Beyond developable: computational design and fabrication with auxetic materials

We present a computational method for interactive 3D design and rationalization of surfaces via auxetic materials, i.e., flat flexible material that can stretch uniformly up to a certain extent. A key motivation for studying such material is that one can approximate doubly-curved surfaces (such as the sphere) using only flat pieces, making it attractive for fabrication. We physically realize surfaces by introducing cuts into approximately inextensible material such as sheet metal, plastic, or leather. The cutting pattern is modeled as a regular triangular linkage that yields hexagonal openings of spatially-varying radius when stretched. In the same way that isometry is fundamental to modeling developable surfaces, we leverage conformal geometry to understand auxetic design. In particular, we compute a global conformal map with bounded scale factor to initialize an otherwise intractable non-linear optimization. We demonstrate that this global approach can handle non-trivial topology and non-local dependencies inherent in auxetic material. Design studies and physical prototypes are used to illustrate a wide range of possible applications

IST Austria Thesis

Fabrication of curved shells plays an important role in modern design, industry, and science. Among their remarkable properties are, for example, aesthetics of organic shapes, ability to evenly distribute loads, or efficient flow separation. They find applications across vast length scales ranging from sky-scraper architecture to microscopic devices. But, at the same time, the design of curved shells and their manufacturing process pose a variety of challenges. In this thesis, they are addressed from several perspectives. In particular, this thesis presents approaches based on the transformation of initially flat sheets into the target curved surfaces. This involves problems of interactive design of shells with nontrivial mechanical constraints, inverse design of complex structural materials, and data-driven modeling of delicate and time-dependent physical properties. At the same time, two newly-developed self-morphing mechanisms targeting flat-to-curved transformation are presented. In architecture, doubly curved surfaces can be realized as cold bent glass panelizations. Originally flat glass panels are bent into frames and remain stressed. This is a cost-efficient fabrication approach compared to hot bending, when glass panels are shaped plastically. However such constructions are prone to breaking during bending, and it is highly nontrivial to navigate the design space, keeping the panels fabricable and aesthetically pleasing at the same time. We introduce an interactive design system for cold bent glass façades, while previously even offline optimization for such scenarios has not been sufficiently developed. Our method is based on a deep learning approach providing quick and high precision estimation of glass panel shape and stress while handling the shape multimodality. Fabrication of smaller objects of scales below 1 m, can also greatly benefit from shaping originally flat sheets. In this respect, we designed new self-morphing shell mechanisms transforming from an initial flat state to a doubly curved state with high precision and detail. Our so-called CurveUps demonstrate the encodement of the geometric information into the shell. Furthermore, we explored the frontiers of programmable materials and showed how temporal information can additionally be encoded into a flat shell. This allows prescribing deformation sequences for doubly curved surfaces and, thus, facilitates self-collision avoidance enabling complex shapes and functionalities otherwise impossible. Both of these methods include inverse design tools keeping the user in the design loop

‘Betek, Tali ngan Atap’ ‘Knots, String and Blades’: Production and Use of Organic Utility Objects by the Orang Ulu of Sarawak

The Orang Ulu people of the East Malaysian State of Sarawak comprise many indigenous groups. They live predominantly in the north-east of the State in highland rainforest areas and are both swidden farmers and hunter-gatherers. Many of the utility objects they use are manufactured locally from forest resources. As communications in the area have improved, new materials and technology have arrived and are influencing their traditional production. This thesis documents the production of material culture by some of these groups. Using a comparative approach, it examines the processes that feature in material preparation, the tools used, and the various styles of objects made and the designs chosen. During fieldwork the techniques used in the production of the documented objects were learnt by observer participation until they were fully understood and the fieldworker could replicate them. The study includes many illustrations and explanations of designs and manufacturing techniques. In addition the thesis discusses the changes that have occurred within these material culture assemblages. It considers these in relation to various issues,such as people’s identity concerns and the commodification of their local products. It relates the objects to their maker, user and usage, investigating labour co-ordination in the region and gender issues pertaining to them

Fabrication-Aware Design with Performative Criteria

Artists and architects often need to handle multiple constraints during design of physical constructions. We define a performative constraint as any constraint on design that is tied to the performance of the model--either during fabrication, construction, daily use, or destruction. Even for small to medium scale models, there are functional criteria such as the ease of fabrication and the assembly process, or even the interplay of light with the material. Computational tools can greatly aid in this process, assisting with the lower-level performative constraints, while the designer handles the high-level artistic decisions. Additionally, using new fabrication methods, our tools can aid in lowering the difficulty of building complex constructions, making them accessible to hobbyists. In this thesis, we present three computational methods for designing with different approaches, each with a different material, fabrication method, and use case. The first method is a construction with intersecting planar pieces that can be laser cut or milled. These 3D forms are assembled by sliding pieces into each other along straight slits, and do not require other support such as glue or screws. We present a mathematical abstraction that formalizes the constraints between pieces as a graph, including fabrication and assembly constraints, and ensure global rigidity of the sculpture. We also propose an optimization algorithm to guide the user using automatic constraint satisfaction based on analysis of the constraint relation graph. We demonstrate our approach by creating several small- to medium-scale examples including functional furniture. The second method presents a solution to building a 3D sculpture out of existing building blocks that can be found in many homes. Starting from the voxelization of a 3D mesh we merge voxels to form larger bricks, and then analyze and repair structural problems based on a graph representation of the block connections. We then output layer-by-layer building instructions to allow a user to quickly and easily build the model. We also present extensions such as hollowing the models to use less bricks, limiting the number of bricks of each size, and including color constraints. We present both real and virtual brick constructions and associated timings, showing improvements over previous work. The final case presented tackles the inverse design problem of finding a surface to produce a target caustic on a receiver plane when light is refracted or reflected. This is an example where the performative constraint is the principal driver of the design. We introduce an optimal transport formulation to find a correspondence between the incoming light and the output target light distribution. We then show a 3D optimization that finds the surface that transports light based on the correspondence map. Our approach supports piecewise smooth surfaces that are as smooth as possible but allow for creases, to greatly reduce the amount of artifacts while allowing light to be completely diverted producing completely black regions. We show how this leads to a very large space of high-contrast, high-resolution caustic images, including point and line singularities of infinite light density as well as photo-realistic images. Our approach leads to surfaces that can be milled using standard CNC milling. We demonstrate the approach showing both simulated and fabricated examples

2013, UMaine News Press Releases

This is a catalog of press releases put out by the University of Maine Division of Marketing and Communications between January 2, 2013 and December 31, 2013