• Computers and Concrete
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• 제30권5호
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• pp.323-337
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• 2022

This paper proposes a numerical model to simulate the rotational behavior of steel fiber in fresh cement-based materials in the presence of a magnetic field. The results indicate that as the aspect ratio of fiber increases, the required minimum magnetic field intensity to make fiber rotate in viscous fluid increases. The optimal magnetic field intensity is 0.03 T for aligning steel fiber in fresh cement-based materials to ensure that the applying time of the magnetic field can be conducted concurrently with the vibrating process to increase the aligning efficiency. The orientation factor of steel fiber in cement mortar can exceed 0.85 after aligning by 0.03 T of the uniform magnetic field. When the initial angle of the fiber to the magnetic field direction is less than 10°, the magnetic field less than 0.03 T cannot make the fiber overcome the yield stress of fluid to rotate. The coarse aggregate in steel fiber-reinforced concrete is detrimental to the rotation and alignment of the steel fiber. But the orientation factor of ASFRC under the 0.03T of the magnetic field can also exceed 0.8, while the orientation factor of SFRC without magnetic field application is around 0.6.

• Journal of Electrical Engineering and Technology
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• 제11권5호
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• pp.1316-1322
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• 2016

• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.193-200
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• 2023

본 논문에서는 전자기장 노출을 통한 강섬유의 방향 정렬 방법이 휨파괴거동에 미치는 영향을 비교, 분석하였다. 강섬유의 방향을 휨공시체의 종방향으로 정렬할 수 있는 규모의 솔레노이드를 설계, 제작하였다. 설계강도 30MPa의 강섬유보강콘크리트 휨공시체를 제작하였으며, 이를 전자기장에 노출한 공시체와 노출하지 않은 공시체로 구분하여 휨파괴 실험을 수행하였다. 실험변수는 강섬유의 혼입률과 형상비로 하였다. 실험결과, 전자기장에 노출된 시험체의 휨강도, 최대하중에서의 개구변위가 미소하게 증가하였으며, 특히 파괴에너지의 증가가 명확하게 확인되었다. 잔존강도의 증가가 파괴에너지 증가에 가장 큰 영향을 준 것으로 확인되었다.

• Smart Structures and Systems
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• 제20권3호
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• pp.329-342
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• 2017

In this paper, the dispersion characteristics of elastic waves propagation in sandwich nano-beams with functionally graded (FG) face-sheets reinforced with carbon nanotubes (CNTs) is investigated based on various high order shear deformation beam theories (HOSDBTs) as well as nonlocal strain gradient theory (NSGT). In order to align CNTs as symmetric and asymmetric in top and bottom face-sheets with respect to neutral geometric axis of the sandwich nano-beam, various patterns are employed in this analysis. The sandwich nano-beam resting on Pasternak foundation is subjected to thermal, magnetic and electrical fields. In order to involve small scale parameter in governing equations, the NSGT is employed for this analysis. The governing equations of motion are derived using Hamilton's principle based on various HSDBTs. Then the governing equations are solved using analytical method. A detailed parametric study is conducted to study the effects of length scale parameter, different HSDBTs, the nonlocal parameter, various aligning of CNTs in thickness direction of face-sheets, different volume fraction of CNTs, foundation stiffness, applied voltage, magnetic intensity field and temperature change on the wave propagation characteristics of sandwich nano-beam. Also cut-off frequency and phase velocity are investigated in detail. According to results obtained, UU and VA patterns have the same cut-off frequency value but AV pattern has the lower value with respect to them.