Papers by Keyword: Lattice Model

Abstract: This paper presents a numerical study of failure behavior of cementitious composite materials differing in their composition (aggregate size). A set of four different materials was tested in atypical splitting test geometry. During these tests, apart from the typical outputs such as the load–displacement curves, signals from failure events causing acoustic emission (AE) were recorded. However, reliability of the procedures of the failure events localization might seem questionable in some cases – therefore, the test evaluation procedures were accompanied by analyses using 3D numerical simulation tools based on nonlinear fracture-mechanics approach and propagation of fracture events in the specimens are performed using two computational codes. One is a commercial non-linear FEM code with implementation of cohesive crack model (in the smeared cracks formulation). The second one is an own developed discrete lattice-type model. The comparison of AE records from the tests with the results of the performed numerical simulations can answer questions on the distribution and magnitude (and possibly the energy dissipation amount) of the recorded failure events and generally help in the interpretation and exploitation of AE in the research of failure of non-electric building materials.

Abstract: The heterogeneous lattice model is presented to simulate the behaviors of concrete, in which the concrete is regarded as random medium and the stochastic damage constitutive model is proposed. The parameters of the stochastic damage constitutive is identified compared with the experiment results of concrete under uniaxial tension and uniaxial compression.

Abstract: The algorithm for fast evaluation of the hysteresis loops of uniaxial or textured ferroelectric microcrystal or grains with long-range interactions is developed. Two types of ceramic microstructures are considered: 1. Random ceramics with complete isotropic distribution function of the crystallographic orientations of grains; and 2. Textured ceramics with anisotropic distribution function of the crystallographic orientations of grains. The qualitative analysis of the hysteretic behavior in terms of the grain distribution function is successfully demonstrated. Comparison of the calculated results with experimental data for Pb (Mg_1/3Nb_2/3)O₃ PbTiO₃ ceramics is presented.

Abstract: Based on Nagatani’s model, an extended car following model named flow and density difference lattice model (FDDLM) was proposed. Using the linear stability theory, the stability condition of the new model was obtained. The phase diagram presents that density difference effect is more efficiently than flow difference effect in improving the traffic flow stability and FDDLM could suppress traffic jam effectively. The numerical simulations are consonant with the analytical results and show that considering the flow and density difference leads to the stabilization of the system.

Abstract: This paper contains the results of an investigation into the effect of the discretization of lattice models. The study is performed with homogeneous models where all elements share the same strength. Elemental constitutive law is linearly-brittle, meaning that elements behave linearly but are completely removed from the structure as soon as they reach the limit of their strength. The relation between structural size and discretization density is studied with unnotched beams loaded in three point bending (modulus of rupture test). We report the results for regular discretization and irregular networks obtained via Voronoi tessellation. This is carried out for two types of models: these being with and without rotational springs (normal and shear springs are always present). The numerically obtained dependence of strength on discretization density is compared to the analytical size effect formula.

Abstract: A new lattice model of traffic flow is proposed by considering the information of front multiple sites with relative current. The linear stability condition is obtained by using the linear stability theory. Numerical simulation shows that the proposed model is consistent with the theoretical analysis.

Abstract: Protein folding problem is one of the most important problems in bioinformatics. By combining simulated annealing method with pull moves which is a local move set and conformation update mechanism, we put forward an improved simulated annealing (ISA) algorithm for the two-dimensional hydrophobic- polar (2D HP) protein folding problem. Numerical results show that the ISA algorithm can find the known lowest-energy ground state more rapidly and efficiently than the genetic algorithm (GA) for the several given HP sequences. For the sequence with length 20, we obtain the lower-energy conformation than GA. The performance of the algorithm show ISA is an effective method for protein folding simulation

Abstract: The paper explores possible fracture laws that can be used in meso-level lattice-typemodels for simulating the behaviour of cohesive frictional materials like concrete and rock. A newfailure criterion is proposed, which includes three possible mechanisms that appear to explain thefracture of these materials at the macro-level.

Abstract: This study aims to develop computer models, with a microstructure representative of the PGA graphite, to contribute to the understanding of the relationship between the amount of porosity, the load-displacement behaviour and crack propagation. The project is in two linked parts, the first provides a model of the porous graphite which is then introduced into a lattice type finite element model to provide the load-displacement and crack propagation predictions. Microstructures consisting of matrix and pores with added aligned filler particles, typical of needle coke, were studied. The purpose was to isolate the effect of filler particles on fracture strength and the fracture path. In the paper crack paths and fracture mechanisms are discussed for different amounts of porosity and various filler particle arrangements.

Abstract: This paper presents a numerical method that can predict the Young’s modulus of ceramic with reasonable accuracy. By introducing periodic conditions, the distribution of pores in the matrix phase is simulated. The lattice model is then employed for the analysis of stress in the pore structure and for the determination of the maximum element length. Finally, the validity of the proposed numerical method is preliminarily verified with the experimental results obtained from the literature.