AGMA 2003-B97 PDF

This standard provides a method by which different gear designs can be
compared.

The formulas in this standard are intended to establish a uniformly
acceptable method for calculating the pitting resistance and bending
strength capacity of generated straight bevel, zerol bevel and spiral
bevel gear teeth; curved and skewed tooth.  They apply equally to
tapered depth and uniform depth teeth.

The knowledge and judgment required to evaluate the various rating
factors come from years of accumulated experience in designing,
manufacturing and operating gear units.  Empirical factors given in this
standard are general in nature.  AGMA application standards may use
other empirical factors that are more closely suited to the particular
field of application.  This standard is intended for use by the
experienced gear designer, capable of selecting reasonable values for
the factors.  It is not intended for use by the engineering public at
large.

Exceptions.

The rating formulas in this standard are not applicable to other types
of gear tooth deterioration such as scuffing, wear, plastic yielding,
scoring, case crushing and welding are not applicable when vibratory
conditions exceed the limits specified for the normal operation of the
gears (see ANSI/AGMA 6000-B96, Specification for Measurement of Lateral
Vibration on Gear Units).

The formulas of this standard are not applicable when any of the
following conditions exist:

   -  bevel gears with offset, such as hypoids;

   -  straight and zerol bevel gears with transverse contact ratios,
      mp (epsilon alpha) less than 1.0;

   -  bevel gears with modified contact ratios, mo (epsilon omicron)
      less than 1.0;

   -  bevel gears which have a poor contact pattern;

   -  interference exists between tips of teeth and root fillets;

   -  teeth are pointed;

   -  backlash is zero;

   -  bevel teeth finished by forging, casting or sintering.

Design considerations to prevent fractures emanating from stress risers
on the tooth profile, tip chipping and failures of the gear blank
through the web or hub should be analyzed by general machine design
methods.

Scuffing

Formulas for scuffing resistance on bevel gear teeth are not included in
this standard.  At the present time, there is insufficient agreement
concerning the method for designing bevel gears to resist scuffing
failure.

Wear

Very little attention and concern have been devoted to the study of gear
tooth wear.  This subject primarily concerns gear teeth with low surface
hardness or gears with with improper lubrication.  No attempt has been
made to cover gear tooth wear in this standard.

Plastic yielding

This standard does not extend to stress levels above those permissible
for 10(3) cycles, since stresses in this range may exceed the elastic
limit of the gear tooth in bending or in surface compressive stress.
Depending on the material and the load imposed, a single load cycle
exceeding the stress level for 10(3) life cycles (see clause 16) can
result in plastic yielding of the gear tooth.

ABSTRACT

This standard specifies a method for rating the pitting resistance and bending strength of generated straight bevel, zerol bevel and spiral bevel gear teeth. A detailed discussion of factors influencing gear survival and a calculation method are provided.