31 creep machines of own construction allowing:
- constant tensile load tests
- max. load 8000 N
- max. elongation (50 mm gauge length of specimens) 0.60 (0.47 true)
- constant tensile stress tests
(Hostinský and Čadek, J. Test. Eval. 4, 1976, p. 26)
- max. initial load 8000 N
- max. elongation 0.42 (0.35 true)
- specimen gauge lengths 25, 35 and 50 mm
- constant compressive stress tests
( Dobeš et al., J. Test. Eval. 14, 1986, p. 271)
- max. load 8000 N
- max. elongation 0.32 (0.28 true)
- specimen gauge lengths 10, 12, 15 mm
- constant tensile stress (or load) with a possibility of rapid cooling under stress at a predetermined time of creep exposure - see a) or b) - 1 machine
- combined creep and fatigue tests - 2 machines
- max. load 8000 N
- frequency 25 Hz
- load amplitude 500 A
- small punch creep test (ceramic ball is penetrated through a thin disk under a given force, central deflection of the disc is measured)
In all tests - possibility of protective atmosphere: purified dry argon, hydrogen, nitrogen
Testing temperatures:
R.T., 150 - 1000 °C, constant within:
- 1 deg for 150 - 600 °C
- 2 deg for 650 - 1000 °C
Temperature gradient along the whole 50 mm gauge length - lower than 2 deg
Elongation detection:
- continuous analog and digital recording
- range of creep rates: 10-10 to 10-2 s-1
- registration of data - PROGRAM CRTES1
Creep curves processing:
- fitting by standard constitutive equations; statistical treatment.
Possibility of recording of creep tests with varying applied stress:
- computer treated creep dip tests, tests with slow applied stress cycling
Laboratory of Viscous Creep
The laboratory is equipped with two special creep machines for low stress/low strain rate creep tests using helicoid spring specimen technique and one special creep machine for low stress / low strain rates torsion tests of brittle materials (ceramics, intermetallics). Optical measurement of strain eliminates any influence on the stress state and provides high strain sensitivity.
Helicoid spring machines
- Temp. range: 150°C to 1000°C
- Stress range: 0.2MPa to approx. 100MPa
- Strain sensitivity: better than 10-6
- Strain rate range: 10-9 to 10-13 s-1
- Protective atmosphere: purified argon or hydrogen, air
Two methods have been developed to produce the helicoid spring specimens from metallic materials
- (right) Wire drawing, wounding on the threaded bolt and annealing. The method is suitable for pure metals and mild model alloys.
- (left) Machining from tube. The method is suitable for structural materials. The microstructure of the original tube is maintained
Torsion machine
- Temp. range: 300°C to 1200°C
- Stress range: 2MPa to approx. 100MPa
- Strain sensitivity: better than 10-6
- Strain rate range: 10-9 to 10-13 s-1
- Atmosphere: air
