• Title/Summary/Keyword: Equivalent Strain

Search Result 520, Processing Time 0.021 seconds

Effect of Bending Test Procedure on the Degradation Behavior of Critical Current in ReBCO Coated Conductor Tapes

  • Shin, H.S.;Dedicatoria, M.J.;Lee, N.J.;Oh, S.S.
    • Progress in Superconductivity and Cryogenics
    • /
    • v.11 no.4
    • /
    • pp.12-15
    • /
    • 2009
  • The $I_c$ degradation behavior of critical current in differently processed YBCO and SmBCO CC tapes with IBAD template has been investigated. It has been known that the residual strain in the CC tape will influence the shape of the $I_c$-strain window; $I_c$ may show a peak value if there exist a residual strain induced in the tape during manufacturing. The difference of residual strain may be resulted from the adopted different deposition techniques. In this study, bending test of CC tapes has been done using the Goldacker bending test rig which can produce both compressive and tensile bending strain continuously or alternately to the sample. For SmBCO CC tapes, in continuous compressive bending test, $I_c$ showed a minimal increase and did not degrade up to the largest strain that can be applied using the bending rig equivalent to 1.15% based on the sample thickness. However, in the case of alternate application of compressive and tensile bending strain, $I_c$ showed a larger degradation and a lower reversible limit when compared with the case of continuous application of the bending strain. When $I_c$ started to degrade significantly at the tension side, the reversibility ended, also at the compression side which is resulted from the permanent deformation like delamination or cracks that was induced due to tensile bending strain.

Plasticity and Fracture Behaviors of Marine Structural Steel, Part III: Experimental Study on Failure Strain (조선 해양 구조물용 강재의 소성 및 파단 특성 III: 파단 변형률에 관한 실험적 연구)

  • Choung, Joon-Mo;Shim, Chun-Sik;Kim, Kyung-Su
    • Journal of Ocean Engineering and Technology
    • /
    • v.25 no.3
    • /
    • pp.53-65
    • /
    • 2011
  • This is the third of several companion papers dealing with the derivation of material constants for ductile failure criteria under hydrostatic stress. It was observed that the ultimate engineering stresses and elongations at fracture from tensile tests for round specimens with various notch radii tended to increase and decrease, respectively, because of the stress triaxiality. The engineering stress curves from tests are compared with numerical simulation results, and it is proved that the curves from the two approaches very closely coincide. Failure strains are obtained from the equivalent plastic strain histories from numerical simulations at the time when the experimental engineering stress drops suddenly. After introducing the new concept of average stress triaxiality and accumulated average strain energy, the material constants of the Johnson-Cook failure criterion for critical energies of 100%, 50%, and 15% are presented. The experimental results obtained for EH-36 steel were in relatively good agreement with the 100% critical energy, whereas the literature states that aluminum fits with a 15% critical energy. Therefore, it is expected that a unified failure criterion for critical energy, which is available for most kinds of ductile materials, can be provided according to the used materials.

Equivalent Stiffness Analysis of Rubber Bushing Considering Large Deformation and Size Effect (부싱의 대변형거동과 크기를 고려한 등가 강성 해석)

  • Lee, Hyun Seong;Sung, Myung Kyun;Kim, Heung Soo
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.41 no.4
    • /
    • pp.271-277
    • /
    • 2017
  • In this paper, the amplitude and frequency dependent dynamic characteristics of the equivalent stiffness of a rubber bushing are investigated. A new mathematical model is proposed to explain the large deformation and size effect of a rubber bushing. The proposed model consists of elastic, viscous, and frictional stress components and the equivalent strain. The proposed model is verified using experimental results. The comparison shows that the proposed model can accurately predict the equivalent stiffness values of a rubber bushing under various magnitudes and frequencies. The developed model could be used to predict the dynamic equivalent stiffness of a rubber bushing in automotive engineering.

Similitude Law An Equivalent Three Phase Similitude Law for Pseudodynamic Test on Small-scale Reinforced Concrete Structures (철근콘크리트 구조물의 유사동적실험을 위한 Equivalent Three Phase Similitude LaW)

  • ;;;Guo, Xun
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • 2003.09a
    • /
    • pp.303-310
    • /
    • 2003
  • Small-scale models have been frequently used for experimental evaluation of seismic performance because of limited testing facilities and economic reasons. However, there are not enough studies on similitude law for analogizing prototype structures accurately with small-scale models, although conventional similitude law based on geometry is not well consistent in the inelastic seismic behavior. When fabricating prototype and small-scale model of reinforced concrete structures by using the same material, added mass is demanded from a volumetric change and scale factor could be limited due to size of aggregate. Therefore, it is desirable that different material is used for small-scale models. Thus, a modified similitude law could be derived depending on geometric scale factor and equivalent modulus ratio. In this study, compressive strength tests are conducted to analyze equivalent modulus ratio of micro-concrete to normal-concrete. Equivalent modulus ratios are divided into elastic, weak nonlinear and strong nonlinear phases, which are based on ultimate strain level. Therefore, an algorithm adaptable to the pseudodynamic test, considering equivalent three phase similitude law based on seismic damage levels, is developed. In addition, prior to tile experiment, it is verified numerically if tile algorithm is applicable to the pseudodynamic test.

  • PDF

Characterization of Bacillus thuringiensis StrainBT-14 having Insecticidal Activity against Plutella xylostella

  • Bok, Song-Hae-Jung, Yong-Chul;Kim, Sung-Uk;Son, Kwang-Hee;Lee, Hyung-Hoan
    • Journal of Microbiology and Biotechnology
    • /
    • v.4 no.4
    • /
    • pp.322-326
    • /
    • 1994
  • Bacillus thuringiensis strain BT-14 was isolated from alfalfa dust in Korea. The strain BT-14 produced one bipyramidal crystal and one spore in the cell. The biochemical characteristics of the strain BT-14 were similar to those of Bacillus thuringiensis subsp. kurstaki HD-l. Examination of its antibiotic resistance revealed that while the strain BT-14 was less resistant than BTK HD-l to ampicillin, gentamycin, neomycin and tobramycin, it was more resistant to amikacin than BTK HD-l. The $\delta$-endotoxin crystal of strain BT-14 consisted of a single protein with a high molecular weight of ca 135 KD on a 10% SDS-PACE. The strain BT-14 contained at least nine different plasmids with sizes of 2.9, 5.3, 5.8, 6.2, 9.4, 15.1, 18.1, 23.1 and 79 Kb. In insect bioassay, the isolated strain BT-14 showed lethality of 67% against Plutella xylostella larvae at dilution of 5$\times$$l0^{-4}$ (5$\times$l0 to 3$\times$$l0^2$ spores/ml), which is, almost equivalent to that of BTK HD-l.

  • PDF

Formulation of Failure Strain according to Average Stress Triaxiality of Low Temperature High Strength Steel (EH36) (저온용 고장력강(EH36)의 평균 응력 삼축비에 따른 파단 변형률 정식화)

  • Choung, Joonmo;Nam, Woongshik
    • Journal of Ocean Engineering and Technology
    • /
    • v.27 no.2
    • /
    • pp.19-26
    • /
    • 2013
  • Stress triaxiality is recognized as one of the most important factors for predicting the failure strain of ductile metals. This study dealt with the effect of the average stress triaxiality on the failure strain of a typical low-temperature high-strength marine structural steel, EH36. Tensile tests were carried out on flat specimens with different notches, from relatively smooth to very sharp levels. Numerical simulations of each specimen were performed by using ABAQUS. The failure initiation points in numerical simulations were identified from a comparison of the engineering stress vs. strain curves obtained from experiments with simulated ones. The failure strain curves for various dimensionless critical energy levels were established in the average stress triaxiality domain and compared with the identified failure strain points. It was observed that most of the failure initiation points were approximated with a 100% dimensionless critical energy curve. It was concluded that the failure strains were well expressed as a function of the average stress triaxiality.

Plastic yield behaviour of perforated sheets (천공판재의 항복거동)

  • 백승철;이동녕;오규환
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1994.03a
    • /
    • pp.101-108
    • /
    • 1994
  • The sheet perforated with a uniform triangular pattern of round holes and subjected to in-plane stress f arbitrary biaxiality was investigated. The equivalent continuum approach was employed to develop a theoretical model for global analysis, which includes defining a yield criterion and the strain hardening in terms of apparent stresses and apparent strains. Finit element analysis and experiment tension test were performed to examine the validity of proposed yield criterion and strain hardening models of perforated sheets.

  • PDF

2-dimensional analytical method of RC column considering nonlinearity of strain distribution in out-of-plane direction (면외 변형률 분포의 비선형성을 고려한 RC 기둥의 2차원 해석에 관한 연구)

  • 김익현;이종석;정혁창
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.11a
    • /
    • pp.621-624
    • /
    • 2003
  • The columns with large widths in out-of-plane direction fail showing the high nonlinearity of strain distribution. In order to predict the nonlinear behavior with reasonable accuracy in 2 dimensional analysis the material models taking this characteristic into account are indispensible. In this study equivalent softening model is developed which releases the same amount of energy at failure as that of 3-D analysis. Its validity is confirmed by comparing the analysis result with that of 3-D.

  • PDF

Dynamic Modeling of Satellite with Deployable Solar Arrays (인공위성 태양전지판 전개 시스템 동적 모델링)

  • Seok Heo;Moon K. Kwak;Kim, Hong-B;Sang M. Moon;Sung H. Woo;Lee, Sang S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.11a
    • /
    • pp.373.2-373
    • /
    • 2002
  • This research is concerned with dynamic modeling of satellite with deployable solar arrays equipped with strain energy hinges (SEH). It is found from experiments that the SEH has nonlinear dynamic characteristics and complex buckling behavior, which is difficult to explain theoretically In this paper, we use an equivalent one dimensional nonlinear torsional spring for the SEH. Lagrangian equations of motion are used for the derivations.

  • PDF

Non-Local Analysis of Forming Limits of Ductile Material Considering Damage Growth (보이드 성장을 고려한 재료의 성형한계에 대한 비 국소 해석)

  • Kim, Young-Suk;Won, Sung-Yeun
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.27 no.6
    • /
    • pp.914-922
    • /
    • 2003
  • In this paper, the strain localization of voided ductile material has been analyzed by nonlocal plasticity formulation in which the yield strength not only depends on an equivalent plastic strain measure (hardening parameter), but also on the Laplacian thereof. The gradient terms in yield criterion show an important role on modeling strain-softening phenomena of material. The influence of the mesh size on the elastic -plastic deformation behavior and the effect of the characteristic length parameter for localization prediction are also investigated. The proposed nonlocal plasticity shows that the load -strain curves converge to one curve. Results using nonlocal plasticity also exhibit the dependence of mesh size is much less sensitivity than that for a corresponding local plasticity formulation.