Special issue article J Strain Analysis 1–7 Ó IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0309324719833227 journals.sagepub.com/home/sdj Application of the hole-drilling method for the evaluation of residual stresses near rounded ends Jesus Manuel Alegre 1 , Andre ´ s Dı ´az 1 , Isidoro Ivan Cuesta 1 and Juan Manuel Manso 2 Abstract The experimental measurement of residual stresses by the hole-drilling method is aversatile technique due to its great simplicity. The technique consists of drilling on a material surface and measuring the relieved deformation on the surface by means of strain gauge rosettes. The most widespread method to obtain residual stresses from relieved deformation is the integral method and is found in the ASTM E837-13a standard. The procedure is standardised for very specific con- ditions, which are based on the application of the technique on a large flat-plate. To apply this technique to situations outside the standard scope, it is necessary to perform studies that validate its applicability. One of these situations is to evaluate the stresses introduced in hot- or cold-rolled profiles, where the residual stresses are concentrated on the rounded corners generated by rolling operations. In this study, a numerical simulation by finite elements has been carried out to obtain the relieved deformations for the case of drilling near rounded ends. The results show that the hole- drilling technique is applicable for the case of rounded ends; however, there is a significant deviation from the flat-plate condition which can be minimised by considering new matrices for the specific rounding radius and thickness of the ana- lysed workpiece. Keywords Residual stress measurement, hole-drilling method, finite element simulation, strain gauges Date received: 14 September 2018; accepted: 30 January 2019 Introduction Almost every manufacturing process associated with the transformation or shaping of metal components introduces residual stresses. In the case of structural member, cold forming especially produces significant residual stresses. 1 The magnitude of these stresses asso- ciated with plastic bending during rolling processes is demonstrated to depend on the rounding radius, R r 2 or, more precisely, on the radius relative to the thick- ness R r /t. 3 Experimental determination of residual stresses in those cold-formed profiles usually relies on X-ray dif- fraction 4 or in sectioning methods. 5,6 However, while the former is expensive, the latter gives coarse and non- localised measurements. As an alternative, hole-drilling method is an experimental technique that can be used to obtain residual stresses in a workpiece point by drill- ing a small hole on a material surface. 7 The hole-drilling method comprises three stages: the drilling operation, registration of relieved strains and stress calculation. Using strain gauge rosettes, the relieved deformations during drilling are measured, determining with enough precision the residual stress state in the surface up to 1–2 mm in depth. 8 Several methods have been developed for the evalua- tion of residual stresses from the relieved deforma- tions. 9 The most widespread method is the integral method 10 and is found in the ASTM E837-13a stan- dard. 11 This procedure uses two matrices of coefficients to determine the stress-state components of a point; however, they can only be used for very particular con- ditions. The coefficients for a particular hole diameter, 1 Structural Integrity Group, Escuela Polite ´cnica Superior, Universidad de Burgos, Burgos, Espan ˜a 2 Sustainable Construction Group (SUCONS), Escuela Polite ´cnica Superior, Universidad de Burgos, Burgos, Espan ˜a Corresponding author: Jesus Manuel Alegre, Structural Integrity Group, Escuela Polite ´cnica Superior, Universidad de Burgos, Av. Cantabria s/n, 09006 Burgos, Espan ˜a. Email: jalegre@ubu.es