The load distribution measurement of gear teeth and the determination of the face load factor for contact
stress KHβ are of fundamental importance for the gear manufacturing industry. The factor KHβ is a measure for
the uniformity of the load distribution along the face width. The closer this factor is to one the more uniform is
the load distributed along the face width. During the design phase this factor is determined with the help of
approximation equations as well as finite element analysis and is used to dimension the flank modifications. In
addition KHβ is used in the lifetime calculations according to DIN 3990 and ISO 6336 required by the
certification societies. In the testing phase this factor is experimentally determined by strain measurements of
tooth fllets in order to verify the load distribution calculations and the suitability of the used modifications.
For spur gears with no helix angle the interpretation of the measurements to a face load factor is intuitively
easy. For helical gears, more frequently used in big gearboxes, the determination of the factor gets tougher.
The line of contact of these gears runs inclined over the face width of the tooth flanks. In this context the
question arises whether the face load factor is evaluated along the face width or along the path of contact.
The evaluation of the measured values and the interpretation to a face load factor is a complex challenge and
is not standardized. A large number of publications make suggestions; however, these suggestions differ to a
large degree. The standardisation of the load distribution evaluation and a uniform definition of KHB for helical
gears enable a safer design for the manufacturers and an easier comparability of the results for the customers.

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