Designing for the 21st Century

Volume II: Interdisciplinary Methods and Findings

Tom Inns

• Publisher: Routledge
• Year: 2016
• eBook ISBN: 9781351964753
• Topic: Business
• Subtopic: Design General
• Index: Business

As we become familiar with the 21st century we can see that what we are designing is changing, new technologies support the creation of new forms of product and service, and new pressures on business and society demand the design of solutions to increasingly complex problems, sometimes local, often global in nature. Customers, users and stakeholders are no longer passive recipients of design, expectations are higher, and increased participation is often essential. This book explores these issues through the work of 21 research teams. Over a twelve-month period each of these groups held a series of workshops and events to examine different facets of future design activity as part of the UK's research council supported Designing for the 21st Century Research Initiative. Each of these 21 contributions describes the context of enquiry, the journey taken by the research team and key insights generated through discourse. Editor and Initiative Director, Tom Inns, provides an introductory chapter that suggests ways that the reader might navigate these different viewpoints.

Stress Computation, Visualisation, and Measurement in: 1. Design of Minimum Energy Forms of Fabric Enclosures, and 2. Painting Conservation and Novel Artist Materials

Prof. Wanda J. Lewis and John S. Brew, (University of Warwick)

Background

Stress Computation, Visualisation, and Measurement was a Designing for the 21^st Century portfolio research project which crossed the boundaries of a number of disciplines. The common theme was the design of tensioned fabrics. These fabrics were studied in two separate applications: as a medium for sculpturing free-form architectural enclosures (roofing forms) and as a material for structural conservation of easel paintings and artists’ canvas.

Paintings and sculptured fabric enclosures perform separate functions and convey different aesthetics. However, their synergy comes from the study of Form, explored by artists, in colour and composition, and by architects, in three-dimensional spaces.

The term ‘free-form’, used to describe architectural enclosures (such as the Millennium Dome), suggests that the shape (form) of these structures cannot be imposed. In fact, it is a form that emerges from two sets of constraints: (i) the assumed boundary configurations and (ii) the assumed tension field. The process of finding the shape is known as form-finding.

Design of fabric structures, whether in the area of conservation of paintings and art or in free-form enclosures requires good understanding of the material behaviour/response to applied loading, temperature, and other environmental factors. To address this, the adopted research methodology involved the University of Warwick (Principal Investigator)in novel form-finding and computational strain analyses, and the Courtauld Institute of Art (Co-investigator) in the measurement and evaluation of fabrics. Accompanying both activities is visualisation of stress and deformation patterns (strain maps) developing in fabric, in response to specific load regimes.

Context

Project 1 – Design of minimum energy forms of fabric enclosures

Fabric enclosures are created from tensioned fabric membranes spanning flexible or rigid boundaries. Their application can be seen in the context of current and future climate change and the consequent demand for more out-door living spaces, and the need for safe and efficient enclosures in areas prone to earthquakes or adverse weather conditions.

The lightweight nature and flexibility of fabric structures makes them versatile in application. They can be used as mobile temporary solutions or semi-permanent enclosures. Their shape is defined through iterative processes, which involve two distinct design stages:¹

• form-finding

• patterning

Figure 1, A tree with a lost branch. The exposed area is ‘healed’ in such a way as to minimise surface area

Figure 2, Soap film model, a surface of constant tension and minimum area

Form-finding addresses the question of shape of a tensioned surface, given the assumed boundary configurations of the structure and tension field. It should involve both physical and computational modelling. The latter gives a more refined (accurate) prediction of shape and employs iterative computations to provide the solution. The computational algorithm used in this study produces minimal surface structures. Their main features of constant surface tension and minimum surface area can be found in animate and inanimate objects, such as trees [Figure 1] and soap films [Figure 2]. It is observed that such objects are optimal in terms of strength, stability, durability and economy of material usage.²

Patterning is the second design stage that influences the form, achieved by further processing of a form-found surface to enable its manufacture out of flat, unstrained fabric. This involves a piecewise mapping of a three-dimensional (3D) membrane surface onto a two-dimensional (2D) plane [Figure 3]. Each piece of the mapped surface has to fit into a strip of fabric which is manufactured, typically, in 2–3m widths.

All minimum-energy surfaces of soap film type are non-developable, i.e., they cannot be mapped onto a 2D plane without distortion. Therefore, the patterning stage has to address the question of (i) as accurate representation of the 3D surface as possible, and (ii) a minimum waste of the material. The final solution has to ensure safety, an aesthetic appearance (wrinkle-free surface) and durability of the fabric membrane.

Figures 3a and b, Geodesic cutting pattern and membrane manufacture from cutting pattern panels. Photograph courtesy of Canobbio S.p.A

Project 2-Painting conservation and artist canvas

Much of the analysis of tensioned fabrics is concerned with determining the stresses and strains in the material, so it is helpful to explain some aspects of this. Material properties of fabrics are described in terms of the following elastic parameters:

• Strain – a ratio of extension to the original size of fabric sample usually expressed as a percentage.

• Stress – a ratio of force to cross-sectional area. For architectural fabrics, stress is given as force per 1m width [kN/m] and the fabric is identified by type, related to the mass per 1m² of fabric.³

• Elastic modulus – a ratio of stress to strain, i.e., it relates stress to strain.

• Strength – a maximum stress that can be applied before damage occurs.

• Poisson’s ratio – a relative amount of contraction in the material perpendicular to the direction of the applied load.

The relationship between warp and weft, shear, and Poisson’s ratio is an important factor determining the general pattern of the mapped strain in fabrics.

The analysis of fabric behaviour under loading falls into an area known as plane stress analysis.⁴ A typical approach to the problem is to use the finite element method. The method replaces the continuous area by a number of smaller domains (finite elements). Unfortunately, this gives a discontinuous representation of stresses and strains at the junctions of the elements. In this project we have developed a new method of analysis that idealises the whole surface in such a way as to give smooth straining of the material. The work leads to comparisons between computational simulations and results obtained from experimental measurements. It also addresses the question of whether a novel computational approach can provide a more accurate stress representation in a canvas painting compared to the finite element modelling, and checks if the results of biaxial tensile testing of fabric properties can be used reliably in the mathematical model predicting fabric response to loading.

The analysis has to consider the fabric structure, which contains two directions of weave: warp, running longitudinally, and weft, running across. There are numerous types of weave; the simplest is the basket weave, shown in Figure 4.

Figure 4, Basket weave

Figure 5, Effects of strain on a sample of fabric

Figure 6, Typical biaxial stress–strain response for PVC-coated polyester. Test results from The Courtauld

Fabric can be strained along the warp, weft and bias direction. The latter produces a shear strain [Figure 5].

The main complication in the analysis lies in the fact that the properties of fabrics vary, depending on the direction of weave and level of loading. This can be illustrated using an architectural fabric as an example [Figure 6].

PVC-coated polyester is one of the most common architectural fabrics. The coating is added to enhance...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Acknowledgements
• Preface
• Introduction
• Design Scoreboard: Development of an Approach to Comparing International Design Capabilities
• 2020 Vision – The UK Design Industry Ten Years On: Implications for Design Businesses of the Future
• Designing for Services in Science and Technology-based Enterprises
• Considerate Design for Personalised Fashion
• Embracing Complexity in Design: Emerging Perspectives and Opportunities
• Metadesign: The Design Practice that Designs Itself
• Emergent Objects: Performance and Interdisciplinary Design at the Human/Technological Interface
• Democratising Technology: A Method
• Branded Meeting Places: Ubiquitous Technologies and the Design of Places for Meaningful Human Encounter
• My Exhibition: Personalising Unencumbered Multimedia Content in a Museum Environment
• Design and Physicality – Towards an Understanding of Physicality in Design and Use
• Making Sense of the City: Representing the Multi-Modality of Urban Space
• Welcoming Workplace: Rapid Design Intervention to Determine the Office Environment Needs of Older Knowledge Workers
• Realising Participatory Design with Children and Young People: A Case Study of Design and Refurbishment in Schools
• Bike Off 2 – Catalysing Anti Theft Bike, Bike Parking and Information Design for the 21st Century: An Open Innovation Research Approach
• Inclusive New Media Design: The Place of Accessibility Guidelines in the Work of Web Designers
• Practical Design for Social Action
• People-centred Computational Environments for Design Discovery: Establishing a Fully Integrated Framework.
• Design Synthesis and Shape Generation
• Stress Computation, Visualisation, and Measurement in: 1. Design of Minimum Energy Forms of Fabric Enclosures, and 2. Painting Conservation and Novel Artist Materials
• Index