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.
Requirement Engineering for Active Safety Pedestrian Protection Systems based on Accident Research
The possibility to assess active safety measures for pedestrian protection is a prerequisite for the definition of reasonable driver assistance systems and their sensor need. The Verps+-index combines In-Depth accident data, driver models and vehicle tests in a new way. As an example, different brake assist strategies are analysed regarding their safety benefit for pedestrian protection. Additionally, requirements for the sensor system will be defined. Different sensing principles can be rated regarding their compliance to these requirements. It can be shown that by use of environmental sensors a brake assist strategy which keeps the driver in the loop already obtains remarkable safety benefits for pedestrians, while more advanced autonomous emergency braking strategies retrieve only limited additional performance. This means that mayor benefits in pedestrian protection can already be obtained by using “simpler” environmental sensors with reduced pedestrian recognition capabilities.