Whitepapers

Mesh construction is a key consideration in the course of building a finite element model. The quality of the analysis results depends on the quality of the mesh; arriving at an acceptable solution requires judicious meshing choices. Specifically, the analyst must consider the type of elements and the density of the mesh, which is often varied throughout the model, with more refinement in critical regions. These considerations need to be balanced against the desire to minimize analysis cost in terms of preprocessing effort, analysis run time, and computer resources. Beginning with Version 6.6 the adaptive Remeshing features in Abaqus allow Abaqus/CAE and Abaqus/Standard to work together automatically in an iterative fashion to determine an optimal mesh. The goal of this capability is to obtain a solution that satisfies discretization error indicator targets while minimizing the number of elements and, hence, the cost. To demonstrate the adaptive remeshing technique, this technology brief describes how a sequentially coupled thermal-structural analysis is performed with a model of the Shippingport nuclear reactor.

Filament winding has become a popular construction technique in a wide variety of industries for creating composite structures with high stiffness-to-weight ratios. The difficulty in accurately analyzing the structural behavior of a filament wound body derives from the continually varying orientation of the filaments. The standard capabilities of commercial finite element codes are inadequate to model the spatial variation of fiber orientation in a practical way. In this Technology Brief, an Abaqus/CAE plug-in for the analysis of filament wound composite pressure vessels is presented. The application allows the user to create, run, and post process a finite element model and allows for detailed specification of structural geometry and winding layout parameters.

Metal welding processes are employed in various industries. Gas welding techniques use the heat from a flame to melt the parts to be joined and a filler material simultaneously. Extreme thermal loading is applied to the parts being joined, and complex material responses are initiated. The steep, localized thermal gradients result in stress concentrations in the welding zone. Consequently, modeling and simulation of welding processes are often complex and challenging. In this technology brief the use of Abaqus for this class of problems is discussed and an example analysis is presented.

Spudcans are conical footings used as foundations for offshore platforms. Installation in soft marine soil forces them deeply into the seabed, inducing gross motion and severe plastic deformation in the soil.

A pure Lagrangian-based finite element approach for modeling spudcan installation and extraction can be very difficult. Because the mesh moves with the material, element distortion typically accompanies severe deformation and convergence difficulties follow.

In an Eulerian-based method, material flows through a fixed mesh; it is therefore more amenable to the simulation of large material motion and extreme deformation. Abaqus/Explicit offers the coupled Eulerian-Lagrangian technique, in which chosen portions of the model can be modeled as Eulerian or Lagrangian, while automatically maintaining contact between the distinct regions.

In this Technology Brief the coupled Eulerian-Lagrangian analysis method is used to model the installation, extraction, and in-situ loading behavior of spudcans.