THE MECHANICAL-BEHAVIOR OF VIBRATED, AERATED BEDS OF GLASS AND STARCHPOWDER

A model which describes the movement of a powder bed subjected to vibr ation and aeration through a porous support plate is proposed and solv ed. The calculated bed movement is shown graphically both as a functio n of time and - taking discrete Fourier transforms - of frequency. To validate the model experimentally, a new experimental technique was de veloped. This involved measuring the movement of a porous disc inserte d in the bed and following the bed movement. The methodology and the d ifficulties involved are discussed. The experimental results are prese nted as Fourier transforms of the bed movement. Both model and experim ent show that at the higher vibration intensities, where the bed loose s contact with the support plate, bed movement with a period of more t han one vibration cycle causes the appearance of a peak in the Fourier spectrum at half the plate excitation frequency. The intensity at whi ch this first occurs is acceptably well predicted by the model. On the whole, taking into account the assumptions made in the model and unav oidable experimental errors, predictions and experimental results show good agreement. (C) 1998 Elsevier Science Ltd. All rights reserved.