INVESTIGATION OF ELASTIC DEFORMATION OF POLYURETHANE PARTS OF THE DIE-TOOL

The polyurethanes of different brands are widely used in designs of the deforming tool for small-scale forming of sheet metal and tubular blanks. The replacing of metal parts of the stamp-tools on the elastic makes some advantages and disadvantages of polyurethane forming process. The elastic deformation of the cylindrical samples of polyurethane grade SKU-7L and SKU-PFL was investigated. As a consequence, the equipment for forming and stamping by polyurethane requires a margin of the nominal power more then in three times greater than the force of deformation in rigid die-tools or stamp-tools. In addition, there is evidence that for drawing of complex configurations parts with polyurethane is requiring the force, almost an order of magnitude greater than the force for drawing in rigid dies. Authors found in results of analysis of the literature that the known equations for the calculation of the power modes of polyurethane deformation into account only from geometrical factors and the amount of pressure that depends on the degree of polyurethane upsetting. It should share the upsetting of elastomeric materials in closed and open volume. The information about experimental studies of the effect of compression force from deformation rate of polyurethane, which is in production conditions determined by the type and characteristics of the equipment are quite restriction, which requires the formulation and conduct the laboratory experiments on polyurethane upsetting at different rates of compression. It was experimentally studied the strain-speed and power parameters of upsetting of polyurethane grade SKU-7L and SKUPFL in the elastic field. It is shown that pressure of upsetting primarily depends from the degree of deformation, and relative heights of samples. It is found that at least on the upsetting pressure has influence of strain rate. Equations of different species for determining the pressure of upsetting from the degree of deformation and deformation rate of polyurethane and also from the relative height of the samples. On the basis of the researches the conclusions are following. When polyurethane SKU-7L grade without limiting from the transverse deformation the increase of degree of deformation from 0.1 to 0.3 is increases the pressure in the precipitation of 2.0...2.7 times, strain rate and the decrease in 30 times (from 3.0 to 0.1 mm/sec) is reduces pressure in the upsetting in 1.7 ... 2.6 times, the most extensively (1.4...1.7 times) precipitation reduced pressure in the range of small reduction of strain rates from 0.2 to 0.1 mm/sec. Increasing of relative samples height in 1.67 times is reduces the pressure of upsetting in diapason of deformation rate 0,1...3,0 mm/sec and deformation degree 0,1...0,3 in 1.4 to 1.7 times. Analytical dependences for calculation of force parameters and pressure of forming by polyurethane from degree of upsetting, rate of deformation, strain rate and the relative height of the polyurethane samples are proposed.