Speaker
Description
Bulk materials are used in many areas of technology and are often stored in silos. Examples can be found in mining, plastics technology or food technology.
In some cases, extremely loud noises can occur when silos are discharged, which are caused by self-excited vibrations. However, the excitation mechanism for these vibrations is still not clearly understood. The noise is emitted by bending vibrations of the silo wall via the surrounding air. The energy for the bending vibrations comes from the potential energy of the bulk material, which leads to a vertical movement of the bulk material during discharging. The excitation mechanism transfers energy from the vertical movement of the bulk material via the boundary layer of the particles to the bending vibration of the silo wall.
Therefore, this work has observed the interaction in contact between particles of the bulk material and the silo wall more closely. Interesting interactions between the silo wall and particles in normal contact and in friction are revealed. Investigations into the contact surfaces between particles and a vibrating silo wall show that a strong coupling of silo movement and the boundary layer of the particles only occurs with a sufficiently large compression of the bulk material. This was established by observing the contact surfaces between particles and a transparent silo wall using a model test rig. Friction tests on a specially developed tribometer for bulk solids showed a dependence of the friction force on the sliding velocity. In addition, the friction shows pronounced hysteresis properties.
These more detailed investigations of the interactions between the particles of the boundary layer and the silo wall are the basis for possible future modelling of silo vibration.
Literature:
K. Popp, M. Rudolph, M. Kröger, M. Lindner: Mechanismen für die Entstehung und Vermeidung von reibungsselbsterregten Schwingungen. Konstruktion, 2004.
T. Falke, M. Kröger: Erweiterungen der tribologischer Modellierungen zur Abbildung reibungsselbsterregter Schwingungen. In: 61. Tribologie-Fachtagung, 2020, pp. 09/1-09/9.
T. Fürstner: Reibkontakteinflüsse zwischen Partikeln und Festkörpern auf die Schwingungsselbsterregung. Dissertation, TU Bergakademie Freiberg, 2021.
