Description

The rig incorporates a simple, two-part, miniature autoclave, comprising a base plate and an upper body, mounted on a voice coil actuator. Specimen tooling and pipe connections are mounted on the base plate, leaving the upper body free to be removed, allowing the system to be set up and tested open.

Autoclave lid fitted

The complete assembly is vibrated about a vertical axis, inducing relative motion between two sets of moving and fixed specimen carriers. A non-contact displacement measurement sensor is provided for sensing the relative motion.
The fixed specimens are mounted on lever arms and are loaded against moving specimens by a stainless steel spring, tensioned between the levers.

Fretting test assembly

The moving specimens are carried on an armature, mounted between flexural spring discs, allowing one degree of freedom, along the vertical axis. With the assembly vibrating along that axis, at a set amplitude and low frequency, the armature moves in phase with the motion. At a certain point, as the frequency is increased, the armature motion changes to 180 degrees out of phase, with amplified amplitude, relative to the excitation amplitude, inducing motion between the fixed and moving specimens.
Control is achieved by choosing an operating frequency and adjusting the excitation amplitude, with armature response varied by adding or removing small masses and by varying the disc stiffness.
Test adapters for fretting/sliding motion and impact sliding are provided.

Heating mantle lowered ready for test

The autoclave is heated by an electric furnace, which is raised and lowered by pneumatic actuators.

Autoclave Operation

The autoclave is design to operate under two separate regimes:
• Gas over water
• Steam over water
Two severe service Back Pressure Regulators are included, one with an operating range 0 – 2 bar and one, 0 – 25 bar, with a manual changeover valve between for selection. The lower pressure valve is typically used for pre-test purge with inert gas to deoxygenate the water. The high pressure valve is used for setting and controlling the maximum pressure in the vessel, during operation.
The recommended method of operation is gas over water, with nitrogen as the gas. A fixed volume of water is added to the vessel, with the free space then purged with nitrogen. After purging, the vessel is pressurised with nitrogen, to the required test pressure. As the vessel is heated, nitrogen is released, at the pressure set on the regulator.

Control and Data Acquisition

COMPEND 2000 control and data acquisition system, providing control of voice coil actuator, supervisory control and data recording of autoclave and real-time measurement of specimen motion.