DN 55 High Temperature Dry Sliding & Fretting Machine

Description:

The DN 55 High Temperature Dry Sliding & Fretting Machine is based on a conventional vertical axis servo hydraulic test machine. The actuator is mounted on the lower crosshead of the machine with the fixed specimen tooling mounted on the upper crosshead. An electrically fired furnace is provided allowing tests to be run under un-lubricated conditions at temperatures up to 1200°C.

The machine incorporates a servo hydraulic actuator driven by a high frequency analogue controller, which derives its set points via a 16 bit control and data acquisition card from a standard PC running COMPEND 2000 software. Real time adaptive control features provided within the software allows high precision control of the actuator when working against highly non-linear loads. Sine, square, triangular and random waveforms may be programmed and, depending on the physical capabilities of the hydraulic system, oscillating frequencies up to 500 Hz may be controlled.

Sliding and Sliding Fretting Tests:

The moving specimen carrier is designed to hold a ball or roller of 20 mm diameter in either point, line or area contact. The fixed specimen tooling comprises two forks each carrying a fixed specimen and loaded against either side of the moving specimen. This arrangement ensures that there are no significant out of balance forces acting on the moving specimen. Each fork reacts against its own independent piezo force transducer, thus allowing the friction between the moving specimen and each fixed specimen to be monitored independently. This allows two different fixed specimen materials to be tested simultaneously under identical conditions of load and temperature.

Load is applied to the fixed specimen forks by means of a PID controlled pneumatic bellows with force transducer feedback. The loading system is mounted freely on a horizontal linear slide allowing the fixed specimens to self-centre on the moving specimen.

Impact Sliding and Impact Fretting Tests:

For impact sliding and fretting tests, the standard fixed specimens are replaced by wedge shaped specimens. The moving specimen is withdrawn from contact and the fixed specimens are loaded against a stop with a pre-set force applied by means of the pneumatic bellows. To perform a test, the moving specimen is brought into contact with the fixed specimens under velocity control. Adaptive control functions in the software allow peak to peak tuning of the displacement in order to achieve either a required displacement or a required impact force.

Impact and Hertzian Fretting Tests:

For impact and Hertzian fretting tests, to twin fork tooling is replaced by a single fixed specimen mounting system. Impact tests are performed with the fixed and moving specimens coming in and out of contact. Hertzian fretting tests are performed with the specimens in continuous contact.

DN 55/1 Small Perturbation Signal Generator:

This optional additional signal generator and signal analysis system allows combined sliding motion with co-axial vibration to be generated. The standard servo amplifier incorporates a summing junction on the input stage with dual inputs. This means that with the addition of a second signal generator, two separate signal inputs, one low frequency and long stroke and one high frequency and short stroke, can be combined, thus producing reciprocating motion with superimposed vibration from a single servo hydraulic actuator.

General Specification:

Performance Specification:

Pure Sliding:

Fretting:

DN 55/1 Small Perturbation Signal Generator:

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