Relationship between mechanical properties and damage of Hetao muskmelons under static compression

The mechanical properties of Hetao muskmelons and the effective factors，such as loading rate, fruit’s stiffness and compressing position, were experimentally studied in order to solve the problem of damage due to quasi-static loading during storage and transportation. The results show that with the increasing loading rate, the yield force Fy and deforming energy Uy increase and reach maximum values, but both the break force Fb and break energy Ub continue to increase. The values of Fy and Uy, Fb, Ub obviously decrease with the decrease of fruit’s stiffness. Stress-strain curves of about spherical body of intact Hetao muskmelon fruit under quasi-static loading were originally developed. These curves indicate that the stress increase lags behind the increase of the contact area of the sample at early compressing stage. The results also reveal that the damage volume is significantly affected by both the mechanical property parameters and the effective factors. The micro tissues of the fruits under compression at a smaller loading rate are more easily destroyed, which lead to damage diffusion. The fruits compressed in the vertical stem direction are more easily to get to state of yield than that of compression in the horizontal stem direction, resulting in much serious damage degree. Both the linear regression equations of the relationships between the mechanical property parameters and damage volumes, and the linear regression equations of the relationships between the effective factors and damage volumes are innovatively developed. Statistic analysis indicate that the above equations are all meaningful and suitable for predicting and controlling the damage due to quasi-static loading during storage and transportation. Moreover, correlation exits between the mechanical property parameters. Statistic analysis indicate that Fy presents a significant positive correlation with Uy , with a highest coefficient r of 0.870, and Fb presents a least correlation with and Fy, with a coefficient r of 0.366 .