Warning: users are advised that there is a corrigendum to Clause C.6 of Annex C; see ISO 6336-6:2006/Cor.1:2007(E) - included in the document.

SCOPE
This part of ISO 6336 specifies the information and standardized conditions necessary for the calculation of the service life (or safety factors for a required life) of gears subject to variable loading.  While the method is presented in the context of ISO 6336 and calculation of the load capacity of spur and helical gears, it is equally applicable to other types of gear stress.

FOREWORD
[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of ANSI/AGMA ISO 6336-6-A08, Calculation of Load Capacity of Spur and Helical Gears - Part 6:  Calculation of Service Life Under Variable Load.]

It is recommended that the cumulative fatigue damage criteria proposed by Miner (Miner’s Rule) be employed to evaluate the effects of variable loading on the life of gearing. Miner’s Rule was developed in 1945 by M. A. Miner to assess the effects of cumulative fatigue damage under repeated and variable intensity loads.  The method was developed for aircraft part design and tested for aluminum alloys by Miner, but was subsequently verified for steel by others. It was commonly used in vehicle gearing design.  An explanation of Miner’s Rule was included in AGMA 170.01 (1976), Design Manual for Vehicle Spur and Helical Gears, and the calculation method was later included as annex D in AGMA 218.01 (1982), AGMA Standard for Rating and Pitting Resistance and Bending Strength of Spur and Helical Involute Gear Teeth.

In the 1990’s, AGMA proposed a project to ISO Technical Committee 60 (TC 60) as an international standard.  However, agreement could not be reached on the total content.

Therefore, an ISO Technical Report of type 2 was prepared by lSO/TC 60, Subcommittee 2 for gear capacity calculation.  The resulting document, ISO/TR 10495, Cylindrical gears - Calculation of service life under variable load - Conditions for cylindrical gears in accordance with ISO 6336, was published in 1997.

In 2002, a revision of ISO/TR 10495 was begun, agreement was obtained and the work resulted in the new ISO standard, ISO 6336-6 Calculation of load capacity of spur and helical gears - Part 6: Calculation of service life under variable load, which was published in August 2006.

ANSI/AGMA ISO 6336-A08 represents an identical adoption of ISO 6336-6:2006, and includes Technical Corrigendum 1 (August 1, 2007).

The first draft of ANSI/AGMA ISO 6336-6-A08 was made in February, 2007.  It was approved by the AGMA membership in March, 2008.  It was approved as an American National Standard on May 20, 2008.

Suggestions for improvement of this standard will be welcome.  They should be sent to the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350, Alexandria, Virginia  22314.

NORMATIVE REFERENCES
The following referenced documents are indispensable for the application of this document.  For dated references, only the edition cited applies.  For undated references, the latest edition of the referenced document (including any amendments) applies.

• ISO 1122-1:1998, Glossary of gear terms - Part 1: Geometrical definitions
• ISO 6336-1:2006, Calculation of load capacity of spur and helical gears - Part 1: Basic principles, introduction and general influence factors
• ISO 6336-2:2006, Calculation of load capacity of spur and helical gears - Part 2: Calculation of surface durability (pitting)
• ISO 6336-3:2006, Calculation of load capacity of spur and helical gears - Part 3: Calculation of tooth bending strength

ISBN: 978-1-55589-928-8 Pages: 20