Thermal cycling

Thermal cycling test
(based on ESA ECSS-Q-ST-70-04)

Space vehicles are exposed to continu­ous temper­at­ure changes e.g. due to chan­ging sun irra­di­ation. For mater­i­als to be capable for space applic­a­tions the perform­ance under chan­ging ambi­ent temper­at­ures in vacuum is an import­ant issue. The thermal-cycling test may be used to assess mater­i­als for their space capab­il­ity.
The test setup used for thermal cycling of samples consists of a heating/cooling plate made of copper which can be temper­at­ure controlled in a range between 80K and 500K. Cooling is performed with liquid nitro­gen, heat­ing is performed elec­tric­ally. A maximum temper­at­ure-gradi­ent of 8°C/min can be used for thermal cycling.
The temper­at­ure of the heating/cooling plate is monitored and adjus­ted by an Eurotherm® temper­at­ure control­ler. Furthermore, several ther­mos-couples are imple­men­ted in the setup continu­ously monit­or­ing and record­ing temper­at­ures on differ­ent relev­ant spots of the setup (pre-defined by customer). All thermo-sensors are calib­rated and have accur­acy better than ±2°C.
The entire setup is placed in a vacuum cham­ber capable of pres­sures down to 10-7 mbar. For thermo-cycling processes a pres­sure better than 10-5 mbar is required. For pump­ing a turbo-molecu­lar pump is used. A PC program controls and meas­ures all relev­ant vari­ables and allows auto­mat­ic­ally complet­ing complic­ated temper­at­ure profiles.
On customer request addi­tional elec­trical feed­throughs are avail­able and may be used for in-situ meas­ure­ment of diverse prop­er­ties (e.g. elec­trical resistiv­ity) during the thermal cycling test. The meas­ured values are recor­ded together with the temper­at­ure and vacuum values.
Post exam­in­a­tion (SEM-, LO-micro­scopy, NDT) and test­ing (e.g. mech­an­ical tests, elec­trical tests) can be carried out at AAC.

thermal cycling.jpg_1FIG.: Typical temper­at­ure and vacuum plots during thermal cycling test

According to differ­ent customer require­ments a vari­ety of vacuum cambers are avail­able offer­ing differ­ent dimen­sions and differ­ent feed-feed­throughs to perform in-situ meas­ure­ment of vari­ous prop­er­ties (e.g. elec­trical resistiv­ity) during the thermal cycling test.

Test rig Size of

heating/cooling plate

Temperature range
TVC

Thermal vacuum Chamber

100x70cm, 2 plates -160 to +250°C
LVC

Large Vacuum Chamber

100x70cm, 2 plates

Shroud 100x100x40cm

-160 to +250°C
Outgassing 30cm diameter -180 to +300°C
WRK 50x50cm -180 to +300°C
MiniWRK 35x30cm -180 to +500°C
Thermal Cycling facts:

Temperature range
Tmin -180 °C
Tmax +300 °C

Vacuum
< 10-5 mbar

Typical temper­at­ure cycles (if not other­wise specified by customer)
Temperature extremes: -160 °C and +160 °C
Heating and cool­ing rates: 6 °C /min
Dwell times at temper­at­ure extremes: 15 min
Number of cycles: 100