Evaluating Non‐Uniform Residual Stress by the Hole‐Drilling Method with Concentric and Eccentric Holes. Part I. Definition and Validation of the Influence Functions

Abstract

Residual stresses play a fundamental role in predicting the resistance of several structural components, in particular when operating under alternating loads or in aggressive environments. Among the measurement techniques, the hole‐drilling method is unrivalled in terms of cost and flexibility. The currently available data reduction techniques do not account for some important parameters, in particular the hole eccentricity, and can be directly used only with certain rosettes or require the partial holes to be drilled at fixed depths. This paper presents a general approach for interpreting hole‐drilling measurements that includes the hole eccentricity and several other geometric and material parameters. The method is based on analytical influence functions relating the measured relieved strains to the residual stress by means of integral equations. By elaborating the results of accurate finite‐element simulations, continuous analytical influence functions are produced, which can be used to reduce the error in the reconstructed residual stress. We focus on the definition of the influence functions, their evaluation and assessment.

Hole Drilling and Ring Coring

“…Beghini et al [44] have proposed a stress evaluation correction method using influence coefficients from finite element models. In practical terms, misalignment during setting up and clearance/wear in locating elements of the drill head and optical head are likely to be the greatest sources of eccentricity.…”

Decomposition Theory of the Hole-Drilling Method for the Stress State Identification

“…Relieved strain j ε is multiplied with a unit dummy load vector introduced in the direction of principal stress and transformed to the winding direction using the strains γ ε ε θ , , r of the point j (see (13)). The both considered sensitivities t i of the i-th strain gauge to the strains relieved during the drilling can be formulated by average strain in the direction of the strain gauge winding according to (14). The curvilinear integral of strain along the winding length w i has an argument including strain j ε .The angle φ j from (10) is function of the particular position of the point M j on the winding and is not a function of the parameter α .…”

“…The relative radius r j = ρ j / R 0 in M j integration point on the strain gauge winding is identified. The integrands of (14) are set in (16) and (17) by a substitution ε r , ε θ ,γfrom (12) to (13) …”

“…Then the hole drilling experiment as formulated by E 837 standard cannot be used for any more complex determination of the strain state in the vicinity of the drilled hole, which would be necessary for any eventual improve corrections. Therefore, this paper on the elimination of the influence of the drilled hole eccentricity on the stress evaluation by the drilling method is actual [7,8,14 ]. …”

Desarrollo de métodos para la acotación de la incertidumbre en medidas de tensiones residuales en materiales metálicos tratados por LSP

“…c o m / l o c a t e / m e a s u r e m e n t possible. A correction for the eccentricity is available [12][13][14] but it is not directly applicable to the integral method. To date, it is not possible for the correction of hole-bottom fillet radius and plasticity effect for non-uniform stresses.…”