Dictionary of mechanical engineering PDF
Preview Dictionary of mechanical engineering
DICTIONARY DF MECHANICAL ENGINEERING ALFRED DEL VECCDID B.M.E., M.M.E., New York University P.E., New York State Associate Professor Director of Mechanical Engineering Manhattan College PHILOSOPHICAL LIBRARY New York I IIJKARY UNUiiKMlY OF CALIFORNIA PAVIS e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:55 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP © Copyright, 1961, by Philosophical Library, Inc. 15 East 40th Street, New York Library of Congress Catalog Number 60-13664 Printed in the United States of America e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:55 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP FOREWORD This book is written for the practicing engineer, the stu- dent and teachers engaged in the fields of architecture, auto- matic controls, engineering mechanics, fuels and combustion, and power plants. Some definitions are also included in the related fields of electricity, heat treatment of metals, mathe- matics, and welding. As Humpty Dumpty said to Alice in Wonderland, "When I use a word, it means just what I choose it to mean- neither more nor less." It is only natural that an inquisitive and active mind seek out precise definitions to scientific terms. Unfortunately, this is not always possible. Many scientific terms have three or more dimensions. It is difficult to depict in the mind's eye beyond the third dimension. Hence, the definitions in this category become intangible and must be presented as properties. For instance the term—moment of inertia—as used in architecture or engineering mechanics has units of inches to the fourth power (in.)4. This is defined as measure of the rigidity of a structural member. There is no tangible definition here which can be depicted. Hence we must study the term as a property and content ourselves with the definition that it is a measure of something. There are other needed definitions, not all covered in this work, which take a lot of explaining. Tons of Refrigeration has nothing to do with weight—Boiler Horsepower has noth- ing to do with horsepower—Specific Gravity has nothing to do with gravity. It is unfortunate that these terms were allowed to take hold, but as a science develops, it is only natural that there should be trouble with the meanings of words. e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:55 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP The author wishes to express his thanks to The Industrial Press, American Boiler and affiliated industries, Society of Automotive Engineers, and the American Society of Me- chanical Engineers (Instruments and Regulators Division) for permission to quote their publications on definitions. Alfred Del Vecchio e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:55 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP abbreviations used in this work arch.—architecture A.C.—automatic controls E. M.—engineering mechanics elect.—basic electricity F. &G—fuels & combustion math.—basic mathematics P.P.—power plants weld.—welding abrasive Any rough material such as sandpaper, pumice, or emery, used for polishing, sanding, or grinding. abscissa (math.) The horizontal distance from the origin of a set of co- ordinates. Y Abscissa t Ordinate X absolute humidity The weight of water vapor in a gas water-vapor mixture per unit volume of space occupied, as, for example, grains or pounds per cubic foot. In an air-vapor mixture, the unit 1 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP usually given is grains of water vapor per pound of air or pounds of water vapor per pound of air. absolute pressure The pressure above zero pressure. The sum of the gage and atmospheric pressures. absolute strength The actual breaking strength of a bar or structure, as distinguished from the safe or working load. absolute temperature The temperature measured from approximately —460 degrees Fahrenheit, which is absolute zero. abutment (arch.) In architecture, it is that part of a pier, wall, buttress or any masonry structure which receives thrust, i.e. the part from which an arch springs. A bridge abutment is the sup- porting pier at the extreme ends of a bridge. Its function is to support the bridge and hold the adjacent earth in position. Thus it functions both as a pier and a retaining wall. abuttals The boundings of land on other land. Boundary. acceleration (E.M.) Acceleration is the ratio of the change in velocity of a body to the elapsed time. It is expressed mathematically by dv/dt. Since the velocity has direction and magniture, the ac- celeration must be treated as a vector. Acceleration may be rectilinear (straight line) or curvilinear (curved path). If the acceleration is along a curved path, it will have tangential and normal components at every point along the traveled path. The tangential component is directed tangent to the curve and is equal to the rate of change of speed along the point. The normal component is perpendicular to the tangent and is equal to the square of the tangential speed divided by the radius of curvature at the point. 2 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP Tangential Ax A = Ax + A, acceleration—time curve (E.M.) A curve showing the variation of acceleration with time is called an acceleration-time curve. The area under the curve represents the change in velocity during the time interval. Thus: a 3 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP accelerator (P.P.) The foot pedal in a motor vehicle which controls its power and speed. The accelerator is linked to a butterfly valve in the carburetor which controls the amount of fuel entering an engine. accelerometer An accelerometer is an instrument for measuring the ac- celeration of a system to which it is attached. The field of accelerometry is becoming increasingly important and there are many different designs for special applications. accumulator (P.P.) A pressure vessel containing water and steam, which is used to store the heat of steam for use at a later period and at some lower pressure. accuracy in measurement (automatic controls) The degree of correctness with which a measuring means yields the "true" value of a measured quantity. The "true" value refers to accepted engineering standards, such as the standard meter, gram, etc. It is assumed that a "true" value always exists even though it may be impossible to determine. Acetylene (CHi) A colorless gas which burns when ignited in air. It is made by the reaction of calcium carbide and water. Acety- lene is used with oxygen as a source of high temperature for welding and cutting. acid cleaning (P.P.) The process of cleaning the interior surfaces of steam gen- erating units by filling the unit with a dilute acid accompanied by an inhibitor to prevent corrosion, and subsequently drain- ing, washing and neutralizing the acid by a further wash of alkaline water. 4 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP acid sludge (F.&C.) Oil refinery waste fuel from acid treatment of unrefined petroleum. acidity (F.&C.) Represents the amount of free carbon dioxide, mineral acids and salts (especially sulphates of iron and aluminum) which hydrolize to give hydrogen ions in water and is re- ported as milliequivalents per liter of acid, or p.p.m. acidity as calcium carbonate, or pH the measure of hydrogen ions con- centration. acme thread A screw thread used extensively for feed screws. The cross-section is a mean between a square and vee thread. acoustics Having to do with the transmission of sound. across the grain (arch.) Perpendicular to the run of the wood grain. actinometer An instrument for measuring the heating and chemical effects of light. action (E.M.) A concept in advanced dynamics expressing the product of twice the mean total kinetic energy of a particle during a time interval. It is defined mathematically by 5 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP A — 2 I (kc) 5t (Action Integral) The English unit is foot-pound-second. The cgs system of units is erg-seconds. The action, A, is very useful in the de- velopment of dynamics from variational principles. Maupertuis postulated a law known as the "principle of least action" which states that any unaided change which takes place in a dynamically isolated system will do so in such a manner that the action integral will have the least possible value. actual size A pictorial representation in true proportions. actuating signal (automatic controls) The difference at any time between the reference input and a signal related to the controlled variable. acute angle Any angle which is less than ninety degrees. adiabatic temperature The theoretical temperature that would be attained by the products of combustion provided the entire chemical energy of the fuel, the sensible heat content of the fuel, and combus- tion air above the datum temperature were transferred to the products of combustion. This assumes: a. combustion is complete, b. there is no heat loss, c. there is no dissociation of gaseous compounds formed, and d. inert gases play no part in the reaction. addendum (E.M.) The height of a gear tooth above pitch circle or the radial distance between the pitch circle and the top of the tooth. 6 e 8gl 9o 6o 2g 3d- 5p b# 1.$se cu u_ 7/ss 2e 0c et/2g/ac dl.handle.nathitrust.or hh p://ww. MT / htthttp://w 24 08:56 Gdigitized / 5-e- 3-0ogl 1o 0G on 2ain, d m eo neratblic D eu GP
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