An integrated CAD system for design of heterogeneous objects

Abstract

Introduction Design of heterogeneous objectsRecent developments in the field of structural optimization have lead to techniques in which geometry and material distribution are both optimized simultaneously (Bendsoe and Kikuchi, 1988;Bendsoe et al., 1993;Cherkaev, 1994;Cherakaev and Kohn, 1997). These techniques result in heterogeneous objects in which there is a continuous material variation along with the geometry. Such optimization techniques are automated and output the final (optimal) geometry and material distribution for a given set of loading, domain specification and boundary conditions. However, there are situations which require the designer to create heterogeneous objects. For example, a number of emerging applications in various fields of engineering require materials to satisfy multiple objectives (Markworth and Saunders, 1995;Tanaka et al., 1996;Kwon, 1994;Suh, 1999). Rather than abruptly joining the different materials, each of which satisfies a specific objective, it is advantageous from the standpoint of maximizing structural performance gradually to vary the material composition from one material to the other in a controlled manner (Holt et al., 1993). The designer has the flexibility to tailor the material distribution to achieve a desired set of objectives. This design scenario is elucidated with the following example.The specific example under consideration is a heterogeneous pressure vessel, cross section shown in Figure 1 (Kwon, 1994). The pressure vessel is subjected to a high temperature/pressure on the inside while the outer surface is subjected to ambient conditions. It is desirable to have ceramic on the inner surface of the pressure vessel due to its good high temperature properties while it is also desirable to have metal away from the inner surface owing to its good mechanical properties. Joining the two materials abruptly will lead to high stresses at the interface. The composition of the metal is therefore gradually increased in a controlled manner starting with zero at the inner surface and gradually increasing to unity on the outer

A survey of virtual prototyping techniques for mechanical product development

“…The accuracy of these models can be a ected by the post-processing operations, especially if done manually. Furthermore, RP of sophisticated designs with multiple and graded materials in one uni®ed part [4] may soon become commercially available too. A number of publications [5±11] discuss various RP developments in great depth, and numerous Internet websites provide useful information for those who wish to embark on using this rapidly evolving technology.…”

Synthesis of shape and topology of multi-material structures with a phase-field method

“…The representation and modeling schemes have been a primary focus of the research on heterogeneous object design. A typical class of representation schemes is based on the subdivision concept in which the solid model is discretized into sub-regions and analytical blending functions are assigned for each region to describe material composition [1,2]. These schemes have many theoretical and practical complications and are extensive to compute [2].…”

“…The use of heterogeneous objects has increased rapidly in the past decade due to the rise of emerging technologies [1]. Objects with varying material properties across spatial domain are common in biomedical, geophysical and nano-scale modeling.…”

Solid Freeform Fabrication Proceedings -1999

“…Regularized set operations are then defined on these solids. Furthermore, in another work several blending functions between primary materials are extracted from the literature [28]. Note that no detailed representation structure of the data is proposed to date It is only recently [27], with the use of a DMD (Direct Material Deposition) apparatus that the attention has shifted to the entire design process: from design to manufacturing while including design homogenization to obtain the ideal microstructure pattern distribution.…”