Shape memory actuators - potentials and specifics of their technical use and electrical activation
Due to a martensitic phase change shape memory alloys can revert to their original shape by heating when they undergo an appropriate treatment. Actuator elements with this shape memory effect can show a significant design change combined with a considerable force. Therefore they can be used to solve many technical tasks in the field of actuating elements and mechatronics. These intelligent materials will play an increasing role in the next years, especially within the automotive technology, energy management, power and mechanical engineering as well as medical technology. In order to use the potential of these materials in an optimal way it is necessary to know and understand the extraordinary and unconventional properties of shape memory alloys. This paper will present the commonly used systems of shape memory alloys of today including their performance characteristics and will explain the basics of the shape memory effect in a vivid way. A multitude of application possibilities of shape memory actuators will be presented, in particular the research and development projects that have been carried out at the Konstanz University of Applied Sciences during the last years. In this way a solid state heat engine and an intramedullary nail for bone elongation will be presented as well as various adaptive systems for automotive safety and comfort systems, driven by shape memory elements. Regarding the applications in the automotive field a special focus will be given to different electrical activations to enable very fast contraction times of the shape memory components.
Types of wear and tear of biomaterials used in orthopaedic surgery
Purpose: Purpose of this paper is presentation of observations on different kinds of wear and tear of biomaterials used in contemporary orthopaedic surgery. Design/methodology/approach: Types of prosthesis damage, encountered in medical practice, and their causes have been described. Results of many clinical studies were analysed to review prosthesis damage from the stage of implanting (such as intrusion of a foreign object between its components) to their natural wear and tear after many years of use (abrasive wear, biological corrosion). Findings: It has been shown that prostheses heads may also succumb to quick wear and tear despite being made of harder and more durable materials than sockets. Research limitations/implications: Clinical and laboratory of defective implants discover the reasons of damage, but they are time consuming. There are also difficulties in obtaining objects for research. Originality/value: The research has helped to systematise the knowledge on the mechanisms of wear and damage of endoprostheses, which is vital for improvement of their life cycle.
Shape memory alloy resetable spring lift for pedestrian protection
Pedestrian protection has become an increasingly important aspect of automotive safety with new regulations taking effect around the world. Because it is increasingly difficult to meet these new regulations with traditional passive approaches, active lifts are being explored that increase the "crush zone" between the hood and rigid under-hood components as a means of mitigating the consequences of an impact with a non-occupant. Active lifts, however, are technically challenging because of the simultaneously high forces, stroke and quick timing resulting in most of the current devices being single use. This paper introduces the SMArt (Shape Memory Alloy ReseTable) Spring Lift, an automatically resetable and fully reusable device, which couples conventional standard compression springs to store the energy required for a hood lift, with Shape Memory Alloys actuators to achieve both an ultra high speed release of the spring and automatic reset of the system for multiple uses. Each of the four SMArt Device subsystems, lift, release, lower and reset/dissipate, are individually described. Two identical complete prototypes were fabricated and mounted at the rear corners of the hood, incorporated within a full-scale vehicle testbed at the SMARTT (Smart Material Advanced Research and Technology Transfer) lab at University of Michigan. Full operational cycle testing of a stationary vehicle in a laboratory setting confirms the ultrafast latch release, controlled lift profile, gravity lower to reposition the hood, and spring recompression via the ratchet engine successfully rearming the device for repeat cycles. While this is only a laboratory demonstration and extensive testing and development would be required for transition to a fielded product, this study does indicate that the SMArt Lift has promise as an alternative approach to pedestrian protection.