Читать книгу Rethinking Prototyping - Группа авторов - Страница 8

While physical form-finding provides agile means for studying relationships of materiality and structural action within a single model, there is a limitation for any such study to predict behaviour beyond its own specific arrangement and scale. With a homogeneous material description, bending-active behaviour is generally scale-able as long as the topological input is repeated (Levien 2009). To establish a vehicle for design search, an individual study must serve as a prototypical case, projecting a design space, which implies a new vocabulary for form, performance and generative means (Coyne 1990). When integrating textile behaviour into a bending-active system, the extensibility of any one prototypical constructional model becomes further limited as the structural and spatial performance of the textile shifts greatly between scales.

While the physical prototype projects a narrow set of parametric rules and material descriptions, it can be a resource in defining fundamental logics of topology, proportion and behaviour, for further computational exploration. In this research, computational explorations occur through two venues: modelling and simulation of relative material descriptions with spring-based numerical methods, and finite element analysis defining precise mechanical (material and force) relationships. Spring-based methods calculate force based upon linear elastic stress-strain relationships (Hooke’s Law of Elasticity); using a numerical integration method such as Euler or Runge-Kutta to approximate the equilibrium of multiple interconnected springs (Kilian and Oschendorf 2005). Such methods are deployed to primarily explore varied relationships between topology and force. Both conditions are easily manipulable during the process of spring-based form-finding, enabling immediacy for feedback and ability to extract how minute manipulations affect the overall system behaviour. A fundamental layer of this research is the continued development of a modelling environment, programmed in Processing (Java) with a particle-spring library, allowing for complex topologies and force descriptions to be initially generated then actively re-modelled through an interface.

Fig. 3 Decomposition of material behaviour for spring-based modelling and simulation (Ahlquist 2013)

Finite element methods (FEM), on the other hand, contribute to forming complex equilibrium structures in defining the complete mechanical behaviour of the system. The given necessity for simulation of large elastic deformations in order to form-find bending-active structures poses no problem to modern nonlinear finite element analysis (Fertis 2006). However, software using FEM does not serve well as an expansive design environment, specifically for textile hybrid systems due to the inability to manipulate geometry and behaviour during the form-finding process. This necessitates the input data, for the pre-processing of the simulation, to be based upon the unrolled geometry of either physical form-finding or a computational environment such as the spring-based methods described above. Though the advantage, as well as necessity, of FEM in the development of textile hybrids, lies in the possibility of a complete mechanical description of the system. Provided that form-finding solvers are included in the software, the possibility of freely combining shell, beam, cable, coupling and spring elements, enables FEM to simulate the exact physical properties of the system in an uninterrupted mechanical description. Such means allows the FEM environment to accomplish, in a single model, the complete scope of form-finding, analysis of performance under external loads, and finally, the unrolling and patterning for fabrication.