Ultimate tensile strength is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials the ultimate tensile strength is close to the yield point, whereas in ductile materials the ultimate tensile strength can be higher.
In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface. The crack will continue to grow until it reaches a critical size, which occurs when the stress intensity factor of the crack exceeds the fracture toughness of the material, producing rapid propagation and typically complete fracture of the structure.
Fellowship of the Royal Society is an award granted by the Fellows of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathematics, engineering science, and medical science".
Fibrils are structural biological materials found in nearly all living organisms. Not to be confused with fibers or filaments, fibrils tend to have diameters ranging from 10–100 nanometers. Fibrils are not usually found alone but rather are parts of greater hierarchical structures commonly found in biological systems. Due to the prevalence of fibrils in biological systems, their study is of great importance in the fields of microbiology, biomechanics, and materials science.
The fatigue limit or endurance limit is the stress level below which an infinite number of loading cycles can be applied to a material without causing fatigue failure. Some metals such as ferrous alloys and titanium alloys have a distinct limit, whereas others such as aluminium and copper do not and will eventually fail even from small stress amplitudes. Where materials do not have a distinct limit the term fatigue strength or endurance strength is used and is defined as the maximum value of completely reversed bending stress that a material can withstand for a specified number of cycles without a fatigue failure.
Susan Randi Wessler, ForMemRS, is an American plant molecular biologist and geneticist. She is Distinguished Professor of Genetics at the University of California, Riverside (UCR).
Alan Needleman is a professor of materials science & engineering at Texas A&M University. Prior to 2009, he was Florence Pirce Grant University Professor of Mechanics of Solids and Structures at Brown University in Providence, Rhode Island.
Daan Frenkel is a Dutch computational physicist in the Department of Chemistry at the University of Cambridge.
Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Typically these tissues form a protective shield or structural support. Bone, mollusc shells, deep sea sponge Euplectella species, radiolarians, diatoms, antler bone, tendon, cartilage, tooth enamel and dentin are some examples of mineralized tissues.
MEMS for in situ mechanical characterization refers to microelectromechanical systems (MEMS) used to measure the mechanical properties of nanoscale specimens such as nanowires, nanorods, whiskers, nanotubes and thin films. They distinguish themselves from other methods of nanomechanical testing because the sensing and actuation mechanisms are embedded and/or co-fabricated in the microsystem, providing—in the majority of cases—greater sensitivity and precision.
Polymer fracture is the study of the fracture surface of an already failed material to determine the method of crack formation and extension in polymers both fiber reinforced and otherwise. Failure in polymer components can occur at relatively low stress levels, far below the tensile strength because of four major reasons: long term stress or creep rupture, cyclic stresses or fatigue, the presence of structural flaws and stress-cracking agents. Formations of submicroscopic cracks in polymers under load have been studied by x ray scattering techniques and the main regularities of crack formation under different loading conditions have been analyzed. The low strength of polymers compared to theoretically predicted values are mainly due to the many microscopic imperfections found in the material. These defects namely dislocations, crystalline boundaries, amorphous interlayers and block structure can all lead to the non-uniform distribution of mechanical stress.
Crack closure is a phenomenon in fatigue loading, where the opposing faces of a crack remain in contact even with an external load acting on the material. As the load is increased, a critical value will be reached at which time the crack becomes open. Crack closure occurs from the presence of material propping open the crack faces and can arise from many sources including plastic deformation or phase transformation during crack propagation, corrosion of crack surfaces, presence of fluids in the crack, or roughness at cracked surfaces.
A Bouligand structure is a layered and rotated microstructure resembling plywood, which is frequently found in naturally designed materials. It consists of multiple lamellae, or layers, each one composed of aligned fibers. Adjacent lamellae are progressively rotated with respect to their neighbors. This structure enhances the mechanical properties of materials, especially its fracture resistance, and enables strength and in plane isotropy. It is found in various natural structures, including the cosmoid scale of the coelacanth, and the dactyl club of the mantis shrimp and many other stomatopods.
In materials science, toughening refers to the process of making a material more resistant to the propagation of cracks. When a crack propagates, the associated irreversible work in different materials classes is different. Thus, the most effective toughening mechanisms differ among different materials classes. The crack tip plasticity is important in toughening of metals and long-chain polymers. Ceramics have limited crack tip plasticity and primarily rely on different toughening mechanisms.
Ginés Morata Pérez ForMemRS is Research Professor at the Autonomous University of Madrid in Spain and an expert in developmental biology of the fruit fly (Drosophila), a specialty he has worked on for over 40 years.
Rachel Angharad Oliver is a Professor of Materials Science at the University of Cambridge and a fellow of Robinson College, Cambridge. She works on characterisation techniques for gallium nitride materials for light-emitting diodes and laser diodes.
Jacqueline Manina Cole is the Head of the Molecular Engineering group in the Cavendish Laboratory at the University of Cambridge. Her research considers the design of functional materials for optoelectronic applications.
Brian John Staskawicz ForMemRS is professor of plant and microbial miology at the University of California, Berkeley and scientific director of agricultural genomics at the Innovative Genomics Institute (IGI).
The European Society for Structural Integrity (ESIS) is an international non-profit engineering scientific society. Its purpose is to create and expand knowledge about all aspects of structural integrity and the dissemination of that knowledge. The goal is to improve the safety and performance of structures and components.
