The Measurement of Residual Stress using Laboratory Based X-Ray Diffraction Instruments - Follow up

Provisional Programme will include

• Troubleshooting; how to spot what’s gone wrong (if anything) and what to do about it.
• How to check that your diffractometer is working correctly.
• Layer removal, the practicalities. How to determine the measurement depth etc.
• How to measure rough surfaces, shot peened samples etc.
• Sample geometry; the effects of curvature, shadowing, complex, compound curves.
• How to optimise your particular type of diffractometer.
• Variation of residual stress across sample surfaces, gradients across the surface.
• Measuring residual stress as part of the manufacturing process.

A Round Robin study was proposed at the 2023 meeting and samples are currently being prepared and results will be discussed at the meeting. Why not bring something to measure?

Exhibition
We will be having an exhibition with live X-Ray diffractometers again. If you are interested in exhibiting please contact the BSSM at info@bssm.org

Provisional Timetable

09:50 - 10:20 Registration, Coffee and Exhibition
12:40 - 13:45 Lunch, Exhibition and Demonstrations
15:00 - 15:20 Tea, Exhibition and Demonstrations
17:00 Close of Meeting

Speakers

Troubleshooting and optimizing the measurement and critical assessment of data
Mikko Palosaari, R & D and Measurement Laboratory Manager, Stresstech
Evaluation of residual stresses (RS) by X-ray diffraction can lead to wrong or misleading results if the measurement process and the measured data are not critically assessed. Although standards like EN 15305 explain what needs to be taken into consideration when doing RS measurements, there are still subtle things that can go wrong. In this presentation some of the not so obvious root causes for unsuccessful measurement results are gone through and means of detecting and avoiding them are discussed.

Measuring residual stress on curved samples
Jörg Behler, , Sentenso GmbH
This presentation will explore the limitations of existing equations for residual stress determination, which are typically applicable only to flat surface geometries. Samples need to be almost flat, because the laboratory equipment to measure residual stress does not track the location of the peaks gathered for stress determination, but assumes a uniform flat surface for stress determination. The has also implications for certain kinds of waviness like turning marks. While these limitations are mostly known, what is the subject of debates is the question what can be considered a flat surface for a given measurement spot? The focus will be on the practical implications for everyday measurements and best practices for using cos-alpha devices. Insights will be drawn from relevant literature, established standards and findings from an ongoing Round Robin test that investigates this issue.

The Measurement of Residual Stress by laboratory Based X-Ray Diffraction Methods
Judith Shackleton, BSSM
At the last meeting it was agreed to set up a new Round Robin test for the measurement of residual stress using laboratory based X-ray diffraction methods.
Two sets of samples were kindly donated. There are four, small shot peened titanium samples and four larger pieces of machined, ferritic steel. None of these sample are easy to measure. The samples have now been distributed around the UK. The X-ray tube anode and the reflection, {hkl} to measured was specified in the work sheets for consistency. Several sets of results have now been submitted.
It's not proposed to discuss the absolute values of the results as the samples have still to be sent overseas though the relative values will be compared.

Depth Profiling of Curved Samples – Measurement and Data Analysis
Tony Fry, National Physical Laboratory, Teddington, UK
Abstract to follow.