• Steel and Composite Structures
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• 제38권1호
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• pp.79-86
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• 2021

Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

• 한국광학회지
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• 제8권4호
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• pp.333-339
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• 1997

클래딩 지름이 다른 광섬유 브래그 격자를 용융 접착하여 스트레인과 온도를 분리하여 측정할 수 있는 센서를 구성하였다. 굵기차에 의해서 스트레인에 대한 각 브래그 파장 변화량은 서로 다르며, 동일한 모재(perform)에서 생산된 광섬유를 사용하였으므로 온도에 대한 파장 변화량은 같았다. 두 브래그 파장의 변화량을 측정하고 잘 정의된 행렬함수에 대입하여, 가해진 스트레인과 온도의 양을 분리하여, 계산할 수 있었다. 0-1500 .mu.strain, 20-100.deg. C 범위의 스트레인과 온도 변화를 가하면서 제작된 센서의 특성을 관측하였고, 브래그 파장 변화를 측정하여 계산한 결과, 온도계와 마이크로미터 값에 비하여 10% 이내의 측정오차를 얻을 수 있었다. 스트레인의 측정 정일도를 높이기 위해서 일정한 광경로차를 갖는 마하젠더 간섭계를 이용하여 두 격자의 상대 파장변화를 간섭 신호의 크기변화로 변환하는 새로운 방법을 제안하였으며, 시스템을 구축하여 실험한 결과로 온도에 무관하게 분광분석기에 비항 80배 이상 향상된 스트레인 측정 정밀도를 얻을 수 있었다.

• 대한기계학회논문집B
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• 제32권8호
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• pp.604-611
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• 2008

Detailed analysis of NO formation routes and its contributions with strain rate in hydrogen/air flames were numerically investigated. LiG detailed reaction mechanism has been used for calculation, which is compared with experimental data in literature. It shows good agreement with experiment for both temperature and NO mole fraction. Three routes have been found important for NO formation in hydrogen flames. These are the Thermal route, NNH route and $N_2O$ route. Strain rate were varied to discuss the $EI_{NO}$ reduction trend in hydrogen nonpremixed flames, which are analyzed by each NO formation routes. As a result, as the strain rate increase, $EI_{NO}$ decrease sharply until strain rate $100s^{-1}$ and decrease slowly until strain rate $310s^{-1}$ again, after that $EI_{NO}$ keeps nearly constant. It can be identified that $EI_{NO}$ trend with the strain rate is well explained by a combination of variation of production rate of above Thermal, NNH and $N_2O$ route. Also result of Thermal-Mech. that includes only thermal NO reaction is compared with those of Full-Mech. As a result, It can be identified that there was difference between the two results of calculation. It is attributed to result that Thermal-mech did not consider contributions of NNH and $N_2O$ route. From these result, we can conclude that NOx emission characteristics of hydrogen nonpremixed flames should consider contributions of above three routes simultaneously.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.488-495
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• 1997

The stability of bridgehead olefins containing 8 and 10 membered rings has been investigated by the MMX molecular mechanics calculation together with the GMMX conformational searching program. A number of 'hyperstable' bridgehead olefins, which have negative olefin strain values, have been found from the calculated values of strain energy and olefin strain for the series of in- and out-bicyclo[n.3.3]alk-1-ene and in- and out-bicyclo[n.4.4]alk-1-ene (n=1 to 8). For the bridgehead olefins with 'out' topology, hyperstable olefins were found in the systems having cyclononene or larger rings. For the bridgehead olefins with 'in' topology, hyperstable olefins were found in the systems having cyclodecene or larger rings.

• 한국광학회지
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• 제9권2호
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• pp.111-116
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• 1998

활성층의 변형이 0.9%의 압축변형에서 1.4%의 인장변형에 이르는 13개의 InGaAs/InGaAsP 따로가둠 이종접합 다중양자우물 레이저의 문턱전류밀도 값을 계산하여, 변형이 문턱전류밀도에 미치는 영향을 살펴보았다. 양자우물의 띠간격이 1.55.mu.m가 되도록 양자우물의 두께를 정하였고, 레이저의 이득계산을 위한 띠구조 및 전이행렬요소의 계산에는 블록대각화된 8 * 8 이차 $k^{\rarw}$ * $p^{\rarw}$ 해밀토니안을 사용하여 전도띠의 비포물선형 효과 및 원자가띠의 섞임을 모두 고려하였다. 실온의 문턴전류밀도는 중양공띠와 경양공띠가 교차하는 0.4% 인장변형의 값과 두번째 전도부띠가 생기기 시작하는 0.5% 인장변형의 값에서 불연속점을 가졌다. 실온의 문턱전류밀도는 이 0.4-0.5% 인장변형 부근에서 극대가 되고, 양쪽으로 변형값이 달라지면서 감소하였다가 극소점을 거쳐 다시 약간 증가하는 모습을 보였는데, 이는 실험결과와 대체로 일치한다. 이 계산결과를 변형의 효과에 관한 다른 여러 이론적 혹은 실험적인 논문들과 비교 토론하였다.

• Geomechanics and Engineering
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• 제12권3호
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• pp.347-360
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• 2017

The problem of cylindrical cavity expansion incorporating deformation dependent of intermediate principal stress in rock or soil mass is investigated in the paper. Assumptions that the initial axial total strain is a non-zero constant and the axial plastic strain is not zero are defined to obtain the numerical solution of strain which incorporates deformation-dependent intermediate principal stress. The numerical solution of plastic strains are achieved by the 3-D plastic potential functions based on the M-C and generalized H-B failure criteria, respectively. The intermediate principal stress is derived with the Hook's law and plastic strains. Solution of limited expansion pressure, stress and strain during cylindrical cavity expanding are given and the corresponding calculation approaches are also presented, which the axial stress and strain are incorporated. Validation of the proposed approach is conducted by the published results.

• 터널과지하공간
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• 제3권1호
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• pp.40-49
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• 1993

In this study, the indirect estimation method of the support load which is based upon the integrated measuring technique suggested by Kovari was applied to the calculation of support load in the mine roadway. Four test supports were installed in the area where they had to be replaed. Two of those were GI-130 rigid supports and the others were U-26 yieldable supports. The vibrating wire strain gages which were attached inpairs on the steel arch support were used to provide an accurate measurement. Bending moments and normal forces obtained from strain gage pairs were used to calculate the support load. This method was also verified by laboratory bending tests. The results obtained from the back-calculction method showed relatively good agreement with the measured convergence for each crossection.

• Journal of Welding and Joining
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• 제6권4호
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• pp.35-43
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• 1988

Welding residual stresses were calculated by two dimensional thermal elasto-plastic analysis using element method. Complicated plastic behavior during heat transfer was simulated with time. Fist, temperature distributions. To consider time varying behavior of material properties and loading and unloading processes, iterative calculation based on initial stiffness method was carried out. The method proposed by Yamata was used in time increment control which determined the accuracy of claculation. comparison with other caculated and experimental results shows fairly good agreement.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.121-124
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• 2002

This paper resents a virtual forming system to simulate deep drawing process for stress-strain information by utilizing virtual system designed using Virtual Reality Modeling Language (VRML) and computer aided analysis (CAE) tool. The CAE tool to calculate stress, strain, and deformation is designed using Finite Element Method. Stress distributions and deformation profiles as well as the operation of forming machine can be simulated and visualized in the web. The developed system consists of three modules, input module, virtual forming machine module, and output module. The input nodule was designed using HTML and ASP. The input data for FEM calculation is directed to the forming machine module for calculation. The results from the forming machine module can be visualized through output module as well as the forming process simulation.

• 한국자동차공학회논문집
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• 제8권1호
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• pp.17-22
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• 2000

The transient process simplified by the 1-D stretched laminar flame formed at the fuel-oxidizer interface was investigated using the coherent flame sheet model. Under the combustion environment of high temperatures and pressures the results show that the time required to reach the steady state was relatively short compared to the reverse of strain rate. Hence the employment of the tabulation of precalculated steady-flame results in the calculation of turbulent diffusion flames using the coherent flame sheet model is concluded valid, Also upstream temperatures were found to have only a minor effect on the nondimensional flame temperature and nondimensional fuel even through the letter is sensitive to pressure changes.