Banca de DEFESA: Samuel de Almeida Torquato e Silva

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Samuel de Almeida Torquato e Silva
DATE: 18/06/2024
TIME: 14:00
LOCAL: Videoconferência
TITLE:

"HYBRID LATTICE-DISCRETE ELEMENT METHOD FOR MODELING BALLAST VIRTUAL TESTS".

KEY WORDS:

Hybrid LDEM, DEM, RBSN lattice model, Particle crushing, Ballast.

PAGES: 113
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Geotécnica
SPECIALTY: Pavimentos
SUMMARY:

Railway ballast modeling can be performed by different approaches, through continuous or discrete models, which have their comparative advantages and disadvantages. Continuum mechanics-based methods often rely on numerous empirical parameters and require significant laboratory effort for calibration. Conventional discrete element methods have a high capacity to represent railway ballast; however, due to physical inconsistencies in their formulation, they may encounter similar issues. This study aims to adapt and propose the Hybrid Lattice-Discrete Element Method (Hybrid LED) for virtual modeling of railway ballast tests. The advantages of employing this technique include: (i) simplified determination of input parameters and optimization of laboratory efforts, (ii) realistic representation of complex geometries of railway ballast particles, (iii) visualization of micromechanical phenomena, such as particle fracturing, and (iv) monitoring of state variables throughout simulations, such as stress state, breakage indices, porosity, and particle size distribution. Initially, material parameters were defined based on laboratory test results obtained from the literature. Then, particle generation, Voronoi discretization and packing algorithms were used to build models of railway ballast samples. These models were used to simulate mechanical tests, namely single particle compression, confined uniaxial compression, monotonic triaxial compression and cyclic triaxial compression. There was consistency between the results and the empirical observations reported in the literature. In addition, variations in particle size distribution were observed during the simulations, and the causes of failure, primarily attributed to particle slippage or breakage, were investigated. Moreover, predominant particle breakage modes were assessed, such as corner breakage or crushing. By analyzing these elements together, a detailed understanding of the mechanical behavior of the studied material may be obtained. The primary drawback of the method was its computational cost, which, although not prohibitive, is higher than conventional methods. However, this challenge can be overcome through the utilization of computational resources such as clusters and cloud computing. In conclusion, the Hybrid LED method proves to be effective for simulating laboratory tests on railway ballast, capable of representing complex geometries and various boundary conditions.

COMMITTEE MEMBERS:
Externa à Instituição - LIEDI LEGI BARIANI BERNUCCI - USP
Externa à Instituição - VERONICA TEIXEIRA FRANCO CASTELO BRANCO - UFC
Interno - 1549489 - MANOEL PORFIRIO CORDAO NETO
Presidente - 404227 - MARCIO MUNIZ DE FARIAS
Interno - 3132829 - RAFAEL CERQUEIRA SILVA