Investigating the stress–strain of wheat in silos using triaxial tests based on local deformation measurements

Abstract

To safely store wheat in silos considering filling and discharging process, the stress–strain behaviour of wheat plays a key role for silos design. A series of triaxial tests of wheat were performed using a digital imaging triaxial apparatus, which can capture local deformation across the entire surface of the specimen. By comparing the global and local stress–strain behaviour of wheat, the non-uniform deformation affected by the end restraints of triaxial apparatus were identified during the pre-failure and failure processes. The radial strain contour corresponding with non-uniformity coefficient values was presented. It was concluded that local stress–strain of the 40 mm-high specimens from the central regions of the specimen was less affected by the end restraints, indicating that they better characterise the stress–strain behaviour of wheat. A constitutive model of wheat was then deduced based on local measurements, from which strength and deformation characteristics were quantificationally analysed. It was concluded that the mechanical parameters from the local data of wheat specimen were greater than the global ones identified from the whole data.