Дослідження ефекту релаксації напруження та залишкової деформації сучасних полімерних матеріалів для захисту поверхонь деталей від зношування

Abstract

Stress relaxation during compression of rubber and polymers is one of the indicators of their viscoelasticity. The purpose of the work is research on stress relaxation during compression and determination of the residual deformation of polymeric materials used in modern engineering for the production of protective coatings for machine parts. Experimental studies were carried out on a DM-30M laboratory unit with a ring dynamometer and a maximum compression force of 20kN. The DM-22M device is fixed on the press table.Samples for testing were cut from parts made of rubber produced by NVP «Valsa-GTV» and thermoplastic polyurethane with the trade name "Desmopan". During the test, the dependence of the stress drop in compressed samples of materials on time, the rate of stress relaxation was determined,the magnitude of the stress drop to the equilibrium value, the equilibrium modulus, as well as the residual deformation after the load is removed. The conducted studies established that at a constant relative deformation of 40%, thermoplastic polyurethane "Desmopan" is characterized by a lower tendency to stress relaxation, a higher modulus of elasticity under compression than lining rubbers, but has a larger residual deformation after unloading. Lining rubber, when comparing samples from new rubber and with about 9,300 hours of operation in difficult working conditions, showed itself as a material that is prone to internal structural transformations with an increase in the time of load perception. These transformations cause a change in the indicators of relaxation processes: the rate of stress relaxation decreases, the magnitude of the stress drop to the equilibrium state decreases, with a simultaneous increase in the modulus of elasticity.The results of the study can be used in the selection of material and calculations ofparts of protective coatings for performance and reliability.