An automated a priori knowledge-based p-adaptive three-dimensional finite element mesh improvement method for stress analysis of underground excavations with prismatic cross-sections

This paper describes the structure and application of a software system that automates the fatigue initiation and crack propagation analysis based on FEM. The system automatically performs necessary procedures to track propagation history of cracks: insertion of a crack and updating of three-dimensional finite element mesh in accordance with the crack propagation. Most of the meshing is carried out by a Delaunay tessellation method. A tubular hexahedral mesh is generated at the crack front and the fracture mechanics parameters are computed using commercial codes to ensure accuracy. The generation of this tubular hexahedral mesh is fully automatic as well. The system is equipped with a function to automatically perform fatigue analyses using the stress-strain histories at nodes of a three-dimensional FEM model. The standard low cycle fatigue analysis approach is adopted. Using the function, cumulative fatigue for a given FEM model is provided. Some analyses for several examples were carried out for validation. The important example is the surface crack propagation in steel pipes with residual stress.

Download Full-text

Researches on the Generation of Three-Dimensional Manifold Element under FEM Mesh Cover

Mathematical Problems in Engineering ◽

10.1155/2014/140180 ◽

2014 ◽

Vol 2014 ◽

pp. 1-17

Author(s):

Li HaiFeng ◽

Zhang Guoxing

Keyword(s):

Three Dimensional ◽

Detection Algorithm ◽

Dimensional Manifold ◽

Hexahedral Mesh ◽

Element Mesh ◽

Dimensional Finite Element ◽

Definition Of ◽

Three Dimensional Finite Element ◽

Numerical Manifold ◽

Contact Detection Algorithm

Three-dimensional manifold element generation and contact detection algorithm between blocks are the bottleneck for the development of three-dimensional numerical manifold method (NMM). For building mathematics cover, the technology of three-dimensional finite element mesh generation is utilized in the paper. Aiming at the characteristics of complex formation and difficult identification of three-dimensional manifold block, three-dimensional manifold cutting technology is developed. It is important to achieve the coding of mathematical cover (MC) and physical cover (PC) for NMM, which directly determines the correctness of three-dimensional manifold element generation. Based on the character that the coding of three-dimensional manifold is the same as two-dimensional field essentially, coding algorithm of PC system proposed by Dr. Shi is extended to be three-dimensional. A three-dimensional manifold cutting program 3D MC.f90 is developed in this paper, which can generate an arbitrary three-dimensional manifold element under tetrahedral and hexahedral mesh cover. Several examples are made, and results show that three-dimensional manifold block shape and the coding of manifold node and element generated by three-dimensional manifold cutting program all agree well with the definition of three-dimensional manifold element.

Download Full-text