Project Details
Projekt
Emission of Microwaves and Light during the Contact Deformation and Breakage of Particles
Applicant
Dr. Sergej Aman
Subject Area
Mechanical Process Engineering
Term
from 2010 to 2016
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 169317854
The goal of the project is the investigation of micro processes during the mechanical loading of single particles and particle layers. The deformation of the particle, breakage at the contacts be-tween the particles, friction and the creation of new contacts are caused due to mechanical loading. The basic physical micro processes, which correspond to these processes, are different. The characteristic duration of these micro processes varies in the micro and nanosecond range. A new method has to be developed, to record these processes with a corresponding temporal resolution. This method will be realized by means of irradiation of particles with an intensive microwave. The reflected microwave will be recorded and analyzed. It contains three components, to which differ-ent micro processes can be assigned. The time behavior and specific frequencies of the reflected microwave will be used as distinguishing features of these basic micro processes. Numerous breakage processes take place in the contacts. The electrons emitted during the break-age are accelerated in the electrical field of the incident microwave and become oscillating. Due to oscillation the free electrons radiate the energy in form of an electromagnetic wave in the frequen-cy of the incident microwave. That means that the Thomson-Scattering of the microwave takes place. Due to the collision with air molecules, which penetrate into the cracks from the atmosphere, the number of oscillated electrons drastically decreases and the Thomson-Scattering can take place only a few microseconds. Consequently, the microwave impulse with a characteristic dura-tion of few microseconds and the frequency of the incident microwave may be considered as a distinguishing feature for micro breakage. During the compression of the particle layer a strong friction between the particles takes place. This process is accompanied by an intensive electron emission and charge of surface that occurs at the contacts between particles. Numerous micro gas discharges will be caused due to the action of incident microwaves. The micro gas discharges generate the microwave impulses in a wide-band frequency range with a characteristic duration of few nanoseconds. This is a distinguishing feature for friction. The low-frequency component of the signal is caused by the change of particle layer density during the deformation. The characteristic time of this process is in the millisecond range. Based on the above described features one can characterize the micro processes independently from each other. A verification of this measurement method will be carried out by means of the DEM-simulation. A variation of the number of the particles, particle sizes and material properties will be approved. The number of developing and separating contacts, as well as the relative speed of particles as a function of the loading time, will be simulated and compared with data obtained during the experiment.
DFG Programme
Priority Programmes
