Velocity hardening of polyurethane parts of die-tools

The authors investigated the elastic deformation of the cylindrical polyurethane samples. The samples were 30 mm in diameter and consisted of 3-5 parts along the full extent of the sample. The height of each part is 12 mm, the relative height of the samples was equal to 1,2, 1,6 and 2,0. Deforming force, directed along the axis of the sample, was applied to the butt end of the sample. The relative degree of deformation was equal to 0,1, 0,2 and 0,3. The experiments were carried out at the deforming speed equal to 0,1, 0,2 and 3,0 millimeters per second. The authors have found out that relative degree of the sample deformation has the greatest impact on the change in deformation pressure. Rate of deforming and deformation rate also influence on deformation pressure but much less. Relative height of the samples has the least impact on the deformation pressure. The authors have identified approximating functions to be of linear type and in the form of polynoms. The functions state that the deformation pressure depends on the relative degree of deformation, rate of deforming and deformation rate and the relative height of the samples as well. Experiments have shown that: 1)if the relative increase of deformation degree is trebled the deformation pressure increases 1,8-2,4 times; 2) 30 times decrease of deforming rate reduces deformation pressure 2-2,7 times. 3) if the relative height of the samples increases 1,7 times `deformation pressure decreases 1,4-1,7 times. The authors have concluded that deformation of sheet billets by means of polyurethane must be carried out on hydraulic presses using the modes ?keeping billets under a predetermined pressure?. In this case, the press automatically sets the deforming speed at which the punching power does not exceed the maximum force of the press. Authors have established polyurethane deformation pressure high sensitivity to its deformation rate over the investigated interval. Polyurethane velocity hardening coefficient at these rates of deformation is equal to m = 0,71-0,97