## 1 Introduction  
Material defects usually arise during manufacturing, processing, or even in service conditions due to environmental factors. Furthermore, defects can be generated when materials are subjected to mechanical loading. The main defects that commonly exist in materials are point defects, line defects, surface defects, and volume defects. Cylindrical voids (volume defects) and dislocations (line defects) are two types of material defects considered in this study. The formation of cylindrical voids can result from several different causes. Specifically, cylindrical voids can form in compressible hyperelastic materials through a cavitation process, which is triggered when the applied radial stretch reaches a critical value [1]. In the additive manufacturing (AM) process or 3D printing, undesirable voids, such as interlayer voids, can be produced by incomplete material filling within part layers [2, 3]. Additionally, voids can be generated from the extrusion process in additive manufacturing. Movement of the printhead and the speed of printing are driving factors that affect a void's shape. For instance, a cylindrical void forms if the printhead follows a circular path that does not fuse properly with the material beneath. In casting, improper mold filling or cooling can trap gases or cause shrinkage, especially in directional solidification, where voids align with the cooling gradient. Cylindrical voids, located along the axial direction, can be produced by continuous casting. Closure of these cylindrical voids by flat-die forging was investigated in [4; 5] as these voids detrimentally affect material properties. The effects of voids on mechanical properties of materials are well documented, such as in [6; 7]. A dislocation is a type of crystallographic defect in a material, specifically a line defect, where an extra half-plane of atoms is inserted into the crystal structure (edge dislocation) and the crystal layers are sheared in such a way that the atoms form a spiral ramp around the dislocation line (screw dislocation) [8; 9]. Much research has been devoted to investigating dislocation problems regarding the scale of a material as well as its type and geometry. Research on developing analytical solutions for elastic fields of dislocations has been performed and presented in previous literature. Some research has focused on the elastic fields of an infinite dislocation [10; 11; 12], the stress fields of a prismatic rectangular dislocation loop [13], and the displacement fields of a rectangular loop [14] in an infinite isotropic material. As for studies involving dislocations near a traction-free surface, a correction term is added to calculate the total stress fields of the dislocations in order to ensure zero-traction conditions on the free surface. Analytical solutions for elastic fields of dislocations near a planar or flat free surface have been provided in previous studies [15; 16; 17; 18]. In addition, a stress field due to an infinite edge dislocation outside, and parallel to, an infinite cylinder in an infinite isotropic material is presented analytically or in exact form in [19]. Nonetheless, analytical solutions for the stress field of dislocation segments (of finite length, and not just infinite, and of any orientation with respect to the void) near a finite-sized cylindrical void or any other void shape have not been identified. Hence, numerical solutions for such problems need to be developed and applied. The collocation point method is one of the main numerical methods used to resolve traction-free surface problems. The employment of a collocation point method to treat zero-traction boundaries in three-dimensional discrete dislocation dynamics was carried out by [20; 21; 22].