Showing papers in "Applied Mechanics Reviews in 2015"

A Review on Bistable Composite Laminates for Morphing and Energy Harvesting

Abstract: Bistable composite laminates have received a considerable attention due to their fabulous behavior and potential for morphing and energy harvesting. A bistable or multistable laminate is a type of composite structure that exhibits multiple stable static configurations. The characterization of unsymmetric fiber-reinforced laminated composite plates as a bistable structure is well established and quantitatively determined after about 30 years of research. As predicting cured shapes of unsymmetric composite laminates became well identified, attention was directed to the design of these structures for morphing applications. Bistable composite laminates have attracted researchers as a morphing structure because a bistable structure settles at one of its equilibrium positions without demanding continuous power to remain there. If the structure is triggered to leave an equilibrium position, it will snap or jump to the other equilibrium position. The snapthrough response is highly geometrically nonlinear. With the increased demand for broadband vibration energy harvesters, bistable composite laminates, which are able to gain large-amplitude vibrations in snapthrough motion, have recently attracted attention. This paper aims to summarize, review, and assess references and findings concerned with the response of bistable composite laminates for morphing and energy harvesting to date. It also highlights the remaining challenges and possible future research work as research in bistable composites transitions from phenomena to application.

Simulation Methods for Guided Wave-Based Structural Health Monitoring: A Review

Abstract: This paper reviews the state-of-the-art in numerical wave propagation analysis. The main focus in that regard is on guided wave-based structural health monitoring (SHM) applications. A brief introduction to SHM and SHM-related problems is given, and various numerical methods are then discussed and assessed with respect to their capability of simulating guided wave propagation phenomena. A detailed evaluation of the following methods is compiled: (i) analytical methods, (ii) semi-analytical methods, (iii) the local interaction simulation approach (LISA), (iv) finite element methods (FEMs), and (v) miscellaneous methods such as mass–spring lattice models (MSLMs), boundary element methods (BEMs), and fictitious domain methods. In the framework of the FEM, both time and frequency domain approaches are covered, and the advantages of using high order shape functions are also examined.

Synthesis of Fibrous Complex Structures: Designing Microstructure to Deliver Targeted Macroscale Response

Abstract: In Mechanics, material properties are most often regarded as being given, and based on this, many technical solutions are usually conceived and constructed. However, nowadays manufacturing processes have advanced to the point that metamaterials having selected properties can be designed and fabricated. Three-dimensional printing, electrospinning, self-assembly, and many other advanced manufacturing techniques are raising a number of scientific questions which must be addressed if the potential of these new technologies is to be fully realized. In this work, we report on the status of modeling and analysis of metamaterials exhibiting a rich and varied macroscopic response conferred by complex microstructures and particularly focus on strongly interacting inextensible or nearly inextensible fibers. The principal aim is to furnish a framework in which the mechanics of 3D rapid prototyping of microstructured lattices and fabrics can be clearly understood and exploited. Moreover, several-related open questions will be identified and discussed, and some methodological considerations of general interest are provided.

Structure and Dynamics of Rotating Turbulence: A Review of Recent Experimental and Numerical Results

Abstract: Rotating turbulence is a fundamental phenomenon appearing in several geophysical and industrial applications. Its study benefited from major advances in the recent years, but also raised new questions. We review recent results for rotating turbulence, from several numerical and experimental researches, and in relation with theory and models, mostly for homogeneous flows. We observe a convergence in the statistical description of rotating turbulence from the advent of modern experimental techniques and computational power that allows to investigate the structure and dynamics of rotating flows at similar parameters and with similar description levels. The improved picture about the anisotropization mechanisms, however, reveals subtle differences in the flow conditions, including its generation and boundary conditions, which lead to separate points of view about the role of linear mechanisms—the Coriolis force and inertial waves—compared with more complex nonlinear triadic interactions. This is discussed in relation with the most recent diagnostic of dynamical equations in physical and spectral space. [DOI: 10.1115/1.4029006]

Multiscale Modeling of Cardiovascular Flows for Clinical Decision Support

Abstract: Patient-specific cardiovascular simulations can provide clinicians with predictive tools, fill current gaps in clinical imaging capabilities, and contribute to the fundamental understanding of disease progression. However, clinically relevant simulations must provide not only local hemodynamics, but also global physiologic response. This necessitates a dynamic coupling between the Navier–Stokes solver and reduced-order models of circulatory physiology, resulting in numerical stability and efficiency challenges. In this review, we discuss approaches to handling the coupled systems that arise from cardiovascular simulations, including recent algorithms that enable efficient large-scale simulations of the vascular system. We maintain particular focus on multiscale modeling algorithms for finite element simulations. Because these algorithms give rise to an ill-conditioned system of equations dominated by the coupled boundaries, we also discuss recent methods for solving the linear system of equations arising from these systems. We then review applications that illustrate the potential impact of these tools for clinical decision support in adult and pediatric cardiology. Finally, we offer an outlook on future directions in the field for both modeling and clinical application.

Modeling Gravity and Turbidity Currents: Computational Approaches and Challenges

Abstract: In this review article, we discuss recent progress with regard to modeling gravity-driven, high Reynolds number currents, with the emphasis on depth-resolving, high-resolution simulations. The initial sections describe new developments in the conceptual modeling of such currents for the purpose of identifying the Froude number–current height relationship, in the spirit of the pioneering work by von Karman and Benjamin. A brief introduction to depth-averaged approaches follows, including box models and shallow water equations. Subsequently, we provide a detailed review of depth-resolving modeling strategies, including direct numerical simulations (DNS), large-eddy simulations (LES), and Reynolds-averaged Navier–Stokes (RANS) simulations. The strengths and challenges associated with these respective approaches are discussed by highlighting representative computational results obtained in recent years.

Fatigue Damage Modeling Techniques for Textile Composites: Review and Comparison With Unidirectional Composite Modeling Techniques

Abstract: Composite structural parts have been successfully introduced in high performance industries. Nowadays, also lower performance, high volume production industries are looking for the application of composites in their products. Especially attractive are textile composites (woven, braided, etc.) because of their better drapability and higher resistance to out-of-plane and dynamic loads. Currently, however, extensive mechanical tests are needed to properly design a composite structure. This is a requirement the large volume industries typically do not have the resources nor the time for. Reducing the need for structural tests can only be done if reliable simulation techniques are available. Simulation techniques for fatigue loading are particularly interesting because products generally have to perform their function over a period of time. For the textile structural composites concerned in this paper, some notable modeling techniques have been developed over the past 15 years. These techniques are presented here and the state of the art is established together with insights for future development by comparing the state of the art with the modeling techniques for laminates from unidirectional (UD) laminae.

A Review of Computational Hemodynamics in Middle Cerebral Aneurysms and Rheological Models for Blood Flow

Abstract: Cerebrovascular accidents are the third most common cause of death in developed countries. Over recent years, Computational Fluid Dynamics simulations using medical image-based anatomical vascular geometries have been shown to have great potential as a tool for diagnostic and treatment of brain aneurysms, in particular to help advise on the best treatment options. This work aims to present a state of the art review of the different models used in Computational Fluid Dynamics, focusing in particular on modelling blood as a viscoelastic non-Newtonian fluid in order to help understand the role of the complex rheological nature of blood upon the dynamics of middle cerebral aneurysms. Moreover, since the mechanical properties of the vessel walls also play an important role in the cardiovascular system, different models for the arterial structure are reviewed in order to couple Computational Fluid Dynamics and Computational Solid Dynamics to allow the study of the fluid-structure interaction.

Instabilities of the von Kármán Boundary Layer

Abstract: Research on the von Karman boundary layer extends back almost 100 years but remains a topic of active study, which continues to reveal new results; it is only now that fully non-linear direct numer ...

The Contribution of Kawada to the Analytical Solution for the Velocity Induced by a Helical Vortex Filament

Abstract: The basic solution for the velocity induced by helical vortex filament is well known as Hardin's solution, published in 1982. A study of early publications on helical vortices now shows that the Japanese scientist Kawada from Tokyo Imperial University also produced many of these results in 1936, which predates Hardin by 46 years. Consequently, in order to honor both, we have studied their derivations to establish the originality of both solutions.

Celebrating the 100th Anniversary of Inglis Result: From a Single Notch to Random Surface Stress Concentration Solutions

Abstract: We celebrate the first quantitative evidence for the stress concentration effect of flaws analyzed by Inglis. Stress concentration factor (SCF) studies have evolved ever since Inglis' 1913 result related to the problem of the elliptical hole in a plate, which also approximately applies to the half-elliptical notch case. We summarize a hundred years of development of the SCF with the exclusive focus on analytical solutions, with a very specific route: the series of works reviewed and presented herein include a parade of solutions beginning with (and those that followed) Inglis famous result, continue with periodic discrete discontinuities, sinusoidal periodic surfaces, and end with more complex continuous configurations such as random surfaces. Furthermore, we show that the form of Inglis' result is powerful enough to serve as first-order approximation for some cases of multiple discontinuities and even continuous rough topologies. Thus, we proposed the Modified Inglis formula (MIF), to estimate the SCF for a variety of configurations, in honor to Inglis' historical result. The impetus of this review stems from the fact that for many engineering problems involving multiphysical solid–fluid interactions, there is a broad interest to couple stress concentration relationships with thermodynamics, fluid dynamics, or even diffusion equations in order to expand understanding on stress-driven interactions at the solid–fluid interface. Additionally, a handy first-order estimate of the SCF can serve in the initial stage of designs of structures and parts containing discontinuities.

A Simple Treatment of Constraint Forces and Constraint Moments in the Dynamics of Rigid Bodies

Abstract: In this expository article, a simple concise treatment of Lagrange's prescription for constraint forces and constraint moments in the dynamics of rigid bodies is presented. The treatment is suited to both Newton-Euler and Lagrangian treatments of rigid body dynamics and is illuminated with a range of examples from classical mechanics and orthopedic biomechanics. Copyright © 2015 by ASME.