Towards Understanding Nonlinear Wave Propagation in Three-dimensional Microscale Granular Crystals

Towards Understanding Nonlinear Wave Propagation in Three-dimensional Microscale Granular Crystals
Author: Morgan Hiraiwa
Publisher:
Total Pages: 157
Release: 2020
Genre:
ISBN:

Elastic waves and vibrations play central roles in numerous engineering fields and technologies such as impact mitigation, vibration isolation, ultrasonic imaging, and even electronic filtering components. Enhanced control over such dynamics has the potential to enhance existing applications or create entirely new technologies, with one avenue of such control being waveform manipulation using dispersion and nonlinearity. An attractive approach that has seen significant advancement recently is the field of phononic crystals and acoustic metamaterials, which use structure to tailor existing, and enable new, effective material properties. One such structure is the granular crystal, defined as ordered arrays of discrete elastic particles in contact, which supports dispersion tailoring in addition to nonlinearity resulting from the contact mechanics between the particles. This interplay between dispersion and nonlinearity has produced a large amount of research recently, however, it has mostly been limited to macroscale systems with millimeter to centimeter-sized spheres. Such macroscale systems have limited applicability to many engineering solutions with size and weight constraints. Using microscale spheres to create architectured material with enhanced functionality is a promising idea, however, the dynamic behavior can not be assumed to be identical to macroscale systems because different physics are expected to become important at small scales, the most consequential being adhesive forces. This work experimentally investigates whether three-dimensional microgranular crystals support nonlinear dynamics analogous to their macroscale counterparts, which is currently an open question. Key elements known to allow wave tailoring in macroscale systems are studied individually before building up to direct analysis of nonlinear dynamics in three-dimensional microgranular crystals. First, a two-dimensional microgranular crystal monolayer adhered to a substrate is utilized to investigate, within linear dynamical regimes, interparticle vibrational modes and horizontal-rotational degrees of freedom, both known to affect propagation in three-dimensional systems. Using this experimental design, horizontal-rotational interparticle modes were observed, and described by a recently developed unified theory, for the first time in a microgranular crystal, with the key takeaway being that adhesive forces enhance the role of rotations and form interparticle networks that drastically alter the mode frequency. Next, the contact mechanics of a microsphere monolayer was studied with three different methods of estimating the adhesive force and compared by assuming an elastic contact mechanics model. This unique comparison found the measurements varied widely, suggesting adhesion-induced plasticity may play a major role for polymer microspheres. Subsequently, the behavior of a disordered three-dimensional assembly of microspheres was explored by controlling static and dynamic loading amplitudes, which directly reveal the nonlinear nature of the contact and the weakly nonlinear dynamics that result from it. It was discovered that the nonlinear behavior was drastically different from macroscale counterparts initially, however, the behavior was approximately similar after mechanical conditioning. Lastly, strongly nonlinear dynamics of an ordered three-dimensional microscale granular crystal was investigated in a preliminary study by characterizing the dependence of sound speed on acoustic wave amplitude and found to behave approximately similar to macroscale systems, though additional data is needed for a rigorous analysis. This finding bodes well for translating the promise of macroscale granular crystals to the microscale. The work contained in this thesis lays out a path to exploring even more complex microgranular crystal dynamics.

Coherent Structures in Granular Crystals

Coherent Structures in Granular Crystals
Author: Christopher Chong
Publisher: Springer
Total Pages: 100
Release: 2018-03-29
Genre: Science
ISBN: 3319778846

This book summarizes a number of fundamental developments at the interface of granular crystals and the mathematical and computational analysis of some of their key localized nonlinear wave solutions. The subject presents a blend of the appeal of granular crystals as a prototypical engineering tested for a variety of diverse applications, the novelty in the nonlinear physics of its coherent structures, and the tractability of a series of mathematical and computational techniques to analyse them. While the focus is on principal one-dimensional solutions such as shock waves, traveling waves, and discrete breathers, numerous extensions of the discussed patterns, e.g., in two dimensions, chains with defects, heterogeneous settings, and other recent developments are discussed. The emphasis on the subject was motivated by models in condensed matter physics, ferroelectrics, high energy physics, and statistical mechanics, leading to developments in mathematical analysis, numerical computation and insights on the physical aspects of the model. The book appeals to researchers in the field, as well as for graduate and advanced undergraduate students. It will be of interest to mathematicians, physicists and engineers alike.

Micro and Nanomechanics, Volume 5

Micro and Nanomechanics, Volume 5
Author: La Vern Starman
Publisher: Springer
Total Pages: 79
Release: 2016-09-16
Genre: Technology & Engineering
ISBN: 3319422286

Micro-and Nanomechanics, Volume 5 of the Proceedings of the 2016 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the fifth volume of ten from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on a wide range of areas, including: MEMS: Materials & Interfaces Microscale & Microstructural Effects on Mechanical Behavior Novel Nano-scale Probes Nanoindentation & Beyond Nanomechanics Dynamic Micro/Nano Mechanics

Analytical and Computational Modeling of Mechanical Waves in Microscale Granular Crystals

Analytical and Computational Modeling of Mechanical Waves in Microscale Granular Crystals
Author: Samuel P. Wallen
Publisher:
Total Pages: 139
Release: 2017
Genre:
ISBN:

Granular media are one of the most common, yet least understood forms of matter on earth. The difficulties in understanding the physics of granular media stem from the fact that they are typically heterogeneous and highly disordered, and the grains interact via nonlinear contact forces. Historically, one approach to reducing these complexities and gaining new insight has been the study of granular crystals, which are ordered arrays of similarly-shaped particles (typically spheres) in Hertzian contact. Using this setting, past works explored the rich nonlinear dynamics stemming from contact forces, and proposed avenues where such granular crystals could form designer, dynamically responsive materials, which yield beneficial functionality in dynamic regimes. In recent years, the combination of self-assembly fabrication methods and laser ultrasonic experimental characterization have enabled the study of granular crystals at microscale. While our intuition may suggest that these microscale granular crystals are simply scaled-down versions of their macroscale counterparts, in fact, the relevant physics change drastically; for example, short-range adhesive forces between particles, which are negligible at macroscale, are several orders of magnitude stronger than gravity at microscale. In this thesis, we present recent advances in analytical and computational modeling of microscale granular crystals, in particular concerning the interplay of nonlinearity, shear interactions, and particle rotations, which have previously been either absent, or included separately at macroscale. Drawing inspiration from past works on phononic crystals and nonlinear lattices, we explore problems involving locally-resonant metamaterials, nonlinear localized modes, amplitude-dependent energy partition, and other rich dynamical phenomena. This work enhances our understanding of microscale granular media, which may find applicability in fields such as ultrasonic wave tailoring, signal processing, shock and vibration mitigation, and powder processing.

Nonlinear Dynamics of Three-dimensional Solitary Waves

Nonlinear Dynamics of Three-dimensional Solitary Waves
Author: Yeunwoo Cho
Publisher:
Total Pages: 108
Release: 2010
Genre:
ISBN:

In problems of dispersive wave propagation governed by two distinct restoring-force mechanisms, the phase speed of linear sinusoidal wavetrains may feature a minimum, cmin, at non-zero wavenumber, kmin. Examples include waves on the surface of a liquid in the presence of both gravity and surface tension, flexural waves on a floating ice sheet, in which case capillarity is replaced by the flexural rigidity of the ice, and internal gravity waves in layered flows in the presence of interfacial tension. The focus here is on deep-water gravity-capillary waves, where cmin = 23 cm/s with corresponding wavelength Amin = 27r/kmin = 1.71 cm. In this instance, ignoring viscous dissipation, cmin is known to be the bifurcation point of two-dimensional (plane) and three-dimensional (fully localized) solitary waves, often referred to as "lumps"; these are nonlinear disturbances that propagate at speeds below cmin without change of shape owing to a perfect balance between the opposing effects of wave dispersion and nonlinear steepening. Moreover, Cmin is a critical forcing speed, as the linear inviscid response to external forcing moving at Cmin grows unbounded in time, and nonlinear effects as well as viscous dissipation are expected to play important parts near this resonance. In the present thesis, various aspects of the dynamics of gravity-capillary lumps are investigated theoretically. Specifically, it is shown that steep gravity-capillary lumps of depression can propagate stably and they are prominent nonlinear features of the forced response near resonant conditions, in agreement with companion experiment for the generation of gravity-capillary lumps on deep water. These findings are relevant to the generation of ripples by wind and to the wave drag associated with the motion of small bodies on a free surface.

Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports
Author:
Publisher:
Total Pages: 1126
Release: 1987
Genre: Aeronautics
ISBN:

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Living on an Active Earth

Living on an Active Earth
Author: National Research Council
Publisher: National Academies Press
Total Pages: 431
Release: 2003-09-22
Genre: Science
ISBN: 0309065623

The destructive force of earthquakes has stimulated human inquiry since ancient times, yet the scientific study of earthquakes is a surprisingly recent endeavor. Instrumental recordings of earthquakes were not made until the second half of the 19th century, and the primary mechanism for generating seismic waves was not identified until the beginning of the 20th century. From this recent start, a range of laboratory, field, and theoretical investigations have developed into a vigorous new discipline: the science of earthquakes. As a basic science, it provides a comprehensive understanding of earthquake behavior and related phenomena in the Earth and other terrestrial planets. As an applied science, it provides a knowledge base of great practical value for a global society whose infrastructure is built on the Earth's active crust. This book describes the growth and origins of earthquake science and identifies research and data collection efforts that will strengthen the scientific and social contributions of this exciting new discipline.

Acoustic Waves in Periodic Structures, Metamaterials, and Porous Media

Acoustic Waves in Periodic Structures, Metamaterials, and Porous Media
Author: Noé Jiménez
Publisher:
Total Pages: 0
Release: 2021
Genre:
ISBN: 9783030843014

This book delivers a comprehensive and up-to-date treatment of practical applications of metamaterials, structured media, and conventional porous materials. With increasing levels of urbanization, a growing demand for motorized transport, and inefficient urban planning, environmental noise exposure is rapidly becoming a pressing societal and health concern. Phononic and sonic crystals, acoustic metamaterials, and metasurfaces can revolutionize noise and vibration control and, in many cases, replace traditional porous materials for these applications. In this collection of contributed chapters, a group of international researchers reviews the essentials of acoustic wave propagation in metamaterials and porous absorbers with viscothermal losses, as well as the most recent advances in the design of acoustic metamaterial absorbers. The book features a detailed theoretical introduction describing commonly used modelling techniques such as plane wave expansion, multiple scattering theory, and the transfer matrix method. The following chapters give a detailed consideration of acoustic wave propagation in viscothermal fluids and porous media, and the extension of this theory to non-local models for fluid saturated metamaterials, along with a description of the relevant numerical methods. Finally, the book reviews a range of practical industrial applications, making it especially attractive as a white book targeted at the building, automotive, and aeronautic industries.