• Title/Summary/Keyword: Shape Criterion

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Optimal design of shape of a working in cracked rock mass

  • Mirsalimov, Vagif M.
    • Geomechanics and Engineering
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    • v.24 no.3
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    • pp.227-235
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    • 2021
  • A criterion and a method for solving a problem on the prevention of mine working fracture under the action of tectonic and gravitational forces are offered. Based on minimal criterion, theoretical analysis of the definition of the optimal shape of working in the rock mass weakened by arbitrarily located rectilinear cracks was carried out. A closed system of algebraic equations allowing to minimize the stress state and stress intensity factors depending on mechanical and geometrical characteristics of the rock, is constructed. The relation between the shape of the working and the stress intensity factors and also location and sizes of the cracks is obtained. The found optimal shape of working increases load-bearing capacity of the rock.

Decision-making of alternative pylon shapes of a benchmark cable-stayed bridge using seismic risk assessment

  • Akhoondzade-Noghabi, Vahid;Bargi, Khosrow
    • Earthquakes and Structures
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    • v.11 no.4
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    • pp.583-607
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    • 2016
  • One of the main applications of seismic risk assessment is that an specific design could be selected for a bridge from different alternatives by considering damage losses alongside primary construction costs. Therefore, in this paper, the focus is on selecting the shape of pylon, which is a changeable component in the design of a cable-stayed bridge, as a double criterion decision-making problem. Different shapes of pylons include H, A, Y, and diamond shape, and the two criterion are construction costs and probable earthquake losses. In this research, decision-making is performed by using developed seismic risk assessment process as a powerful method. Considering the existing uncertainties in seismic risk assessment process, the combined incremental dynamic analysis (IDA) and uniform design (UD) based fragility assessment method is proposed, in which the UD method is utilized to provide the logical capacity models of the structure, and the IDA method is employed to give the probabilistic seismic demand model of structure. Using the aforementioned models and by defining damage states, the fragility curves of the bridge system are obtained for the different pylon shapes usage. Finally, by combining the fragility curves with damage losses and implementing the proposed cost-loss-benefit (CLB) method, the seismic risk assessment process is developed with financial-comparative approach. Thus, the optimal shape of the pylon can be determined using double criterion decision-making. The final results of decision-making study indicate that the optimal pylon shapes for the studied span of cable-stayed bridge are, respectively, H shape, diamond shape, Y shape, and A shape.

Limit analysis of rectangular cavity subjected to seepage forces based on Hoek-Brown failure criterion

  • Yang, X.L.;Qin, C.B.
    • Geomechanics and Engineering
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    • v.6 no.5
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    • pp.503-515
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    • 2014
  • On the basis of Hoek-Brown failure criterion, a numerical solution for the shape of collapsing block in the rectangular cavity subjected to seepage forces is obtained by upper bound theorem of limit analysis. The seepage forces obtained from the gradient of excess pore pressure distribution are taken as external loadings in the limit analysis, and the pore pressure is easily calculated with pore pressure coefficient. Thus the seepage force is incorporated into the upper bound analysis as a work rate of external force. The upper solution of the shape of collapsing block is derived by virtue of variational calculation. In order to verify the validity of the method proposed in the paper, the result when the pore pressure coefficient equals zero, and only hydrostatic pressure is taken into consideration, is compared with that of previous work. The results show good effectiveness in calculating the collapsing block shape subjected to seepage forces. The influence of parameters on the failure mechanisms is investigated.

The Elasto-Plastic Finite Element Analysis of Ductile Fracture in Shape Rolling (형상압연시 연성파괴의 탄소성 유한요소해석)

  • 원영목;오규환
    • Transactions of Materials Processing
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    • v.5 no.1
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    • pp.72-80
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    • 1996
  • During the shape rolling process the influence of reduction ration and taper of shape roller on deformation and limit of ductile fracture such as free surface cracks developing in the workpiece has been studied. The deformation behaviours were analyzed by the 3-dimensional elasto-pastic finite element method and the conditions of ductile fracture were determined from 3-dimensional elasto-plastic finite element method and modified Cockrogt-Latham criterion. The deformed geometry and prediction of ductile fracture by 3-dimensional elasto-plastic finite element method are compared with experimental results The calcuated results are in good agreements with experimental data. The analysis used in the study was found to be effective in predicting the shape rolling process.

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The Notched Strength and Fracture Criterion in Plain Woven Glass/Epoxy Composites With a Crack (노치부를 가진 Glass/Epoxy 복합재료의 노치강도 평가와 불안정 파괴조건)

  • 김정규;김도식
    • Journal of Ocean Engineering and Technology
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    • v.7 no.2
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    • pp.57-67
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    • 1993
  • The fracture behavior of plain woven glass/epoxy composite plates with a crack is investigated under static tensile loading. It is shown in this paper that the characteristic length associated with the point stress criterion depends on the crack length. To predict the not ched tensile strength, the point stress criterion proposed by Whitney and Nuismer are modified. An excellent agreement is found between the experimental results and the analytical prediction of the modified point stress criterion. The condition of unstable crack growth in the presence of a per-existing flaw(machined notch) is examined by means of the maximum stress intensity factor $K_max$ using maximumload P$_max$. The values of $K_max$ evaluated from energy release rate G$_max$(the compliance me thod) indicate a wide difference. Therefore in regard to anisotropy and heterogeneity of the composite materials studied, the modified shape correction factor f(a/W) is obtained. $K_max$evaluated by the compliance method a little or insignificantly depends on the initial crack length a, the specimen thickness B, the crack angle .theta. and the specimen geometry.

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The Determination of Initial Blank Shape by Using the One-Step FEM (One-Step FEM을 이용한 초기 블랭크 형상 결정에 관한 연구)

  • Jung, Dong-Won;Lee, Sang-Je
    • Journal of Ocean Engineering and Technology
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    • v.13 no.3 s.33
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    • pp.21-28
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    • 1999
  • In this paper, a finite element method for the determination of initial blank shape in sheet metal forming process will be introduced. The initial blank shape is determined by the only one step from the final to the initial blank. The used finite element inverse method adopted Henky's deformation theory, Hill's anisotropic yield criterion and simplified boundary conditions. Based on this theory. a three-dimensional membrane finite element code was developed. The developed code will be applied to several sheet metal forming examples for the demonstration of its validity.

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A Study on the Shape of Efficient Retroreflective Articles (고효율 재귀 반사체 형상에 관한 연구)

  • So, Bum-Sik;Jung, Yoong-Ho;Lee, Deug-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.2
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    • pp.160-170
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    • 2002
  • Retroreflective article is different from other reflecting objects as it returns the incidence ray to the near of its source. This characteristic makes the retroreflectors have many applications in reflective highway signs, reflective vests, and other safety-relaxed items. These articles may have various shapes. However, the quantitative evaluation of performance for the best shape of retroreflector needs much time and cost for manufacturing prototypes and for performance experiments. In this work, we have developed a program for simulating the trace of ray entered into a retroreflective element, in order to determine the optimal shape of retro-reflection. We have also proposed new performance criterion of retroreflective articles, which can confide the range of incidence angle, instead of the criterion with the merely retroreflective strength.

Noninformative priors for the common shape parameter of several inverse Gaussian distributions

  • Kang, Sang Gil;Kim, Dal Ho;Lee, Woo Dong
    • Journal of the Korean Data and Information Science Society
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    • v.26 no.1
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    • pp.243-253
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    • 2015
  • In this paper, we develop the noninformative priors for the common shape parameter of several inverse Gaussian distributions. Specially, we want to develop noninformative priors which satisfy certain objective criterion. The probability matching priors and reference priors of the common shape parameter will be developed. It turns out that the second order matching prior does not exist. The reference priors satisfy the first order matching criterion, but Jeffrey's prior is not the first order matching prior. We showed that the proposed reference prior matches the target coverage probabilities in a frequentist sense through simulation study, and an example based on real data is given.

Structural Dynamics Modification Using Surface Grooving Technique (임의의 형태를 갖는 흠을 이용한 표면형상변형을 통한 동특성 변경)

  • 박미유;박영진;박윤식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.859-863
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    • 2004
  • Structural Dynamics Modification is very effective technique to improve structure's dynamic characteristics by adding or removing auxiliary structures, changing material property, changing shape of structure. In this research, using the surface grooving technique, shape of base structure was changed to improve its first natural frequency. Utilizing the result of sensitivity analysis, groove shape was formed gathering the many small embossing elements. For this process, Sensitivity Criterion Factor was introduced. To reduce its amount of calculation, the range of target area was restricted to their neighboring area and that result was very successful.

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Modeling of the Reorientation Behavior of a Single Crystalline Shape- Memory Alloy by a Micromechanical Approach (미시역학적 접근에 의한 단결정 형상기억합금의 리오리엔테이션 거동 모델링)

  • 구병춘
    • Proceedings of the KSR Conference
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    • 2000.05a
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    • pp.250-257
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    • 2000
  • A Helmholtz free energy for a martensitic transformation of a single crystalline shape-memory alloy is obtained by a micromechanical approach, 24 variants of the single crystal are taken into account. In the framework of irreversible thermodynamics, a kinetic relation, a martensitic nucleation criterion and the reorientation criterion of martensitic variants are obtained. These relations are valid for a three-dimensional proportional or non-proportional mechanical loading or a combination of mechanical and thermal loading. Reorientation behavior of a single crystalline shape-memory alloy CuZnAl is simulated. When a tensile load is applied to a thermally-induced martensite, 24 self-accommodated martensitic variants are reoriented to the most favorable variant. In the following unloading, the most favorable variant in the tensile load is reoriented to the most favorable variant in this loading condition.

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