XRD Burnishing: Investigating Residual Stress Measurements

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SUMMARY

The discussion centers on the challenges of measuring residual stresses in Ti-6Al-4V samples using X-ray diffraction (XRD) techniques. The user reports inconsistent stress measurements of 99MPa, -300MPa, and -360MPa across theoretically identical samples, with a standard deviation of +/- 300MPa, indicating significant inaccuracies. Issues such as surface scratches and pitted holes on the samples are suspected to affect the results. The user employs a Philips Analytical X-Ray B.V. machine with a Cu tube anode and mentions similar problems with a Bruker D8 XRD machine, seeking alternative methods for accurate residual stress measurement.

PREREQUISITES
  • Understanding of X-ray diffraction (XRD) principles
  • Familiarity with the sin^2 PSI method for residual stress measurement
  • Knowledge of Ti-6Al-4V material properties
  • Experience with XRD equipment, specifically Philips and Bruker models
NEXT STEPS
  • Research alternative residual stress measurement techniques, such as neutron diffraction
  • Investigate the impact of surface preparation on XRD results
  • Learn about the effects of sample geometry on residual stress measurements
  • Explore advanced XRD analysis software for improved data interpretation
USEFUL FOR

This discussion is beneficial for materials scientists, mechanical engineers, and researchers involved in residual stress analysis, particularly those working with titanium alloys and XRD technology.

zenite
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I am doing a research project on measurement of residual stresses for Ti-6Al-4V that has been burnished. I did the first scan to get my peaks, and selected the last peak (the highest 2 theta value) for the stress scan (sin^2 PSI method).

The problem is that the value I got for 3 samples (that are theoretically identical) is 99MPa, -300MPa, -360MPa. Also, the standard deviation for all 3 samples are in the region of +/- 300MPa (!). That is highly inaccurate.

Now, I have read many texts on XRD and the theories. But I have no idea why the accuracy for my sample is so bad. Can anyone advise me? My samples have some scratches are really small pitted holes, so will that affect the result?

I did another scan on the highest peak (instead of the one with the largest 2theta value), I ended up with -3000MPa. Really lost now.


I am using Philips Analytical X-Ray B.V. with Cu tube anode. Let me know if I have to provide any other details.
 
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I also have same problem. I have been used Bruker D8 XRD machine. Some results are higher than 0.2% proof stress and tensile strength. I am confuse it can or can not. I need another accurate way to measure residual stress. but my sample is small (20mm diameter disk sample)
 

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