Mechanical model of grape under compression load

A nonlinear mechanical model of grape was constructed. The grape was assumed as a spherical homogeneous, isotropic elastic membrane, which was fully-filled with incompressible, high viscous liquid. The stress distribution and deformation of grape under compression load by two rigid plates were studied. The equilibrium equations for contacted regions and non-contacted regions were obtained by using the theories of membrane. The boundary conditions and continuity conditions for the solution of the differential equations were determined.The tension of grape skin under compression load was analyzed numerically, usingRunge-Kutta iteration method. The results indicate that the stress in circumference is greater than that in the meridian direction. The failure of grape under compressive load was mainly caused by the maximal stretch stress which occurred at the equator. The results are consistent with the previous experimentalobservations.