Genki Yagawa

Implicit constitutive modelling for viscoplasticity using neural networks

Up to now, a number of models have been proposed and discussed to describe a wide range of inelastic behaviours of materials. The fatal problem of using such models is however the existence of model errors, and the problem remains inevitably as far as a material model is written explicitly. In this paper, the authors define the implicit constitutive model and propose an implicit viscoplastic constitutive model using neural networks. In their modelling, inelastic material behaviours are generalized in a state-space representation and the state-space form is constructed by a neural network using input–output data sets. A technique to extract the input–output data from experimental data is also described. The proposed model was first generated from pseudo-experimental data created by one of the widely used constitutive models and was found to replace the model well. Then, having been tested with the actual experimental data, the proposed model resulted in a negligible amount of model errors indicating its superiority to all the existing explicit models in accuracy.

Automatic mesh generation of quadrilateral elements using intelligent local approach

This paper describes a new automated mesh generation method named Intelligent Local Approach (ILA), which well controls both size and aspect ratio of quadrilateral element in a two-dimensional plane. The ILA can be straightforwardly extended to hexahedral elements in a three-dimensional solid. Here elements are created sequentially, considering local information on geometrical constraints and users demand on quality of elements. A user can specify the following two numerical fields, (a) a field of element size and (b) that of element aspect ratio. A field of priority of element creation is also specified within the ILA. To efficiently deal with various complicated geometrical constraints for high quality quadrilateral elements, a fuzzy knowledge processing technique is effectively utilized. The ILA is implemented using an object-oriented technique. Fundamental performances of the ILA are demonstrated in detail through generating several quadrilateral meshes.

Parallel Finite Element Analysis with Internet.

As computers can be connected to each other through the internet, we are able to use a remote computer even if it is located overseas in the same way as using a computer which is located nearby. This paper describes a parallel finite element system using the domain decomposition method, which is implemented on a computer network made from remote computers at the Internet. The above system was successfully applied to the 3 D structural analyses with a high parallel efficiency.