Tension Test

Tension tests are performed for the following reasons: test results are used in selecting materials for engineering applications tensile properties are frequently included in the material specifications to ensure quality often tensile properties are measured during the development of new materials and processes so that different materials and processes can be compared. Tensile properties are often used to predict the behavior of a material under different forms of loading, other than uniaxial tension.

The strength and ductility of metals are generally obtained from a simple uniaxial tension test in which a machined specimen is subjected to an increasing load while simultaneous observations of extension are made. If the loading is continued the specimen will eventually break.

In a welding application, tension tests involve applying a load to the ends of a standard test specimen and recording the point at which the specimen fails by permanent shape change yielding) and by fracture. A number of mechanical properties can be determined from a tension test, including the following which are of particular significance in welding:

Yield strength (the stress at which permanent deformation occurs)

Ultimate strength (the highest stress the material is able to withstand)

Breaking or fracture strength (the stress at which the material fails by breaking)

Ductility (the percentage of elongation or reduction of area of a defined segment of the specimen)

Two specific types of tension test specimens are used extensively in testing welding materials and welded joints.

One of these uses specimens taken from the weld material only (all weld metal tests), and the other uses specimens taken across the weld (reduced section tension specimens).

The latter specimens are machined so that the smallest dimension of width is in the weld area (reduced section tension test).

All Weld Metal Tests

This test is used to determine the tensile properties of a specimen that consists entirely of weld metal. The test specimen is oriented parallel to the weld axis, and is machined entirely from the weld metal. There are two reasons for performing an all weld metal test:

To qualify a filler metal or 

Determine the properties of the weld metal in a particular weldment. To qualify filler metal the melting of the base metal is minimized when making a test weld. This procedure is described in the various filler metal standards. If the purpose of the test is to determine weld metal properties in a particular weldment, then the welding process and procedure used in the actual fabrication should be employed to make the test weld. The following are typically properties that are measured and reported in an all weld metal tension test:

Tensile strength - yield strength - elongation - reduction of area