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Neutral Plane
In mechanics, the neutral plane or neutral surface is a conceptual plane within a beam or cantilever. When loaded by a bending force, the beam bends so that the inner surface is in compression and the outer surface is in tension. The neutral plane is the surface within the beam between these zones, where the material of the beam is not under stress, either compression or tension. As there is no lengthwise stress force on the neutral plane, there is no strain or extension either: when the beam bends, the length of the neutral plane remains constant. Any line within the neutral plane parallel to the axis of the beam is called the deflection curve of the beam. To show that every beam must have a neutral plane, the material of the beam can be imagined to be divided into narrow fibers parallel to its length. When the beam is bent, at any given cross-section the region of fibers near the concave side will be under compression, while the region near the convex side will be under tension ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bending
In applied mechanics, bending (also known as flexure) characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically 1/10 or less, of the other two.Boresi, A. P. and Schmidt, R. J. and Sidebottom, O. M., 1993, Advanced mechanics of materials, John Wiley and Sons, New York. When the length is considerably longer than the width and the thickness, the element is called a beam. For example, a closet rod sagging under the weight of clothes on clothes hangers is an example of a beam experiencing bending. On the other hand, a shell is a structure of any geometric form where the length and the width are of the same order of magnitude but the thickness of the structure (known as the 'wall') is considerably smaller. A large diameter, but thin-walled, short tube supported at its ends and loa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scantling
Scantling is a measurement of prescribed size, dimensions, or cross sectional areas. Shipping In shipbuilding, the scantling refers to the collective dimensions of the framing (apart from the keel) to which planks or plates are attached to form the hull. The word is most often used in the plural to describe how much structural strength in the form of girders, I-beams, etc. is in a given section. The scantling length refers to the structural length of a ship. In shipping, a "full scantling vessel" is understood to be a geared ship, that can reach all parts of its own cargo spaces with its own gear. Timber and stone In regard to timber the scantling is (also "the scantlings are") the thickness and breadth, the sectional dimensions; in the case of stone the dimensions of thickness, breadth and length. The word is a variation of scantillon, a carpenter's or stonemason's measuring tool, also used of the measurements taken by it, and of a piece of timber of small size cut as a sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutral Axis
The neutral axis is an axis in the cross section of a beam (a member resisting bending) or shaft along which there are no longitudinal stresses or strains. If the section is symmetric, isotropic and is not curved before a bend occurs, then the neutral axis is at the geometric centroid. All fibers on one side of the neutral axis are in a state of tension, while those on the opposite side are in compression. Since the beam is undergoing uniform bending, a plane on the beam remains plane. That is: \gamma_=\gamma_=\tau_=\tau_=0 Where \gamma is the shear strain and \tau is the shear stress There is a compressive (negative) strain at the top of the beam, and a tensile (positive) strain at the bottom of the beam. Therefore by the Intermediate Value Theorem, there must be some point in between the top and the bottom that has no strain, since the strain in a beam is a continuous function. Let L be the original length of the beam (span) ε(y) is the strain as a function of coordinate on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airy Points
Airy points (after George Biddell Airy) are used for precision measurement (metrology) to support a length standard in such a way as to minimise bending or drop of a horizontally supported beam. Choice of support points A kinematic support for a one-dimensional beam requires exactly two support points. Three or more support points will not share the load evenly (unless they are hinged in a non-rigid whiffle tree or similar). The position of those points can be chosen to minimize various forms of gravity deflection. A beam supported at the ends will sag in the middle, resulting in the ends moving closer together and tilting upward. A beam supported only in the middle will sag at the ends, making a similar shape but upside down. Airy points Supporting a uniform beam at the Airy points produces zero angular deflection of the ends. The Airy points are symmetrically arranged around the centre of the length standard and are separated by a distance equal to : 1/\sqrt=0.57 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tresca Section
Tresca may refer to: * Carlo Tresca (1879–1943), Italian-born American anarchist * Henri Tresca Henri Édouard Tresca (12 October 1814 – 21 June 1885) was a French mechanical engineer, and a professor at the Conservatoire National des Arts et Métiers in Paris. Work on plasticity He is the father of the field of plasticity, or non-recov ... (1814–1885), French mechanical engineer {{surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Prototype Metre
The history of the metre starts with the Scientific Revolution that is considered to have begun with Nicolaus Copernicus's publication of ''De revolutionibus orbium coelestium'' in 1543. Increasingly accurate measurements were required, and scientists looked for measures that were universal and could be based on natural phenomena rather than royal decree or physical prototypes. Rather than the various complex systems of subdivision then in use, they also preferred a decimal system to ease their calculations. With the French Revolution (1789) came a desire to replace many features of the Ancien Régime, including the traditional units of measure. As a base unit of length, many scientists had favoured the seconds pendulum (a pendulum with a half-period of one second) one century earlier, but this was rejected as it had been discovered that this length varied from place to place with local gravity. A new unit of length, the ''metre'' was introduced – defined as one ten-milliont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metrology
Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France when a length standard taken from a natural source was proposed. This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements. Several other countries adopted the metric system between 1795 and 1875; to ensure conformity between the countries, the Bureau International des Poids et Mesures (BIPM) was established by the Metre Convention. This has evolved into the International System of Units (SI) as a result of a resolution at the 11th General Conference on Weights and Measures (CGPM) in 1960. Metrology is divided into three basic overlapping activities: * The definition of units of measurement * The realisation of these units of measurement in practice * Traceabi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bronze Yard No
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such as arsenic or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties, such as strength, ductility, or machinability. The archaeological period in which bronze was the hardest metal in widespread use is known as the Bronze Age. The beginning of the Bronze Age in western Eurasia and India is conventionally dated to the mid-4th millennium BCE (~3500 BCE), and to the early 2nd millennium BCE in China; elsewhere it gradually spread across regions. The Bronze Age was followed by the Iron Age starting from about 1300 BCE and reaching most of Eurasia by about 500 BCE, although bronze continued to be much more widely used than it is in modern times. Because historical artworks were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portsmouth Naval Shipyard
The Portsmouth Naval Shipyard, often called the Portsmouth Navy Yard, is a United States Navy shipyard in Kittery on the southern boundary of Maine near the city of Portsmouth, New Hampshire. Founded in 1800, PNS is U.S. Navy's oldest continuously operating shipyard. Today, most of its work concerns the overhaul, repair, and modernization of submarines. As of November 2021, the shipyard employed more than 6,500 federal employees. As well, some of the work is performed by private corporations (e.g., Delphinius Engineering of Eddystone, Pennsylvania; Oceaneering International of Chesapeake, Virginia; Orbis Sibro of Mount Pleasant, South Carolina; and Q.E.D. Systems Inc. of Virginia Beach, Virginia). History The Portsmouth Naval Shipyard was established on June 12, 1800, during the administration of President John Adams. It sits on a cluster of conjoined islands called Seavey's Island in the Piscataqua River, whose swift tidal current prevents ice from blocking navigation to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andrew McKee
Rear Admiral Andrew I. McKee (February 17, 1896 – January 24, 1976) was a pioneer in modern submarine design and development. The destroyer was named for his maternal great-grandfather, Admiral James F. Schenck. McKee graduated from the United States Naval Academy at the top of his class in navigation and was commissioned an Ensign in March 1917.Alden, John D., CDR USN "Andrew Irwin McKee, Naval Constructor" ''United States Naval Institute Proceedings'' June 1979 p.50 He served with USS ''Huntington'' until he severely injured both legs in a fall from the mast in August 1917. He was declared unfit for sea duty, and assigned first to the Naval Academy as a navigation and physics instructor, and then as the supervisory naval constructor at Bethlehem Steel Corporation Fore River Shipyard in Quincy, Massachusetts, pending admission to the Massachusetts Institute of Technology (MIT). In 1921 he received a master's degree in naval architecture from MIT, and was assigned to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
