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In this paper, by expanding Muskhelishvili’s stress functions and with use of Schwarz’s alternating method, the stress distribution in a plate with two quasi-rectangular cut outs has been studied. Muskhelishvili represented the mentioned stress functions for studying the stress distribution in an isotropic plate with a circular or an elliptical cut out. In order to expand the Muskhelishvili’s analytical solution for deriving the stress functions related to quasi-rectangular cut outs, a conformal mapping function has been used. This conformal mapping transformed the area external of the quasi-rectangular cut out into the area outside the unit circle. Considering Schwarz’s alternating method, for calculating the stress distribution around two cut outs, complex series with unknown coefficients have been used. In this study, the effect of different parameters such as the location of the cut outs relative to each other, bluntness and aspect ratio of cut out sides on stress concentration factor can be investigated. The finite element method has been used to verify the accuracy of semi-analytical results. Comparison of two methods demonstrates the precision of obtained semi-analytical solution and indicates that it can be used for computing stress distribution in plates with two rectangular cut outs. Analysis of the proposed solution shows that the mentioned parameters have a significant effect on stress distribution and stress concentration factor decreases noticeably with selection of appropriate values of these parameters.

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One of the concerns of designers of engineering structures is structural failure due to stress concentration caused by geometric discontinuities in the structures. Therefore, by considering that perforated composite plates are used in most engineering structures, their study is very important. The purpose of this paper is to present a new model based on the regression method for estimating stress concentration factor of a circular hole in orthotropic plates. One of the important applications of providing stress distribution around holes in terms of mechanical properties is the use of these relationships in the stress analysis of perforated viscoelastic plate using the effective modulus method or Boltzmann's superposition principle. First, using different values of the mechanical properties of the composites plates, and employing an analytical solution based on the complex variable method, the stress concentration factor of circular hole is calculated for a number of these materials. Then, using multiple linear regression, an explicit expression for the stress concentration factor is given in terms of mechanical properties. The results show that the multiple regression model is able to predict the circumferential stress with a maximum error of less than 1%.