Flexible multibody impact simulations based on the isogeometric analysis approach

Usually detailed impact simulations are based on isoparametric finite element models. For the inclusion in multibody dynamics simulation, e.g., in the framework of the floating frame of reference, a previous model reduction is necessary. A precise representation of the geometry is essential for modeling the dynamics of the impact. However, isoparametric finite elements involve the discretization of the geometry. This work tests isogeometric analysis (IGA) models as an alternative approach in the context of impact simulations in flexible multibody systems. Therefore, the adaption of the flexible multibody system procedure to include IGA models is detailed. The use of nonuniform rational basis splines (NURBS) allows the exact representation of the geometry. The degrees of freedom of the flexible body are afterwards reduced to save computation time in the multibody simulation. To capture precise deformations and stresses in the area of contact as well as elastodynamic effects, a large number of global shape functions is required. As test examples, the impact of an elastic sphere on a rigid surface and the impact of a long elastic rod are simulated and compared to reference solutions.

Finite Element Method for Fluid Flow in 3D Domains Containing Moving Interfaces

This study presented a three-dimensional (3D) finite element method (FEM) for the numerical analysis of fluid flow in domains containing moving interfaces. This method falls into the general category of Arbitrary Lagrangian Eulerian (ALE) method; based on a fixed mesh that is locally adapted at the moving interfaces and reverts to its original shape once the moving interfaces go over the elements. The 3D domain occupied by the fluid at any time in the simulation is used as the reference domain and is discretized using a mesh of hexahedral tri-linear isoparametric finite elements. The moving interfaces are defined by sets of marker points so that the global mesh is independent of interface movement and eliminates the possibility of mesh entanglement. The mesh never becomes unsuitable due to its continuous deformation, thus eliminating the need for repeated re-meshing and interpolation. A validation is presented via a problem with an analytical solution for the 3D flow between two planes separating at a prescribed speed that shows second order accuracy. The model’s capabilities are illustrated through application to laminar incompressible flows in different geometrical settings that show the flexibility of the technique.

Computer-aided identification of the water diffusion coefficient for maize kernels dried in a thin layer

Uncertainties in mathematical modelling of water transport in cereal grain kernels during drying and storage are mainly due to implementing unreliable values of the water diffusion coefficient and simplifying the geometry of kernels. In the present study an attempt was made to reduce the uncertainties by developing a method for computer-aided identification of the water diffusion coefficient and more accurate 3D geometry modelling for individual kernels using original inverse finite element algorithms. The approach was exemplified by identifying the water diffusion coefficient for maize kernels subjected to drying. On the basis of the developed method, values of the water diffusion coefficient were estimated, 3D geometry of a maize kernel was represented by isoparametric finite elements, and the moisture content inside maize kernels dried in a thin layer was predicted. Validation of the results against experimental data showed significantly lower error values than in the case of results obtained for the water diffusion coefficient values available in the literature.

Definition of ANCF Finite Elements

Since the absolute nodal coordinate formulation (ANCF) was introduced, a large number of fully parametrized and gradient deficient finite elements were developed. Some of the finite elements (FE) proposed do not fall into the ANCF category, and for this reason, this technical brief describes the general requirements for ANCF finite elements. As discussed in this paper, some of the conventional isoparametric finite elements can describe arbitrary rigid body displacements and can be used with a nonincremental solution procedure. Nonetheless, these isoparametric elements, particularly the ones that employ position coordinates only, are of the C0 type and do not ensure the continuity of the position vector gradients. It is also shown that the position vector gradient continuity conditions can be described using homogeneous algebraic equations, and such conditions are different from those conditions that govern the displacement vector gradients. The use of the displacement vector gradients as nodal coordinates does not allow for an isoparametric representation that accounts for both the initial geometry and displacements using one kinematic description, can make the element assembly more difficult, and can complicate imposing linear algebraic constraint equations at a preprocessing stage. Understanding the ANCF geometric description will allow for the development of new mechanics-based computer-aided design (CAD)/analysis systems as briefly discussed in this paper.

Experiment and Elastic-Plastic Modelling of the IPN160 Beam

The paper compares the numerical models of and experiments with a beam. The purpose is to evaluate the nonlinear material model of a steel structure. The steel is modelled as an ideal elastic-plastic material. The FEM and eight-node isoparametric finite elements are considered in the analysis. The 3D calculations use different material constants and several approaches are being tested in order to create the computational models. The calculations are performed in the software application developed by our university.

Analysis of Bolt Joint Using the Finite Element Method

Analysis of Bolt Joint Using the Finite Element Method A numerical analysis of the initially clamped bolt joint subject to the working pressure is presented in the paper. Special, hexahedral 21- and 28-node isoparametric finite elements have been employed to model the contact zone. In this model, one takes into account loading due to the working pressure in the gap between the gasket and the flange arising as an effect of the progressing joint opening, what has not been considered in recent papers. Nonlinear stiffness characteristics of the bolt and the flange with the gasket are developed. Working pressure corresponding to the critical bolt force resulting in the joint leakage (complete opening between the gasket and the flange) is determined. FE computational results are compared with the available experimental results. The numerical results are presented using the authors' own graphical postprocessor.

STUDY OF COMPLEX ELECTROMAGNETIC FIELD USING HYBRID ISOPARAMETRIC FINITE ELEMENTS

For complex electromagnetic fields in modern physics, a hybrid isoparametric finite element method (HIFEM) with high accuracy is introduced in the paper. The complex electromagnetic field in an electromagnetic device has been calculated successfully by the hybrid isoparametric finite element method (HIFEM) and the electromagnetic properties of the electromagnetic device under specific work conditions are evaluated. With the help of microcomputers, the electromagnetic simulation given in this paper is very useful in the analysis of operating properties under different work conditions and design of electromagnetic devices.