Recently, some studies, especially in rocks, have been considering the post peak region of stress-strain curve due to the large number of practical instances such as post rupture strains in mine and tunnel piles. The difficulty lies in that the samples exhibit an intrinsically instable state in this region. For the samples rupture be controlled, after the maximum stress have been attained, servo controlled machines are currently being used. The matter is that, even in these machines in some materials, which have a class II behavior, the propagation velocity of the fissures is so high that the control system is not able to receive on time the feedback signal and the sample ends up disrupted with no suitable control. Accordingly, traditional control methods, such as constant load and strain, have given raise to alternatives techniques, which exhibit a more efficient post peak control in rocks. Among these techniques, there is the linear combination of stress and strain, which will be used in this work to control the post peak of rocks and mortars in a not very rigid servo controlled machine of tests. This fact is very important because with this alternative control it is possible to control a material Class II in which most of the practical situations to obtain the behavior post rupture of curve tension x deformation, the machine of tests should have a very high rigidity. Along with the work problems concerned with a uniaxial compression test and that intimately associated with post peak region are discussed.