Resonant Column Apparatus (Hardin Type)

Product Code : H-RCA

Hardin Type Resonant Column Apparatus (H-RCA) is a system that allows samples to be tested in resonance while maintaining an anisotropic loading up to 2kN. This is achieved by a slender, thin walled loading column passing through the drive system to the topcap. The GDS Hardin Oscillator contains an electro-magnetic drive system incorporating precision wound coils and composite sintered neodymium iron boron (NdFeB) “rare-earth” magnets.

The GDS Hardin Oscillator can be mounted in a standalone system with an integral axial force actuator (shown opposite) for post resonance testing up to 5kN. Or as a cell for integration into a standard loadframe up to 50kN.

Key features Benefits to the user
Hardin Type Oscillator:
The specific benefit of the Hardin Oscillator is the ability to perform torsional resonance anisotropically.
Hardin Oscillator can be loaded beyond its useable load:
The Hardin head is designed to be able to apply up to 2kN axial force whilst still being able to perform resonance tests. The GDS head is designed such that the load cell can be loaded beyond this value to 50kN, allowing a full suite of triaxial tests to be performed to shearing post resonance.
Choice of two systems, one to 5kN axial load and one to 50kN axial load:
The 5kN max load system is neat because it has an actuator built into the top of the cell. The cell is a hybrid style cell that allows the cell wall to be lifted clear of the sample while the top-cap is supported in place for easy and accurate sample installation and alignment. The 50kN version (using a traditional load frame) has the obvious benefit of the additional load that can be achieved post resonance, however it does not have the advantage of a hybrid cell and has a traditional removable cell top instead.
Integrated reaction mass:
The reaction mass is integrated into the drive system so it is as close to the force generation as possible. This eliminates uncertainties due to transferal of forces.
Current driven using a transconductance power amplifier:
The impedance of magnet / coil devices change with frequency. At higher frequencies, using a constant voltage amplifier the current would be seen to reduce. As the torque is directly proportional to current, the torque will also reduce and a non-linear torque input would affect results. This effect is removed in the GDSRCA by using a current driven power amplifier.
Dedicated GDS RCA software is used for control and data acquisition of the apparatus:
Simple automated tests allow tests to be consistent.
Accuracy of Pressure Measurement
0.15% FRO

1005mm (H), 330mm (W) (500mm with valves)

Load Range (kN)


Operating Frequency (Hz)


Pressure Range (MPa)


Sample Sizes

50, 70, 100mm

Weight Approx (kg)

128 (Approx)

  • Sample shearing at 5kN or 50kN.
  • High pressure systems up to 20MPa.
  • Temperature controlled systems.
  • Bender elements.
  • Unsaturated testing.
  • Gas Hydrate