• Structural Engineering and Mechanics
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• 제12권2호
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• pp.119-134
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• 2001

This paper deals with an experimental and numerical study of a mono-strand wedge anchor head mechanism. First, the experimental program is presented and monitored data such as wedge slippage, anchor deflection and strain distributions along external peripheral surfaces of the anchor head are presented and discussed. In accordance with the experimental set up, these data concern only the global behaviour of the mechanism and cannot provide valuable information such as internal stress-strains distributions, stress concentrations and percentage of yielded volume. Therefore, the second part of this paper deals with the development of an efficient numerical finite element model capable of providing mechanism of the core information. The numerical model which includes all kinematics/material/contact non-linearities is first calibrated using experimental data. Subsequently, a numerical study of the anchorage mechanism is performed and its behaviour is compared to the behaviour of a slightly geometrically modified mechanism where the external diameter has been increased by 5 mm. Finally, different topics influencing the anchorage mechanism behaviour are addressed such as lubrication and wedge shape.

• Geomechanics and Engineering
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• 제16권6호
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• pp.619-626
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• 2018

A simple prediction procedure was investigated for calculating the stresses and displacements of a circular opening. Unlike existed approaches, the proposed approach starts each step with a radius increment. The stress for each annulus could be obtained analytically, while strain increments for each step can be determinate numerically from the compatility equation by finite difference approximation, flow rule and Hooke's law. In the successive manner, the distributions of stresses and displacements could be found. It should be noted that the finial radial stress and displacement were equal to the internal supporting pressure and deformation at the tunnel wall, respectively. By assuming different plastic radii, GRC and the evolution curve of plastic radii and internal supporting pressures could be obtained conveniently. Then the real plastic radius can be calculated by using linear interpolation in the evolution curve. Some numerical and engineering examples were performed to demonstrate the accuracy and validity for the proposed procedure. The comparisons results show that the proposed procedure was faster than that in Lee and Pietrucszczak (2008). The influence of annulus number and dilation on the accuracy of solutions was also investigated. Results show that the larger the annulus number was, the more accurate the solutions were. Solutions in Park et al. (2008) were significantly influenced by dilation.

• 한국안전학회지
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• 제19권4호
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• pp.135-140
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• 2004

마모구조는 대략적으로 기계, 화학 및 열적 마모 등으로 구분되어 진다. 평면변형 유한요소법이 지속적인 칩 형성을 갖는 대각선 가공을 시뮬레이션 하기 위하여 새로운 재료의 응력 및 온도 필드와 같이 사용되었다. 작업소재의 변형은 등방성 변형 경화를 갖는 탄성-점소으으로 취급되며, 수치해석의 해는 소성 변형과 온도 필드의 결합을 설명하며, 온도 종속적인 재료 물성치로 취급된다. 이 논문에서 개발된 모델에서는 전단영역 주위의 변형률, 응력 및 온도 분포에 대한 구성모델의 불확실성의 영향들을 보여주며 예측된 전단영역의 응력, 변형률 및 온도의 평균값들은 기존의 실험 치와 비교해서 잘 맞는 것으로 사료된다.

• 대한기계학회논문집A
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• 제22권2호
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• pp.408-415
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• 1998

The analysis model is the power law creep material containing an elliptical rigid inclusion subjected to the arbitrarily directional stress on infinite boudary. The stress analysis is performed using the conformal mapping function and complex pseudo-stress function. The stress distributions near an elliptical rigid inclusion are obtained with various ellipse shapes, strain hardening exponents and directions of applied stress.

• Journal of Welding and Joining
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• 제14권5호
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• pp.95-105
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• 1996

Korea Gas Corporation has operated high pressure gas transmission line of about 600 kilometers and, therefore, a series of repair welding processes are required in order to cope with external defects such as dent, gouge, cracking usually due to mechanical attacks. Most of gas pipelines repair processes are performed after completely venting remaining gas. However, in some case, though it is very unusual, repairs require without venting gas. For instance, this case is that damaged pipeline is remedied with split sleeve by welding. In this paper, in an effort to confirm a safe application of the split sleeve welding, residual stress, strain and temperature distributions are evaluated by computer simulation and experiments. The results obtained are as follows : 1) Computer modelling is supposed to be reasonable because microstructure changes due to welding is simulated coincidently as compare to that of real condition. 2) The maximal temperature on inside surface of pipeline is 50$0^{\circ}C$ for the repair welding process. 3) The amount of residual stress is estimated as the stress corresponding to 0.8% strain. 4) The repair process employed is determined to be technically preferable because of its avoiding cracks and fractures in the course of welding.

• 소성∙가공
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• 제11권4호
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• pp.355-362
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• 2002

In this study, an axi-symmetric finite element program for elastic analysis of the die set shrink fitted in cold extrusion was developed. The geometrical constraint according to shrink fit was enforced by employing the Lagrange multiplier method. The numerical results for strain and stress distributions in the die set including single and multi stress rings assembled by shrink fit were compared well with the Lame's equation for thick-walled solution available in the literature. To extend the applicability of the analysis program developed, various cases without or with stress ring and with pre-stress applied on stress ring were numerically investigated as well. This numerical approach enables the optimization study to determine optimal dimensions of die set to improve tool life for practical use in industry.

• Smart Structures and Systems
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• 제30권1호
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• pp.63-74
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• 2022

The deformation coordination between a rock/soil mass and an optical sensing cable is an important issue for accurate deformation monitoring. A stress-controlled triaxial apparatus was retrofitted by introducing an optical fiber into the soil specimen. High spatial resolution optical frequency domain reflectometry (OFDR) was used for monitoring the strain distribution along the axial direction of the specimen. The results were compared with those measured by a displacement meter. The strain measured by the optical sensing cable has a good linear relationship with the strain calculated by the displacement meter for different confining pressures, which indicates that distributed optical fiber sensing technology is feasible for soil deformation monitoring. The performance of deformation coordination between the sensing cable and the soil during unloading is higher than that during loading based on the strain transfer coefficients. Three hypothetical strain distributions of the triaxial specimen are proposed, based on which theoretical models of the strain transfer coefficients are established. It appears that the parabolic distribution of specimen strain should be more reasonable by comparison. Nevertheless, the strain transfer coefficients obtained by the theoretical models are higher than the measured coefficients. On this basis, a strain transfer model considering slippage at the interface of the sensing cable and the soil is discussed.

• 한국운동역학회지
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• 제19권1호
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• pp.13-25
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• 2009

Existing footwear biomechanics studies rely on simplified kinetics and kinematics, plantar pressure and muscle electromyography measurements. Because of the complexity of foot-shoe interface and individualized subject response with different footwear, consistent results regarding the biomechanical performance of footwear or footwear components can yet be achieved. The computational approach can be an efficient and economic alternative to study the biomechanical interactions of foot and footwear. Continuous advancement in numerical techniques as well as computer technology has made the finite element method a versatile and successful tool for biomechanics researchdue to its capability of modelling irregular geometrical structures, complex material properties, and complicated loading and boundary conditions. Finite element analysis offers asystematic and economic alternative in search of more in-depth biomechanical information such as the internal stress and strain distributions of foot and footwear structures. In this paper, the current establishments and applications of the computational approach for footwear design and evaluation are reviewed.

• Advances in nano research
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• 제12권3호
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• pp.231-251
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• 2022

Dynamic behavior of temperature-dependent Reddy functionally graded (RFG) nanobeam subjected to thermomagnetic effects under the action of moving point load is carried out in the present work. Both symmetric and sigmoid functionally graded material distributions throughout the beam thickness are considered. To consider the significance of strain-stress gradient field, a material length scale parameter (LSP) is introduced while the significance of nonlocal elastic stress field is considered by introducing a nonlocal parameter (NP). In the framework of the nonlocal strain gradient theory (NSGT), the dynamic equations of motion are derived through Hamilton's principle. Navier approach is employed to solve the resulting equations of motion of the functionally graded (FG) nanoscale beam. The developed model is verified and compared with the available previous results and good agreement is observed. Effects of through-thickness variation of FG material distribution, beam aspect ratio, temperature variation, and magnetic field as well as the size-dependent parameters on the dynamic behavior are investigated. Introduction of the magnetic effect creates a hardening effect; therefore, higher values of natural frequencies are obtained while smaller values of the transverse deflections are produced. The obtained results can be useful as reference solutions for future dynamic and control analysis of FG nanobeams reinforced nanocomposites under thermomagnetic effects.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.505-510
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• 2008

FBG Sensor, which is smaller than strain gauge and has better durability and does not have a noise from electromagnetic waves, was adapted to develope a smart anchor. A series of pullout tests were performed to verify the feasibility of smart anchor and find out the load transfer mechanism around the steel wire fixed to rock with grout. Distribution of shear stresses at steel wire-grout interface is assessed from the measured strain distribution by the optical fiber sensors and compared with stress distributions predicted by Farmer's and Aydan's formulas. It was found that present theoretical formulas may underestimate the failure depth and magnitude of shear stresses when the pullout loads increase.