with the collaboration of Iranian Society of Mechanical Engineers (ISME)

Document Type : Research Article


1 Department of Biosystem Engineering, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran

2 Bu-Ali Sina University

3 Department of Mechanical Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran


Today, the increasing demand of consumers for high-quality products has led to the development of new technologies for the quality assessment of agricultural products. Iran is ranked the 9th in the world in terms of orange production. Annually, large quantities of agricultural products are degraded due to mechanical and physical damage during various operations such as harvesting, packaging, transportation, sorting, processing, and storage. This study is performed to identify natural frequencies and vibration modes of the Thomson orange fruit in small and large groups using finite element modal analysis by ANSYS software. In addition, physical properties including mass, volume, density and main dimensions were measured and mechanical properties were determined using Instron Texture Profile Analysis. Dynamic behavior of the orange fruit was simulated using the pendulum impact test. Next, the obtained impact was applied to the orange fruit by force gauge and three-axis accelerometer sensors in both polar and equatorial directions. The three-dimensional geometric model of the orange fruit was drawn in the ANSYS software. After meshing and applying the boundary conditions, the first 20 modes and corresponding natural frequencies were obtained. Since the objective of this study was to identify the natural frequencies of the orange fruit, it was considered free to move and rotate in space. The results showed that the natural frequencies of orange fruit are in the range of 0 to 248.41 Hz. Knowledge of the texture characteristics and dynamic behavior of horticultural products is essential for the design and development of agricultural machinery. Also, the design and development of agricultural machinery are directly related to the biological properties of agricultural products.
Materials and Methods
In the present study, Thomson orange variety is used. For experiments, a certain number of oranges were harvested from the Citrus and Subtropical Fruits Research Institute, Ramsar (50° 40′ E and 36° 52′ N). Performing finite element analysis needs knowing the physical and mechanical properties of the flesh and skin of the orange fruit. The physical and mechanical properties of the tested samples include geometric dimensions, modulus of elasticity, Poisson’s ratio, and density. In the present study, the dynamic behavior of orange fruit under dynamic loads was investigated by performing an impact test using a pendulum. The orange fruit was hung from the ceiling using a thin thread to perform experimental tests and extract the modal parameters. Impact on orange samples was applied at three angles of 7° (below the yield point), 10° (dynamic yield point), and 20° (above the dynamic yield point).
Results and Discussion
To validate the experimental (laboratory) natural frequencies and simulation, the comparison between these frequencies showed that in large-group oranges, the first, second, and third modes have experimental natural frequencies of 125.4, 146.9, and 180.4 Hz, respectively. Also, the simulation frequencies (modal frequencies) are 133.80, 146.16, and 196.66 Hz. The lowest and the highest differences were observed in the second (0.5%) and third mode (9.01%), respectively. in small-group oranges, the first, second, and third modes have experimental natural frequencies of 152.2, 188.8, and 242.2 Hz, respectively, and simulation frequencies are 167.79, 187.50, and 248.30 Hz. the lowest and highest differences between experimental and simulation natural frequencies were observed in the second and first modes (i.e., 0.68% and 10.24%, respectively).
Although there are some limitations, it can be agreed that Computer Aided Engineering (CAE) applications are very useful in predicting natural frequencies and modes of vibration of round fruits such as oranges. Using the obtained frequencies, especially the resonance frequency and the vibrational mode shape, In the actual transportation of orange, it is possible to avoid the resonance frequency by using appropriate packaging and transportation methods, so as to reduce the decay of fruit quality and predict the shelf life.


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