Determination of dynamic deformation behavior of Golden Delicious apple using finite element method and its validation by scanning electron microscopy

Abstract

Apple fruit is affected by operations such as harvesting, packing, grading, storage, and transportation on the way from the garden to the sales centers. During these stages, the products are subjected to several static and dynamic loads applied to each product, damaging them. The aim of this study was to determine the dynamic deformation behavior using finite element simulation and to investigate the surface temperature changes of Golden Delicious apple cultivar due to impact loads. For this purpose, the physical, mechanical and rheological properties of the internal components of apples were determined in three parts: skin, flesh and core. A viscoelastic material model was defined for more accurate simulation. Scanning electron microscope is used to measure the volume of damage and a thermal camera is used to measure the surface temperature of the product. To collect valid data in the dynamic loading section, the pendulum impact test was performed in the form of a factorial design. In this test, the independent variables included impact levels at 3 levels, product temperature at 2 levels and product radius of curvature at 2 levels, and dependent variables included bruising volume and surface temperature difference. The simulation results showed that the difference in bruise volume in the force-time and velocity-time methods with the bruise volume in the experimental test was 14.12% and 18.53%, respectively, and the maximum difference in reaction force was 9.36% and 15.97%. Therefore, in dynamic simulation based on pendulum impact test results, the use of force-time data offers better results than velocity-time data. The results of surface temperature measurements showed that with a gradual increase in apple temperature, the surface temperature of the bruised area is lower than the temperature of the healthy area. The highest surface temperature difference was observed in 30 minutes after impact and in the third impact level (33 N) equivalent (0.4 °C). Also, the results of the experimental pendulum impact test showed that all three factors of impact level, product temperature and radius of curvature had significant differences in bruising volume. Thus, the volume of bruising is directly related to the impact surface and the radius of curvature and inversely related to the apple temperature.