Akitake Makinouchi

Computer simulation of trabecular remodeling in human proximal femur using large-scale voxel FE models : Approach to understanding Wolff's law

Ever since Julius Wolff proposed the law of bone transformation in the 19th century, it has been widely known that the trabecular structure of cancellous bone adapts functionally to the loading environment. To understand the mechanism of Wolffs law, a three-dimensional (3D) computer simulation of trabecular structural changes due to surface remodeling was performed for a human proximal femur. A large-scale voxel finite element model was constructed to simulate the structural changes of individual trabeculae over the entire cancellous region. As a simple remodeling model that considers bone cellular activities regulated by the local mechanical environment, nonuniformity of local stress was assumed to drive the trabecular surface remodeling to seek a uniform stress state. Simulation results demonstrated that cell-scale ( approximately 10microm) remodeling in response to mechanical stimulation created complex 3D trabecular structures of the entire bone-scale ( approximately 10cm), as illustrated in the reference of Wolff. The bone remodeling reproduced the characteristic anisotropic structure in the coronal cross section and the isotropic structures in other cross sections. The principal values and axes of a structure characterized by fabric ellipsoids corresponded to those of the apparent stress of the structure. The proposed large-scale computer simulation indicates that in a complex mechanical environment of a hierarchical bone structure of over 10(4) length scale (from approximately 10microm to approximately 10cm), a simple remodeling at the cellular/trabecular levels creates a highly complex and functional trabecular structure, as characterized by bone density and orientation.

Volume-CAD: An Integrated Environment for Virtual Manufacturing and Structural Analysis

The Volume-CAD System Research Program aims at developing a core technology for data integration of computerized design, analysis, manufacturing, and testing processes. The potential applications of the Volume-CAD environment cover a large area of engineering and biomedical design. In this paper, we shall mainly focus on the VCAD-based software for the structural analysis and the simulation of casting processes.

Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces

This paper presents the effect of tool modelling accuracy on the simulation accuracy of springback in high strength steels. Simulations of a two‐dimensional draw‐bending process are carried out by using a polyhedral tool model whose surface is approximated by a polyhedron, and a model whose surface is smoothed by quadratic parametric surfaces proposed by Nagata [Nagata, Comput. Aided Geom. D, 22(2005), 55–59] (Nagata patch model). It is found that not only the shape accuracy but also the normal vector accuracy of tool models are of importance for accurate springback predictions. The use of the Nagata patch model is an efficient approach not only to improve the simulation accuracy but also to make the simulation be hardly influenced by the tool mesh, even for simulations of a high strength steel in which large amount of springback is involved.

CHIKAKU DB/CAD: A System for Modeling 3D Tectonic Structure

We have developed the systems of reconstructing the 3D computational models of tectonic structure called CHIKAKU DB/CAD as a part of projects for developing simulation software, for the purpose of the clarification of the mechanism of earthquakes, and the prediction of the earthquake wave propagation. The main purpose of the development of CHIKAKU DB/CAD is to manage measured data such as earthquake center points, to edit the upper plate surface from such data, and to offer the data for the numerical simulations of tectonic activity. Today, it is quite difficult to measure the tectonic structure directly. Here we also discuss the method for creating 3D tectonic models of in and around Japanese Islands from given measurement data.

A criterion for the fracture of high-strength aluminum alloy in bending.

A bending tests of high strength aluminum alloy are carried out under hydrostatic pressure and with backup compression provided mechanically, and the stress and strain histories in the processes are calculated by the elastic-plastic FEM. The experimental results and the calculated results are used to study the fracture criteria. From the results, it becomes clear that the slip type fracture which occurs in bending with high backup compression using a small radius punch can be predicted by the criterion of a maximum shear stress, and the Oyanes criterion is successful in prediction of the critical punch strokes in bending in which the normal type fracture occurs. But the constants of Oyanes equation in bending do not agree with that in tensile test and in compression test.