Abstract: Solid granules medium forming (SGMF) is an advanced forming technology used for deep drawing and bulging of sheet metals and pipes, where the rigid punch (or die) is replaced by solid granules medium, and it has unique advantages in precision forming of complicated parts, hard deformation materials forming, warm forming etc. To reveal the pressure-transfer characteristics of granules medium in SGMF, the stressed process of solid granule medium under uniaxial compression is numerically calculated in discrete/distinct element method (DEM), besides, the evolution law of micro structure of the solid granule medium in the compression process is analyzed in terms of force chains. To verify the discrete element method, a granules medium force-transfer performance test is designed, in which the stainless steel balls with diameter of 1mm are used as pressure-transfer medium, and the simulation result is in good agreement with the actually measured value. It is also found that the coordination number changes with the solid fraction in power function, so does the lateral pressure coefficient with the compressive stress, and the lateral pressure coefficient tends to be constant when the internal force chains structure keeps stable. In addition, the pressure decay law and limit pressure-transfer distance for solid granules medium are both deduced from mechanics of granular media, which has important significance for accurately controlling the pressure distribution and improving the formability of the workpieces.

Key words: Discrete element method, Force chains, Granular materials