Hey,
i have to choose a fatigue testing machine for additive manufactured metal parts.
Materials would be generic metals such as stainless steel, inconel etc.
The goal is to create simplified woehler / SN curves in a short time.
How can i decide which machine fits best?
Im looking for advantages and limits of the different machine types such as servohydraulic, electrodynamic, resonant pulsators and ultrasonic testing machines.
Also what is the limit for my test frequency to not get false results?
Thank you
Greetings,
I used servohydraulic Instron to conduct fatigue test. I'm satisfied with the overall set-up of the machine. Ultrasonic fatigue test is developed to save time for very high cycle fatigue (10^7 to 10^10) at 20 kHz. Frequency indeed has effect on the fatigue behavior of the materials. High frequency could induce self-heating during the fatigue test, affecting the S-N curve. Therefore, self-heating of the materials should be eliminated to obtain reliable results.
Kind regards.
Thank you Ng Lin Feng ,
i also read that there's an influence but the self-heating at high frequencies could be countered by a pulse-pause operation or by using a cooling system in ultrasonic testing or not?
Also at what frequencies did you test with the servohydraulic system?
As far as I can tell servohydraulic systems are used most of the time, but what is their advantage compared to resonant pulsators, which are a lot cheaper in maintenance and power and can test at higher frequencies (300Hz)?
You're welcome Jannik Pöllmann,
Yes, the pulse-pause operation/compressed air cooling are possible for cooling purpose in ultrasonic testing.
The frequency was fixed at 10 Hz during the fatigue test. It is commonly to fix low frequency when using servo-hydraulic machine. The higher the test frequency, the higher the possibility of getting phase lag in the sinusoidal wave at constant amplitude. The output amplitude will be lesser than the input amplitude, reducing the reliability and accuracy of the results.
As I know, the overall power consumption of the servo-hydraulic system is high since energy is required to generate the oil pressure for each cyclic loading.
Kind regards.
We use a frequency less than 15 Hz and set 2 million cycles for run out samples with the servo hydraulic system. Overall, the dynamic set-up is excellent and user friendly. Our group learned within a short span of time.
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