Non-Conventional Deformations: Materials and Actuation

Abstract

This paper reviews materials and structures displaying non-conventional deformations as a response to different actuations (e.g., electricity, heat and mechanical loading). Due to the various kinds of actuation and targeted irregular deformation modes, the approaches in the literature show great diversity. Methods are systematized and tabulated based on the nature of actuation. Electrically and mechanically actuated shape changing concepts are discussed individually for their significance, while systems actuated by heat, pressure, light and chemicals are condensed in a shared section presenting examples and main research trends. Besides scientific research results, this paper features examples of real-world applicability of shape changing materials, highlighting their industrial value.The optimal shape-changing concept always depends on the application. In some cases, we do not want the material to adapt to its environment; instead, we wish to control its deformation actively. In these cases, systems actuated by electricity [5], heat [6] or pressure [7] may be considered. On the other hand, there are situations when environmental adaptation is what we are after to achieve maximum working efficiency of a structural part. In the case of marine or wind turbine blades, for instance, their shape for optimal energy yield depends on the direction and speed of the flowing fluid, i.e., the mechanical loading the blades are subjected to [8]. A mechanically actuated shape-changing material could passively modulate its shape (e.g., twisting) in response to changing loads (e.g., bending moments), resulting in significant efficiency gains.This review aims to introduce some selected shape-changing concepts from the literature categorized by the type of actuation giving an up-to-date overview of this field of research.

Determining Hot Deformation Behavior and Rheology Laws of Selected Austenitic Stainless Steels

“…The blanks of such steels can be further processed using conventional methods of plastic deformation, such as rolling [35,36]-for example, sheets of 08Ch18N10T steel are typically rolled under hot, and, subsequently, cold conditions [37]-drawing (tubes [38,39]), or forging [24]. However, non-conventional methods [40], e.g., rotary swaging [41][42][43][44], modified rolling processes [45,46], or methods of severe plastic deformation (SPD), such as various types of the equal channel angular pressing (ECAP) method, [47][48][49][50][51][52][53], can also be used. Last but not least, austenitic stainless steels have recently been a subject of additive manufacturing (3D printing) [54][55][56][57], possibly in combination with other deformation processes, which can advantageously affect the final properties of as-built materials [58,59].…”

Designing Shape Morphing Behavior through Local Programming of Mechanical Metamaterials

“…[ 1–3 ] The implementation of specific shape morphing behavior in devices has been studied on many scales and for different external triggers. [ 4 ] On the one hand there are many approaches on the system level where morphing is often actuated by electric motors, [ 3,5 ] piezoactuators [ 6,7 ] or multi‐material systems, for example, bi‐metals. [ 8 ] On the other hand, shape morphing is realizable through an adaption of the geometry of the micro‐structure.…”