PERIDYNAMIC UNIT CELL ENABLED FINITE ELEMENT MODELING OF FIBER STEERED COMPOSITES

This study presents an approach based on traditional finite elements and peridynamic unit cell (PDUC) to perform structural analysis of fiber steered composite laminates. Effective material property matrix for each ply in the plate element is computed by employing the PDUC based on the orientation of the fiber path and orthotropic ply properties. Each element defines the unit cell domain if the element shape is rectangular. Otherwise, the rectangle that circumscribes the element defines the domain of the unit cell. The element stiffness matrix is constructed through a traditional finite element implementation. This approach provides an accurate and simple modeling of variable angle tow laminates. It can be readily integrated in commercially available finite element programs.

A Computationally Efficient, Mass Conserving Generalized Short Bearing Formulation for Dynamically-Loaded Journal Bearings

This paper describes a computationally efficient, finite element implementation of a generalized short bearing (GSB) formulation to account for mass conservation in cavitated bearing regions. The method is applied to a set of examples representing partial and full journal bearings under transient loads and kinematics. Bearing performance trends are captured well by the GSB formulation when compared with results obtained from complete two-dimensional formulations and from experiments. The computational speed of the GSB formulation is approximately 40 to 200 times faster than the complete formulation for the examples provided in the paper.

Fundamentals of electro-mechanically coupled cohesive zone formulations for electrical conductors

Motivated by the influence of (micro-)cracks on the effective electrical properties of material systems and components, this contribution deals with fundamental developments on electro-mechanically coupled cohesive zone formulations for electrical conductors. For the quasi-stationary problems considered, Maxwell’s equations of electromagnetism reduce to the continuity equation for the electric current and to Faraday’s law of induction, for which non-standard jump conditions at the interface are derived. In addition, electrical interface contributions to the balance equation of energy are discussed and the restrictions posed by the dissipation inequality are studied. Together with well-established cohesive zone formulations for purely mechanical problems, the present developments provide the basis to study the influence of mechanically-induced interface damage processes on effective electrical properties of conductors. This is further illustrated by a study of representative boundary value problems based on a multi-field finite element implementation.

FINITE ELEMENT IMPLEMENTATION OF GEOMETRICALLY NONLINEAR CONTACT

The OOFEM finite element software has been recently updated to include contact algorithms for small strain applications. In this work, we attempt to extend the contact algorithms to large strain problems. Reviewing the current code and comparing it with approaches encountered in literature, we arrive at a specific algorithmic solution and integrate it into the current code base. The current code is explained, the necessary extensions are derived and documented, and the algorithmic changes are described. Tests confirm the functionality and quadratic rate of convergence of the proposed implementation.

A finite element implementation of the stress gradient theory

In this contribution, a finite element implementation of the stress gradient theory is proposed. The implementation relies on a reformulation of the governing set of partial differential equations in terms of one primary tensor-valued field variable of third order, the so-called generalised displacement field. Whereas the volumetric part of the generalised displacement field is closely related to the classic displacement field, the deviatoric part can be interpreted in terms of micro-displacements. The associated weak formulation moreover stipulates boundary conditions in terms of the normal projection of the generalised displacement field or of the (complete) stress tensor. A detailed study of representative boundary value problems of stress gradient elasticity shows the applicability of the proposed formulation. In particular, the finite element implementation is validated based on the analytical solutions for a cylindrical bar under tension and torsion derived by means of Bessel functions. In both tension and torsion cases, a smaller is softer size effect is evidenced in striking contrast to the corresponding strain gradient elasticity solutions.