A finite element simulation of the spherical mandrelling process of holes with cracks

Residual compressive circumferential normal stresses around fastener holes enhance the fatigue life of the service components in metal structures. Fastener holes are considered as potential crack initiation sites for structures that undergo cyclic fatigue loading because of the stress and strain concentration. However, the use of a cold holes expansion by means of spherical mandrelling process to introduce a compressive residual stress field in the material surrounding the hole can enhance the service life of stressed structural components. This paper presents the outcomes from finite element simulation of spherical mandrelling process of holes with cracks. Isotropic plastic hardening and Von Mises yielding criterion have been used in the analysis. Two cases of depth of the crack have been analyzed. A two-dimensional elastic–plastic coupled thermomechanical finite element analysis has been performed. A tensile stress is then applied to the cold-expanded pre-cracked hole to assess the benefit of the spherical mandrelling process.