If you are asking what is happening to the sample, the graph shows the elastic and plastic deformatiom. As the stress is increased the material deforms elastically, which is the straight line region. At a value of stress the material begins to deform plastically and the material begins to neck down at the same or less level of stress. While this material is deforming plastically it is also work hardening, until the point in the graph where the curve swings upwards again ( workhardening has made the material stronger ). As you progress along the curve, more stress results in more plastic deformation, and more work hardening, until the ultimate tesile stress is reached, after which the specimen necks down and rupture occurs.Do tensile testing machines reduce the value of load in these regions? If yes, why? If no, what's happening in the graph?