Fracture analysis of spherical shells : application to cracking of macadamia nuts

The main consideration in recovering the macadamia kernal is to crack the spherical nutshell without damaging the kernal. Five mechanical cracking tools were tested, and the fracture mechanisms of nutshells, under various cracking loads, were studied. A classical theoretical approach and a numerical method were both used to investigate the influence of crack face closure on the stress intensity factor for a cracked spherical shell subjected to membrane forces and bending moments.