STUDY OF STRESS AND STRAIN STATES OF REINFORCEMENT IN RUBBER-METAL PRODUCTS DURING THEIR MANUFACTURE
Stress and strain states are typical for rubber-to-metal bonding areas in the rubber-metal products developed specifically for the space industry, particularly those with thin-walled reinforcement, i.e. dampers and brackets. To achieve maximum rubber adhesion to metal, 80-120 µm shot or aluminum oxide blasting at the air pressure of 0.6-0.8 MPa is applied to the reinforcing steel of straight or any other shape. The blasting process causes an improvement in the hardness of the material by strain hardening, which results in the backward deformation of the reinforcement. After the blasting process, the reinforcing steel changes its geometry and stress and strain state. A new equilibrium state appears.
Rubber-metal products are typically cast under pressure using press molds by vulcanizing a rubber mix at high temperatures. Bonding rubber to metal using an adhesive takes place simultaneously. During the molding process, the deformed reinforcement returns to its original shape once the pressure is applied and preserves its shape for some time due to strong rubber-to-metal bonds. Yet, after the rubber-metal product is taken out of the mold, the stress and strain state emerges in the rubber-to-metal bonding area, as the reinforcing steel wants to return to its equilibrium state. With the relaxation developing as time passes, delamination of the rubber-to-metal system occurs and the product can no longer be used.
As a result of our research, we determined the relationship between the strength of the rubber-to-metal adhesion and the deformation using standard samples and proposed the methods of the stress and strain state simulation that can be used for development of new technologies enabling manufacturing of rubber-metal products with no or small stress and strain levels. The paper outlines the key approaches to relieving the stress and strain states in the rubber-metal products with thin-walled reinforcement. Using the standard samples, we proved that relieving of the stress and strain state will ensure product operability during the entire period of warranty.
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