There are many reasons for the failure mode of the timing belt, and sometimes it is difficult to determine the failure mode of the belt. The purpose of this product application memorandum is to define, illustrate and determine the failure mode of the usual timing belt so that we can take appropriate preventive measures and corrective actions.
Normal wear and failure of the belt
After the belt has been in operation for 2 to 3 years, when the core wire reaches the fatigue life, it is normal for the belt to fail. After long-term operation, the belt fails because the core wire reaches the fatigue life, which is an ideal belt failure mode. Figure 1 shows a jagged and broken belt with a jagged 45 degree angle, which is caused by the normal fatigue life of a typical belt core.
The teeth of the timing belt will also fail, but this is not an ideal belt failure mode. Under long-term operation, although the belt can maintain the original size and shape, the belt teeth will wear out. The exposed fibers of the belt canvas will make the belt teeth look rough and frizzy, as shown in Figure 2.
Belts that have been running for 2 to 3 years do not require any improvement measures. Belt life will vary greatly due to different applications and various objective factors. Factors affecting belt life include transmission power level, environment, belt installation tension, belt and wheel matching, pulley quality level, and even how to cut, package, transport and install the belt.
Belt bending failure
The failure mode of belt bending is usually manifested as a straight line arrangement of the core wires of the fracture surface.
This failure mode occurs when the belt core wire is bent to a very small diameter. The sharp bending will cause the belt core fiber to bend and be damaged under huge pressure, thereby reducing the tensile strength of the belt. Belt bending failure is the most common failure mode, usually related to improper belt operation, too low installation tension, too small diameter of the pulley, and foreign matter in the pulley.