Chain strength

Author : Rosie

Update time : 2023-02-20 14:12:51

Chain strength

Overview

Chains used for transmission or conveying may be subjected to some or all of the tensile loads described above, so they must have sufficient tensile strength. The main strength properties of chains are discussed below.

Tensile Strength

The tensile strength of a chain is the maximum tensile load that the chain can withstand before being broken in one go. All standard chains must have a certain tensile strength, regardless of the application. The yield and fatigue strengths are in some proportion to the tensile strength, but the proportion is not fixed. The most important aspect of mimum tensile strength is to ensure that all parts have been manufactured and handled correctly and that the chain has been assembled correctly.

The tensile strength should not be used as an indicator for the selection of drive or conveyor chains. Only the maximum permissible working load of certain special chains can be used as an indicator for chains. The selection of chains should be based on fatigue limits or hinge pressures, as well as on a number of evaluation criteria which are not usually in fixed proportion to the tensile strength.

Yield Strength

The yield strength of a chain is the maximum load to which the chain can be restored to its initial condition (length). The yield strength of many standard chains is approximately 40% to 60% of the tensile strength. If the chain is loaded beyond its yield strength, even once, the chain will be permanently elongated and deformed, and even if the chain is not later adapted to the sprocket, the loaded chain beyond the yield strength will be weakened by the reduced pressure fit that keeps the frame strong. Fatigue Strength

The fatigue strength of a chain is the pulsating load that the chain can withstand for a specific number of cycles. A more detailed description of the fatigue strength of roller chains can be found in the standard ASME B29.26 "Fatigue Test Methods for Roller Chains for Drives". Typical chain fatigue tiger:

Typical chain load tension curve. The graph clearly shows that the chain yield strength is 60% of the tensile strength

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Not all chains are the same

Fatigue Strength

The fatigue strength of a chain is the pulsating load that the chain will withstand for a specific number of cycles. A more detailed description of the fatigue strength of roller chains can be found in the standard ASME B29.26 "Fatigue Test Methods for Roller Chains for Power Transmission". A typical chain fatigue strength curve (also known as the F-N curve) is shown in Figure 3-4. The vertical axis indicates the maximum pulsating load value; the horizontal axis indicates the number of cycles the chain has withstood before it fails under load. The graph shows that as the pulsating load value decreases, the number of cycles before failure increases.

When considering fatigue strength, special attention should be paid to the fatigue strength in the range of 1x104 to 1x10° cycles. This range is known as the finite life range and chains are sometimes carried in this range.

5. Fatigue Limit

The fatigue limit of a chain is defined as the pulsating load subjected to 1x10 cycles with a probability of failure of only 0.135%. The fatigue limit is approximated by a load below which the chain is subjected to a pulsating load.

Fatty Tiger:

The fatigue limit is not just a theoretical value. It is the basis for the power ratings of roller chains, engineered steel chains and toothed chains of the American Chain Association in the low speed range. The maximum permissible working load value of cloth is usually equal to the fatigue limit.

The chain fatigue limit is not directly related to the chain tensile strength. The fatigue limit of a chain cannot be obtained by multiplying the chain tensile strength by a certain factor and can only be measured by extensive tests.

Some manufacturers state that the ratio of the maximum permissible working load of their chains to their own published tensile strength is a constant. This does not contradict the above statement, but rather these manufacturers are stating the maximum allowable working loads in a different way and they can guarantee that these working loads are valid.

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