A novel computer aided engineering method for comparative evaluation of nonlinear structures in the conceptual design phase

Selection of the preferred design concept during design represents a major challenge to design engineers as the required level of information and rigour to achieve an objective evaluation at early stage of design is typically not available. This is particularly evident during evaluation of design concepts of complex load-bearing mechanical structures. The engineering design concepts during concept design phase typically lack detail and more specific performance indicators to enable accurate evaluation. Hence in such cases, a prevailing evaluation approach is based primarily on qualitative scores inferred through personal intuition and historical experience of the design team or individual experts. The principal motivation behind this research is to improve the ability and confidence to select a superior design concept early in the design process. The conventional approach is sensitive to individual expertise and availability of experienced designers. Therefore, in order to make more informed decisions especially in case of complex engineering designs, the concept evaluation methods require more detailed and accurate information. This research is concerned with the development of a novel method for comparative evaluation of engineering design concepts that exhibit nonlinear structural behaviour under load. The approach is based on two key concepts: i) an expansion of the conventional substructuring technique into the nonlinear domain to enable FEA to be more applicable, effective and computationally affordable in early stages of the conceptual design phase; and ii) a restructuring of the traditional process by incorporating the optimisation search to provide orderly rule-guided evolution of design concepts in order to produce objective development metrics which alleviates the dependence on personal intuition and historical experience of the engineering designers. A series of experiments and validation case studies conducted in this research provide conclusive evidence that demonstrates the applicability and the significance of the developed method in terms of reduced time for evaluation and amount of recurrent knowledge generated compared to the more traditional approaches based on the application of FEA in the conceptual design phase. Furthermore, a Confidence Index as a performance measure is developed in this research to describe the quality of the obtained solutions. The derived Confidence Index is a novel contribution to the fields of metaheuristic measurements and engineering concept validation methodology

Sustainable design of a side door reinforcing assembly - optimisation and material selection

As an extension of the author's previous work, an optimization study of a door reinforcing assembly was presented. It was found that by a careful selection of the cross-sectional shape and usage of 'smart' materials, the crash resistance is possible to improve by a factor of 3 while reducing the mass by up to 45%

Extension of substructuring technique in the nonlinear domain

Conventional finite element models based on substructures allow only linear analysis. Some load-bearing structures such as energy absorbers and impact attenuators are designed to perform their useful functions in the nonlinear domain. Evaluating engineering design concepts of those structures objectively and with a certain rigour is challenging. Finite element analysis (FEA) as a potentially suitable tool for the evaluation typically is not computationally efficient and affordable in the conceptual design phase. An idea of extending the substructuring technique to be used for the concept evaluation by allowing substructures to exhibit a nonlinear response and use them in finite element models to reduce the computational cost is investigated in this chapter. For this reason, it was necessary to introduce a new algorithm capable of substructuring nonlinear structural models with sufficient accuracy. The main requirement for successful application of substructuring to this class of design problems is the definition of structural stiffness within an engineering design concept, which is, in fact, the minimal requirement for FEA functionality as well. In this work, the expansion of the substructuring technique beyond the linear response expectancy application is achieved by employing a scalar qualifier to economically modify original substructure matrix for substructures to exhibit a nonlinear response. This extension and integration of substructuring are crucial in allowing FEA to become more computationally efficient and affordable in the conceptual design phase. This chapter provides a comprehensive overview of the traditional substructuring process, followed by a detailed description of the developed method that extends substructures beyond the linearity domain. The implementation of the extended substructures within a commercial FEA code (ABAQUS) is then presented

Utilising latent benefits of substructures in computer aided design and optimisation of complex vehicle assemblies

Collaborative information technologies and tools are successfully used in computer aided design providing numerous benefits, such as better productivity and reduced time and cost to their users. However, availability and usage of such tools amongst fine element (FE) analysts has been relatively poor because of the inability to save or reuse computational time and effort taken during a FE analysis. This paper presents an innovative methodology that utilises substructures to enable collaboration for FE analysis in vehice design. The methodology is proposed and an extended example involving the design and optimisation of a car seat adjuster mechanism assembly is presented to highlight feasability of the methodology and showcase flexability and adaptability of the methodology

Unconstrained Shape Optimisation Of A Lightweight Side Door Reinforcing Crossbar For Passenger Vehicles Using A Comparative Evaluation Method

This paper presents an efficient and extensive exploratory search for lightweight side-door intrusion-bar assembly design concepts using the approach previously developed by the author. The study aimed to discover latent dependence or other relationships between the geometry based design input parameters and the performance objectives (strength and lightweight) to identify the best engineering concept designs. The utilisation of the adopted approach and the extended substructures in particular, allowed for more than 2.6 times more design alternatives to be explored in the same time frame, which significantly increased necessary confidence in the acquired discoveries since a priori hypothesis about factors or patterns of input parameters was absent. The Pearson product-moment correlation coefficient and the Spearman's rank correlation coefficient were used to discover any potential and latent relationships, and the effects significance plots were utilised to deduce the best settings for each parameter and construct a generalised preferred shape

Comparative evaluation of engineering design concepts based on non-linear substructuring analysis

The paper presents a novel approach to comparative evaluation of engineering design concepts that exhibit non-linear structural behaviour under load. The developed method has extended the substructures technique in order to apply the Finite Element Analysis (FEA) method to complex non-linear structural problems in the conceptual design phase. As conventional FE models based on substructures allow only linear analysis, it was necessary in this research to introduce a new algorithm capable of linearizing non-linear structural problems with sufficient accurac y in order to enable comparative evaluation of design concepts relative to each other under the given constraints and loading conditions. A comparative study with respect to model size, efficiency, accuracy and confidence was performed to validate the developed method. Obtained results indicate significant improvement over more traditional approaches to applying FEA in the conceptual design phase. The improvements achieved using the developed method compared to the traditional FE based approach are superior by a factor of 2.7 in efficiency and by a factor of 4.5 in confidence while not sacrificing the optimality of the solutions

A collaborative FEA platform for rapid design of lightweight vehicle structures

This paper presents a novel methodology for rapid design of sustainable vehicle structures using a collaborative Finite Element Analysis (FEA) platform. The developed platform utilises FEA substructures in a novel way to increase the vehicle development efficiency by speeding up analysis and reducing the number of iterations in the product development process. It also allows rapid validation of design changes early in a design and therefore reduction of computational effort and time without compromising accuracy. The underpinning methodology was described and illustrated here using a case study dealing with the design and optimisation of a car seat actuator assembly

Three-Dimensional Printing of Sports Equipment

As an emerging technology in the 1980s, additive manufacturing (AM) has been penetrating the world of manufacturing ever since. From the beginning with the development of the stereolithography technique AM offered a less-expensive and less-time consuming approach to prototyping using only photopolymers such as acrylates and epoxies. Some years later with the development of many new layer-based processes, the focus shifted from just prototyping to the direct manufacture of products. Currently, AM can process all classes of engineering materials from plastics and metals to ceramics as well as nontraditional material

Finite Element Modelling of Additive-Manufactured PA11

The ability to manufacture geometrically complex structures with superior mechanical properties is a key value proposition for the use of additive manufacturing techniques. However, this advantage can only be fully realised when the part design is driven by the knowledge of the mechanical behaviour of the selected material. Finite element modelling can act as a convenient tool for applying said knowledge during the design process. However, anisotropy in mechanical properties of additive-manufactured parts and the non-linear elasticity of polymeric materials have made it challenging to model additive-manufactured polymers without the use of complex and custom material models. In this work, polyamide-11 (PA11) fabricated with the Multi Jet Fusion (MJFTM) process was modelled using elastic-plastic material models native to a commercial finite element package Abaqus. The Nelder- Mead method was applied to calibrate the material model with experimental tensile and compression test data. Simulated flexural properties were then compared against the experimental bending test data to verify the material models. It was found that the elastic-plastic model, applied with the combined hardening option, accurately predicts material flexural modulus

Conceptual design evaluation of lightweight load bearing structural assembly for an automotive seat adjuster mechanism

An application of a novel methodology in a redesign of the load bearing subassembly of an automotive seat adjuster is presented. This novel methodology efficiently evaluated concept variations at a higher rate than the traditional approach based on FEA and therefore enables a comparison of the objective spaces rather than undesirable point design comparisons. This significant increase in efficiency increased the amount of generated knowledge that was presented to the design engineer in a form of the Pareto front comparisons. The comparisons of the Pareto fronts allowed for a clear identification of Concept #3 as the preferred solution, given the load-bearing and the light weighting criteria only. The results also indicated that Concept #2 could also be promising solution after major enhancements, as it showed potential to outperform the current solution in some cases