Analysis of static forces has an important role in bulk storage of agricultural products. The forces exerted on individual fruits, vegetables, or grains cause mechanical damage to them and lead to their permanent deformation. By analyzing the forces involved, we can manage them with proper methods and prevent the creation of waste. In this research, by conducting experiments, the required parameters for potato samples were obtained and simulated through the finite element method under load. Creep and tension tests were conducted on a cylindrical potato sample with the diameter and height of 25 mm. Apparent shear modulus had been extracted over time and imported to the Abaqus 2016. Simulation results showed that the maximum tension of 0.061 MPa occurred in layers near the pressure plate. Tension concentration caused the maximum tension of 0.07 MPa in the center of the potato. In accordance with the created tension, maximum displacement of 0.35 mm occurred in contact layer with the pressure plate and by moving away from this plate, displacement decreased linearly and reached to zero at bottom layer. The results showed that measuring the forces in storage and knowing the forces applied to the product can be effective in controlling the storage quality of agricultural products and reducing waste. Practical Applications Analysis of static forces has important role in bulk storage of agricultural products. By analyzing the involving forces, they can be managed with proper methods and prevent the creation of waste. This paper found that maximum stress and damage occur at force inserted areas and in areas of tubers are in contact with external material like transporting and storage boxes. Then, it should be tried to fabricate new flexible and viscoelastic materials such as polymers which acts like tubers in contact areas to decrease tubers’ stress to minimum value at contact points. Also more attention should be paid to stress concentration that may occur inside tubers which can lead to crush and destroy the product. Stacking more tubers on storage which can increase inserted stress beyond the value that leads to stress concentration should be avoided.

Summary This paper presents a discontinuous thick level set model for modeling delamination initiation and propagation in composites. Interface elements are widely applied in delamination models to define a discontinuity between layers of a laminate. In this paper, the common damage definition in the constitutive relation of interface elements is replaced with a new definition developed using the thick level set approach. Following this approach, a band of damage with predefined length is considered where the damage is defined as a function of distance to the damage front. The specifications of suitable damage functions for the developed method are investigated, and an efficient damage function is introduced. A sensitivity analysis of numerical input parameters is performed, which proves that the model is not sensitive to the length of the damage band. Because the required element size is linked to the length of the damage band, the insensitivity to this length provides freedom to use coarser meshes. Furthermore, the model provides a direct link between fracture mechanics and damage mechanics, which enables further development of the model for fatigue analysis. Validation of this model is presented by conducting three‐dimensional mode I, mode II, and mixed‐mode simulations and comparing the results with analytical solutions. Copyright © 2016 John Wiley & Sons, Ltd.

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The analysis of static forces is essential in the storage of agricultural products because these forces are applied in fruits, vegetables, or grains that can lead to their permanent deformation. This mechanical damage increases the product waste. Given that the potato tuber is surrounded by other tubers in the storage, then every tuber is pressurized from all sides or so-called triaxial stress. To measure the deformation of the specimens, a device was developed to conduct uniaxial and triaxial creep tests on the viscoelastic agricultural products (e.g., potatoes). Accordingly, the creep experiments were performed on potato samples for 5, 30, 60, 120, 240, 360, 420, and 480 min under the constant load of 72.5 N at 3 and 11 replications via uniaxial and triaxial tests, respectively. The results showed that in the creep test, the loading time was significant on the deformation of the specimens at the 0.05 level of probability.Triaxial test showed that the tuber deformation and strain of top layer were more than the middle and bottom layers. The results showed that the deformation of tubers under uniaxial test was more than triaxial one. K E Y W O R D Screep, potato, triaxial, uniaxial