The Reinhold Hermann creep laboratory at The Open University has recently been relocated, expanded and upgraded to provide a dedicated facility in support of our nuclear materials and solder research programmes. It houses some 25 straining frames used by the Group in its various studies on time dependent deformation of engineering materials.
A comprehensive materials characterisation service is now provided by StressMap.
An evaluation of metallurgical variables...
The laboratory has 10 operating constant load monotonic tensile creep frames having a 10:1 loading arm ratio. An additional 5-10 frames are in reserve for future expansion. It also has an Instron electro-mechanical slow-strain rate test (SSRT) machine with high temperature capability for applying controlled transients during testing and for testing at intermediate strain rates. SSRT, also termed a constant extension rate test (CERT), is a modification of monotonic constant load tension testing, where the constant load is replaced by a slow extension of the specimen until failure. One benefit of SSRT is that it allows evaluation of metallurgical variables such as alloy composition, heat treatment, processing and/or environmental parameters in a relatively short period of testing.
All the creep frames have integral three zone vertical tube furnaces, with temperature control to ±1 C of set temperature. We also have a three-zone split furnace with a front port to allow measurement of strain by optical devices (LASER speckle pattern or digital image correlation). This allows high positional resolution of measured strain in materials having positional variation in microstructure or residual stress distribution.
Gauge length temperatures
Gauge length temperatures are gathered by 3 K-type thermocouples, with temperature profile maintaining a variation of less than 5°C over the gauge length. Temperatures are logged on a PICO temperature logger. Displacement data is obtained vide two calibrated Solartron linear variable differential transformers (LVDT) mounted 180° apart, with an average of the two LVDT readings being monitored.
Data (Clock time, cumulative time, displacement, strain and thermocouple temperatures) is recorded on real time basis using in-house developed software to dedicated instrument PC. The software offers flexibility in data monitoring frequency and can be monitored at 1 second intervals on a real time basis.
Recent studies have been on 6246 titanium alloy, metal matrix composites, turbine rotor steels and research into Nuclear materials.