Fatigue performance test is an important physical performance test. It is like the vulcanized rubber wear test, there are a variety of test methods.
Vulcanized rubber under the action of periodic stress or strain, any change in its structure and performance is called the fatigue phenomenon. The main sign of fatigue phenomenon of vulcanized rubber is the gradual decrease of hardness or elastic modulus, etc. The so-called fatigue life of the rubber is the time experienced by the rubber to reach breaking under the action of cyclic stress or strain. And the service life of rubber products is the rubber products from the beginning of use to the loss of use of the function of the time experienced. A variety of rubber products such as tires, shock-absorbing rubber products, or conveyor belts are used under dynamic deformation, so the fatigue breakage of rubber often determines the service life of these products. Therefore, in order to ensure the safety and reliability of rubber products in use, it is extremely important to predict the dynamic fatigue damage performance of rubber materials.
The rubber material is an uneven system, and the reduction of mechanical strength under cyclic stress or strain is the main reason for the breakage of vulcanized rubber. However, breakage does not show up quickly, so the number of revolutions or accumulated time at breakage is a very important indicator of this performance, i.e. fatigue life. In essence, the so-called fatigue is mainly the presence of potential defects in vulcanized rubber. Under a small deformation causes a stress concentration around the defect and is accompanied by a slight progressive growth of its scar, finally reaching damage. If this defect is structural, the physical properties are also changed.
The factors affecting the fatigue phenomenon of vulcanized rubber are very complex. From a macroscopic point of view, the first is the raw material, formulation, and process. Next is the shape factor of rubber products. Finally, it is the use conditions, including the use environment and technical conditions. From a microscopic point of view, the flow of polymer molecules, the permanent deformation caused by the sliding of secondary structures, the orientation of molecular chains, and the breakage of polymer molecular chains or cross-linked bonds due to stress concentration can all promote the formation of potential defects and prompt early fatigue breakage.
The fatigue life of vulcanized rubber is obviously related to the degree of added cyclic stress or strain. The fatigue life gradually decreases when the stress increases; if the stress decreases, the fatigue life increases. The relationship curve between fatigue life and applied stress or strain, elongation, etc. is essential and is an important way to predict the fatigue life of vulcanized rubber.