187 

 TABLES 184-209.— PHYSICAL AND MECHANICAL PROPERTIES 



OF MATERIALS 



Introduction and definitions. — The mechanical properties of most ma- 

 terials vary between wide limits ; the following figures are given as being repre- 

 sentative rather than what may be expected from an individual sample. 

 Figures denoting such properties are commonly given either as specification 

 or experimental values. Unless otherwise shown, the values below are 

 experimental. 



Credit for the information included on metals is due to the National Bureau 

 of Standards 55 and the publications of the Aluminum Co. of America, 56 the 

 American Brass Co., and the Chase Brass & Copper Co. 57 



Most of the data shown in these tables are as determined at ordinary room 

 temperature, averaging 20°C (68°F). The properties of most metals and 

 alloys vary considerably from the values shown when the tests are conducted 

 at higher or lower temperatures. 



The following definitions govern the more commonly confused terms shown 

 in the tables. In all cases the stress referred to in the definitions is equal to the 

 total load at that stage of the test divided by the original cross-sectional area 

 of the specimen (or the corresponding stress in the extreme fiber as computed 

 from the flexure formula for transverse tests). 



Brinell hardness numeral (abbreviated B. h. n.). — Ratio of pressure on 

 a sphere used to indent the material to be tested to the area of the spherical 

 indention produced. The standard sphere used is a 10-mm-diameter hardened 

 steel ball. The pressures used are 3000 kg for steel and 500 kg for softer 

 metals, and the time of application of pressure is 30 seconds. Values shown in 

 the tables are based on spherical areas computed in the main from measure- 

 ments of the diameters of the spherical indentations, by the following formula : 



B. h. n. = P + TrtD = P + 7rD(D/2-\/D 2 /4-d 2 /4). 



P = pressure in kg, f — depth of indentation, D = diameter of ball, and d = 

 diameter of indentation — all lengths being expressed in mm. Brinell hardness 

 values have a direct relation to tensile strength, and hardness determinations 

 may be used to define tensile strengths by employing the proper conversion 

 factor for the material under consideration. 



Elastic limit. — Stress which produces a permanent elongation (or short- 

 ening) of 0.001 percent of the gage length, as shown by an instrument capable 

 of this degree of precision (determined from set readings with extensometer 

 or compressometer). In transverse tests the extreme fiber stress at an appre- 

 ciable permanent deflection. 



Erichsen value. — Index of forming quality of sheet metal. The test is con- 

 ducted by supporting the sheet on a circular ring and deforming it at the 

 center of the ring by a spherical pointed tool. The depth of impression (or 

 cup) in mm required to obtain fracture is the Erichsen value for the metal. 

 Erichsen standard values for trade qualities of soft metal sheets are furnished 

 by the manufacturer of the machine corresponding to various sheet thicknesses. 



Alloy steels are commonly used in the heat-treated condition, as strength 

 increases are not commensurate with increases in production costs for annealed 

 alloy steels. Corresponding strength values are accordingly shown for an- 

 nealed alloy steels and for such steels after having been given certain rec- 

 ommended heat treatments of the Society of Automotive Engineers. The heat 



55 Everhart, Lindlief, Kanegis, Weissler, and Siegel, Nat. Bur. Standards Circ. C-447, 

 1943. 



58 Selected from Nat. Bur. Standards Circ. C-447, Mechanical properties of metals and 

 alloys, and from Alcoa's circular, Aluminum and its alloys. 



67 Chase Brass & Copper Co.'s circular, Copper and commercially important copper 

 alloys, 1948; American Brass Co., Copper and copper alloys, 1945. 



SMITHSONIAN PHYSICAL TABLES 



