ISO 10300-2:2014

INTERNATIONAL ISO
STANDARD 10300-2
Second edition
2014-04-01
Calculation of load capacity of bevel
gears —
Part 2:
Calculation of surface durability
(pitting)
Calcul de la capacité de charge des engrenages coniques —
Partie 2: Calcul de la résistance à la pression superficielle (formation
des piqûres)
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, units and abbreviated terms . 2
5 Pitting damage — General aspects . 3
5.1 Acceptable versus unacceptable pitting . 3
5.2 Assessment requirements . 3
5.3 General rating procedure . 4
6 Gear flank rating formulae — Method B1 . 4
6.1 Contact stress formula. 4
6.2 Permissible contact stress . 6
6.3 Calculated safety factor for contact stress . 6
6.4 Contact stress factors . 6
6.5 Permissible contact stress factors .10
7 Gear flank rating formulae — Method B2 .13
7.1 Contact stress formula.13
7.2 Permissible contact stress .14
7.3 Calculated safety factor for contact stress .14
7.4 Contact stress factors .15
8 Factors for contact stress and permissible contact stress common for method B1 and
method B2 .20
8.1 Elasticity factor, Z .
E 20
8.2 Lubricant film influence factors, Z , Z , Z .
L v R 20
8.3 Work hardening factor, Z .
W 24
8.4 Life factor, Z .
NT 25
Annex A (informative) Bevel slip factor Z — Method B1 .28
S
Bibliography .30
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
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on the ISO list of patent declarations received. www.iso.org/patents
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assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 60, Gears, Subcommittee SC 2, Gear capacity
calculation.
This second edition cancels and replaces the first edition (ISO 10300-2:2001), which has been technically
revised.
ISO 10300 consists of the following parts, under the general title Calculation of load capacity of bevel
gears:
— Part 1: Introduction and general influence factors
— Part 2: Calculation of surface durability (pitting)
— Part 3: Calculation of tooth root strength
iv © ISO 2014 – All rights reserved

Introduction
When ISO 10300:2001 (all parts, withdrawn) became due for (its first) revision, the opportunity was
taken to include hypoid gears, since previously the series only allowed for calculating the load capacity
of bevel gears without offset axes. The former structure is retained, i.e. three parts of the ISO 10300
series, together with ISO 6336-5, and it is intended to establish general principles and procedures for
rating of bevel gears. Moreover, ISO 10300 (all parts) is designed to facilitate the application of future
knowledge and developments, as well as the exchange of information gained from experience.
In view of the decision for ISO 10300 (all parts) to cover hypoid gears also, it was agreed to include a
separate clause: “Gear flank rating formulae — Method B2” in this part of ISO 10300, while the former
method B was renamed method B1. So, it became necessary to present a new, clearer structure of the
three parts, which is illustrated in ISO 10300-1:2014, Figure 1. Note, ISO 10300 (all parts) gives no
preferences in terms of when to use method B1 and when method B2.
This part of ISO 10300 deals with the failure of gear teeth by pitting, a fatigue phenomenon. Two varieties
of pitting are recognized, initial and destructive pitting.
In applications employing low hardness steel or through hardened steel, initial pitting frequently occurs
during early use and is not deemed serious. Initial pitting is characterized by small pits which do not
extend over the entire face width or profile depth of the affected tooth. The degree of acceptability
of initial pitting varies widely, depending on the gear application. Initial pitting occurs in localized
overstressed areas, and tends to redistribute the load by progressively removing high contact spots.
Generally, when the load has been redistributed, the pitting stops.
In applications employing high hardness steel and case carburized steel, the variety of pitting that occurs
is usually destructive. The formulae for pitting resistance given in this part of ISO 10300 are intended to
assist in the design of bevel gears which stay free from destructive pitting during their design lives (for
[4]
additional information, see ISO/TR 22849 ).
The basic formulae, first developed by Hertz for the contact pressure between two curved surfaces,
have been modified to consider the following four items: the load sharing between adjacent teeth, the
position of the centre of pressure on the tooth, the shape of the instantaneous area of contact, and the
load concentration resulting from manufacturing uncertainties. The Hertzian contact pressure serves
as the theory for the assessment of surface durability with respect to pitting. Although all premises for
a gear mesh are not satisfied by Hertzian relations, their use can be justified by the fact that, for a gear
material, the limits of the Hertzian pressure are determined on the basis of running tests with gears,
which include the additional influences in the analysis of the limit values. Therefore, if the reference is
within the application range, Hertzian pressure can be used to convert test gear data to gears of various
types and sizes.
NOTE Contrary to cylindrical gears, where the contact is usually linear, bevel gears are generally manufactured
with profile and lengthwise crowning: i.e. the tooth flanks are curved on all sides and the contact develops an
elliptical pressure surface. This is taken into consideration when determining the load factors by the fact that the
rectangular zone of action (in the case of spur and helical gears) is replaced by an inscribed parallelogram for
method B1 and an inscribed ellipse for method B2 (see Annex A for method B1 and Annex B for method B2). The
conditions for bevel gears, different from cylindrical gears in their contact, are thus taken into consideration by
the longitudinal and transverse load distribution factors.
INTERNATIONAL STANDARD ISO 10300-2:2014(E)
Calculation of load capacity of bevel gears —
Part 2:
Calculation of surface durability (pitting)
1 Scope
This part of ISO 10300 specifies the basic formulae for use in the determination of the surface load
capacity of straight and helical (skew), Zerol and spiral bevel gears including hypoid gears, and comprises
all the influences on surface durability for which quantitative assessments can be made. This part of
ISO 10300 is applicable to oil lubricated bevel gears, as long as sufficient lubricant is present in the mesh
at all times.
The formulae in this part of ISO 10300 are based on virtual cylindrical gears and restricted to bevel
gears whose virtual cylindrical gears have transverse contact ratios of ε < 2. The results are valid
vα
[1]
within the range of the applied factors as specified in ISO 10300-1 (see ISO 6336-2 ). Additionally, the
given relations are valid for bevel gears of which the sum of profile shift coefficients of pinion and wheel
is zero (see ISO 23509).
The formulae in this part of ISO 10300 are not directly applicable to the assessment of other types of
gear tooth surface damage, such as plastic yielding, scratching, scuffing or any other type not specified.
WARNING — The user is cautioned that when the formulae are used for large average mean spiral
angles (β +β )/2 > 45°, for effective pressure angles α > 30° and/or for large face widths
m1 m2 e
b > 13 m , the calculated results of ISO 10300 should be confirmed by experience.
mn
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable to its a
...