MTS Acumen Testing Systems
Strain-controlled testing with MTS Acumen Test

MTS Acumen Testing Systems
Controlling a strain with a load amplitude ± 50 newtons

Optimizing Strain Control for Low-Force Fatigue Testing

Small specimen testing with an MTS Acumen® Electrodynamic Test System enables fatigue life studies with lower forces, higher frequencies and precision control technology.

As researchers, product developers and engineers work with smaller and smaller specimens, they can no longer rely on the bulk modulus or nominal strength to understand the mechanisms of deformation and failure. For example, the test specimen may be cut out of a larger structure, such as a turbine blade or samples from a nuclear reactor and may only be a few crystalline grains instead of a homogeneous bulk sample. The small number of grain boundaries in the region of interest could dramatically affect the failure mechanism. When evaluating material properties in homogenous structures, the unique crystalline features of the microstructure do not correlate well with bulk measurements.
In order to validate designs, manufacturers need to conduct fatigue studies on a smaller scale with lower loads where strain deformation is significant. In these and many other applications, conventional fatigue life testing in load or stress control no longer delivers the predictive results engineers require.

For more accurate and meaningful fatigue and fracture testing results, MTS recommends strain-controlled testing with an MTS Acumen Electrodynamic Test System. Equipped with a high-resolution digital encoder to ensure precise control and measurement of specimen position, the MTS Acumen systems feature a rigid load frame and direct-drive linear motor, enabling exacting control of force and displacement. MTS Acumen systems also offer unique integration with test software, which allows for automatic tuning. Automatic tuning improves test efficiency and alleviates the typical complexity of preparing strain-controlled tests.

To precisely test small specimens in close proximity and eliminate the need to compensate for other elements of the load train that may introduce additional movement, changes in stiffness or other inconsistencies in displacement, MTS recommends a third transducer solution. Using an extensometer in addition to the load cell and encoder allows for measurements closer to the specimen area of interest. An extensometer gage specifically designed to measure small deformations, bend testing or specimens with unusual geometries is placed in direct contact with the specimen to measure displacement.

The MTS Acumen systems are capable of testing very small specimens, including complete structures or devices in strain-control at very low loads and a wide range of frequencies (0.001 Hz to more than 100 Hz). Precision control is the cumulative result of key design features, including high-quality load cells, high-stiffness reaction frame configuration and the unique direct drive linear motor. The patented automated tuning feature makes it easier for any test engineer to perform high-cycle strain-controlled fatigue testing with speed and confidence. MTS also offers numerous clip gages and extensometers specifically designed for measuring displacement very close to the specimen in applications that involve complex or unusual linkages within the load train.
Strain-controlled testing and third transducer solutions are suitable for a diverse range of test applications in which conventional stress controlled fatigue testing is no longer adequate for obtaining accurate life predictions. Using MTS Acumen systems for small specimen low-force fatigue testing provides more precise and comprehensive results that are vital for test labs to maintain high productivity while generating accurate results.



MTS Systems

14000 Technology Drive
Eden Prairie, MN USA

Tel: 952.937.4000
Tel: 800.328.2255
Fax: 952.937.4515