HYGROTHERMAL AND MECHANICAL BEHAVIOUR OF ABRASIVE AGGLOMERATE. APPLICATION TO RECTIFICATION WHEELS DRYING.

ABSTRACT

The distribution of the water content and temperature have been modelised and numerically investigated within the body of unbaked rectification wheels during convective drying. The obtained profiles have been applied to mechanical stress distribution simulations, fitting process parameters in order to avoid crack formation. The thermophysical, cinetical and mechanical properties of the abrasive agglomerate were determined experimentally.

The transport phenomena within the medium have been described by a classical water vapour diffusion and thermal conduction model with convective boundary conditions. The water vapour diffusivity and thermal conductivity were obtained respectively by water content profile analysis during 1-D isothermal diffusional water vapor transfer and by the flash method. The heat and mass transfer coefficients at the boundaries were calculated on the basis of itterature correlations. The set of coupled non-linear differential equations was discretized in the space domain by the finite-volume method and integrated in the time domain by Runge-Kutta-Fehlberg procedure widi ACSL package.

A finite-element variational formulation with elasto-plastic behaviour laws has been used to assess the mechanical strain and stress distribution resulting from the pre-calculated water content and temperature profiles. The simulations were carried out with the industrial Abaqus package. The shrinkage coefficient was measured by means of a laser beam displacement detector on samples dried by micro-wave radiation. The elasticity modulus, tangential plastic modulus, compression and tension failure stress were determined by compression and bending tests on hygro thermally conditioned samples.