[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.

Soft matter with hard skin : From skin wrinkles to templating and material characterization

Computer Methods in Applied Mechanics and Engineering

Shape-Memory Materials

This book describes the key role played by thermally excited defects such as vortices, disclinations, dislocations, vacancies and interstitials in the physics of crystals, superfluids, superconductors, liquid crystals and polymer arrays Geometrical aspects of statistical mechanics become particularly important when thermal fluctuations entangle or crumple extended line-like or surface-like objects in three dimensions In the case of entangled vortices above the first-order flux lattice melting transition in hightemperature superconductors, the lines themselves are defects A variety of theories combined with renormalization-group ideas are used to describe the delicate interplay among defects, statistical mechanics and geometry characteristic of these problems in condensed matter physics This indispensible guide has its origins in Professor Nelson’s contributions to summer schools, conference proceedings and workshops over the past twenty years It provides a coherent and pedagogic graduate-level introduction to the field of defects and geometry

/pdf/defects-and-geometry-in-condensed-matter-physics-79be1ox611.pdf

Defects and Geometry in Condensed Matter Physics

Smart Morphable Surfaces enable switchable and tunable aerodynamic drag reduction of bluff bodies. Their topography, resembling the morphology of golf balls, can be custom-generated through a wrinkling instability on a curved surface. Pneumatic actuation of these patterns results in the control of the drag coefficient of spherical samples by up to a factor of two, over a range of flow conditions. (Figure Presented).

Smart Morphable Surfaces for Aerodynamic Drag Control

https://backend.orbit.dtu.dk/ws/files/145410334/Tusek_et_al_2018.pdf

Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling

Titanium is a transition metal. It is present in several minerals including rutile and ilmenite, which are well dispersed over the Earth’s crust. Even though titanium is as strong as some steels, its density is only half of that of steel. Titanium is broadly used in a number of fields, including aerospace, power generation, automotive, chemical and petrochemical, sporting goods, dental and medical industries. The large variety of applications is due to its desirable properties, mainly the relative high strength combined with low density and enhanced corrosion resistance. This chapter discusses the applications of titanium and its alloys in the medical field.

Titanium and Titanium Alloy Applications in Medicine

The elastocaloric cooling, utilizing latent heat associated with martensitic transformation in shape-memory alloys, is being considered in the recent years as one of the most promising alternatives to vapour compression cooling technology. It can be more efficient and completely harmless to the environment and people. In the first part of this work, the basics of the elastocaloric effect (eCE) and the state-of-the-art in the field of elastocaloric materials and devices are presented. In the second part, we are addressing crucial challenges in designing active elastocaloric regenerators, which are currently showing the largest potential for utilization of eCE in practical devices. Another key component of elastocaloric technology is a driver mechanism that needs to provide loading for active elastocaloric regenerators in an efficient way and recover the released energy during their unloading. Different driver mechanisms are reviewed and the work recovery potential is discussed in the third part of this work.

/pdf/elastocaloric-cooling-state-of-the-art-and-future-challenges-230agcnh7m.pdf

Elastocaloric cooling : state-of-the-art and future challenges in designing regenerative elastocaloric devices

We present the results of an experimental investigation on the crystallography of the dimpled patterns obtained through wrinkling of a curved elastic system. Our macroscopic samples comprise a thin hemispherical shell bound to an equally curved compliant substrate. Under compression, a crystalline pattern of dimples self-organizes on the surface of the shell. Stresses are relaxed by both out-of-surface buckling and the emergence of defects in the quasi-hexagonal pattern. Three-dimensional scanning is used to digitize the topography. Regarding the dimples as point-like packing units produces spherical Voronoi tessellations with cells that are polydisperse and distorted, away from their regular shapes. We analyze the structure of crystalline defects, as a function of system size. Disclinations are observed and, above a threshold value, dislocations proliferate rapidly with system size. Our samples exhibit striking similarities with other curved crystals of charged particles and colloids. Differences are also found and attributed to the far-from-equilibrium nature of our patterns due to the random and initially frozen material imperfections which act as nucleation points, the presence of a physical boundary which represents an additional source of stress, and the inability of dimples to rearrange during crystallization. Even if we do not have access to the exact form of the interdimple interaction, our experiments suggest a broader generality of previous results of curved crystallography and their robustness on the details of the interaction potential. Furthermore, our findings open the door to future studies on curved crystals far from equilibrium.

/pdf/wrinkling-crystallography-on-spherical-surfaces-4wba9fo9yx.pdf

Miha Brojan

Papers

Smart Morphable Surfaces for Aerodynamic Drag Control

Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling

Titanium and Titanium Alloy Applications in Medicine

Elastocaloric cooling : state-of-the-art and future challenges in designing regenerative elastocaloric devices

Wrinkling crystallography on spherical surfaces