The weld is laid on the top surface of a sample either longitudinal (Varestraint, Figure 3-1(a)) or transverse (Transvarestraint, Figure 3-1(b)) to a loading device/bending block. Near the end of welding, a load is applied to ends of the sample. Bending (strain) is normally applied very rapidly, and is provided by accurate loading devices, capable of maintaining high linear strain accuracy. The bending load can be applied during welding, or exactly when the arc is extinguished, at the time when the welding torch is positioned at a pre-determined point over the dye curvature. [206]
The load deforms the sample around the radius of a bending block. The deformation induces a strain to the weld. The strain is controlled by the sample thickness, t, and radius of the die block, R, as described below