A systematic approach for Integrated Computer-Aided Design and Finite Element Analysis of Functionally-Graded-Material objects

https://doi.org/10.1016/j.matdes.2006.10.024Get rights and content

Abstract

Computer-Aided Design (CAD) and Finite Element Analysis (FEA) of Functionally-Graded-Material (FGM) objects are generally regarded as separate domains of interest in CAD and Computer-Aided Engineering (CAE) community. Such a separation of CAD modeling and FEA of FGM objects makes it cumbersome and tedious for both designers and engineers to exchange the necessary information in the entire design process. Without appropriate CAD models, complex material distributions can hardly be represented and the FGM objects under examination remain simple in material variations (e.g. unidirectional gradations). With CAD modeling tools only, the end users are still uncertain whether or not the designed objects can really meet the functional requirements in terms of structural, thermal or other prescribed properties. This paper proposes a systematic approach to integrate these domain-dependent design tools in FGM object design. Integrated solutions to CAD modeling and property analysis of FGM objects are utilized to design complicated (bi-directional or even tri-variate) FGM objects. Complex FGM distributions are encoded into the proposed Heterogeneous Feature Tree (HFT) structure; and the material compositions of a given point of interest are interrogated from the CAD models at runtime. Integrated FEA of FGM objects are then carried out by establishing a link between the proposed CAD modeler (CAD4D) and a commercial FEA package (COMSOL Multiphysics). Four different (three unidirectional and one bidirectional) FGM objects are modeled with traditional analytic function based approaches and the proposed methods. Under the same thermal and mechanical conditions, the properties of each model are compared in terms of temperature fields, residual thermal stresses and the strain energy densities. Results show that the proposed approach can facilitate the design of complex FGM objects in a systematic way.

Introduction

Objects with Functionally Graded Material (FGM) distributions have shown superior advantages in applications where multi-fold functional requirements are demanded [1], [2], [3]. For instance, in aerospace applications, modern aerospace shuttles are subjected to super high temperatures and enormous mechanical loads; sufficient heat-resistance and stiffness properties are required. In aircraft engine design, “reduced weight and increased strength and stiffness are the major requirements for highly stressed fan blades” [4]. In biomedical applications, both the mechanical properties and the biocompatibilities of the implanted components play critical roles in clinical therapies [5], [6]. In industrial applications, the machinability of metals and the excellent heat resistance of ceramics are usually required in the same component. In all these applications, homogeneous objects can hardly meet the multi-fold functional requirements, whereas using FGM objects, different properties and advantages of various materials can be fully exploited within the single solid. Traditional problems due to material incompatibility (stress concentration, non-uniform thermal expansion, etc.) can be naturally alleviated with gradual material variations. Due to these excellent performances and unique features, FGM objects have gained great popularities in recent years. The past few decades have witnessed significant advances in FGM object design. Research efforts range from Computer-Aided Design (CAD modelling), Computer-Aided Engineering (design evaluation/validation/simulation) to optimizations and Computer-Aided Manufacturing (fabrication).

In the past, CAD modelling and FEA of FGM objects are generally regarded as separate domains of interest in CAD and CAE community. Such a separation makes it cumbersome for both designers and engineers to exchange the necessary information in the entire design process. Therefore, applications in both domains are impeded and the designable complex FGM objects are limited. This paper proposes a systematic approach to integrate these “domain-dependent” [7] design tools in FGM object design. The modelled geometry and material distribution are represented with CAD models and relevant data can be further transferred to FEA modules for design validations. Based on the proposed approach, objects with complex (bi-directional or tri-variate) FGM distributions can be intuitively modeled and properly analyzed.

Section snippets

Motivations and related work

Design of functionally graded objects with 1D dependent or unidirectional material gradations have been extensively studied in recent years. Elishakoff et al. [8] conducted a finite element analysis of an all-round clamped FGM plate based on the Ritz energy method; 3D plates with unidirectional power-law based FGM distributions are examined. Huang et al. [3] analyzed FGM objects whose materials follow a distribution characterized by the generic Bezier curves, an optimal FGM distribution is

CAD modeling of FGM objects

CAD modeling of FGM objects primarily deals with representing the geometry, topology and material distributions of FGM objects with appropriate mathematical/computer models. As there have been mature data representations for modeling the geometries and topologies, in this section, only the material distribution modeling problem will be considered. Due to the simplicities of unidirectional FGM object modeling, particular emphasis is laid on modeling non-unidirectional material gradations. For

Intergraded FEA of FGM objects

This section further presents the methodologies of using finite element method in the intergraded analysis of complex FGM objects. Thermo-mechanical analysis is conducted on the four FGM objects modeled earlier. Under the same thermal and mechanical conditions, the properties of each model are compared in terms of temperature fields, residual thermal stresses and the strain energy densities.

Results and discussion

By applying the proposed methodologies of integrating CAD modeling with finite element analysis, complex FGM objects can be intuitively designed and their properties can be properly analyzed via finite element analysis. This section presents the FEA results based on the proposed approach.

Conclusions and future work

A systematic approach for integrated CAD modeling and FEA analysis of FGM objects is proposed in this paper. The designed geometries and material compositions are represented with CAD models and further transferred to FEA modules for design validations. By integrating such domain-dependent design tools, objects with complex FGM distributions, which are hardly modeled with traditional approaches, can be intuitively modeled and analyzed; the designer’s intents can be properly captured.

Four

Acknowledgements

The authors thank the Department of Mechanical Engineering, The University of Hong Kong and the Research Grant Council for supporting this project. Grateful thanks go to the Croucher Foundation for providing the second author with a senior fellowship.

References (42)

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