Standardization of Load Distribution Evaluation: Uniform Definition of KHb for Helical Gears


The load distribution measurement of gear teeth and the determination of the face load factor for contact stress KHß are of fundamental importance to the gear manufacturing industry. The factor is a measure for the uniformity of the load along the face width. The closer this factor is to one the more uniform is the load distributed along the face width. In the design phase this factor is determined with the help of approximation equations and finite element analysis and is used to dimension the flank modifications. In addition KHß 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 the tooth fillets 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, used more frequently in large gearboxes, the determination of the factor gets more difficult. The line of contact of these gears runs inclined over the face width of the teeth flank. In this context the question arises whether the face load factor is evaluated along the face width or along the path of contact.
Evaluation of the measured values and the interpretation to a face load factor is a complex challenge and is not standardized. The standardization of load distribution evaluation and a uniform definition of KHß especially for helical gears enable a safer design for the manufacturers and an easier comparability of the results for the customers.
The paper will compare the different suggestions to the KHß definition and will derive a new definition suitable for the calculation methods in DIN 3990 and ISO 6336.
ISBN: 1-978-61481-008-7 Pages: 18
Author: K. Nazifi
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