The Measurement of Residual Stress using Laboratory Based X-Ray Diffraction Instruments; the Positives, the Pitfalls and a Round Robin

Workshop and Exhibition

Date/Time: 27 September 2023

Location: National Physical Laboratory, Teddington, UK

Price: Prices inc VAT. BSSM Members including students £70 . Special offer join the BSSM today and attend at the member rate £140. Non Member £95.

Register

A one day workshop which will include the following topics:.

• The basic principles of crystallography and of the laboratory based X-ray diffraction (XRD) method
• Advantages and limitations of the method
• Measurement of awkward samples including curved, large ones and anisotropic materials
• Elastic constants, after all, we measure strain, not stress
• Methods layer removal which do not introduce additional stresses

There will be an instrument Manufacturer's forum and live demonstrations

A programme of Round Robin XRD residual stress measurements will be discussed at the meeting.

This event will be a one day workshop which will include a wide range of topics including, the basic principles of crystallography and of the laboratory based X-ray diffraction (XRD) method; it’s advantages and limitations. The measurement of awkward samples including curved ones, large ones and anisotropic materials should be covered. We will also discuss elastic constants given that we measure strain, not stress as well as methods layer removal.

The results from the recent EASI-STRESSers Round Robin will be described as well as a comparison with hole drilling techniques.
There will be an instrument manufacturer's forum with live demonstrations of portable residual stress diffractometers.
We also intend to initiate a Round Robin to test the reproducibility XRD method with as wide a range of instruments and participants as possible.

Confirmed Speakers

• Tony Fry, National Physical Laboratory, Teddington, UK
• Dr Joe Kellerher, ISIS Pulsed Neutron & Muon Source, Harwell Campus, Didcot
• Prof John Bouchard, Stress-Space Ltd
'Measurement of Awkward Components'
• Dr Ioannis Violatos, Materials Modelling Theme Lead, Advanced Forming Research Centre, Strathclyde.
• Prof. Matthew Roy, Department of Engineering, University of Manchester
'Laboratory XRD determination of residual stress of EASI-STRESS benchmarks''
• Dr Jeferson Araújo de Oliveira, Residual Stress Measurement Services, StressMap, Open University, UK. 'Depth profiling of residual stresses using X-ray diffraction – A practical review' 
• Judith Shackleton, Rolls-Royce, Civil Large Engines (Retired)
'How the X-ray Diffraction Based Method Works and Some Crystallography'

Would you like to give a talk? Would you like to attend?

Please contact the BSSM via the following link.

Confirmed Manufacturers

Bruker
Proto
Pulsetec
Quantum Design
Stresstech

Presentations

Introduction to the National Physical Laboratory
Tony Fry, NPL
A brief introduction to the activities of the National Physical Laboratory
NPL is the UK’s National Measurement Institute and was founded in 1900 for "standardising and verifying instruments, for testing materials, and for the determination of physical constants." We are one of the oldest standardising laboratories in the world. Since its establishment, the research work at NPL has included all branches of physics, light, electricity and magnetism, radio communication, engineering, metallurgy, aeronautics and ship design. Some of the world’s most significant innovations have origins at NPL, including radar; packet switching, the forebearer of the internet; the ACE computer; and the caesium atomic clock. One route to impact and improvement of the quality of measurements in industry is through training and the production of Measurement Best Practice Guides. This presentation will outline the core roll of NPL and provide an overview of the history of the XRD Residual Stress Best Practice Guide and plans for future developments of this guide.

Elastic Constants
Dr Joe Kellerher, ISIS Pulsed Neutron & Muon Source, Harwell Campus, Didcot
Material performance and structural integrity is usually best understood by considering values of stress in the material. However, the atomic lattice spacings measured by X-ray and neutron diffraction are more directly related to elastic strain. Elastic constants for the material of interest, which quantify the relationship between stress and strain, are therefore required when using diffraction methods to measure residual or applied stress. Experimental methods to measure elastic constants are described, along with the various ways they may be specified and quoted in the scientific literature. Moreover, the elastic properties of materials are often of research interest in their own right. Physical origins are considered for the relationship between the elastic constants used for diffraction and the macroscopic elastic quantities familiar in engineering like the Young's modulus and Poisson's ratio. The anisotropy of the single crystal grains within a microstructure can cause the hkl-specific diffraction elastic constants to differ substantially from those that might be expected from just considering the bulk elastic behaviour, and examples of these effects in common engineering materials are considered.

Measurement of Awkward Components
Prof John Bouchard, Stress-Space Ltd
Awkward components can be defined as those having a global shape and/or local geometric surface form that can compromise accurate positioning or limit the X-ray measurement optics that can be applied. This classification includes components that are physically too large or too heavy to measure using a typical laboratory-based X-ray diffractometer, and structures that cannot be dismantled or are situated in hostile environments. The talk will present some measurement strategies for dealing with such awkward components, including a laser-guided XRD measurement system that maps the detailed surface form of parts large and small and accurately positions XRD measurements in both laboratory and field application contexts. The talk will be illustrated by recent measurements on large samples made using the laser guided system described.

Materials Modelling
Dr Ioannis Violatos, Advanced Forming Research Centre, Strathclyde
Determination of residual stresses throughout the manufacturing route of high value engineering products is particularly challenging. There are inherit limitations with the measurement techniques for residual stresses and a number of uncertainties associated with the condition of the material and the measurement procedures for in-situ or ex-situ investigations. X-ray diffraction is the industry's gold standard, because it can provide a fast, accurate, and reliable non-destructive assessment of in-plane surface stresses. These information can be used as part of i) a design and optimisation process to address distortion and/or material failures in manufacturing, ii) a metric for the quality of manufacturing and the integrity of a product, and iii) a digital passport for a product and its manufacturing route. Thus, x-ray diffraction is indispensable in the assessment of residual stresses and it can complement other techniques to synthesize the full stress state of a material/product and gain an invaluable insight about a processing step. This talk will attempt to provide a critical comparison between x-ray diffraction and other residual stress measurement techniques within the broader context of manufacturing through case studies on forging, welding, machining and additive manufacturing of metallic materials, showcasing challenges and good practises in the assessment of residual stresses.

How the X-ray Diffraction Based Method Works and Some Crystallography
Judith Shackleton, Rolls-Royce plc (Retired)
This talk will cover some basic crystallography including, crystal systems, Bravais lattices, Miller indices and Bragg’s Law as this information is required to specify measurements. We will also describe, briefly how the sin2psi method works, its advantages and disadvantages.

Laboratory XRD determination of residual stress of EASI-STRESS benchmarks
Prof. Matthew Roy, Department Of Engineering , University of Manchester
The recent EASI-STRESS programme (www.easi-stress.eu) aims to improve industrial user access to non-destructive diffraction techniques such as high energy synchrotron X-ray and neutron diffraction. As part of this initiative, a series of benchmarks were developed such that they could be subjected to the widest range of residual stress measurement techniques. One of these benchmarks was configured and measured by three different practitioners of commercial, laboratory-based X-ray diffraction with the sin2psi technique. It was found that while planar stresses could be found such that the magnitudes of peak tension and compression as well as errors all agreed, repeatable location of measurement sites was challenging. A description of the ferritic steel benchmark used will be described, the protocol employed for both performing and reporting measurements, and finally the results will be presented in the context of measurement standardization.

Depth profiling of residual stresses using X-ray diffraction – A practical review
Dr Jeferson Araújo de Oliveira, Residual Stress Measurement Services, StressMap, Open University, UK
In many engineering applications, the variation of residual stresses with depth is a key aspect for the accuracy of structural integrity assessments. Laboratory X-ray diffraction is normally limited to surface measurements ~5-30 µm , depending on the material and measurement conditions.To overcome this limitation and assess a residual stress depth profile, thin layers of material need to be removed from the region of interest. This presentation will review the practical aspects of this approach, including the techniques for material removal, problems that normally occur in theory and practice and how we normally overcome or mitigate these challenges.

A New Round Robin
Judith Shackleton, Rolls-Royce plc (Retired)
It's some time since a round robin was undertaken for laboratory based X-ray diffraction residual stress measurements. As these measurements are frequently made on safely critical components it's very important to check the reproducibility across as many laboratories as possible. It's proposed to set up as new test at this meeting. We will consider the sort of samples should which would be most suitable, for example, which alloys, shot peened specimens or bent bars. Suggestions most welcome!

Programme

Register