英语原文共 27 页
Structural Engineering and Mechanics, Vol. 17, No. 3-4 (2004) 000-000
On magnetostrictive materials and their use in adaptive structures
Marcelo J. Dapinodagger;
Department of Mechanical Engineering, The Ohio State University, 2091 Robinson Laboratory, Columbus, OH 43210-1107, USA
(Received , 2003, Accepted August 30, 2003)
Abstract. Magnetostrictive materials are routinely employed as actuator and sensor elements in a wide variety of noise and vibration control problems. In infrastructural applications, other technologies such as hydraulic actuation, piezoelectric materials and more recently, magnetorheological fluids, are being favored for actuation and sensing purposes. These technologies have reached a degree of technical maturity and in some cases, cost effectiveness, which justify their broad use in infrastructural applications. Advanced civil structures present new challenges in the areas of condition monitoring and repair, reliability, and highauthority actuation which motivate the need to explore new methods and materials recently developed in the areas of materials science and transducer design. This paper provides an overview of a class of materials that because of the large force, displacement, and energy conversion effciency that it can provide is being considered in a growing number of quasistatic and dynamic applications. Since magnetostriction involves a bidirectional energy exchange between magnetic and elastic states, magnetostrictive materials provide mechanisms both for actuation and sensing. This paper provides an overview of materials, methods and applications with the goal to inspire novel solutions based on magnetostrictive materials for the design and control of advanced infrastructural systems.
An adaptive or smart structure consists of four main elements: actuators, sensors, control strategies, and power electronics (Chopra 2002, Garg et al. 2002). A smart structure responds to changing external conditions - e.g., loads or deformations - as well as internal conditions - e.g., damage or failure. Microprocessors analyze the responses from the sensors in real or nearly real time and use integrated control theory to command the actuators to apply localized deflections and forces. These inputs effect changes in the structure which counteract or otherwise modify system response in a controlled manner. Numerous applications of smart structures to physical systems are evolving to actively control vibration, noise, damping, shape change, stress distribution, and even microscopic properties (Kessler et al. 2003).
自适应或智能结构由四个主要元素组成：执行器，传感器，控制策略和电力电子（Chopra 2002，Garg等2002）。 智能结构响应于变化的外部条件 - 例如负载或变形 - 以及内部条件 - 例如损坏或故障。 微处理器实时或近乎实时地分析来自传感器的响应，并使用集成控制理论来命令致动器施加局部偏转和力。 这些输入影响结构的变化，从而以受控的方式抵消或以其他方式修改系统响应。 智能结构在物理系统中的众多应用正在发展，以主动控制振动，噪声，阻尼，形状变化，应力分布，甚至微观特性（Kessler等，2003）。
The benefits of smart structures as compared with passive or conventional structures have been
recognized in both traditional and emerging areas. In the area of civil infrastructure, for example, there are clear technological challenges in regard to the declining state of the civil infrastructure in the United States and other countries. Smart materials and structures research can enable “smart” bridges, buildings and highways that can detect and repair structural damage caused by extreme events - for example earthquakes - or long-term deterioration. Furthermore, due to their solid state operation, smart structures can offer an environmental advantage as compared to conventional systems based on hydraulic fluid. Other structural applications stand to benefit from smart materials research as well. The aging aircraft fleet currently in use by U.S. and foreign airlines necessitates sensors and actuators that can provide real-time prevention, detection and repair of damage in a number of critical structural components. Similar needs apply to the automotive sector, in which the ability of smart structures to operate safely, quietly, efficiently and reliably can enable novel solutions in areas such as NVH (Noise, Vibration amp; Harshness), structural crash-worthiness and condition monitoring, and restraint system design.
Magnetostrictive materials are a class of active metallic compounds which deform when exposed to magnetic fields. These deformations are a manifestation of the magnetoelastic coupling and corresponding dependency of magnetic moment orientation with interatomic spacing. The most common form of magnetoelastic coupling, the linear or Joule magnetostriction, pertains to the case when strains are measured along the magnetic field direction, as shown in Fig. 1. It is noted that if the magnetostriction is positive, the material elongates irrespective of the direction of rotation of the magnetic moments, and the transverse dimension is reduced such that the volume remains constant. If the magnetostriction is negative, the sample length decreases, and the diameter increases. A symmetric magnetostriction curve is then obtained as the magnetic field is cycled. While most magnetic mater