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Photoelasticity
Photoelasticity describes changes in the optical properties of a material under mechanical deformation. It is a property of all dielectric media and is often used to experimentally determine the stress distribution in a material, where it gives a picture of stress distributions around discontinuities in materials. Photoelastic experiments (also informally referred to as ''photoelasticity'') are an important tool for determining critical stress points in a material, and are used for determining stress concentration in irregular geometries. History The photoelastic phenomenon was first discovered by the Scottish physicist David Brewster, who immediately recognized it as stress-induced birefringence. That diagnosis was confirmed in a direct refraction experiment by Augustin-Jean Fresnel.A. Fresnel, "Note sur la double réfraction du verre comprimé" (read 16 September 1822), ''Annales de Chimie et de Physique'', Ser. 2, vol. 20, pp. 376–83 (nominally f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoelasticity Stiffener
Photoelasticity describes changes in the optical properties of a material under mechanical deformation. It is a property of all dielectric media and is often used to experimentally determine the stress distribution in a material, where it gives a picture of stress distributions around discontinuities in materials. Photoelastic experiments (also informally referred to as ''photoelasticity'') are an important tool for determining critical stress points in a material, and are used for determining stress concentration in irregular geometries. History The photoelastic phenomenon was first discovered by the Scottish physicist David Brewster, who immediately recognized it as stress-induced birefringence. That diagnosis was confirmed in a direct refraction experiment by Augustin-Jean Fresnel.A. Fresnel, "Note sur la double réfraction du verre comprimé" (read 16 September 1822), ''Annales de Chimie et de Physique'', Ser. 2, vol. 20, pp. 376–83 (nominally for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Napoleon George Filon
Louis Napoleon George Filon, FRS (22 November 1875 – 29 December 1937) was an English applied mathematician, famous for his research on classical mechanics and particularly the theory of elasticity and the mechanics of continuous media. He also developed a method for the numerical quadrature of oscillatory integrals, now known as ''Filon quadrature''. He was Vice Chancellor of the University of London from 1933 to 1935. Early life He was born at Saint-Cloud, near Paris, as the only child of Augustin Filon, the French ''littérateur'' who was appointed as the official tutor to the Prince Imperial. Accompanying the Prince Imperial in his exile, the Filon family came to England in 1878 and lived at Margate. He was educated at Herne House School in Margate. Career In 1894 Filon became a student at University College, London and received his BA in 1896 with a gold medal in Greek. He was appointed in the college as Demonstrator in Applied Mathematics under the supervision of Karl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rigid Line Inclusion (stiffener, Anticrack)
A rigid line inclusion, also called stiffener, is a mathematical model used in solid mechanics to describe a narrow hard phase, dispersed within a matrix material. This inclusion is idealised as an infinitely rigid and thin reinforcement, so that it represents a sort of ‘inverse’ crack, from which the nomenclature ‘anticrack’ derives. From the mechanical point of view, a stiffener introduces a kinematical constraint, imposing that it may only suffer a rigid body motion along its line. Theoretical model The stiffener model has been used to investigate different mechanical problems in classical elasticity (load diffusion, inclusion at bi material interface ). The main characteristics of the theoretical solutions are basically the following. # Similarly to a fracture, a square-root singularity in the stress/strain fields is present at the tip of the inclusion. # In a homogeneous matrix subject to uniform stress at infinity, such singularity only arises when a normal stress ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ernest George Coker
Prof Ernest George Coker FRS FRSE MIME MICE Wh.Ex. (1869–1946) was a British mathematician and engineer. He won the Howard N. Potts Medal for Physics in 1922, and the Rumford Medal for work on polarised light in 1936. He was an expert on stress analysis and Photoelasticity. He contributed to Encyclopædia Britannica and other works under the initials E.G.C. Life He was born on 26 April 1869 in Wolverton in Buckinghamshire the son of George Coker, an engine-fitter, and his wife, Sarah Tompkins. His birthplace is often wrongly stated as Wolverhampton. He was educated at a private school at Stony Stratford. In 1890 he won a Whitworth Scholarship allowing him to study at the Royal College of Science in London and then both the University of Edinburgh and Peterhouse, Cambridge where he graduated with a Mechanical Sciences Tripos in 1896. His early jobs included Assistant Examiner of Patents at H M Patent Office in London. In 1898 he won the post of Assistant Professor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Properties
The optical properties of a material define how it interacts with light. The optical properties of matter are studied in optical physics, a subfield of optics. The optical properties of matter include: *Refractive index *Dispersion *Transmittance and Transmission coefficient *Absorption *Scattering *Turbidity *Reflectance and Reflectivity (reflection coefficient) *Albedo *Perceived color *Fluorescence *Phosphorescence *Photoluminescence *Optical bistability * Dichroism *Birefringence *Optical activity *Photosensitivity A basic distinction is between isotropic materials, which exhibit the same properties regardless of the direction of the light, and anisotropic ones, which exhibit different properties when light passes through them in different directions. The optical properties of matter can lead to a variety of interesting optical phenomena. Properties of specific materials *Optical properties of water and ice *Optical properties of carbon nanotubes *Crystal optics See also *Rama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Carl Alwin Pockels
Friedrich Carl Alwin Pockels (18 June 1865 – 29 August 1913) was a German physicist. He was born in Italy to Captain Theodore Pockels and Alwine Becker. He obtained a doctorate from the University of Göttingen in 1888, and from 1900 to 1913 he was professor of theoretical physics at the University of Heidelberg. In 1893 he discovered that a steady electric field applied to certain birefringent materials causes the refractive index to vary, approximately in proportion to the strength of the field. The coefficient of proportionality is of the order of to . This phenomenon is now called the Pockels effect. His sister Agnes Pockels (1862–1935) was a pioneer in chemistry. See also *Photoelasticity Photoelasticity describes changes in the optical properties of a material under mechanical deformation. It is a property of all dielectric media and is often used to experimentally determine the stress distribution in a material, where it gives ... 19th-century German phys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Augustin-Jean Fresnel
Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Isaac Newton, Newton's corpuscular theory of light, corpuscular theory, from the late 1830s until the end of the 19th century. He is perhaps better known for inventing the Catadioptric system, catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving countless lives at sea. The simpler Dioptrics, dioptric (purely refractive) stepped lens, first proposed by Georges-Louis Leclerc, Comte de Buffon, Count Buffon and independently reinvented by Fresnel, is used in screen magnifying glass, magnifiers and in condenser lenses for overhead projectors. By expressing Christiaan Huygens, Huygens's principle of secondary waves and Thomas Young (scientist), Young's principle of interference ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dentistry
Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions of the mouth, most commonly focused on dentition (the development and arrangement of teeth) as well as the oral mucosa. Dentistry may also encompass other aspects of the craniofacial complex including the temporomandibular joint. The practitioner is called a dentist. The history of dentistry is almost as ancient as the history of humanity and civilization with the earliest evidence dating from 7000 BC to 5500 BC. Dentistry is thought to have been the first specialization in medicine which have gone on to develop its own accredited degree with its own specializations. Dentistry is often also understood to subsume the now largely defunct medical specialty of stomatology (the study of the mouth and its disorders and diseases) for which reas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infinitesimal Strain Theory
In continuum mechanics, the infinitesimal strain theory is a mathematical approach to the description of the deformation of a solid body in which the displacements of the material particles are assumed to be much smaller (indeed, infinitesimally smaller) than any relevant dimension of the body; so that its geometry and the constitutive properties of the material (such as density and stiffness) at each point of space can be assumed to be unchanged by the deformation. With this assumption, the equations of continuum mechanics are considerably simplified. This approach may also be called small deformation theory, small displacement theory, or small displacement-gradient theory. It is contrasted with the finite strain theory where the opposite assumption is made. The infinitesimal strain theory is commonly adopted in civil and mechanical engineering for the stress analysis of structures built from relatively stiff elastic materials like concrete and steel, since a common goal in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hooke's Law
In physics, Hooke's law is an empirical law which states that the force () needed to extend or compress a spring (device), spring by some distance () Proportionality (mathematics)#Direct_proportionality, scales linearly with respect to that distance—that is, where is a constant factor characteristic of the spring (i.e., its stiffness), and is small compared to the total possible deformation of the spring. The law is named after 17th-century British physicist Robert Hooke. He first stated the law in 1676 as a Latin anagram. He published the solution of his anagram in 1678 as: ("as the extension, so the force" or "the extension is proportional to the force"). Hooke states in the 1678 work that he was aware of the law since 1660. Hooke's equation holds (to some extent) in many other situations where an elasticity (physics), elastic body is Deformation (physics), deformed, such as wind blowing on a tall building, and a musician plucking a string (music), string of a guitar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
