Cubic Lattice Rib Shape: Tuning of Poisson's Ratio and Cosserat Characteristic Length

Auxetics and Other Systems of Anomalous Characteristics

Recent experiments have shown that the elastic deformation behaviors of a polymeric material are consistent with the Cosserat elasticity under nonuniform deformation at a millimeter scale. Thus, an elastohydrodynamic lubrication model in the framework of the Cosserat continuum theory is proposed to explore the lubrication performance that deviates from the classical elastohydrodynamic lubrication theory for the small polymer journal bearings with millimeter size. The elastic deformation of the bearing sleeve made of polymeric material and the pressure distribution in a lubricating film are obtained through an iterative solution of the equation of the Cosserat elasticity and the modified Reynolds’ equations with considering the boundary slippage. The effect of bearing size and Cosserat characteristic lengths for torsion and bending on the lubrication performance of the small polymer journal bearings is studied using the proposed Cosserat elastohydrodynamic lubrication model. It was found that the small changes in film thickness due to the Cosserat effect can result in large changes in film pressure. The Cosserat characteristic length of bending possesses a significant effect on the lubrication behaviors of the journal bearings, because the size effect is mainly caused by the increased apparent modulus due to the bending elastic deformation of the bearing sleeve. The boundary slip behaviors dependent on the Cosserat characteristic length are also studied using the Cosserat elastohydrodynamic model, and the numerical results show that the Cosserat characteristic length changes the optimal geometric parameters of the slip zone in terms of load carrying capacity for the small polymer journal bearings.

Chapter 15 - What Causes Earthquakes?

Cracks in heterogeneous materials with rotating constituents – Small and Intermediate scale Cosserat continua

3D Printing and Industrial Ecology

In this work, continuous fiber reinforced thermoplastic negative Poisson's ratio structures (CFNPRSs) with rotating squares are fabricated by 3D printing based on a symmetrical orthogonal and one‐stoke path planning method. The influences of the printing path on the Poisson's ratio, elastic modulus and energy absorption of the structures under compression are systematically researched. The distribution of continuous fiber at the hinge has a great influence on the compression behavior of the structures. As the number of cross laps of continuous fibers at the hinge increases, the negative Poisson's ratio effect decreases while the elastic modulus and energy absorption increase. The printed CFNPRSs with no cross lap have the most obvious negative Poisson's ratio effect, with an average Poisson's ratio of −0.61. A comparative study on Poisson's ratio of the 3D printed polylactic acid negative Poisson's ratio structures (PANPRSs) is carried out, and the results show that the PANPRSs cannot achieve the negative Poisson's ratio effect because the insufficient stiffness of the printed rotation units violates the rigid assumption in theoretical model. Furthermore, the printed CFNPRSs with a lower relative density of 0.18 has an even better negative Poisson's ratio effect than the existing fiber‐reinforced auxetic structures fabricated by 3D printing. This work can provide a significant reference for the preparation of lightweight functional structures using 3D printing.Highlights The CFNPRSs with rotating squares are prepared by 3D printing technique. The path planning of the fiber at the hinge affects the properties of CFNPRSs. The negative Poisson's ratio of CFNPRSs is more obvious than that of PANPRSs. The relative density and Poisson's ratio of CFNPRSs have obvious advantages.

Chapter 24 - M-Synchronizations: The B-Megasignal and Large Earthquakes

Chapter 4 - Stress Along the Faults

First of all, the overall framework of 3D printing is briefly introduced, including the basic principles of the additive manufacturing process, the classification and summary of the seven processes. Secondly, the common negative Poisson's ratio structure is introduced. Compared with the conventional structure, the negative Poisson's ratio structure has stronger energy absorption capacity, better fracture resistance and better indentation resistance, which are its advantages in printing manufacturing. Finally, 3D printing, the application of negative Poisson's ratio structure and the combination of the two are introduced from the different perspective of medical field, for example, the application of cardiovascular stent, biomedical material structure preparation, and lumbar disc implants. This paper suggests that the structural design of negative Poisson's ratio in 3D printing guides the development of new application directions in the medical field. Negative Poisson's ratio materials have a wide range of applications, not only in the medical field but also in mechanical equipment, automotive manufacturing, aerospace, and other high-tech industries.

Three-dimensional (3D) printing or additive manufacturing, as a revolutionary technology for future advanced manufacturing, usually prints parts with poor control of complex gradients for functional applications. We present a single-vat grayscale digital light processing (g-DLP) 3D printing method using grayscale light patterns and a two-stage curing ink to obtain functionally graded materials with the mechanical gradient up to three orders of magnitude and high resolution. To demonstrate the g-DLP, we show the direct fabrication of complex 2D/3D lattices with controlled buckling and deformation sequence, negative Poisson's ratio metamaterial, presurgical models with stiffness variations, composites for 4D printing, and anti-counterfeiting 3D printing.

Additionally known as three-dimensional (3D) printing, additive manufacturing has made major advancements possible in the fields of engineering, business, the arts, education, and medical. Thanks to recent developments, it is now possible to print three-dimensional to create complex, useful living tissues, biocompatible substances, cells, and supporting structures are combined. Regenerative medicine is utilizing 3D bioprinting. Additive manufacturing technology, or 3D printing, has been labelled the “next big thing” and is predicted to overtake cell phones in popularity. 3D printers use digital templates to produce actual, three-dimensional items. Adding layers to a print, commonly referred to as additive manufacturing, allows for the use of more than a hundred different materials, including nylon, metal, and plastic. Applications for 3D printing can be found in many different industries, such as industrial design, manufacturing, dental, automotive, aerospace, civil engineering, education, jewellery, footwear, and geographic information systems. It has shown to be a simple and affordable solution for a variety of use cases. Using computer-aided design tools and programming, three-dimensional printing is a sophisticated technique that adds material to a base surface to create three-dimensional things. Additive layer manufacturing, also referred to as 3D printing, is the technique of creating three-dimensional things by depositing or solidifying material one layer at a time. Using a computer-aided design module, pharmaceutical components are organized in a three-dimensional pattern. Afterwards, the constituents are converted into a machine-readable format resembling the surface of a three-dimensional dosage form. 3D printing has been used for jewelry, shoe-making, architecture, engineering & construction, the automotive industry as well as the aerospace field, dentistry and medicine, plus geographic information systems (GIS), civil engineering and education. After that stage of the process is completed, the surface transferred to the machine is then printed in different layers. Bioprinting is an interdisciplinary domain that integrates additive manufacturing with biology and material sciences to manufacture threedimensional structures representative of living organisms. The ability to create biological tissues and organs has attracted considerable attention in biomedical research owing to the rising demand for personalized medicine. This scenario propelled bioprinting forward which received much interest thus triggering comprehensive research efforts by various players such as companies, universities as well as research institutes. The goal of this book is to provide a thorough analysis of the complex and rapidly evolving field of bioprinting by critically analyzing and evaluating the existing scientific literature.

In this work, using additive manufacturing via fused filament fabrication 3D printing and finite element simulations conducted in ABAQUS software, the influences of structural parameters on negative Poisson's ratio of a newly designed auxetic structure were studied. The key parameters included the length of the arrow-head element (g), the length of the missing rib element (e), and the thickness of the structure (t). From linear to quadratic and polynomial models, the machine learning regression models have been used to investigate the structure-property relationship. The linear model was statistically significant but with an R-square value of only 70.88% shows that a large amount of variability in the data was not accounted for. The quadratic model slightly improved with an R-square value of 77.17%. However, the polynomial model that depicts outstanding predictive power was the one having an R-squared value of 93.52%, which indicated high accuracy with high generalizability. Quantitatively, the support of findings from this study was evidenced with a very low root mean square error of 0.029, supporting evidence of a highly accurate polynomial machine learning algorithm. Optimization analysis revealed that the most negative Poisson's ratios, less than -0.92, were reached at the highest magnitude of g and e. This research gave a methodological framework on how to predict and optimize the negative Poisson's ratio of newly designed auxetic structures.

Additive manufacturing (AM), commonly known as 3D printing, has garnered significant attention across various industries for its flexibility and simplicity in fabrication. This review explores the evolution of AM technologies, encompassing rapid prototyping and 3D printing, which have revolutionized conventional manufacturing processes. The paper discusses the transition from rapid prototyping to AM and highlights its role in creating fully customized products, optimizing topologies, and fabricating complex designs, especially in the aerospace, medical, automotive, defense energy and food industries. The study delves into the fundamental principles of 3D and 4D printing technologies, detailing their processes, materials, and applications. It provides an overview of the various AM techniques, such as Vat photopolymerization, powder bed fusion, material extrusion, and directed energy deposition, shedding light on their classifications and applications. Furthermore, the paper explores the emergence of 4D printing, which introduces an additional dimension of “time” to enable dynamic changes in printed structures. The role of AM in different industries, including aerospace, medical, automotive, energy, and Industry 4.0, is thoroughly examined. The aerospace sector benefits from AM's ability to reduce production costs and lead times, while the medical field leverages bioprinting for synthetic organ fabrication and surgical equipment development. Similarly, AM enhances flexibility and customization in automotive manufacturing, energy production, and Industry 4.0 initiatives Overall, this review provides insights into the growing significance of AM technologies and their transformative impact on various industries. It underscores the potential of 3D and 4D printing to drive innovation, optimize production processes, and meet the evolving demands of modern manufacturing.

Is This the Future of Medical Technology?

Additive manufacturing of cementitious composites: Materials, methods, potentials, and challenges