Energy absorption during compression and impact of dry elastic-plastic spherical granules

Abstract

The discrete modelling and understanding of the particle dynamics in fluidized bed apparatuses, mixers, mills and others are based on the knowledge about the physical properties of particles and their mechanical behaviour during slow, fast and repeated stressing. In this paper model parameters (modulus of elasticity, stiffness, yield pressure, restitution coefficient and strength) of spherical granules ( γ -Al 2 O 3 , zeolites 4A and 13X, sodium benzoate) with different mechanical behaviour have been measured by single particle compression and impact tests. Starting with the elastic compression behaviour of granules as described by Hertz theory, a new contact model was developed to describe the force-displacement behaviour of elastic-plastic granules. The aim of this work is to understand the energy absorption during compression (slow stressing velocity of 0.02 mm/s) and impact (the impact velocity of 0.5-4.5 m/s) of granules. For all examined granules the estimated energy absorption during the impact is found to be far lower than that during compression. Moreover, the measured restitution coefficient is independent of the impact velocity in the examined range and independent of the load intensity by compression (i.e. maximum compressive load). In the case of repeated loading with a constant load amplitude, the granules show cyclic hardening with increasing restitution coefficient up to a certain saturation in the plastic deformation. A model was proposed to describe the increase of the contact stiffness with the number of cycles. When the load amplitude is subsequently increased, further plastic deformation takes place and the restitution coefficient strongly decreases.

Dynamic response of shear thickening fluid under laser induced shock

“…Many kinds of materials such as metal foams, 1,2 ceramics, 3,4 and granular materials [5][6][7] are found to show excellent high impact resistance at high pressure and high strain rates. However, the irreversible deformations are happened for these kinds of materials after a single impact.…”

Rigidity versus deformability hypothesis in impact dynamics

“…One of the most significant differences between the two methods consists in the fact that while the rigid body model estimates that tangential percussion increases or at least is constant during the last phase of collision, the deformable body model assumed the occurrence of a maximum for tangential percussion during collision, and afterwards a decrease of it. Given the variety of applications in the domain of multibody dynamics, [10][11][12][13], the results could be a base for future research. …”

Cohesive strength of iron ore granules

“…These model granules are produced in a laboratory-scale batch drum granulator with iron ore controlled in size and nature. Rather than impact tests ( [4,5]), we perform compression tests [6,7] in order to measure the strength of the granules as a function of granulation parameters. In parallel, simulations of compression tests are performed by means of the Discrete Element Method [8,9] (DEM) coupled to a model of capillary bonding.…”