Special Issue of Applied Mechanics Reviews in Collaboration With the Journal of Vibration and Acoustics (2014)

Applied Mechanics Reviews (AMR) is an international review journal that serves as a premier venue for state-of-the-art and retrospective survey articles and reviews of research areas and curricular developments across all subdisciplines of applied mechanics and engineering science, including fluid and solid mechanics, heat transfer, dynamics and vibration, and applications. AMR works closely with other ASME Technical Journals in serving the broad ASME community with unique content of high quality and long shelf life. Collaborative special issues between AMR and other ASME Technical Journals collect contributions of all forms described above for a specific discipline within a single issue.Since its first publication in 1983, the Journal of Vibration and Acoustics (JVA) has been the premier journal to publish original research results of permanent interest in all areas of vibration and acoustics. Examples of specific topic areas covered include: vibration of continuous and lumped parameter systems; linear and nonlinear vibrations; random vibration; modal analysis; mechanical signatures; structural dynamics and control; vibration suppression; vibration isolation; passive and active damping; machinery dynamics; rotor dynamics and vibration; acoustic emission; noise control; machinery noise; structural acoustics; fluid-structure interaction; aeroelasticity; and flow-induced noise and vibration.The goal of this collaborative issue is to equally serve the readerships of AMR and JVA by focusing on topics of importance to the applied mechanics and vibration and acoustics communities alike. The four state-of-the-art review papers collected in this issue capture key areas of investigation of both theoretical and applied significance. They provide authoritative commentary on the existing literature, and unique value to both researchers and applied engineers. Two of the four papers are further accompanied by independent reflection and author responses that highlight complementary viewpoints and open challenges.For the past several decades, vibratory energy harvesters (VEHs) have emerged as an alternative means to power small and low-power devices, such as wireless sensing, data transmission, and medical implants. With the ability to generate power from ambient vibration, VEHs offer potential advantage over batteries such as scalability and continuity. Linear VEHs, however, have a very limited bandwidth and their performance is very sensitive to uncertainties from the ambient environment or manufacturing variations. The review by Daqaq, Masana, Erturk, and Quinn is a follow-on to a special issue of the Journal of Vibration and Acoustics on energy harvesting (JVA, 133(1), Dec. 2010). The paper thoroughly reviews ways to engage nonlinearities in order to significantly enhance the performance of VEHs through broadband transduction. It also systematically describes monostable, bistable, and piecewise linear VEHs under various excitations (e.g., harmonic and random). The authors end the paper by identifying future research directions of nonlinear VEHs, including performance metrics and compatible nonlinear electric circuits. The companion discussion by Brian Mann not only concisely summarizes the paper by Daqaq et al., but also provides an additional reference to confirm that nonlinear, bistable VEHs may outperform linear VEHs when subjected to colored-noise excitations.The review by Hussein, Leamy, and Ruzzene is a follow-on to a special issue of the Journal of Vibration and Acoustics on the dynamics of phononic materials and structures (JVA, 135(4), Jun. 2013). The paper provides a comprehensive review of the dynamics of periodic media, including periodic structures, phononic crystals, and acoustic/elastic metamaterials. This topic traces back to Sir Isaac Newton, and yet this research area continues to grow due to new discoveries. Periodic media possess a frequency band structure that enables various applications, such as acoustic filtering, defect engineering, wave collimation and rectification, acoustic and vibration isolation, subwavelength focusing, and cloaking of acoustic or elastic waves. The article opens with an in-depth review of past and present research on periodic media with an abundant list of references. The authors concisely yet thoroughly explain the underlying mathematics and physics of periodic media dynamics. The paper closes by highlighting emerging research directions, including damped and nonlinear phononic systems, coupling of elastic and other types of waves (e.g., electromagnetic waves) in phononic systems, tunability, phononic logic circuits, and phononic energy harvesting devices. The commentary by Brian Mace complements the article by Hussein et al. with a discussion of wave motion in periodic structures, with a special emphasis on multicoupled and continuous systems, as well as further considerations of the concepts of “negative group velocity” and “negative mass.”Another research topic that has been widely studied for the past 20 years is vibration of systems that present cyclic symmetry, also known as rotationally periodic structures. Such systems have wide industrial applications, such as turbine bladed disks, propellers, compressors, wind turbines, planetary gear systems, and torsional dampers. Many remarkable research topics are also derived from the paradigm of cyclic symmetric structures, including phenomena of mode localization of mistuned cyclic symmetric bladed disks and the dynamics of spinning cyclic symmetric rotors. The mathematical foundation underlying these systems is circulant matrices, which is the main theme of the review article by Olson, Shaw, Shi, Pierre, and Parker. In this paper, the authors present the theory of circulant matrices in an elegant and concise way. Three examples are discussed: general cyclic systems, cyclic systems with one degree of freedom per sector, and cyclic systems with two degrees of freedom per sector. The treatment is comprehensive, covering important yet subtle topics including generalized eigenvalue problems, discrete Fourier transforms, engine-order force excitations, and traveling waves.Planetary gear designs provide an example of cyclic symmetric systems, which has been the object of intensive study in recent years. Planetary gears remain a major source of vibration and noise for various applications, such as wind turbines, helicopters, aircraft engines, and power transmission systems. The review by Cooley and Parker summarizes both theoretical and experimental research on planetary gear dynamics and vibration in a comprehensive and in-depth manner. After an informative introduction, Cooley and Parker lay out a two-dimensional lumped-mass dynamical model, which can be modified to include advanced features such as out-of-plane vibration and elasticity of the ring gear. Several important issues are subsequently discussed. The first is that of planet load sharing, ensuring that loads are shared equally among all planets. Vibration mode shapes are introduced and classified (in agreement with the results of the review by Olson et al.). Forced response as the gears move, resulting from varying contact conditions at the gear tooth mesh interface, is discussed via four types of mesh models. To minimize forced response, the concept of planet phasing is introduced to arrange planet configuration and tooth numbers so that the mesh forces self-equilibrate. The authors end the article by considering the effects on planetary gear dynamics of component elasticity, high-speed operating conditions, manufacturing errors, and profile modification.This collaborative issue focuses on several vibrant research topics spanning vibration and acoustics. We believe the articles herein will serve the applied mechanics and vibration and acoustics communities by stimulating further discussions and discoveries that have both theoretical and practical values.