Optics and Lasers in Engineering 137 (2021) 106355 Contents lists available at ScienceDirect Optics and Lasers in Engineering journal homepage: www.elsevier.com/locate/optlaseng Experimental and computational analyses on residual stress of composite plate using DIC and Hole-drilling methods based on Mohr’s circle and considering the time eﬀect Mehrdad Babaeeian, Mehdi Mohammadimehr ∗ Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran a r t i c l e i n f o Keywords: Residual stress Digital image correlation (DIC) Hole-drilling method Composite plate Mohr’s circle Time elapsed eﬀect a b s t r a c t Due to residual stress eﬀects in ﬁnal parts, researchers have always been interested to measure residual stress in diﬀerent structures as well as comparing and analysing diﬀerent methods in order to increase the accu- racy and select the best method to measure it in diﬀerent conditions and materials. The hole-drilling by ap- plying the rosette strain gauge is one of the most commonly used methods for measuring residual stress and besides, the use of digital image correlation (DIC) method is expanding because of its advantages in measur- ing residual stress. So, these two methods have been studied by researchers. In this study, the results of resid- ual stress measurements on composite plate by the hole-drilling and DIC methods are compared, but employ- ing the Mohr’s circle in this comparison as an innovation is discussed to understand better this issue. Also, considering that the other researchers have usually paid attention to measure the residual stress immediately just after drilling in the hole-drilling method using the strain gauge. Thus, the eﬀect of elapsed time on the residual stress measurement is investigated in the results application. In both of these methods, the residual stress is calculated based on the principles of calibration coeﬃcient measurement and the ﬁnite element method (FEM). 1. Introduction Due to the positive and negative eﬀects of the residual stresses on structures and components, computing and studying them in diﬀerent ways have always been of interest to researchers [1–3]. In the struc- tures with diﬀerent materials, the composite parts because of their ex- tensive applications, has been studied by researchers [4–6], as such, research into the residual stress in these materials has also expanded [7–11] even in micro scale [12–15]. Residual stresses are calculated using destructive, semi-destructive and non-destructive methods [16]. The hole-drilling as a semi-destructive method and the digital image correlation (DIC) as a semi-destructive or a non-destructive method in the measurement of residual stresses repeatedly have been used by re- searchers [17–23]. Babaeeian and Mohammadimehr [7] considering diﬀerent times after hole drilling, investigated the residual stress on the composite plate around the hole with diﬀerent diameters using DIC method based on the point-wise local least-squares ﬁtting tech- nique(PLS). The results showed that the calculated residual stresses and their direction changes over time and these changes are considerable. ∗ Corresponding author. E-mail address: mmohammadimehr@kashanu.ac.ir (M. Mohammadimehr). Hagara et al. [24] used the FIB (Focused Ion Beam) -DIC ring-core milling method to measure the residual stresses in a plastically bent titanium alloy bar, so that the proﬁles of the results are very similar to the expected proﬁle for a bent bar. Duohua et al. [25] measured the initial residual stresses in a glass/polyester pultruded thick composite proﬁle by using incremental hole drilling, DIC and ﬁnite element meth- ods and by minimizing least-squares diﬀerence between experimental and numerical strains relaxation after drilling, so that a maximum of 20 percent diﬀerence was found in the estimated stresses for uniform and non-uniform initial stress states. Brynk et al. [26] considered the 3D DIC process during drilling with algorithm for inverse method cal- culation and also FLM with the purpose of estimating the residual stress around hole so that the eﬀects of drilling on results is expressed cause the diﬀerence in expected and obtained stress values. Vasylevskyi et al. [27] employed the electronic speckle pattern interferometry (ESPI) to measure displacements caused by the localized stress relief associated with blind hole drilling in various locations in 3D woven composites and observed that the surface displacements around the hole are sensi- tive to the hole location because of the diﬀerence in thermal expansion https://doi.org/10.1016/j.optlaseng.2020.106355 Received 22 June 2020; Received in revised form 11 August 2020; Accepted 24 August 2020 0143-8166/© 2020 Elsevier Ltd. All rights reserved.