A device for accurately determining the tensile strength of metals, particularly welded specimens. Tensile testing machines are usually power driven when located in a test laboratory, however, some portable models available for field testing are operated by hydraulic pumps which apply the necessary pressure to a piston which draws the jaws apart.
The laboratory machines are usually large in scale, with means for gripping the specimen, applying tension and accurately recording the results. See Figure T-2. The machine applies tension to the specimen until it reaches the yield point, or the point at which permanent distortion begins. The yield point indicates the elasticity of the metal, and the final breaking strength, or tensile strength, is indicated on the machine when the specimen breaks.
In many tests, the specimen stretches, and the area at the break is reduced. The percent reduction in area is computed by comparing the reduced cross section with the original cross section of the specimen. The percent reduction in area is indicated on the machine, and the tension continues until the specimen breaks.