Simulation of Central Hole Drilling Process for Measurement of Residual Stresses in Isotropic, Orthotropic, and Laminated Composite Plates

Abstract

In this article, a new method for calculating the calibration factors for measuring the residual stresses in different material systems is presented. The simulated hole drilling method can be used instead of experimental techniques. In this method the process of hole drilling, using a finite element method, is simulated. The drilling location is simulated by a finite element technique and after applying the initial load in the form of residual stresses, the elements in the hole area are deleted from the model. Then, the strain around the hole area under the strain gages are calculated. The two- and three-dimensional simulations of the hole drilling method for isotropic materials are presented. The calibration factors are calculated and compared with those available in the standards. The results show a difference of about 0.3% between the two methods. For orthotropic materials, the calibration coefficient matrix is obtained using the method presented in this study and the results are compared with theoretical values. The presented method is utilized for laminated composite materials and the calibration coefficient matrix is obtained. Different laminated composites with various lay-ups and materials are considered. Using the simulated hole drilling method and calculating the residual strains around the hole area and calculating the calibration coefficient matrix, the residual stresses due to curing process are calculated. The main advantage of the presented method is the capability to simulate the residual stresses in orthotropic materials with any degree of orthotropy. This method is able to simulate the behavior of different strain gages with different sizes and hole diameters. Simulation of the residual stresses for components and parts with complicated geometry is an application of this method.