Testing the fatigue characteristics of materials used with liquid nitrogen requires a special test machine that includes a LN2 cryostat. The machine consists of a dual column servo hydraulic test machine with the actuator placed in the adjustable height crosshead. A large LN2 cryogenic dewar is located under the actuator. Prior to submersion, a test sample is gripped and a special low temperature extensometer mounted. The frame includes a sub frame located below the actuator so that the loads are reacted against inside the test environment. During setup, the crosshead is lowered, with actuator extended until the subframe is submerged in the media. The cryostat is modular and can be removed with a conventional low temperature chamber (rated -185C) replacing it. 820 test systems feature high resolution (24 bit) digital servo control of an all electric fatigue rated actuator capable of testing at speeds of 1 micron per minute to 125 mm per sec. The actuator features a digital position encoder with resolution of 0.25 micron. The system is rated to 55 kN. An alternative servohydraulic machine would be the model 910LX25.
Applicable Testing Standards
- ASTM E8 Tension Testing of Metallic Materials
- ASTM E9 Compression Testing of Metallic Materials at Room Temperature
- ASTM E466 Load Controlled Constant Amplitude Fatigue Tests of Metals
- ASTM E1450 Tension Metals in Liquid Helium Test Equipment
Recommended Test Machine
Static and fatigue forces up to 50 kN (11,250 lbf)
Frequency ratings up to 75 Hz
Oil-free, all electric actuator for clean test conditions
Lower purchase, operating, and maintenance costs than hydraulic equivalents
Static and fatigue forces up to 25 kN (5,500 lbf)
Frequency ratings up to 100 Hz
Servohydraulic
Small, portable footprint
Recommended Testing Accessories
Load ratings from 50 kN to 300 kN (11,250 lbf to 67,500 lbf)
Hydraulic actuation
Designed to cycle dynamically through zero-load
Temperature ratings up to 1,000°C (1,800°F)
Measures displacement for axial tensile, compression, and cyclic testing
Gage lengths from 10 mm to 50 mm (0.5 in to 2.0 in)
Measuring ranges from 5% to 100% strain
Lightweight and self-supporting
Standard temperature range of -155°C to 620°C (-247°F to 1150°F)
Accompanied by a broad set of accessories that are capable of withstanding the heat or cold
PID controlled internal temperature
Mounts directly to the test frame