REDwire A simple way to avoid tensile and fatigue failure in chains

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An example of tensile failure on a roller chain.

Chains have an important job. They are designed to transmit something from one point to another, whether it's a drive chain transmitting power between one or more rotating shafts, or a conveyor transmitting material from one point to another. Both are designed to pull a predetermined amount of load, and require strength to do so. 

In an article on Tsubaki's website, Tim Morrison, the company's technical support manager, examines tensile and fatigue failure, and explains how to prevent it. 

Tensile and fatigue failure

Maximum pull is divided broadly into two categories: tensile or fatigue. Tensile strength is the maximum stress that the chain can withstand, for example, after a heavy force is applied. Fatigue strength, on the other hand, is the load that can be applied to a chain over and over again. Exceeding both values — too much force at once or too much over time — will ultimately cause the chain to fail. 

Determining type of failure

Visual examination of a fracture can generally determine the type of failure, says Morrison. He explains that tensile fractures typically involve a large amount of deformation. Chains with this type of failure often look like they've been pulled apart. Meanwhile, a fatigue fracture usually takes place on the link plate within 30 degrees of the pitch line. Morrison describes it as a cleaner break with little to no visible deformation.

A stronger chain

Tsubaki carries two types of chains that offer increased strength. Its Super Series chains feature hardened pins, increased waist band, quad-riveted pins and ball-drifted pin link plate holes. These features result in a maximum allowable load 32 per cent higher than a standard chain.

The company also offers Super-H chains. These offer the same features as the Super Series, with the addition of thicker side plates. This results in 23 per cent higher tensile strength.  

Both the Super and the Super-H chains are available in single, double and triple strand versions. Morrison cautions, however, that speed should be limited to 160 feet per minute in applications employing these chains.

For more information, contact Tsubaki.


Tsubaki Of Canada Ltd.

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