Belt failure fabric separation

Test results from experimental studies on belt life suggest the following as the major belt failure modes tooth root cracking, wear, cord failure and fabric separation [14,15,16, 17, 18], and this classification has support from field data [19, 20]. Figure 12.2 shows examples of tooth root cracking, cord delamination and fabric separation failures. 

Figure 12.2 Synchronous belt failure modes, a) tooth root cracking, b) cord delamination, c) fabric separation...

Fabric separation failure occurs when the belt teeth and fabric land become detached from the belt cords [17] and is essentially seen as purely an adhesion failure, although there may be links between this failure mode and the tooth root cracking failures observed by lizuka [18], originating from cracks developed in the cord itself through internal delamination. Wear causes belt failure through changing the tooth profile to such an extent that the belt teeth can no longer support the required load [25]. 

In attempting to identify parameters which allow the belt life to be predicted within the adhesion related failure modes identified above, the most common approach has been to use measures of belt distortion. Dalgarno [17] examined belt life data from belt failures within the tooth root cracking, fabric delamination and cord separation failure modes. 

Because coated fabrics are generally dealt with in separate standards committees, and because the thinner coatings are not strong enough to allow the use of the peel methods described above, separate standards have been developed for these products. The problem of failure in the coating is overcome by using reinforcements of fabric or cement. These methods are really product tests and outside the scope of this book but the appropriate references can be noted. The international standard for coated fabrics is ISO 241144, the British methods are identical as BS EN ISO 2411 and the ASTM methods are in D75145. There are also methods for conveyor belts in ISO 252-146. 

The most common type of failure or damage resulting from repeated flexing is the formation of surface cracks, known as flex cracking. Shoe soles and tires are examples of rubber products that may show flex cracking. Another mode of failure due to flexing is the separation of rubber from fabric in a fabric-supported product such as a conveyor belt. 

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