Search Results

You are looking at 1 - 10 of 36 items for :

  • "Aspect ratio" x
  • All content x
Clear All

In this paper, eight noded iso-parametric curved quadratic shell elements are used for Finite Element formulation to analyze continuous bridge deck curved in plan. The computer program developed based on the formulation presented in this study has been used to evaluate the influence of different parameters such as curvature and aspect ratio on the behavior of continuous curved bridges subjected to uniformly distributed load. Though a curved bridge problem is very regular in structural engineering, a detailed and rigorous analysis is often advised since the introduction of curvature brings complexity in structural response. The parametric study carried out in this investigation to establish the defined relationship between the structural behavior of curved bridge deck and straight bridge would prove to be very useful for bridge engineers to readily assess the behavior of continuous bridge curved in plan, based on the responses for a straight bridge deck without compromising on the accuracy.

Restricted access

Computational load balancing plays a prominent role on the success of domain decomposition based finite element computations on parallel computers. Computational load balancing is achieved through mesh partitioning. In this paper, a mesh-partitioning algorithm is proposed for generating sub-meshes with optimal shape using a steady state elite preserving evolutionary algorithm (EA). Numerical experiments have been conducted by solving several practical engineering problems. Comparisons have also been made with its multi-level counter part by solving several benchmark problems. Numerical studies indicate that performance of the proposed mesh-partitioning algorithm is either comparable or superior to the multi-level algorithm.

Restricted access

freedom, the buckling load Eq. (21) is obtained: (21) N x = D ¯ { ∫ 0 1 ∫ 0 1 [ 1 ϕ 2 ( 1 4 + 3 4 E t E s ) H ∂ 4 H ∂ X 4 + 2 H ∂ 4 H ∂ X 2 ∂ Y 2 + ϕ 2 H ∂ 4 H ∂ Y 4 ] ∂ R ∂ Q } b 2 ∫ 0 1 ∫ 0 1 H ∂ 2 H ∂ X 2     ∂ R ∂ Q where Φ is the aspect ratio. The

Open access
Journal of Thermal Analysis and Calorimetry
Authors: A. Andreescu, Adriana Savin, Rozina Steigmann, Nicoleta Iftimie, E. Mamut, and R. Grimberg

Abstract  

This paper presents a model for evaluation of effective thermal conductivity for the composites with carbon nanotubes (CNT) having log-normal function of distribution of CNT, with direct effect over depolarization factor. The CNT are considered having cylindrical shape with L/d ratio very high. The model parameters are calculated in function of the data from literature. The influence of volume fraction of reinforced materials, of the aspect ratio of the particles included and of the ratio of the two thermal conductivities is presented.

Restricted access

Abstract

Buckling analysis of axially compressed cylindrical shells having one or two localized initial geometric imperfections was performed by using the finite element method. The imperfections of entering triangular form were assumed to be positioned symmetrically at the mid shell length. The buckling load was assessed in terms of shell aspect ratios, imperfection amplitude and wavelength, and the distance separating the imperfections. The obtained results have shown that amplitude and wavelength have major effects, particularly for short and thin shells. Two interacting imperfections were found to be more severe than a single imperfection, but the distance separating them has small influence.

Restricted access

Abstract  

One of the greatest challenges in the application of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. 1-Tetradecanol/Ag nanowires composite PCM containing 62.73 wt% (about 11.8 vol%) of Ag nanowires showed remarkably high thermal conductivity (1.46 W m−1 K−1) and reasonably high phase change enthalpy (76.5 J g−1). This behavior was attributed to the high aspect ratio of Ag nanowires, few thermal conduct interfaces, and high interface thermal conductivity of Ag nanowires in the composite PCM. These results indicated that Ag nanowires might be strong candidates for thermal conductivity enhancement of organic PCMs.

Restricted access

Abstract

In this research, buckling behavior of rectangular plates of symmetric and antisymmetric laminated composite having centered circular hole under in-plane static loadings is analyzed with the aid of first shear deformation theory and the finite element method is used to find critical loads. The presence of hole may cause redistribution of stresses in plates with reduction of stability. The aim of the current paper is to find critical buckling load. The loads depend on many parameters like geometric aspect ratios (a/b) and (d/b), plate thickness (t), diameter of the circular hole (d), orientation of ply and boundary conditions. Numerical simulations for various boundary conditions obtained are shown in tables and graphical forms and compared with each other.

Restricted access

We describe the direct, conformal, atomic layer deposition (ALD) of silica onto carbon nanotubes (CNTs) in the microfabrication of thinlayer chromatography (TLC) plates. As before, these plates were prepared with zig-zag hedge and channel microstructures, with high aspect ratio, porous hedges. After ALD, scanning electron microscopy (SEM) showed an increase in the radius of the CNTs of 8–40 nm. X-ray photoelectron spectroscopy (XPS) showed that the plates were composed almost entirely of silicon and oxygen, without contamination of metals or other elements that might compromise chromatographic performance, e.g., aluminum. Time-of-flight secondary ion mass spectrometry confirmed the extremely low level of aluminum in the plates. The final TLC layer thickness was ca. 50 μm. Separations of a test mixture of dyes from CAMAG (Muttenz, Switzerland) on an uncoated silica plate under traditional, normal phase conditions gave efficiencies of 40,000–140,000 plates m−1 with migration distances ranging from 2 to 36 mm. A separation of two fluorescent dyes, eosin Y disodium salt and sulforhodamine B, on an amino silane-coated plate gave efficiencies of ca. 170,000 and 200,000 plates m−1, with hRF values of 76 and 88, respectively. Run times on these new plates were much faster than on conventional TLC plates.

Restricted access

The Csódi-hegy laccolith belongs to the Middle Miocene Börzsöny and Visegrád Andesite Formation, and is built up by fluidal amphibole biotite dacite. This is a small, typical laccolith as shown by its size (Dl = 11000-1200 m, D2 = 900-1000 m, A ~ 150 m), shape, areal extent of 1 km2 and aspect ratio of 0.08 to 0.14. The fluidal structure of the laccolith is the result of alternation of dark and light bands. The thickness of the bands is in cm-dm scale. This structure and the feeding channels are very well exposed here thanks to quarrying activity. The time span-calculation was performed by counting of the individual bands, by volume estimations and by detailed magnetostratigraphic study. For the calculation of magma transport and growing-time the following assumptions were made: 6-8 km depth of the magma chamber, pressure of 8-10 kbars, temperature of 850-900 °C, a rate of ascent 1 mm/20-36 hours, 15 cm as the average width of a single band, a relative depth for emplacement about 450 m and the volume of the emplaced body of 0.05 km3. A total of 3150 bands were counted along the 330 m-long key section of the laccolith, from the center of the main feeding channel toward both flanks of the body. In this way the calculated total emplacement time for the formation of the Csódi-hegy laccolith varies between 1,100 and 1,900 years. The final episodic kink stage may range from 3 to 6 years and the cooling stage have lasted about 100 years. Volume estimations resulted in similar time spans, varying between 1,800 and 3,300 years. The rapid change from transitional to reverse magnetic polarity may cover some hundreds to some thousands of years.

Restricted access

] Ali-Toudert F. , Mayer H. Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate , Building and Environment , Vol. 41 , No

Open access