Subject to a sufficiently large compression, materials may undergo mechanical instabilities of various types. When the material is homogeneous, creases set in. When the material is a bilayer consisting of a stiff thin film on a thick compliant substrate, wrinkles set in. Creases are localized self-contact regions with large strain deviating from the smooth state, while wrinkles are undulations finite in space with infinitesimal strain deviating from the smooth state. After the formation of wrinkles, if the compression further increases, wrinkles double their period and form localized folds. If the substrate is subject to a sufficiently large pre-tension, wrinkles transit to ridges. This thesis explores different types of mechanical instabilities: creases, wrinkles, folds, and ridges. We start with studying creases in different materials. Soft tissues growing under constraint often form creases. We adopt the model of growth that factors the deformation gradient into a growth tensor and an elastic deformation tensor, and show that the critical conditions for the onset of creases take a remarkably simple form. We then perform simulations to explore creases in strain-stiffening materials. For a solid that stiffens steeply at large strains, as the compression increases, the surface is initially smooth, then forms creases, and finally becomes smooth again. For a solid that stiffens steeply at small strains, creases never form for all levels of compression. In order to better control the formation and disappearance of creases, we design a soft elastic bilayer with same moduli of the film and substrate but the substrate pre-compressed, and show that the bilayer can snap between the flat and creased states reproducibly with tunable hysteresis in a large strain range. We also show that an interface between two soft materials can form creases under compression. We then investigate the critical conditions for the onset of wrinkles and creases in bilayers with arbitrary thicknesses and moduli of the two layers, and show several new types of bifurcation behavior when the film and substrate have comparable moduli and thicknesses. We study the effect of substrate pre-stretch on post-wrinkling bifurcations, and show that pre-tension stabilizes wrinkles while pre-compression destabilizes wrinkles. When the pre-compression is sufficiently large, `chaotic' morphologies emerge. When the pre-tension is sufficiently large, we realize ridge localizations and networks under an equi-biaxial compression, and study the mechanics of ridge formation and propagation. / Engineering and Applied Sciences

No description available.

No description available.

This candidate thesis reports the findings of a study on an objective method for measuring grip stiffness in carton board packages with different geometries and material properties. Syntouch Biotac and a tensile tester were used as an objective method for measuring grip stiffness. In this project tests were carried out on packages with three different grammages and two different geometries. For each grammage and geometry, ten packages were tested. The study identifies that the applied method for the measurement of grip stiffness works to measure the change in grip stiffness regardless of where a load was applied on a package. Furthermore, the method demonstrates reasonable results. Finally, the study concluded that the objective testing method could distinguish between different material properties and geometries of the cartons being measured. / En studie om en objektiv metod för mätning av greppstyvhet hos kartongförpackningar med olika geometrier och materialegenskaper rapporteras här. Syntouch Biotac och en provdragare användes som objektiv metod för mätning av greppstyvhet. I detta projekt utfördes tester på förpackningar med tre olika materialegenskaper (ytvikter) samt två olika geometrier. För varje ytvikt och geometri testades tio förpackningar. Studien visar att den maskinbaserade metoden för mätning av greppstyvhet fungerar för att mäta förändring i greppstyvhet oberoende av på var tryck appliceras på förpackningen. Dessutom påvisade studien rimliga resultat. I studien kom författarna även fram till att den maskinbaserade metoden kan skilja olika materialegenskaper och geometrier åt, vilket är verifierar metoden.

Submitted by Samanta Aline Teixeira null (laranjasat@gmail.com) on 2017-03-30T11:46:07Z No. of bitstreams: 1 Dissertação Design do Origami.pdf: 20794490 bytes, checksum: 9b24019a67986dcaaa22f60facdf2b60 (MD5) / Rejected by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: A versão final da dissertação/tese deve ser submetida no formato PDF (Portable Document Format) e o arquivo não deve estar protegido. Por favor, corrija o arquivo PDF e realize uma nova submissão com o arquivo desprotegido. Agradecemos a compreensão. on 2017-04-07T18:11:01Z (GMT) / Submitted by Samanta Aline Teixeira null (laranjasat@gmail.com) on 2017-04-08T19:17:31Z No. of bitstreams: 1 Dissertação digital DESIGN DO ORIGAMI.pdf: 9074846 bytes, checksum: ef1639468e0bb5a7a46290d0b5875d6e (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-11T18:31:46Z (GMT) No. of bitstreams: 1 teixeira_sa_me_bauru.pdf: 9074846 bytes, checksum: ef1639468e0bb5a7a46290d0b5875d6e (MD5) / Made available in DSpace on 2017-04-11T18:31:46Z (GMT). No. of bitstreams: 1 teixeira_sa_me_bauru.pdf: 9074846 bytes, checksum: ef1639468e0bb5a7a46290d0b5875d6e (MD5) Previous issue date: 2017-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A presente pesquisa busca investigar o papel científico e projetual que o origami, arte de dobrar papel, está desempenhando globalmente e como o design de dobras pode contribuir para o processo criativo e às inovações tecnológicas. Para tal, são consideradas três principais vertentes: 1) investigar o estado da arte do origami, desde o seu surgimento histórico até a evolução cronológica de pesquisa científica, processos de comunicação e segmentos estéticos; 2) analisar diferentes publicações do design do origami, as técnicas envolvidas e áreas de atuação; 3) desenvolver estudos de caso em prototipagem baseados no material estudado. Através do método indutivo-confirmável, o estudo possui dois momentos: pesquisa teórica bibliográfica e pesquisa prática experimental. O estudo teórico baseia-se na leitura e seleção de artigos de periódicos, publicações de congressos e livros que elucidem as diferentes possibilidades de ação projetual das dobraduras como a técnica do crease pattern e as vertentes do design de origami adaptado. O estudo experimental trata-se da construção de protótipos para a comprovação prática das técnicas e segmentos estudados. O objetivo de pesquisa está na compreensão da importância do design de origami em diferentes áreas do conhecimento teórico e aplicado e como as dobraduras são reapropriadas para gerar novas formas de construção e modelagem com os materiais e estruturas. Busca-se uma contribuição geral no sentido de solidificar mais e melhor os conceitos e pesquisas com o design do origami no Brasil. / The present research aims to investigate the projetual and scientific role that origami, folding paper art, is performing globally and how folds design can contribute to the creative process and to technological innovations. To this end, three main aspects are considered: 1) to investigate the state of origami’s art, from its historical emergence to the chronological evolution of scientific research, communication processes and aesthetic segments; 2) analyze different publications of origami design, the techniques involved and acting areas; 3) to develop case studies with prototyping based on the material studied. Through the inductive-confirmatory method, this study has two moments: theoretical bibliographic research and practical experimental research. The theoretical study is based on reading and selection of articles from journals, congress publications and books that elucidate the different possibilities of folds design as crease pattern technique and origami-adapted design. The experimental study is based on prototypes construction for practical verification of techniques and segments studied. The research objective is to understand the importance of origami design in different areas of theoretical and applied knowledge, and how foldings are reappropriated to generate new forms of construction and modeling with materials and structures. A general contribution is considered to solidify more and better the concepts and researches with origami design in Brazil.

This work evaluates a specific origami device known as the kaleidocycle and the broad classof rigidly foldable origami. Both of these have potential for application in the design of deployableand foldable arrays of spatial mechanisms.Origami is considered a compliant mechanisms because it achieves its motion through thedeflection of paper creases. Compliant mechanisms generally do not allow for continuous rotation;however, the compliant kaleidocycle represents an exception to this generality. Along with theirability to rotate continuously, kaleidocycles may also be designed to exhibit multistable behaviorduring this rotation. These two characteristics make the kaleidocycle an interesting device withpotential for applications in engineering. This work presents the multistable characteristics ofkaleidocycles, showing that devices can be made which exhibit one, two, three, or four distinctstable equilibrium positions. Kaleiocycles may also be designed to exhibit a range over which thedevice is neutrally stable.The second type of origami presented in this work is rigidly foldable origami, a special classof origami in which all deflection occurs at the creases, allowing the panels to remain rigid. Thistype of origami is of particular interest because of its ability to be constructed from materials muchstiffer than paper while retaining its mobility. This property allows rigidly foldable origami to beapplied to fields such as architecture and deployable mechanisms. This work presents a method forevaluating rigid foldability in origami tessellations. This method is used to define seven theoremsfor the rigid foldability of origami twists and to develop new rigidly foldable origami “gadgets”and tessellations.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Different methods to predict barrier failure in packaging board or paper after converting were investigated. The approach was to compare substrates before and after creasing/folding by applying different barrier tests and to propose a methodology to predict failure in the barrier layer.  Different coatings were used to develop and verify the methodology; a hemicellulose based dispersion barrier coating, a dispersion coated PVOH coating and an extrusion coated PE. Creasing was performed according to standard procedure using recommended creasing geometries. Folding of paper was performed by a gentle creasing with a board backing followed by folding the paper between two metal plates with a well defined distance. The first step in the evaluation was to visually inspect creased/folded substrates by light microscopy to search for coating failures in form of cracks. Both good and bad samples were then tested for grease resistance with a standard test, i.e. TAPPI 454. The TAPPI 454 test showed to be effective to expose barrier failure since oil would penetrate quite fast through the creasing line of cracked samples. Even some samples that appeared to have no cracks in the light microscope showed failure with the grease test. The results showed that only the PE coated samples could sustain a barrier after creasing and folding. This was probably due to a high ductility of the PE-coating combined with a high thickness. The water vapour transmission rate, WVTR, of the samples that passed the TAPPI 454 test was then measured on the samples that endured the grease resistance test. Since PE is a good water vapour barrier, WVTR-measurements were proper for detecting barrier defects. The VWTR of the creased/folded samples was slightly higher for the creased samples than the un-creased references despite the absence of cracks. This was probably due to that the barrier layer got thinner as a result of the strains applied on the coating during the creasing/folding operation.  A methodology to predict barrier failure in barrier coated packaging board and paper after creasing and folding was proposed. Well defined creasing and folding geometries were used in combination with screening for cracks in the barrier layer, first by visual inspection in light microscopy and then by a standard grease resistance test. The samples that passed then screening tests could then be analyzed using more exact but also more time consuming methods such as WVTR. / Olika metoder att förutspå skador i barriärskikt på kartong eller papper efter konvertering undersöktes. Tillvägagångssättet var att jämföra substrat före och efter bigning och vikning genom att tillämpa olika barriärtest och att föreslå en metod för att förutspå defekter i barriärlager. Olika barriärmaterial användes för att utveckla och bekräfta metoden: en hemicellulosa baserad dispersionsbestrykning, en dispersionsbestrykt PVOH barriär och en extruderad PE barriär. Bigandet utfördes enligt standard proceduren och rekomenderade biggeometrier användes. Vikningen av papret utfördes genom varsam bigning med kartong som stöd följt av vikning av pappret genom två metallplattor med ett bestämt avstånd. Utvärderingen började med visuell inspektion av bigade/vikta substrat i ljusmikroskop för att finna barriärdefekter i form av sprickor. Både bra och dåliga prover testades sedan för fettbeständighet med hjälp av ett standardtest, dvs TAPPI 454. TAPPI 454 testet visades sig att vara ett effektivt sätt att identifiera barriärdefekter på grund av att penetration av olja vid biglinjen skedde snabbt på de prov som uppvisade sprickor. Även några av de prov som ej uppvisade sprickor i ljusmikroskop klarade inte av fettbeständighetstest. Resultatet visade att det enda material som kunde bibehålla barriäregenskaper efter bigning och vikning var de PE belagda proven. Detta är antagligen tack vare PE-bestrykningens höga duktulitet och tjocklek. Vattenångspermeabiliteten, WVTR, uppmättes på de prov som uthärdade fettbeständighetstestet. Eftersom PE är en utmärkt vattenångbarriär, var WVTR-mätningar lämpliga för att upptäcka barriärfel. WVTR resultaten för de bigade/vikta proven visade ett något högre värde än de obigade referenserna även om de inte hade sprickor. Det något högre WVTR värdet beror antagligen på att barriärskiktet blev tunnare på grund av töjningen i barriärskiktet under big/vikningen. En metod för att förutspå skador i barriärbestrykt kartong och papper efter bigning och vikning föreslogs. Definierade big- och vikgeometrier användes i kombination av screening av sprickor i barriärskikten, först genom visuell inspektion i ljusmikroskop och sedan ett standarderiserat fettbeständighetstest. Proven som passerar screeningen kan sedan bli analyserade för mer exakta och tidskrävande metoder som WVTR.