Microsecond time-resolved X-ray diffraction for the investigation of fatigue behavior during ultrasonic fatigue...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Experimental Mechanics

Background:

• Ultrasonic fatigue testing is crucial for understanding material behavior under high-cycle loading.
• Accurate measurement of dynamic elastic strain and stress is essential for fatigue analysis.
• Existing methods often lack the temporal resolution to capture rapid loading cycles.

Purpose of the Study:

• To introduce and validate a new time-resolved X-ray diffraction method for in-situ strain and stress measurement during ultrasonic fatigue.
• To demonstrate the capability of the technique for high-resolution analysis of material response.
• To investigate the relationship between applied displacement and cyclic stress amplitude.

Main Methods:

• Utilized a 20 kHz ultrasonic fatigue machine coupled with a six-circle diffractometer at the SOLEIL synchrotron.
• Employed a two-dimensional hybrid pixel X-ray detector (XPAD3.2) with synchronous data acquisition triggered by strain gauges.
• Analyzed diffraction peak shifts for elastic lattice strain determination and applied the self-consistent scale-transition model for stress calculation.

Main Results:

• Achieved a temporal resolution of 1 µs, enabling precise reconstruction of diffraction patterns during 50 µs loading cycles.
• Estimated elastic lattice strain with a resolution of approximately 10⁻⁵.
• Observed a linear correlation between applied displacement and cyclic stress amplitude (40-120 MPa).
• Reported an increase in diffraction peak broadening with the number of applied cycles.

Conclusions:

• The developed time-resolved X-ray diffraction method is effective for in-situ measurement of elastic strain and stress under ultrasonic fatigue.
• The technique provides high temporal resolution for detailed analysis of material deformation dynamics.
• Results indicate that peak broadening correlates with accumulated fatigue cycles, offering insights into material damage.