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  • On the molecular dynamics analysis of defect effect on mechanical properties and fracture behaviors of carbon nanotubes
  • Abstract Due to the limitation of fabrication technologies nowadays, initial defects in carbon nanotubes (CNTs) are inevitably perceived particularly during the manufacturing process or chemical treatment. The investigation of the effects of initial defects existing in CNTs on their mechanical properties and fracture behaviors becomes essential for their potentiality in engineering applications.
    In this study, the defect effects, including number in percentage, type, and location, are explored using the molecular dynamics (MD) simulation with Tersoff Brenner potential. Results show that the mechanical properties, such as the elastic modulus, failure strength and strain, are strongly affected by the defects. Moreover, the distribution…
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  • Modal identification of structure under varying environmental conditions
  • Abstract Modal identification is essential in structural health monitoring (SHM) because that the modal parameters are often used for model updating and damage detection. However, in practical situations, the variation of environmental conditions (e.g. temperature, temperature gradients, humidity, etc.) will impede the reliability of modal identification. In this paper, firstly, the relation of frequency change and variation of environment temperature of space structure is investigated. Then, a structural state assessment method by combing autoregressive moving average (ARMA) and PCA is proposed. The acceleration data from China National Aquatics Center is employed as an example. The results show that variation of frequencies…
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  • Damage detection on beam structures based on fractal theory and wavelet packet transform
  • Abstract A new damage identification method based on Fractal theory and wavelet packet transform is presented in the paper. The damage identification method utilize frequency-based domain message, time-based domain message and space based domain message effectively. NeXT method were first employed to reduce loading effect of random vibration measured from structures and then the vibration sinal were decomposed into the certain level wavelet packet components. For every time array of wavelet packet component then need to calculate the mean FD values as the ultimated FD values to reduce noise effect. The location of damage in the beam can be determined by…
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  • Efficiency Test of Iterative-Multifrontal Hybrid Solver
  • Abstract A new concept of hybrid iterative-multifrontal linear solution method is presented for large scale structural analysis problems. Multifrontal solution method is the best direct solution method ever known, so it is adequate for Domain decompostion types of iterative solvers. Multifrontal solver is served as an internal subdomain solver for domain decomposition iterative solver for achieving high performance of domain decomposition iterative solver. Lagrange multiplier is introduced to enforce the continuity of interface between subdomains. And corner DOF is introduced to avoid singularities of subdomains. Hybrid solution method is expected to show good parallel performance for extremely large size structural analysis.
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  • An Intuitive Preprocessor Development for the Finite Element Analysis System, DIAMOND/IPSAP
  • Abstract As a finite element structural analysis tool, IPSAP has been developed over a decade ago by ASTL(Aerospace STructures Laboratory in Seoul National University) since early 1990's. IPSAP means 'Internet Parallel Structural Analysis Program' and is able to solve linear static analysis, thermal conduction analysis, and vibration analysis of various types of general complex structures.
    By using Parallel Multi-Frontal solver, IPSAP shows efficient, powerful performance and accuracy in serial and parallel computing system and has been released by website( since 2004. But initial version of IPSAP did not support GUI(Graphic User Interface). To get over this inconvenience of IPSAP, the pre/post…
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  • Gating mechanisms of a mechanosensitive ion channel: experiments and molecular simulations
  • Abstract Mechanosensing is ubiquitous in our body. Not only specialized mechanoreceptors like inner ear hair cells and visceral baroreceptors, but also ordinary cells can respond to mechanical stimuli, by which cells can regulate their volume, shape and motility properly. The major biophysical issue in this field is to understand the physicochemical mechanisms of mechanotransduction based on the molecular structure of mechanosensors. To date the mechanosesnitive (MS) ion channel is the only identified molecular class of mechanosensors. Among them the bacterial MS channel MscL is the best studied one owing to the resolved 3D structure of its closed state. MscL forms a…
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  • Simulations for pool-fire suppression in rolling stock using fluent
  • Abstract Computational Fluid Dynamics (CFD) was carried out to analyze pool-fire suppression in rolling stock for two cases. One is single-pool fire simulation in which fire is located in center of rolling stock, the other is multi-pool fire simulation in which fires are located 4.8m from center of, respectively. Six water mist nozzles are installed and equally spaced along rolling stock for each case. It is assumed that pool fire is volume constant heat source, 50kW, for each case. This analysis was performed using DPM (Discrete Phase Model) from Fluent, a commercial CFD code.
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  • Novel trends in failure analysis of composite structures
  • Abstract Fiber composite structures are usually thin-walled and hence, prone to buckling. Thus, beside material failure also stability problems have to be considered.

    Thin-walled cylindrical composite shells buckle in the elastic region and thus, there is no need to consider material non-linearities or material failure. Never the less, a robust design guide for composite shells does not exist until today. The most frequently guideline is NASA SP-8007, which gives an empirical based knockdown factor. Because this guideline is not intended for composite shells and it turned out to be very conservative in numerous cases several approaches have been developed to…
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  • Structural analysis of a composite target-drone wing
  • Abstract Target-drone is an unmanned remotely controlled aerial vehicle and usually used for shooting training for anti-aircraft screws. Traditional target-drones have been generally manufactured from aluminum and/or wood. Recently, composite materials have been replacing them in virtue of their high strength-to-weight and stiffness-to-weight ratios. In particular, glass fiber-based composite materials are popular for the target-drone level vehicles because of the material cost and fabrication convenience.
    In this paper, as a part of the development activities for a complete target-drone vehicle, the stress analysis results are presented for a 685cc engine target-drone composite aerial vehicle wing. Composite materials used are H612 and…
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  • Strength of composite bonded joints with various manufacturing methods
  • Abstract This paper addresses experimental results on the strength of single-lap composite bonded joints with different manufacturing methods and configurations. The joints were fabricated with 4 different methods; Co-curing with additional adhesive (CCA) and without additional adhesive (CCN) between composite adherends, Co-bonding (COB) and secondary bonding (SEB). Joints have 5 different overlap lengths(l), 3 different lay-up patterns and 4 different thicknesses(t), respectively. Width of the joints(w) is constant at 25.4 mm. A total of 389 single-lap specimens were tested in tension. In the test to examine the effect of manufacturing methods and overlap lengths, the joint CCN showed the highest failure…
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