Monte-Carlo simulation of the durability of glass fibre reinforced composite under environmental stress corrosion

The lifetime distribution of glass fibre subject to permanent environmental stress corrosion is very important for assessing the durability and damage tolerance of composites using glass reinforcement. A mechanical model based on the statistics of flaw spectra during stress corrosion and 3D shear lag model is presented. The proposed approach shows that it is possible to identify the influence of stress corrosion properties on the long term durability of glass fibre reinforced composites (GFRP)

A smoothed four-node piezoelectric element for analysis of two-dimensional smart structures

This paper reports a study of linear elastic analysis of two-dimensional piezoelectric structures using a smoothed four-node piezoelectric element. The element is built by incorporating the strain smoothing method of mesh-free conforming nodal integration into the standard four-node quadrilateral piezoelectric finite element. The approximations of mechanical strains and electric potential fields are normalized using a constant smoothing function. This allows the field gradients to be directly computed from shape functions. No mapping or coordinate transformation is necessary so that the element can be used in arbitrary shapes. Through several examples, the simplicity, efficiency and reliability of the element are demonstrated. Numerical results and comparative studies with other existing solutions in the literature suggest that the present element is robust, computationally inexpensive and easy to implement

An improved quadrilateral flat element with drilling degrees of freedom for shell structural analysis

This paper reports the development of a simple and efficient 4-node flat shell element with six degrees of freedom per node for the analysis of arbitrary shell structures. The element is developed by incorporating a strain smoothing technique into a flat shell finite element approach. The membrane part is formulated by applying the smoothing operation on a quadrilateral membrane element using Allman-type interpolation functions with drilling DOFs. The plate-bending component is established by a combination of the smoothed curvature and the substitute shear strain fields. As a result, the bending and a part of membrane stiffness matrices are computed on the boundaries of smoothing cells which leads to very accurate solutions, even with distorted meshes, and possible reduction in computational cost. The performance of the proposed element is validated and demonstrated through several numerical benchmark problems. Convergence studies and comparison with other existing solutions in the literature suggest that the present element is efficient, accurate and free of lockings

Numerical analysis of the interaction between rockbolts and rock mass for coal mine drifts in Vietnam

The thesis describes the application of anchors in mining and tunneling and gives an up-to-date overview about anchor types, design principles and the interaction mechanisms between anchors and rockmass. A constitutive model was developed, implemented and tested for the 2- and 3-dimensional numerical codes FLAC and FLAC3D to simulate non-linear anchor behaviour including unloading and reloading. The interaction between rockbolts and rockmass was studied in detail via numerical simulations for 5 Vietnamese coal mines. An extended version of the so-called c-Φ reduction method and a new introduced reinforcement factor were applied to quantify the effect of bolting. Mine specific and generalised relations were deduced to quantify the influence of anchor length and distance between anchors on the effect of bolting

Critical Impurity Density in the Mott Metal-Insulator Transition, obtained in the n(p)-Type Degenerate

By basing on the same physical model and treatment method, as used in our recent works (Van Cong, 2024; 2023; 2023), we investigate the critical impurity density in the metal-insulator transition (MIT), obtained in the n(p)-type degenerate Si1−xGex- crystalline alloy, 0≤x≤1, and also applied to determine the optical band gap, being due to the effects of the size of donor (acceptor) d(a)-radius, rd(a), the x-Ge concentration, the temperature T, and finally the high d(a)-density, N, assuming that all the impurities are ionized even at T=0 K. In such the n(p)-type degenerate Si1−xGex- crystalline alloy, we will determine:  (i)-the critical impurity density &nbsp

Maximal Efficiencies in New Single Si 1-x Ge x- Alloy Junction Solar Cells at 300 K

In single n+(p+)−p(n) [X(x)≡Si1−xGex]-alloy junction solar cells at 300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent work (Van Cong et al., 2023; Van Cong, 2023), we will investigate the highest (or maximal) efficiencies, ηImax.(IImax.), obtained at the open circuit voltage Voc(=VocI(ocII)), according to highest hot reservoir temperatures TH(K), obtained from the Carnot efficiency theorem, being proved by entropy law, in the following. (i)-First, in the singl

Maximal Efficiencies in New Single GaAs 1−x Sb x-Alloy Junction Solar Cells at 300 K

In single n+(p+)−p(n) [X(x)≡GaAs1−xSbx]-alloy junction solar cells at 300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent work (Van Cong et al., 2023; Van Cong, 2023), we will investigate the highest (or maximal) efficiencies, ηImax.(IImax.), obtained at the open circuit voltage Voc(=VocI(ocII)), according to highest hot reservoir temperatures TH(K), obtained from the Carnot efficiency theorem, being proved by entropy law. Here, one first remarks that, with increasing x=(0, 0.5, 1), (i)- from Table 3, for the single n+−p X(x)-alloy junction solar cell and for given rSn(Cd)-radius, for example, ηImax.(↘)= 31.14%, 28.72%, 25.36%, according to TH(K)=435.7.420.9.401.9 Voc(V)=1.07 .1.07 1.09 1.17 espectively, while, (ii)- from Table 5, for the single p+−n X(x)-alloy junction solar cell and for given rCd(Sn)-radius, for example, ηIImax.(↗)= 33.04%, 34.26%, 35.47%, according to TH(K)=448.0,456.3