Adaptive Structural Systems

Wang KW, Tang J (2008) Adaptive structural systems with piezoelectric transducer circuitry. Springer, New York, NY... 

In this first chapter, we discuss the definition of adaptive structural systems as well as their associated constituents and relevant applications. On this basis, the targets of the work at hand are set and the necessary steps are illustrated. 

In The Brave New World of Huxley [102], the helicopter represents the dominant means of personal transportation. Huxley s shining but essentially dark vision of the future is still in the future for the most part. No one today would seriously dare to compare the noise of helicopters with the buzzing of bees. Noise and vibrations limit the use of helicopters they are too noisy in towns, too easily detected in warfare. Cabin noise stresses both pilots and passengers. Vibrations can fatigue components and imply frequent and expensive inspections. Adaptive structural systems can mitigate these effects and improve flight performance. Vibration induced problems had to be addressed since the early days of rotorcraft development noise related problems become more and more critical with today s versatile deployment. Figure 2.1 shows how these problems are interrelated and points at their economic impact. 

As pointed out in the introductory chapter, there are many multifunctional materials that can be applied to realize adaptive structural systems. They are distinguished by means of excitation mechanism, application range, and maturity of development. While research in material science will widen the choice in the future, currently only piezoelectric materials are suitable for the intended purpose. Therefore, the piezoelectric effect and its constitutive description is examined in detail in this chapter. 

Adams-Nickerson color space, 7 320 Adapalene, 25 789 Adapress, molecular formula and structure, 5 128t Adaptive control system, 20 698 Adaptive sampling techniques, 26 1016-1019... 

If the innate system fails, the adaptive immune system is mobilized to continue the fight. This system constitutes the second line of defense against disease and has two structural components ... 

The design of smart materials and adaptive structures has required the development of constitutive equations that describe the temperature, stress, strain, and percentage of martensite volume transformation of a shape-memory alloy. These equations can be integrated with similar constitutive equations for composite materials to make possible the quantitative design of structures having embedded sensors and actuators for vibration control. The constitutive equations for one-dimensional systems as well as a three-dimensional representation have been developed (7). 

In the various intergrowth systems examined (see Table 5.3) there is no evidence for the presence of point defects. The origin of long-range periodicity in the complex recurrent intergrowth systems is, however, intriguing. The importance of elastic forces in the formation of polytypes, shear structures and infinitely adaptive structures was... 

Thus we have studied the structure of the Y O iF +2 and Ba-Fe-S systems as typical examples of the vernier structure. In the vernier structure, the deviation from stoichiometry originates from the coexistence of different unit dimensions of the subcells, i.e. Aj and Aj sheets for the Y-O-F system, and Fe2S4 and Ba subcells for the Ba-Fe-S system. The structural principle of the vernier structure can be extended to a more general one, called adaptive structure , in which independent, though mutually related, structures for all the compositions can exist in a limited composition range (see Section 2.6). 

Fig. 2.109 Composition (O/M) versus k curves. In this figure, fe stands for the inverse of the mean distance of distortion planes. Each line corresponds to a fixed value of m. White circles on each line correspond to the compositions derived from DP operations. Closed circles are the compositions observed in this system. This figure clearly indicates the characteristics of the adaptive structure.

Despite their different conclusions, we believe that the approaches of Kittel and of Stoneham and Durham are not incompatible but rather they are complementary. Kittel s approach is probably more appropriate to systems such as the adaptive structures where the lattice parameters of the host and solute may differ considerably. The difference should be much smaller with the non-stoicheiometric systems containing shear planes in which the direct interaction may dominate. The interaction function may clearly differ in these two types of system. 

IR-11.4.5 Defect clusters and use of quasi-chemical equations IR-11.5 Phase nomenclature IR-11.5.1 Introduction IR-11.5.2 Recommended notation IR-11.6 Non-stoichiometric phases IR-11.6.1 Introduction IR-11.6.2 Modulated structures IR-11.6.3 Crystallographic shear structures IR-11.6.4 Unit cell twinning or chemical twinning IR-11.6.5 Infinitely adaptive structures IR-11.6.6 Intercalation compounds IR-11.7 Polymorphism IR-11.7.1 Introduction IR-11.7.2 Use of crystal systems IR-11.8 Final remarks IR-11.9 References... 

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