Biomechanically Inspired Machines, Driven by Muscle Like Acting NiTi Alloys

Abstract

The Shape of the Memory Alloy (SMA) is a very promising class of metallic materials with interesting non-linear properties such as Pseudo-Elasticity (PE), memory (MEM) and damping capacity due to high mechanical hysteresis and internal friction. Research shows a bioinventory approach to Shape Memory Alloy (SMA) design, a class of intelligent materials capable of reacting to a pulse (thermal for SMA) with shrinkage. Martensitic transformations in shape-effect crystals under the effect of external forces lead to large deformations of an inelastic nature. In some materials, these reversible deformations are in the range from one digit to at least two digits. The recovery of accumulated inelastic deformation and, as a consequence, the return to the original shape of the body can occur both in the process of unloading at a constant temperature (superelastic effect) and in heating (a form memory effect). Both effects are exciting with regard to their application in compact servomotors when heating the effect of shape memory generates stresses in most materials. If the shape memory alloy faces any shape recovery resistance, it can generate reactive force. The importance of this effect in technical applications is that the reactive force significantly exceeds the force that caused the initial change of shape. This can be used to produce a useful mechanical work. The biomechanically inspired machine that is discussed in the paper refers to pairs of muscle antagonists that are part of the skeletal muscles and are usually arranged in opposition so that a group of muscles contractors another group that relaxes or prolongs. The study proposes a model, a solution not only to design a specific application but also to provide an approach to be used for a wide range of adaptive applications (switching windows, intelligent shadows, parking and urban shelters, etc.). The shape changes in response to various external stimuli. The use of pairs of antagonists provides a solution for SMA-optimized systems where the main and proven advantages are: Easier and quicker shape change, the energy requirement for system operation, lower costs for SMA training and lack of overheating problems.