X-Ray Diffraction and Hole-Drilling residual stress measurements of shot peening treatments validated on a calibration bench
Author: M. Beghini1, T. Grossi1*, C. Santus1, A. Torboli2, A. Benincasa3 and M. Bandini4 1 Dipartimento di Ingegneria Civile e Industriale, Università di Pisa, Pisa, Italy 2 GNR Srl, Novara, Italy 3 SINT Technology Srl, Firenze, Italy 4 Peen Service Srl, Bologna,
Source: ICSP14 Milan
Doc ID: 2022101
Year of Publication: 2022
Abstract:
Abstract
The inverse problem of determining residual stresses from diffraction or relaxation methods
is notoriously affected by a high sensitivity to errors in input data. A particular care must be
devoted to ensuring that their input errors are minimized, and results shall come with a
quantification of the corresponding uncertainties.
Residual stress measurements are often validated by comparing the results of different
techniques. Although this approach can strengthen the measurement confidence, it does not
highlight potential biases of the methods.
The authors presented a calibration bench [1, 2] which can impose a known bending
distribution on a specimen while simultaneously performing an X-Ray Diffraction (XRD) or
Hole-Drilling Method (HDM) residual stress measurement. Since the external load can freely
be applied and removed, Bueckner’s superposition principle [3] can be exploited to
simultaneously identify both the reference bending distribution and the actual residual stress
distribution with the same experimental setup. As the first is accurately known, the bench
provides a direct estimation of the achieved accuracy. Moreover, it can reveal systematic
errors in the chosen procedures.
Two shot peening treatments were analyzed on the calibration bench with both XRD and
HDM. First, residual stresses on the surface were evaluated with XRD measurements, then
electrochemical material removal was performed to investigate stresses at higher depths.
After that, HDM measurements were carried out and compared with the results of XRD. Both
methods were also used to identify the known bending stresses: that provided an additional
validation of the residual stress results.
Keywords Residual stress, X-Ray Diffraction, Hole Drilling, Shot-peening, Calibration bench
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