Investigating the Fracture Properties of Walnut Shell under Uniaxial Compressive Loading in the Situation of being enclosed in a Transverse Plane

One of the most important stages of walnut processing is cracking the hard skin and shelling it. In this research, to reduce the mechanical damage and improve the extraction quality of walnut kernels during shelling, the fracture properties of the walnut shell were evaluated in a new uniaxial compressive loading test by creating a lateral deformation limitation called the enclosed. The fracture properties of walnut shell for the genotype of hard shell walnut were investigated due to the variables of loading mode, loading direction, and size of a walnut. The results showed that the effect of the state of walnut loading (free and enclosed) on the fracture force and fracture energy was significant at 1% and 5% probability levels, respectively. The breaking force of the hard shell walnut was 273.96 and 441.47 N for free and enclosed loading states, respectively. The breaking force along the longitudinal axis (392.56 N) was significantly more than in other loading directions, such as thickness or suture on the skin (347.85 N) and width (332.65 N). In general, observations showed that in the case of enclosed walnut loading, the rupture development on the shell surface was more than that of freeloading, which can be used as an idea for making a high-performance nutcracker machine.