Assessment and Validation of Incremental Hole-Drilling Calculation Methods for Residual Stress Determination in Fiber-Metal Laminates

Smit, T. C.; Nobre, J. P.; Reid, R.G.; Niendorf, Thoralf; Marais, Deon; Venter, А.M.

doi:10.1007/s11340-022-00848-4

Cited by 6 publications

(1 citation statement)

References 44 publications

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“…In light of this ill-posedness property, regularization approaches and techniques such as in the recent ASTM E837 standard (2020 and 2013 editions) [4,5] are discussed, which are based on the Tikhonov regularization [21]. For example, this approach is followed and implemented in several studies by Smit et al [22][23][24]. However, other approaches are possible, such as simple polynomial, spline filtering, or other techniques such as Gaussian Process Regression [25].…”

Section: Introductionmentioning

confidence: 99%

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

Santus,

Neri,

Romoli

et al. 2024

Applied Sciences

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The hole-drilling method (HDM) is a common technique used for the determination of residual stresses, especially for metal alloy components, though also for polymers. This technique is usually implemented with strain gages, though other methods for determining the fields of displacements are quite mature, such as the use of digital image correlation (DIC). In the present paper, this combined methodology is applied to a 3D-printed PLA precurved specimen that is flattened in order to impose a bending distribution which can be considered known with a reasonable accuracy. The back-calculated stress distribution is in agreement with the expected (imposed) bending stress, however, a converging iterative procedure for obtaining the solution is introduced and discussed in the paper.

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Section: Introductionmentioning

confidence: 99%

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

Santus,

Neri,

Romoli

et al. 2024

Applied Sciences

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Tikhonov Regularization for the Fully Coupled Integral Method of Incremental Hole-Drilling

Smit,

Reid

2024

Exp Mech

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Background The unit pulse integral method is used extensively with the incremental hole-drilling residual stress measurement technique. The ASTM E837 standard, which applies only to isotropic materials, recommends the use of Tikhonov regularization to reduce instability when many depth increments are used. In its current formulation, Tikhonov regularization requires the decoupling of stress, as is possible for isotropic materials. The fully coupled integral method is needed for residual stress determination in layered composite laminates and is currently employed without Tikhonov regularization. This causes greater sensitivity to measurement errors and consequently large stress uncertainties. An approximate method of applying Tikhonov regularization exists for biaxial composites, but is not applicable to more complex laminates. Objective Extend Tikhonov regularization to the fully coupled integral method to improve residual stress determination in composite laminates. Methods This work investigates the use of the approximate and fully coupled regularization approaches in an angle ply composite laminate of [+45/-45/0/90]s construction. Experimental validation in a [0/+45/90/-45]s laminate is also presented where the regularized fully coupled integral method is compared to the series expansion method that includes all in-plane stress and strain directions simultaneously in a least-squares solution. Results The regularized integral method produces comparable results to those of series expansion while requiring twelve times less FE computation to calculate the compliances. The optimal degree of regularization is also more convenient to determine than the optimal combination of series order required by series expansion. Conclusions The new method is easily applied and should find wide application in the measurement of residual stresses in composite laminates.

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Stress Evaluation Through the Layers of a Fibre-Metal Hybrid Composite by IHD: An Experimental Study

Nobre,

Smit,

Reid

et al. 2024

Exp Mech

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Background Incremental hole-drilling (IHD) has shown its importance in the measurement of the residual stress distribution within the layers of composite laminates. However, validation of these results is still an open issue, especially near the interfaces between plies. Objectives In this context, this study is focused on experimentally verifying its applicability to fibre metal laminates. Methods Tensile loads are applied to cross-ply GFRP-steel [0/90/steel]s samples. Due to the difference in the mechanical properties of each ply, Classical Lamination Theory (CLT) predicts a distribution of the uniform stress within each layer, with pulse gradients between them. The interfaces act as discontinuous regions between the plies. The experimental determination of such stress variation is challenging and is the focus of this research. A horizontal tensile test device was designed and built for this purpose. A differential method is used to eliminate the effect of the existing residual stresses in the samples, providing a procedure to evaluate the ability of the IHD technique to determine the distribution of stress due to the applied tensile loads only. The experimentally measured strain-depth relaxation curves are compared with those determined numerically using the finite element method (FEM) to simulate the hole-drilling. Both are used as input for the IHD stress calculation method (unit pulse integral method). The distribution of stress through the composite laminate, determined by classical lamination theory (CLT), is used as a reference. Results Unit pulse integral method results, using the experimental and numerical strain-depth relaxation curves, compare reasonably well with those predicted by CLT, provided that there is no material damage due to high applied loads. Conclusions IHD seems to be an important measurement technique to determine the distribution of residual stresses in fibre metal laminates and should be further developed for a better assessment of the residual stresses at the interfaces between plies.

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Assessment and Validation of Incremental Hole-Drilling Calculation Methods for Residual Stress Determination in Fiber-Metal Laminates

Cited by 6 publications

References 44 publications

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

Tikhonov Regularization for the Fully Coupled Integral Method of Incremental Hole-Drilling

Stress Evaluation Through the Layers of a Fibre-Metal Hybrid Composite by IHD: An Experimental Study

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