Residual Stress Analysis of Orthotropic Materials by the Through-hole Drilling Method

Abstract

The present study deals with the development and the application of the through-hole drilling method for the residual stress analysis in orthotropic materials. Through a systematic theoretical study of the stress field present on orthotropic plates with a circular hole, the relationships between the relaxed strains measured by a rectangular strain gauge rosette and the Cartesian components of the unknown residual stresses are obtained. The theoretical formulas of each influence coefficient allow the user an easy application of the method to the analysis of uniform-residual stresses on a generic homogeneous orthotropic material. Furthermore, to extend the method to the analysis of the residual stresses on orthotropic laminates, caused by initial in-plane loadings, an alternative formulation is implemented. The accuracy of the proposed method has been assessed through 3D numerical simulations and experimental tests carried out on unidirectional, cross-ply and angle-ply laminates.

Analysis and optimization of hybrid double lap aluminum-GFRP joints

“…Obviously, the only knowledge of such maximum stresses is not sufficient for an accurate numerical prediction of the tensile strength of the HBB joint because, as it is well known in literature, a reliable strength prediction of a components made by PMCs and subject to significant stress concentrations, can be obtained only from accurate experimental analyses [33] or by theoretical approaches that take into account the stress concentration sensitivity [31,32] and the possible residual stresses [34].…”

Induced drilling strains in glass fibre reinforced epoxy composites

“…7 [7]. To accurately determine these stresses using the IHD technique, a theoretical background for anisotropic materials must be developed [5,14]. The different behaviour observed for both drilling operations is due to the different drilling parameters.…”

“…For anisotropic materials, a valid calculation method should first be developed to enable the evaluation of in depth residual stress distribution based on the obtained drill(z) curves and on suitable calibration functions determined by FEM, as is already possible to the case of isotropic materials, using, e.g., the integral method [7,10]. The best approach to this problem was developed by Pagliaro et al [5] to analyse the residual stresses in orthotropic laminates caused by initial in-plane loads. Nevertheless, in this context, the HENM methodology is important at two levels.…”

“…Moreover, the residual stresses cannot be relieved by using thermal relaxation due to the mismatch of the thermal expansion coefficients of fibres and matrix and the temperature damage to the polymer matrix. In addition, the incremental hole-drilling technique (IHD) seems to be a promising technique for measuring in-depth non-uniform residual stresses in FRPs [5,6]. However, knowledge of drilling stresses is also crucial for the accuracy of this technique [7].…”

Hole Drilling and Ring Coring

“…However, for orthotropic materials such as fiber composites and wood the strain/stress relationship is not trigonometric. Residual stresses can still be evaluated, but in a more complex matrix format using seven calibration constants [38,39].…”