Torsion machines

Description

In a torsion test a cylindrical specimen (mostly massif, but for some applications thin-walled tubular) is twisted and the torque is measured as function of the number of twists. This test can be carried out at room temperature or at elevated temperatures (hot torsion). The torque-twist data can be converted in true stress - true strain curves, using appropriate formula's.

For this conversion the values of the strain rate sensitivity coefficient and to a lesser extend, the strain hardening coefficient are needed. For practical applications this means that for each test temperature torsion tests at three to four different strain rates are needed. The main advantage of a torsion test is that very high strains can be reached before failure.

Technical details

Torsion tests at room temperature

• Speed: 0.044, 0.098, 0.202, 0.51, 0.99, 2, 5.1, 10.2, 20.2, 48.8, 97, 276, 506, 853, 1440 RPM
• Specimen length: max. 500 mm
• Displacement of grips during test: max. 20 mm
• Encoder: 1/20/100 pulses/rev
• Data: via datalogger
• Displacement of grips during test: max. 20 mm

Tests with MTM Torque cell

• Capacity: 25 Nm
• Grips: 0 - 9.5 mm

Tests with LEBOW Torque cell

• Capacity 0.35 Nm
• Grips: 0 - 1.5 mm

Hot torsion tests

• Torsion machine
  • Servo motor: 30 ... 3000 RPM
  • Gearbox ratio: 1/1 - 1/10
  • Break/Coupling reaction time: 175 msec
  • Encoder: 100 pulses/rev
  • Load cell (Piezo): Kistler 9271A
  • Torsion Axial force -100 ... +100 Nm -5 ... +20 kN
  • Displacement of grips during test: 220 mm
  • Specimen length: 250 ... 280 mm
  • Grips max.: 7/8/10/12 mm
• Heating
  • Induction heating: Aperiodic Generator
  • Machine/type: Cheltenham Induction Heating/CIH-G1HF12
  • Output: 12 kW
  • Frequency 5 - 40 / 100 - 350 kHz
• Cooling/Quenching
  • Atmosphere: Inert gasses
  • Cooling/Quenching: Inert gas/water/LN2
• Temperature
  • Control: Programmer - Controller TCS System 6000
  • Pyrometer:
    • Maurer TMR 95 ( 300 - 900°C)
    • Maurer 85 ( 815 - 1700°C)
  • Thermocouple: Type K
• Control
  • Mode: Man. / Aut.(Via HP computer)
  • Aut. Mode: Possibility to create different temperature ramp and hold positions, also different turns at different times and temperatures
• Data:
  • HP computer (Aut Mode)
  • Datalogger (Man Mode)