Torsional fracture of solid and hollow cylinders

• Fracture of solid and hollow cylinders subjected to torsion. • Spiral fracture in solid and hollow cylinders with different inner/outer radius ratios. • Finite element simulation of incremental crack growth. • 3-D growth of nonplanar cracks. • Experimental torsion tests on PMMA acrylic solid and hollow cylinders. • Formation of secondary cracks due to high tension in hollow cylinder wall. The fracture of solid and hollow cylinders subjected to torsion is examined using an incremental crack growth simulation procedure. Starting with small semi-circular surface cracks on the cylinder’s outer surface, successive fracture surfaces are generated using a mixed-mode crack growth criterion that eventually leads to the formation of a helical spiral crack in the cylinder. The differences between the fracture surfaces obtained for a solid cylinder and the fracture surfaces for hollow cylinders are examined in detail and compared with limited experimental tests. It is shown that a hollow cylinder with a long spiral crack will develop large circumferential tensile stresses on the inner radius of the cylinder, in a narrow region between the spiral crack fronts. These circumferential stresses cause the formation of secondary cracks that eventually split the hollow cylinder along a line parallel to cylinder’s axis.