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Table I shows the ultimate tensile strength and minimum permissible elongation for the most important materials used in locomotive construction.

TABLE I—STRENGTHS OF MATERIALS FOR LOCOMOTIVE CONSTRUCTION

Name and use of Material.	Ultimate tensile strength tons per sq. in.	Percentage elongation above original length not less than
Mild steel boiler plates	26 to 32	22% in 8 ins.
Mild steel boiler rivets	24 to 28	27% in 8 diameters
Mild steel frame plates	28 to 32	20% in 8 ins.
Steel crank axles	not less than 30	20% in 2 ins.
Steel crank axles, oil treated	not less than 35	20% in 2 ins.
Steel straight axles	25 to 40	25% to 20% in 2 in.
Steel tyres, class C	50 to 55	13% to 11% in 2 ins.
Steel tyres, class D	56 to 62	10% to 8% in 2 ins.
Steel castings with wearing surfaces	not less than 35	10% in 2 ins.
Cast steel wheel centres.	not less than 26	15% in 2 ins.
Copper plates for fireboxes	not less than 14	35% in 8 ins.
Copper stays for fireboxes	not less than 14	40% in 8 diameters
Mild steel tubes for boilers	not more than 24	28% in 8 ins,
“Best Yorkshire” iron bars, 1 in. to 4 ins. diameter	21 to 23½	varies according to bars.

Spring steel is not usually tested for tensile strength, but the springs are subjected to rapid deflection tests.

Bending Tests. Other tests specified include “cold bend” and “temper bend” tests. In the former, specimens cut from plates are doubled over cold, until the internal radius is not greater than the thickness of the plate, and the test piece must withstand this without fracture. The “temper bend” test is similar, but the piece is heated beforehand to a red heat and quenched