An Evolutionary Multi-Objective Optimization Approach to the Topology Optimization of Auxetic Structures

Auxetic structures are ones, which exhibit an in-plane negative Poisson ratio behavior. Such structures can be obtained by specially designed honeycombs or by specially designed composites. The design of such honeycombs and composites has been tackled using a combination of optimization and finite elements analysis. Since, there is a tradeoff between the Poisson ratio of such structures and their elastic modulus, it might not be possible to attain a desired value for both properties simultaneously. The presented work approaches the problem using evolutionary multiobjective optimization to produce several designs rather than one. The algorithm provides the designs that lie on the tradeoff frontier between both properties.

Integration of Commercial CAD/CAM System With Custom CAPP Using Orbix Middleware and CORBA Standard

This paper discusses the issues of integrating the Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) programs in commercial software. Integration was achieved through implementation of a computer-aided process planning (CAPP) system within the commercial software. The part model was imported into, or designed in, the commercial CAD system. Manufacturing information was then extracted from the part model by the CAPP system using commercial Application Programming Interfacing (API) methods. The CAPP system then uses the extracted information to produce a process plan consistent with the requirements of the commercial CAM module to produce Numerical Control (NC) code. The internal integration was accomplished using commercial API methods that dynamically bind the CAD, CAPP, and CAM into a single continuous application. These APIs are implemented using the Orbix middleware following the CORBA standard. A case study demonstrating the integration is presented. Strengths and weaknesses of integrating the CAD and CAM domains using APIs and middleware are discussed.

Interactive Product Design Selection With an Implicit Value Function

We present an automated method to aid a Decision Maker (DM) in selecting the ‘most preferred’ from a set of design alternatives. The method assumes that the DM’s preferences reflect an implicit value function that is quasi-concave. The method is iterative, using three approaches in sequence to eliminate lower-value alternatives at each trial design. The method is interactive, with the DM stating preferences in the form of attribute tradeoffs at each trial design. We present an approach for finding a new trial design at each iteration. We provide an example, the design selection for a cordless electric drill, to demonstrate the method.

An Analytical Approach to Functional Design

Functional design is a process in engineering design that dominates the key features of the result to be developed. Designing good functions that both satisfies the requirements and leads to better results is a challenge due to uncertainties on the consequences of the selected functions, and the lack of analysis methods for identifying the properties of function structures. Therefore, extensive experiences are usually required for functional design. This research argues that the physical relationships among the resulting components of a design are the consequences of functional dependencies developed during the functional design process. Therefore based on the understanding of functions and functional dependencies, a reasoning procedure can be developed to predict the performance properties of the design so that the effectiveness of the functional design can be evaluated at an early design stage. This paper proposes a dependency-based function modeling and analysis method that can be applied to represent and assess functions and function structures at the functional design stage. Designers can predict the properties of the functions they designed without having to have similar design experiences. An application software is also developed to implement the method and demonstrate its effectiveness.

Math-Based Performance Evaluation of an Experimental Car: Side Impact Protection

This study used finite element models to assess potential benefits of selected unconventional features implemented in this study for occupant protection in side impact. These features include door lockdown, gullwing door with a corrugated aluminum panel and cross-car beams. The intrusion and intrusion velocity of the B-pillar were used as the parameters for measuring side impact protection performance. No attempt was made here to assess manufacturablity, design feasibility, mass implications or market interest.

Informing Design Using Data Mining Methods

Manufacturing processes produce a considerable amount of data as dimensions are measured, tests are performed and assembly checks are undertaken. Predominantly these data are used to inform and help improve the associated manufacturing processes and procedures. A variety of Knowledge Discovery techniques [1] have been introduced in the engineering field, most typically in areas with large quantities of data [2]. This paper describes research into the use of such techniques in the manufacture and assembly of large complex engineering products, an area which is characterised by low volume of data and dispersed databases. The developed methodology seeks to incorporate various approaches, with emphasis on using extracted knowledge to inform the implementation of subsequent techniques. This investigation centres on discovering and quantifying relationships between the various balance and vibration tests performed throughout assembly of gas turbine rotors, and to highlight critical parameters. Current assembly practices do not use forward prediction of test performance, and the first stages of this project aim to produce a model to enable this. The scope of this model will then be extended to feed this knowledge back to be used in the design and manufacture of future components.

A Study on Optimum Topology of Plate Structure Using Coordinate Transformation by Conformal Mapping

This paper presents a new method to determine an optimum topology of plate structure using coordinate transformation by conformal mapping. We have already proposed a method to determine an optimum topology of planar structure using coordinate transformation by conformal mapping. In that study first we defined simple design domain in which analysis and optimization were performed easily. We calculated optimum topology in this simple design domain. Then we applied coordinate transformation by conformal mapping to optimum topology calculated in simple design domain, and obtained some optimum topologies in complex design domain. We also showed that the invariants of stresses which were the sum and difference of principal stress satisfied Laplace equation and relationshi p between fluid mechanics and electromagnetic could be valid in the theory of elasticity. In this study we clarify two invariants of bending moments satisfy Laplace equation under a certain condition. We note the similarity between Airy stress function of 2-D elastic body and deflection of plate, and will show that the two invariants of bending moments which are the sum and difference of principal bending moments satisfy Laplace equation using this similarity. As a result we will show that corresponding relationship between fluid mechanics, electromagnetic and elasticity may be valid in the theory of plate. Then by using this relationship, we proposed a new method to determine optimum topology using coordinate transformation by conformal mapping. Our proposed method will be useful to determine optimum topology easily in complex design domain. Through numerical examples, we can examine the effectiveness of the proposed method.

Reconfiguration of Kinematic Structure for Changing Motion Requirement Based on Reusability Evaluation in Lie Algebra

This paper presents a new method for adapting the existing manufacturing system for a requirement change, such as the change of a required motion task, by modifying its kinematic structure from the viewpoint of the degrees of freedom of the end effecter of the mechanism. In a previous report, the authors formulated the kinematic structure and motion task using Lie algebra. In this report, using these representations and their inclusion relations, the authors propose a method for evaluating the reusability of a kinematic structure for a newly specified motion task, and then propose a method for reconfiguring the mechanism in Lie algebra according to the result of the reusability evaluation. Finally, in order to evaluate the usefulness of the proposed method, it is applied to a kinematic design example of a mechanism.

Applying Universal Linking of Engineering Objects in the Automotive Industry: Practical Aspects, Benefits, and Prototypes

The bi-directional communication of CAD programs with subsequent applications such as process planning remains a key challenge in design-for-the-lifecycle. While it seems sensible that individual applications use their own collection of feature types and thereby allow users to have their specific perspective of the product, it is still difficult to automatically close the gap between the variety of applications. Universal Linking of Engineering Objects (ULEO) targets this concern. It is general enough to facilitate informational integration of the applications along the process chain. This paper examines a number of scenarios for exploiting ULEO’s benefits in the field of automotive development and reports on the associated prototypical software implementations. Principle alternatives and technical aspects relevant for applying ULEO are discussed in some detail beforehand.

Error Sensitivity Analysis for Optimal Calibration of Parallel Kinematic Machines

In this paper, error sensitivity analysis is discussed for the purpose of optimal calibration of parallel kinematic machines (PKMs). The idea is to find a less error sensitive area in the workspace for calibration. To do so, an error model is developed that takes into consideration all the geometric errors due to imprecision in manufacturing and assembly. Based on this error model, it is shown that the error mapping from the geometric errors to the pose error of the PKM depends on the Jacobian inverse. The Jacobian inverse would introduce spurious errors that would affect the calibration results, if used without proper care. Hence, it is suggested to select the areas in the workspace with smaller condition numbers for calibration. A case study is presented to illustrate the proposed method.