There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

A review of shape memory alloy research, applications and opportunities

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions, but the performance at each condition is sub-optimal. The ability of a wing surface to change its geometry during flight has interested researchers and designers over the years as this reduces the design compromises required. Morphing is the short form for metamorphose; however, there is neither an exact definition nor an agreement between the researchers about the type or the extent of the geometrical changes necessary to qualify an aircraft for the title ‘shape morphing.’ Geometrical parameters that can be affected by morphing solutions can be categorized into: planform alteration (span, sweep, and chord), out-of-plane transformation (twist, dihedral/gull, and span-wise bending), and airfoil adjustment (camber and thickness). Changing the wing shape or geometry is not new. Historically, morphing solutions always led to penalties in terms of cost, complexity, or weight, although in certain circumstances, thes...

A Review of Morphing Aircraft

With the increased emphasis on both reliability and multi-functionality in the aerospace industry, active materials are fast becoming an enabling technology capturing the attention of an increasing number of engineers and scientists worldwide. This article reviews the class of active materials known as shape memory alloys (SMAs), especially as used in aerospace applications. To begin, a general overview of SMAs is provided. Their useful properties and engineering effects are described and the methods in which these may be utilized are discussed. A review of past and present aerospace applications is presented. The discussion addresses applications for both atmospheric earth flight as well as space flight. To complete the discussion, SMA design challenges and methodologies are addressed and the future of the field is examined.

https://journals.sagepub.com/doi/pdf/10.1243/09544100JAERO211

Aerospace applications of shape memory alloys

In this paper, the placement of piezoelectric sensors and actuators has been studied. Genetic algorithms have been used to find efficient locations of piezoelectric sensors and actuators of a smart composite place. Locations of both sensors and actuators have been determined with consideration of controllability, observability and spillover prevention. The composite specimen with piezoelectric sensors and actuators has been prepared according to the optimization result. The experimental vibration control shows significant vibration reduction for the controlled modes with little effect on the residual modes. In addition, the closed loop system is observed to be robust with respect to system parameter variations.

http://iopscience.iop.org/article/10.1088/0964-1726/8/2/012/pdf

Optimal placement of piezoelectric sensors and actuators for vibration control of a composite plate using genetic algorithms

Finite element analysis of transient thermoelastic behaviors in disk brakes

Postbuckling and vibration characteristics of piezolaminated composite plate subject to thermo-piezoelectric loads

Composite damage model based on continuum damage mechanics and low velocity impact analysis of composite plates

In order to reduce the vibrational level of lightweight composite structures, active vibration control methods have been applied both numerically and experimentally. Using the classical laminated beam theory and Ritz method, an analytical model of the laminated composite beam with piezoelectric sensors and actuators has been developed. Smart composite beams and plates with surface-bonded piezoelectric sensors and actuators were manufactured and tested. It is found that the developed analytical model predicts the dynamic characteristics of smart composite plates very well. Utilizing a linear quadratic Gaussian (LQG) control algorithm as well as well known classical control methods, a feedback control system was designed and implemented. A personal computer (PC) was used as a controller with an analogue - digital conversion card. For a cantilevered beam the first and second bending modes are successfully controlled, and for cantilevered plates the simultaneous control of the bending and twisting modes gives a significant reduction in the vibration level. LQG has shown advantages in robustness to noise and control efficiency compared with classical control methods. In this study examples of control spillover are demonstrated via the instantaneous power spectrum of the sensor output.

https://iopscience.iop.org/article/10.1088/0964-1726/6/5/006/pdf

In Lee

Papers

Optimal placement of piezoelectric sensors and actuators for vibration control of a composite plate using genetic algorithms

Finite element analysis of transient thermoelastic behaviors in disk brakes

Postbuckling and vibration characteristics of piezolaminated composite plate subject to thermo-piezoelectric loads

Composite damage model based on continuum damage mechanics and low velocity impact analysis of composite plates

An experimental study of active vibration control of composite structures with a piezo-ceramic actuator and a piezo-film sensor