• Title, Summary, Keyword: Combined Loading

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Experimental training of shape memory alloy fibres under combined thermomechanical loading

  • Shinde, Digamber;Katariya, Pankaj V;Mehar, Kulmani;Khan, Md. Rajik;Panda, Subrata K;Pandey, Harsh K
    • Structural Engineering and Mechanics
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    • v.68 no.5
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    • pp.519-526
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    • 2018
  • In this article, experimental training of the commercial available shape memory alloy fibre (SMA) fibre under the combined thermomechanical loading is reported. SMA has the ability to sense a small change in temperature (${\geq}10^{\circ}C$) and activated under the external loading and results in shape change. The thermomechanical characteristics of SMA at different temperature and mechanical loading are obtained through an own lab-scale experimental setup. The analysis is conducted for two types of the medium using the liquid nitrogen (cold cycle) and the hot water (heat cycle). The experimental data indicate that SMA act as a normal wire for Martensite phase and activated behavior i.e., regain the original shape during the Austenite phase only. To improve the confidence of such kind of behavior has been verified by inspecting the composition of the wire. The study reveals interesting conclusion i.e., while SMA deviates from the equiatomic structure or consist of foreign materials (carbon and oxygen) except nickel and titanium may affect the phase transformation temperature which shifted the activation phase temperature. Also, the grain structure distortion of SMA wire has been examined via the scanning electron microscope after the thermomechanical cycle loading and discussed in details.

Simplified estimations of elastic-plastic fracture mechanics parameters under combined primary and secondary loadings (1차 및 2차 복합 하중을 받는 구조물의 탄소성 파괴역학 매개변수 예측기법)

  • Oh, Chang-Kyun;Kim, Yun-Jae;Park, Jin-Moo;Kim, Jong-Sung;Jin, Tae-Eun
    • Proceedings of the KSME Conference
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    • pp.43-48
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    • 2004
  • When structures are loaded by a combination of primary and secondary stresses, plasticity effects occur which cannot be evaluated by a simple linear addition of the effects resulting from the two independent stress systems. Thermal stress due to temperature gradient is classified as secondary stress. It is known that secondary stress is released as increase of plastic zone. In this paper, two and three dimensional elastic-plastic finite element analyses are performed for the cracked plates and pipes under combined thermal and mechanical loading. And V-factor is introduced to account for plasticity effect. The present results provide that V-factor is function of thermal factor and loading and is consistent regardless of geometry. We developed the prediction method of elastic-plastic fracture mechanics parameter under combined primary and secondary loading from the present results.

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Effects of Melatonin and Fluid Shear Stress on 3T3-L1 Preadipocytes (3T3-L1 지방전구세포에서 멜라토닌과 유체전단응력의 영향)

  • Lee, Jeongkun;Lee, Yeong Hun;Park, Chae Lim;Kim, Chi Hyun
    • Journal of Biomedical Engineering Research
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    • v.39 no.3
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    • pp.109-115
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    • 2018
  • Obesity is a worldwide disease caused by the excessive proliferation of adipocytes. Multiple factors, including melatonin and physical loading, are involved in the control of obesity. Melatonin has been shown to induce apoptosis on preadipocytes while physical loading such as fluid shear stress (FSS) affects the proliferation and differentiation of adipocytes. Here, we studied the combined effects of melatonin and FSS on 3T3-L1 preadipocytes. For physical loading, preadipocytes were stimulated with a maximum dynamic fluid shear stress of 1 Pa at 1 Hz for 2 hours with/without melatonin. The experiment conditions were divided into four groups: (1) control, (2) 1 mM melatonin treatment, (3) FSS, and (4) combined 1 mM melatonin and FSS. All groups had a fixed duration time of 2 hours. ERK, p-ERK, COX-2, $C/EBP{\beta}$, $PPAR{\gamma}$, osteopontin, Bax, caspase-3 and caspase-8 proteins were assessed by Western blot analysis. GAPDH was used as a control. Results showed that combined melatonin and FSS treatment activated the ERK/MAPK pathway but not COX-2. Furthermore, combined melatonin and FSS treatment significantly decreased $C/EBP{\beta}$ and $PPAR{\gamma}$ compared to other groups. However, caspase-3 and caspase-8 did not result in significant changes. In summary, combined melatonin and FSS appears to have the potential to inhibit adipogenesis and treat obesity.

New Engineering J and COD Estimation Method for Circumferential Through-Wall Cracked Pipes-Combined Tension and Bending Load (원주방향 관통균열이 존재하는 배관의 새로운 J-적분 및 COD 계산식-인장하중과 굽힘모멘트가 동시에 작용하는 경우)

  • Huh, Nam-Su;Kim, Yun-Jae;Kim, Young-Jin
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.7
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    • pp.85-90
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    • 2001
  • In order to apply the Leak-Before-Break(LBB)concept to nuclear piping, accurate estimation of J-integral and crack opening displacement(COD) is essential for complex loading, such as combined tension and bending. This paper proposes a new engineering method to estimate J-integral and the COD for circumferential through-wall cracked pipes subject to combined tension and bending loading. The proposed method to estimate the COD is validated against three published pipe test data, generated from a monotonically increasing bending load with a constant internal pressure, which shows excellent agreements.

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A Study on the Stability Boundaries for Single Layer Latticed Domes under Combined Loads (조합하중을 받는 단층 래티스 돔의 안정경계에 관한 연구)

  • 한상을;이갑수
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.85-91
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    • 2000
  • The smallest value of the load when the equilibrium condition becomes to be unstable is defined as the buckling load. The primary objective of this paper is to analyse stability boundaries for star dome under combined loads and is to investigate the iteration diagram under the independent loading parameter In numerical procedure of the geometrically nonlinear problems, Arc Length Method and Newton-Raphson iteration method is used to find accurate critical point(bifurcation point and limit point). In this paper independent loading vector is combined as proportional value and star dome was used as numerical analysis model to find stability boundary among load parameters and many other models as multi-star dome and arches were studied. Through this study we can find the type of buckling mode and the value of buckling load.

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Stress Intensity Factors of Combined Mode(Mode I/II) Crack in a Variable Thickness Plate (두께가 변화하는 부재 내의 혼합모드(모드 I/II) 균열의 응력확대계수)

  • 조명래;양원호;최용식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.8
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    • pp.1875-1882
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    • 1993
  • Variable thickness plates are commonly used as structural members in the majority of industrial sectors. Previous fracture mechanics researches on variable thickness plates were limited to mode I loading cases. In practice, however, cracks are usually located inclined to the loading direction. In this respect, combined mode(mode I/II) stress intensity factors $K_{I}$ and $K_{II}$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a slant edge crack were chosen. The parameters used in this study were dimensionless crack $length{\lambda}$, slant $angle{\alpha}$, thickness $ratio{\beta}$ and width ratio{\omega}$. Stress intensity factors were calculated by crack opening displacement(COD) and crack sliding displacement(CSD)method proposed by Ingraffea and Manu.

Buckling of the multi-vaulted "Aster" shell under axial compression alone or combined with an external pressure

  • Araar, M.;Derbali, M.;Jullien, J.F.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.827-839
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    • 1998
  • This paper presents a study of buckling of the multi-vaulted cylindrical shell ("Aster"), under an axial compression alone or combined with an external pressure. This shell which was presented in a recent paper is a self-stiffened structure having a satisfactory behaviour and a higher buckling strength under external pressure than a circular cylindrical shell with the same dimensions. The results of this study emphasize the interest of the behaviour of the "Aster" shell under two other types of loading, revealing an acceptable level of strength which is favorable for an expansion of its use in other areas.

Combined Economic and Emission Dispatch with Valve-point loading of Thermal Generators using Modified NSGA-II

  • Rajkumar, M.;Mahadevan, K.;Kannan, S.;Baskar, S.
    • Journal of Electrical Engineering and Technology
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    • v.8 no.3
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    • pp.490-498
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    • 2013
  • This paper discusses the application of evolutionary multi-objective optimization algorithms namely Non-dominated Sorting Genetic Algorithm-II (NSGA-II) and Modified NSGA-II (MNSGA-II) for solving the Combined Economic Emission Dispatch (CEED) problem with valve-point loading. The valve-point loading introduce ripples in the input-output characteristics of generating units and make the CEED problem as a non-smooth optimization problem. IEEE 57-bus and IEEE 118-bus systems are taken to validate its effectiveness of NSGA-II and MNSGA-II. To compare the Pareto-front obtained using NSGA-II and MNSGA-II, reference Pareto-front is generated using multiple runs of Real Coded Genetic Algorithm (RCGA) with weighted sum of objectives. Furthermore, three different performance metrics such as convergence, diversity and Inverted Generational Distance (IGD) are calculated for evaluating the closeness of obtained Pareto-fronts. Numerical results reveal that MNSGA-II algorithm performs better than NSGA-II algorithm to solve the CEED problem effectively.

NSGA-II Technique for Multi-objective Generation Dispatch of Thermal Generators with Nonsmooth Fuel Cost Functions

  • Rajkumar, M.;Mahadevan, K.;Kannan, S.;Baskar, S.
    • Journal of Electrical Engineering and Technology
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    • v.9 no.2
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    • pp.423-432
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    • 2014
  • Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is applied for solving Combined Economic Emission Dispatch (CEED) problem with valve-point loading of thermal generators. This CEED problem with valve-point loading is a nonlinear, constrained multi-objective optimization problem, with power balance and generator capacity constraints. The valve-point loading introduce ripples in the input-output characteristics of generating units and make the CEED problem as a nonsmooth optimization problem. To validate its effectiveness of NSGA-II, two benchmark test systems, IEEE 30-bus and IEEE 118-bus systems are considered. To compare the Pareto-front obtained using NSGA-II, reference Pareto-front is generated using multiple runs of Real Coded Genetic Algorithm (RCGA) with weighted sum of objectives. Comparison with other optimization techniques showed the superiority of the NSGA-II approach and confirmed its potential for solving the CEED problem. Numerical results show that NSGA-II algorithm can provide Pareto-front in a single run with good diversity and convergence. An approach based on Technique for Ordering Preferences by Similarity to Ideal Solution (TOPSIS) is applied on non-dominated solutions obtained to determine Best Compromise Solution (BCS).

Buckling Behavior of Reinforced Concrete Columns under Biaxial Loading (2축 휨을 받는 철근 콘크리트 기둥의 좌굴거동)

  • 김진근;이상순
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.480-485
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    • 1996
  • A numerical method for perdicting the behavior of a reinforced concrete column under biaxial loading is proposed, using the layered finite element method. Concrete is assumed to exhibit strain softening and steel reinforcement is elastic-plastic. The bending theory assumptions are used and bond slip of reinforcement is meglected. To perdict the entire load-deformation characteristics, displacement control method is used. This method consider not only combined effect due to axial load and bending moment but also that due to bending moments. Predicted behaviors of reinforced concrete columns under biaxial loading through the numerical method proposed in this study show good agreements with test results.

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