Resonant type fatigue testers have tremendous advantages over servohydraulic testing machines in the field of high cycle fatigue testing. They are faster, consume much less power (<500 W) and are maintenance free since they do not require hydraulics or power packs. 

They are separated into a static and a dynamic part so that mean loads other than zero can be applied. These machines can also go through zero and perform tension-compression testing.
They are ideal for testing metallic samples in the plastic region and components such as connecting rods, crankshafts, chains, rebars, turbine blades etc. They are also ideal for fatigue crack growth testing. 
The frequency drop mechanism provides for a method to monitor failure of the specimen that is not possible using a servo hydraulic machine. These machines do not require a COD gauge for pre-cracking CT specimen.
The control system is the latest available and incorporates a Digital Signal Processor at its core. The software is based on Labview and is specifically designed for these machines allowing even relatively inexperienced operators to use the machines with little training.