• Steel and Composite Structures
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• 제25권1호
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• pp.19-34
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• 2017

The widespread damage to steel Moment Resisting Frames (MRFs) in past major earthquakes have underscored the need to understand the nonlinear inelastic behaviour of such systems. To assess the seismic performance of steel MRF, it is essential to model the nonlinear force-deformation behaviour of beam to column joints. To determine the extent of inelasticity in a beam to column joint, nonlinear finite element analysis is generally carried out, which is computationally involved and demanding. In order to obviate the need of such elaborate analyses, a simplistic method to predict the force-deformation behaviour is required. In this study, a simple, mechanics driven, hand calculation method is proposed to obtain the forcedeformation behaviour of strong axis beam to column moment joints. The force-deformation behaviour for twenty-five interior and exterior beam to column joints, having column to beam strength ratios ranging from 1.2 to 10.99 and 2.4 to 22, respectively, have been obtained. The force-deformation behaviour predicted using the proposed method is compared with the results of finite element analyses. The results show that the proposed method predicts the force-deformation behaviour fairly accurately, with much lesser computational effort. Further the proposed method has been used to conduct Nonlinear Dynamic Time History Analyses of two benchmark frames; close correspondence of results obtained with published results establishes the usefulness and computational accuracy of the method.

• 소성∙가공
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• 제9권3호
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• pp.219-225
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• 2000

Equal channel angular pressing (ECAP) is a convenient forming process to extrude material without substantial changes in the sample geometry and this deformation process gives rise to produce ultrafine grained materials. The properties of the materials are strongly dependent on the plastic deformation behaviour during ECAP. The major process variables during ECAP are 1) die geometries, such as a channel angle and coner angles, and 2) the processes variables, such as lubrication and deformation speed. In this study, the plastic deformation behaviour of materials during the ECAP has been theoretically analysed by the finite element method (FEM). The effect of the die friction on the plastic deformation behaviour during the pressing is discussed by means of FEM calculations.

• 소성∙가공
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• 제14권1호
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• pp.65-70
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• 2005

A phase mixture model was employed to simulate the deformation behaviour of metallic materials covering a wide grain size range from micrometer to nanometer scale. In this model a polycrystalline material is treated as a mixture of two phases: grain interior phase whose plastic deformation is governed by dislocation and diffusion mechanisms and grain boundary 'phase' whose plastic flow is controlled by a boundary diffusion mechanism. The main target of this study was the effect of grain size on stress and its strain rate sensitivity as well as on the strain hardening. Conventional Hall-Petch behaviour in coarse grained materials at high strain rates governed by the dislocation glide mechanism was shown to be replaced with inverse Hall-Petch behaviour in ultrafine grained materials at low strain rates, when both phases deform predominantly by diffusion controlled mechanisms. The model predictions are illustrated by examples from literature.

• 소성∙가공
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• 제5권4호
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• pp.327-336
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• 1996

The effect of dynamic strain aging on high temperature deformation behaviour of the A-Mg alloy was investigated by strain rate change tests and stress relaxation tests between 20$0^{\circ}C$and 50$0^{\circ}C$. Yield point, short stress transient and periodic discontinuities on the stress-strain curve were considered as an evidence of the effect of dynamic strain aging. With this criterion two distinct strain rate-temperature regimes could be manifested. Dynamic strain aging was considered to be effective in the high temperature-low strain rate regime, whereas dynamic recovery was a dominant deformation mechanism in the low temperature-high strain rate regime. It was found that dynamic strain aging in the high temperature deformation was governed by the mechcanism of diffusion-controlled, viscous dislocation movement.

• 터널과지하공간
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• 제8권1호
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• pp.67-73
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• 1998

This paper presents the results of deformation measurement and numerical analysis carried out to study the behaviour of the rock mass around large underground oil storage caverns. Displacements during excavation have been monitored using borehole extensometers which had been installed before the excavation of caverns proceeded. Numerical analysis has been carried out to examine the three-dimensional behaviour of rock and the face advance effect. The input parameters for this analysis were determined from the results of laboratory and field tests. The deformation modulus of the rock mass was determined from plate loading test at the site and in-situ stresses were measured from the overcoring method with USBM deformation gauge. The results from this study gave a clear picture for three-dimensional behaviour of the rock mass, hence would be used for the optimum design.

• 화약ㆍ발파
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• 제29권1호
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• pp.34-40
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• 2011

본 연구에서는 가곡광산 화강암의 변형거동에 열응력과 수압이 미치는 영향을 평가하였다. 열응력과 수압이 미치는 영향을 해석하기 위하여 화강암 시험편에 열을 가하여 200, 300, 400, 500, 600, $700^{\circ}C$ 예열시험편을 제작하였고, 500, 600, $700^{\circ}C$ 예열시험편에 7.5MPa의 수압을 가하였다. 예열시험편에 대한 일축압축시험 결과 예열온도가 증가함에 따라 시험편의 축변형률 및 횡변형률이 증가하는 것으로 나타났으며 특히 $600^{\circ}C$ 이상 시험편에서 변형률의 증가가 현저한 것으로 나타났다. 온도에 따라 시험편의 일축압축강도와 탄성계수는 지수적으로 감소하는 것으로 측정되었다. 수압을 받은 시험편은 그렇지 않은 시험편에 비해 비탄성적인 변형거동이 큰 것으로 나타났으며 이는 수압이 예열시험편 내에 존재하는 균열의 확장과 개구에 영향을 미친다는 것을 뜻한다.

• 소성∙가공
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• 제13권2호
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• pp.168-173
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• 2004

Microforming can be a good application for bulk metallic glasses. It is important to simulate the deformation behaviour of the bulk metallic glasses in a supercooled liquid region for manufacturing micromachine parts. For these purposes, a correct constitutive model which can reproduce viscosity results is essential for good predicting capability. In this paper, we studied deformation behaviour of the bulk metallic glasses using the finite element method in conjunction with the fictive stress constitutive model which can describe non-Newtonian as well as Newtonian behaviour. A combination of kinetic equation which describes the mechanical response of the bulk metallic glasses at a given temperature and evolution equations fur internal variables provide the constitutive equation of the fictive stress model. The internal variables are associated with fictive stress and relation time. The model has a modular structure and can be adjusted to describe a particular type of microforming process. Implementation of the model into the MARC software has shown its versatility and good predictive capability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.238-243
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• 2000

The effect of the temperature, the fatigue and the test speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was stuied. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength is linearly decrease and the fracture energy is first increase by $0^{\circ}C$ and after that decrease. In the same temperature the fracture strength during increasing the notch radius is hardly increase. The fracture behaviour at low and high test speed is different entirely. At high test speed plastic region is small and fracture behaviour was seen to brittle fracture tendency. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix material ahead of the notch/crack occured. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

• Structural Engineering and Mechanics
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• 제42권6호
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• pp.883-897
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• 2012

Cold-formed channel sections are used in a variety of applications in which they are required to absorb deformation energy. This paper investigates the collapse behaviour and energy absorption capability of cold-formed steel channels with flange edge stiffeners under large deformation major-axis bending. The Yield Line Mechanism technique is applied using the energy method, and based upon measured spatial plastic collapse mechanisms from experiments. Analytical solutions for the collapse curve and in-plane rotation capacity are developed, and used to model the large deformation behaviour and energy absorption. The analytical results are shown to compare well with experimental values. Due to the complexities of the yield line model of the collapse mechanism, a simplified procedure to calculate the energy absorbed by channel sections under large bending deformation is developed and also shown to compare well with the experiments.

• Geomechanics and Engineering
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• 제18권4호
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• pp.417-426
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• 2019

Gangue filling in the goaf is an effective measure to control the surface subsidence. However, due to the obvious deformation of gangue compression, the filling effect deserves to be further studied. To this end, the deformation of coal gangue filling in the goaf is analyzed by theoretical analysis, large-scale crushed rock compression test, and field investigation. Through the compression test of crushed rock, the deformation behaviour characteristics and energy dissipation characteristics is obtained and analysed. The influencing factors of gangue filling and predicted amount of main deformation are summarized. Besides, the predicted equation and filling subsidence coefficients of gangue are obtained. The gangue filling effect was monitored by the movement observation of surface rock. Gangue filling can support the roof of the goaf, effectively control the surface subsidence with little influence on the ground villages. The premeter and equations of the main deformation in the gangue filling are verified, and the subsidence coefficient is further reduced by adding cemented material or fine sand. This paper provides a practical and theoretical reference for further development of gangue filling.