrounding soil and its influential factors are not well understood. A pullout model using a hyperbolic shear stress-shear strain relationship is proposed to describe the load-deformation behavior of a cement grouted soil nail. Numerical analysis has been conducted to solve the governing equation and the distribution of tensile force along the nail length is investigated through a parametric study. The simulation results are highly consistent with laboratory soil nail pullout test results in the literature, indicating that the proposed model is efficient and accurate. Furthermore, the effects of key parameters, including normal stress, degree of saturation of soil, and surface roughness of soil nail, on the model parameters are studied in detail.

• 한국지반공학회지:지반
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• 제2권1호
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• pp.15-26
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• 1986

포화된 정규압밀 점토가 비배수 전단을 받을 때 흙 속에 발생하는 과열간극수압과 변형의 관계를 밝히기 위하여 두개의 재성형 점토와 한개의 비휴선 시료를 사용하여 압밀-비배수 삼축위축 시험을 시행하였다. 시험은 등방일정규압밀된 시료이 열색 표준 삼축타축 시험으르 변형 제어와 응력 제어 방식에 의하여 수행되었으며, 시험 결과로 부터 전단중의 과잉간변수압과 변형의 관계를 표현 할 수 있는 쌍유선 함수를 찾아내었다. 이 쌍곡선함수는 응력일변형 거동에 대한 Kondner의 쌍곡선 모형과 같은 형태의 함수이며 이 함점니 사용되는 두 개의 계수는 삼축압축 시험(CU)으로부터 구해진다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.69-72
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• 2002

The high temperature deformation behavior of SiCp/2124Al composite and 2124Al alloy was investigated by hot compression test in a temperature ranged $400~475^{\circ}C$ over a strain rate ranged $10^{-3}~1s^{-1}$. The billets of 2124Al alloy and SiCp/2124Al composite were fabricated by vacuum hot pressing process. The stress-strain curve during high temperature deformation exhibited a peak stress, and then the flow stress decreased gradually into a steady state stress with increasing the strain. It was found that the flow-softening behavior was attributed to the dynamic recovery, local dynamic recrystallization and dynamic precipitation during the deformation. The precipitation phases were identified as S' and S by TEM diffraction pattern. Base on the TEM inspection, the relationship between the Z-H parameter and subgrain size was found based on the experiment data. The dependence of flow stress on temperature and strain rate could be formulated well by a hyperbolic-sinusoidal relationship using the Zener-Hollomon parameter.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.402-413
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• 2006

Strength evaluation of soft soils is a formidable task because of difficulties in sampling, specimen preparation and setting in triaxial cells. In undrained triaxial testing, sampling disturbance, verticality of specimen and bedding effect give a great influence on shear strength measurements. In the other hand, shear wave measurements of specimens are less influenced by these factors. In this research, the bender elements were attached top cap and base pedestal of triaxial cell and shear wave velocities were measured. To initiate a methodology to evaluate shear strength indirectly by measuring shear wave velocity, a relationship between shear strength and shear wave velocity was developed with kaolinite specimens consolidated in the laboratory. Undrained shear strength turns out to increase linearly with shear wave velocity. Stress-strain curves can also be predicted with a hyperbolic model and shear wave measurements.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1159-1166
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• 2005

In the present study, a series of laboratory tests with sands of different silt contents, are conducted and methods to assess non-linear behaviors based on in-situ test results are proposed. Modified hyperbolic stress-strain model is used to analyze non-linearity of silty sands in terms of non-linear degradation parameters f and g as a function of silt contents and relative density $D_R$. Stress-strain relationship results were obtained from a series of triaxial tests on sands containing different amounts of silt. Initial shear modulus which was applied to normalize modulus degradation of silty sands were determined based on the resonant column test results. From the laboratory test results, it was observed that, as the relative density increases, values of f decrease and those of g increase. Cone resistance $q_c$ for silty soil condition used in the triaxial tests were estimated based on the cavity expansion analysis. A suggestion to make an estimation of degradation parameters f and g as a function of fine contents is addressed in terms of cone resistance $q_c$ .

• 대한기계학회논문집A
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• 제21권5호
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• pp.828-834
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• 1997

The knowledge of material stress-strain behavior is an essential requirement for design and analysis of deformation processes. Empirical stress-strain relationship and constitutive equations describing material behavior during deformation are being widely used, despite suffering some drawbacks in terms of ease of development, accuracy and speed. In the present study, back-propagation neural networks are used to model and predict the flow stresses of a HSLA steel under conditions of constant strain, strain rate and temperature. The performance of the network model is comparedto those of statistical models on rate equations. Well-trained network model provides fast and accurate results, making it superior to statistical models.

• 한국농공학회지
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• 제36권3호
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• pp.90-99
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• 1994

To investigate the undrained shear strength characteristics of marine soils with high water content, high compressibility and weak bearing capacity, a series of undrained triaxial tests with pore pressure measurements on undisturbed and disturbed Banwol marine clay in normally consolidated and overconsolidated states is carried out. The results and main conclusions of this study are summarized as follows : 1 . When the consolidation pressure is increased, the maximum deviator stress of disturbed and undistubed clay in normally consolidated state is increased. Pore pressure parameters and internal friction angle of undisturbed clay are greater than those of disturbed clay. 2. The relationship between pore pressure and axial strain of undisturbed clay in normally consolidated state can be expressed as a hyperbolic function like stress-strain relation proposed by Kondner. 3. In the pore pressure-axial strain relation of disturbed clay in normally consolidated state, failure ratio R'f is greatly deviated in the range of 0.7~0.9 proposed by Christian and Desai. 4. For overconsolided clay, when overconsolidation ratio (OCR) is increased, normalized maximum deviator stress is increased and maximum pore pressure is decreased gradually. 5. Cohesion of overconsolidated clay is greater than that of nomally consolidated clay and internal friction angle slightly is decreased. 6. Pore pressure parameter at failure (Af) of overconsolidated clay is varied with OCR, Af becomes negative values with increment in OCR

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.139-146
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• 1996

The torsion tests in the range of 900~1100$^{\circ}C$ and 5.0X10-2~5.0X100/sec were performed to study the high temperasture deformation behavior kinetics of 304 stainless steels. The flow curves and microstructures exhibited the characteristic of dynamic recrystallization(DRX). The relationship between the critical strain($\varepsilon$c) for the initiation of dynamic recrystallization and the peak strain($\varepsilon$p) could be expressed as $\varepsilon$c=0.73$\varepsilon$p. The dependence of the flow stress on temperature(T) and stain rate($\varepsilon$) was expressed by hyperbolic sine law, $\varepsilon$=2.75X1014 (sinh 0.076$\sigma$)5.26 exp(-379.55kJ/mol). Under the Zener-Hollomon parameter, Z value of 1013 order, it was found that the grain size was 20${\mu}$m. The relationship between the grain size, dDRX and Z parameter was expressed as dDRX =139.48-7.33 log Z.

• Geomechanics and Engineering
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• 제11권5호
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• pp.639-655
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• 2016

The effect of particle breakage and intermediate principal stress ratio on the behaviour of crushable granular assemblies under true triaxial stress conditions is studied using the discrete element method. Numerical results show that the increase of intermediate principal stress ratio $b(b=({\sigma}_2-{\sigma}_3)/({\sigma}_1-{\sigma}_3))$ results in the increase of dilatancy at low confining pressures but the decrease of dilatancy at high confining pressures, which stems from the distinct increasing compaction caused by breakage with b. The influence of b on the evolution of the peak apparent friction angle is also weakened by particle breakage. For low relative breakage, the relationship between the peak apparent friction angle and b is close to the Lade-Duncan failure model, whereas it conforms to the Matsuoka-Nakai failure model for high relative breakage. In addition, the increasing tendency of relative breakage, calculated based on a fractal particle size distribution with the fractal dimension being 2.5, declines with the increasing confining pressure and axial strain, which implies the existence of an ultimate graduation. Finally, the relationship between particle breakage and plastic work is found to conform to a unique hyperbolic correlation regardless of the test conditions.