Page:Steamlocomotivec00ahrorich.djvu/123

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inspection and testing
109


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