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abrasion resistance The property of a material that enables it to resist being worn away by friction when rubbed with another object Abrasion resistance Is a measure of toughness rather than hardness a nd Is a necessa ry quality of flooring materials and surface finishes.

dimensional stability The property of a material that enables It to maintain Its original shape and dimensions when subjected to changes In temperature or humidity.

kinetic theory of heat

The theory that the temperatu re of a substance increases with an Increase of the average kinetic energy of Its particles when heat Is absorbed.

thermal expansion

An Increase In length, ansa, or volume of a material caused by a rise In temperature.

thermal contraction

A decrease In length, area, or Volume of a material caused by a drop In temperature.

thermal stress

The tensile or compressive stress devebped In a material constrained against thermal expansbn or contraction.

thermal shock

The sudden stress a rapid change In temperature can produce In a material.

hardness

The property of a material that enables it to resist deformation by compression, indentation, or penetration.

abrasion-resistance index A measure of the abrasbn resistance of a material, commonly expressed as the depth of penetration or material loss after testing with a weighted abrasive wheel for a specified number of cycles.

fatigue

The weakening or failure of a material at a stress below the elastic limit when subjected to a repeated series i of stresses fatigue limit

The maximum stress to whbh a material can be subjected for an Indefinite number of cycles without falling.

^ fatigue ratio

Theratb between the fatigue limit and the tensile strength of a material. Alsocal'ed endurance ratio.

Mobs' scale

A scale for measuring the hardness of a mineral. Its degrees. In Increasing hardness, are: l, tab; 2, gypsum; 3. calcite; 4. fiuorite; 5, apatite; 6, feldspar. 7, quartz; d.topaz; 9, sapphire; 10. diamond.

### Brineil number

A measure of the hardness of a material determined by pressing a standard steel ball Into a test piece using a standard force and dividing the load by the area of indentation. The higher the number, the harder the material.

### Rockwell number

A measure of the hardness of a material, determined by Indenting a test piece with a conoidal diamond indenter, or with a standard steel ball, under two successive bads and measuring the net Increase In depth of the impressions: the higher the number, the harder the material.

### Vickers number

A measure ofthe hardness of a material, determined by Indenting a test piece with the point of a diamond using a known force and dividing the bad by the surface area of Indentatbn: the higher the number, the harder the material.

A unit or standard of measurement used to ascertain the dimensions, quarrtity, or capacity of something.

metric system conversion table

A Jackal system of weights and A tabular arrangement of the equivalent measures, adopted first In France but values of the weight or measure units of no* widespread and universally used In different systems, science.

scale

A system of ordered marks laid down at known Intervals and used as a standard reference In measuring.

Internationa! System of Units An internationally accepted system of coherent physical units, using the "meter, kilogram, second, a mpere, kelvln, and candela as the basic units of the fufldamentalquantlties of length, mass. tine, electric current, temperature, and luminous Intensity.

The extent of anything measured along Its greatest dimension.

square measure

A unit or system of units for reasuring area, derived from units of Snear reasure.

area

A quantitative measure of a plane a carved surface.

SI unit

One of the basic units of the International System of Units

SI unit

One of the basic units of the International System of Units

The basic unltof length In the metric system, equivalent to 3937 Inches, originally defined as one ten-millionth of the distance from the equator to the pole measured on the meridian, later as the distance between two lines on a platlnum-Irldlum barpreservedatthelntematlonal Bureau of Weights and Measures near Pa rls. and now as 1/299.972,465 of the distance light travels In a vacuum In one second. Abbrj m kilometer

A unit of length and distance equal to 1000 meters and equivalent to 3250.5 feet or 0.621 mile. Abbr.: km —■

A metric unltof length equal to Vioo of a meter or 03937 Inch. The use of the centimeter Is not recommended for use in construction. Abbr.: cm

- millimeter A metric unit of length equal to Viooo of a meter or 003937 of an Inch. Abbr.- mm micron

The millionth pa rt of a meter. Also called micrometer. Symbol: mu. n

A unit of length originally derived from the length of the human foot, divided Into 12 Inches and equal to 3043 millimeters. Abbr.: ft.

inch

A unit of length, '/cth of a foot, equivalent to 25.4 millimeters. Abbrj fn.

A unit of length equal to 0D0\of an Inch or 0.0254 mm. used In measuring the diameter of wires and the thickness of very thin sheet materials.

i- yard

A unit of length equal to 3 feet or 36 Inches, and equivalent to 0.9144 meter. Abbr: yd.

A unit of length equal to 5'/2yards or 161/2 feet, and equivalent to 5.029 meters.

mile

Aunlt of dista nee on land equal to 5250 feet or 1760 yards, and equivalent to 1.609 km. Also called statute mile. Abbr.: mi

A metric unit of area equal to Vioo of a hectare, 100 square meters, or TI9.6 square yards. Abbrj a hectare -

A metric unit of area equal to 10,000 square meters or 2.47 acres. Abbr.: ha

acre

A u nit of la nd a rea equa I to '/wo of a square mile,4540 squareyards,43,560 square feet, or 4047 square meters.

circular mil

A unit used principallyfor measuring the cross-sectional area of wire, equal to the area of a circle having a diameter of one mil nautical mile

A unit of distance used In sea or air navigation, equal to 1352 kilometers or about 6,076 feet. Also called air mile.

acre

A u nit of la nd a rea equa I to '/wo of a square mile,4540 squareyards,43,560 square feet, or 4047 square meters.

circular mil

A unit used principallyfor measuring the cross-sectional area of wire, equal to the area of a circle having a diameter of one mil

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