Introduction
The conventional sin2ψ-method in accordance with EN 15305 [1] is an established tool for non-destructive residual stress measurements by means of X-ray diffraction. However, depending on the geometrical and structural properties of the investigated sample, its applicability on laboratory X-ray diffractometers can be limited. The arising difficulties are associated with the dimensioning of the used X-ray detector system, which may lead to insufficient counting statistics or impractically long measurement times. Two-dimensional X-ray diffraction offers new possibilities for residual stress analyses exploiting the full 2D position resolution of an X-ray area detector [2-4]. This work introduces a new approach based on the direct integration of 2D Debye-Scherrer ring sections to 1D intensity spectra for strain determination.
| Material | Hkl | Radiation | 2θ | Δγ |
|---|---|---|---|---|
| α-Fe | 211 | Cr Kα | 156.4° | 45° |
| γ-Fe, INCONEL® | 311 | Mn Kα | 152.5° | 38° |
| α-Ti | 302 | Cu Kα | 148.7° | 34° |
| Al | 311 | Cr Kα | 139.3° | 27° |
| WC | 102 | Cr Kα | 135.8° | 25° |
Standard mode
- Discrete tilt steps
- Number of tilt angles ≥ 9 (5/5)
- Equidistant data points (sin2χ)
- Exposure time per tilt angle ≥ 1 s
Sweep mode
- Continuous tilt movement
- Number of tilt angles ≥ 18 (9/9)
- Non-equidistant data points (sin2χ)
- Sweep time ≥ 5 s
Conclusions
The 2D position resolution of X-ray area detectors allows for a direct integration of the recorded Debye-Scherrer ring sections to 1D intensity spectra for strain determination. Experimental studies were conducted with the Xstress DR45 operated in standard mode with discrete tilt angles and in sweep mode with continuous tilt movement. For large collimator sizes (∅ 1-3 mm) the measurement time in sweep mode can be shortened by a factor of about 7 compared to standard mode, reducing to about 2 for small collimator sizes (∅ 0.3 mm). The results of this work demonstrate the statistical benefit from the replacement of linear X-ray detectors by X-ray area detectors, making the Xstress DR45 a well-suited diffractometer for fast residual stress measurements in various applications.
Written by
Sebastian Send (a),*, Dominik Dapprich (a),
Mikko Palosaari (b)
(a) Stresstech GmbH, Konnwiese 18, 56477 Rennerod, Germany
(b) Stresstech Oy, Tikkutehtaantie 1, 40800 Vaajakoski, Finland
*corresponding email: sebastian.send@stresstech.com
This poster is originally published in ICRS11.
References
[1] EN 15305, Non-destructive testing – Test method for residual stress analysis by X-ray diffraction, 2008.
[2] B. B. He, Two-Dimensional X-Ray Diffraction, second ed., John Wiley & Sons, Hoboken, 2018.
[3] B. B. He, Accuracy and Stability of 2D-XRD for Residual Stress Measurement, Proceedings of ICRS-10, Materials Research Proceedings 2 (2016), 265-270
[4] B. B. He, U. Preckwinkel, K. L. Smith, Advantages of Using 2D Detectors for Residual Stress Measurement, Advances in X-ray Analysis 42 (1998), 429-438