Maximum Stress Calculation For Gear Materials

4 min reading time..

Gears are manufactured from different materials. Each material has characteristic maximum stress and strength values. According to this fact, gears can transmit power in a certain amount according to the gear material.

First of all, you need to define and find the total stress on the gear tooth. So, you can define the gear material according to this total stress. This stress appears as the bending stress which must be considered in the material selection for gear pair.

The bending stress strength of the material must withstand the bending stresses that occur in working conditions. Take a look at the information below about how to calculate a material’s bending strength for gear application.

Allowable Bending Stress Of A Gear Material

It is not recommended to use the bending stress of material directly in the safety calculations of gears. There must be some factors defined to accurately and safely find out the allowable bending stress of a gear material.

Allowable Bending Stress Calculator
















With the calculator above, you can easily calculate ‘Allowable Bending Stress’ by entering required values inside brackets. Just click on the ‘Calculate!’ button to calculate the Allowed bending stress value. If you want to make another calculation, click on the ‘Reset’ button make another calculation.

All the factors are unitless and you will have the Allowed bending stress value in the same unit with max. bending stress of the material.

Maximum Bending Stress Of Gear Material

The first parameter in the calculator above is the maximum bending stress of gear material. Bending stress occurs on the gear tooth in the form of bending of a cantilever beam which is fixed from one side.

So, this is the value of maximum allowable stress value of the gear materials. There are lots of kinds of sources that you can find out this property of gear materials.

Stress Cycle Factor

There are various kinds of sources that provide this factor for different gear materials. First of all, you need to define the number of the cycle in the whole life of gear set to define the stress cycle factor. Use the calculator below to calculate the number of cycles of gear in life.

Number Of Cycles Calculator














Enter the required value inside brackets to see Nc. Number of loads means the total dynamic loads that one tooth carried in each revolution.


You can define the stress cycle factor according to the AGMA chart below. According to Nc that you find, you can find the related stress cycle factor from the chart below. This chart is representative only. There can be other principles to define stress cycle factor can be provided by other authorities.

Stress-cycle factor chart(Source: Robert L. Mott: Machine Elements In Mechanical Design).

Reliability Factor

This is statistical data that you can select this factor according to the failure statistics of your gear. Here a statistical example;

Reliability factor(Source: Robert L. Mott: Machine Elements In Mechanical Design).

Factor Of Safety

This is the most important factor that needed to be defined wisely by the designer. Uncertainties lead to the proper selection of factors of safety. This actually depends on the experience of the designer. But some approaches can be adopted according to some principles. In most applications, the safety factor can reach 4-5.

Conclusion

The calculated maximum stress allowed on gear material must be compared with calculated bending stress on gear tooth. If the allowed stress is bigger than the calculated stress, the design is safe. But if the allowed bending stress is smaller than the calculated stress, the design is not safe and must be re-assessed.

Mechanical Base does not accept any responsibility for the calculations made by the users with calculators. A good engineer must check the results again and again.

You can use the MB-Unit Converter tool to convert your unit sets to another unit system.

Take a look at the other useful engineering calculators available in Mechanical Base!

Do not forget to leave your comments and questions below about the maximum allowable stress on gear materials below.

Your precious feedbacks are very important for us.

Do not forget to leave your comments and questions below about the maximum allowable stress on gear materials below.

Your precious feedbacks are very important for us.

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