The actuator movement can be controlled in both senses to produce tensile, compression or cyclic load. The axial tests can be made controlling strain rate, displacement or load application. These systems are suitable for making fatigue tests of specimens or components.
The response capacity of the hydraulic cylinder under pressure is extremely quick, so the servohydraulic system can be adapted quickly to the changes in the material characteristics, like the crack initiation or the breaking of the specimen. This quality improves the accuracy of the results obtained.
The force measurement systems in axial testing machines use load cells with deformation gauges.
Fatigue damage is the result of the cyclic plastic strain, so it is important to measure the specimen strain during the test. The more accurate methods measure the strain in the gauge length of the specimen. The direct measurements of the gauge length can be made with different elements, like extensometers, strain gauges or optical instruments.