very high cycle fatigue at freiberg - university of...
TRANSCRIPT
Anja Weidner, Horst Biermann
Institute of Materials Engineering
Colloquium Oulu – 2019, February 14th
Very high cycle fatigue at Freiberg
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Very high cycle fatigue at Freiberg
Ultrasonic fatigue testing
• 3 Ultrasonic fatigue testing machines
• (BOKU Wien, 2011 und 2013, Industrial partner 2017)
• high testing frequency (20 kHz)
• (N > 109 within few days)
• Different load ratios (R = -1, R > 0)
• Continuous testing or puls-pause mode
• inclusive compressed air cooling (spot-cooler)
• In situ measurement of resonance frequency (controlling
parameter, non-linearity parameter)
• Coroborrated by infrared thermography
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Very high cycle fatigue at Freiberg
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Very high cycle fatigue at Freiberg
strain
amplitude
vibration
amplitude
Ultrasonic
converter
Spot cooling
Amplification
horn
specimen
Very high cycle fatigue at Freiberg
Principle of ultrasonic fatigue testing
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Very high cycle fatigue at FreibergVery high cycle fatigue at Freiberg
Resonance frequency and non-linearity parameter
• Resonance frequency fres
feedback signal of ultrasonic fatigue testing
strongly influenced by temperature
• Non-linearity parameter brel
change of sinusoidal ultrasonic wave during cyclic loading
use of higher harmonics
different processes: hardening, softening, crack initiation …
Am
plit
ude
Frequency
Fundamental
(1st order)
2nd order
3d order
20 kHz
40 kHz
60 kHz
non-deformeddeformed
Kumar et al. J. Appl. Phys. 106 (2009)
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Very high cycle fatigue at Freiberg
Infrared thermography
• VarioCamhr head (Infratec, Dresden)
• Temperature resolution: 30 mK
• Frame rate: 50-60 Hz
• Infraredt pixel resolution: 640 × 320 pxl
• Lateral resolution (microscopic objective: 25 µm
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Very high cycle fatigue at Freiberg
Infrared thermography – full surface view
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Very high cycle fatigue at Freiberg
Infrared thermography – full surface view
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NHD = 0.225 mmσa = 625 MPa
Nf = 2,182,000
Very high cycle fatigue at Freiberg
Infrared thermography – correlated fractography
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Direct
thermogram
Reflected
thermograms
Very high cycle fatigue at Freiberg
Infrared thermography – full surface view
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Very high cycle fatigue at Freiberg
Resonance frequency, non-linearity parameter and
temperature
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Compressed air cooling
Radial fan
Induction coil
Pyrometer
Photonic sensor
Specimen
Pressure sensor
Temperature sensor
Vibration sensor
Very high cycle fatigue at Freiberg
VHCF at high temperatures
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(5) HF-Generator
Specimen
(1) Pyrometer
Vibration sensor (2) IR-Temperature measurement
(6) Ultraschall-Prüfmaschine
Controll-Parameter:1) Temperature (Pyrometer)
2) Temperature (IR-Sensor)
3) Pressure
4) Elongation (Photonic sensor)
5) Condition HF-Generator
6) Condition USFT
(3) Pressure sensor
(4) Photonic
sensor
Controlling software
Compressed air
Very high cycle fatigue at Freiberg
VHCF at high temperatures
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Very high cycle fatigue at Freiberg
VHCF at high temperatures