ISO 14635-1:2023

INTERNATIONAL ISO
STANDARD 14635-1
Second edition
2023-07
Gears — FZG test procedures —
Part 1:
FZG test method A/8,3/90 for relative
scuffing load-carrying capacity of oils
Engrenages — Méthodes d'essai FZG —
Partie 1: Méthode FZG A/8,3/90 pour évaluer la capacité de charge
au grippage des huiles
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Brief description of method . 2
4.1 General principle . 2
4.2 Precision . . . 4
5 Test materials . 4
5.1 Test gears . 4
5.2 Cleaning fluid . 4
6 Apparatus . 6
6.1 FZG spur-gear test rig. 6
6.2 Heating device . 8
6.3 Revolution counter . 8
7 Preparation of apparatus .8
8 Test procedure .9
9 Reporting of results .10
Annex A (informative) Typical FZG test report sheet .12
Annex B (informative) Checklist for maintenance of FZG gear test rig .13
Bibliography .18
iii
Foreword
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 60, Gears, Subcommittee SC 2, Gear
capacity calculation.
This second edition cancels and replaces the first edition (ISO 14635-1:2000), of which it constitutes a
minor revision. The changes are as follows:
1)
— ISO 1328-1:1995 has been dated as this document uses accuracy grade which is numerically
different than tolerance class in ISO 1328-1:2013;
— replacement of ISO 4287 which has been withdrawn and replaced by ISO 21920-2;
— replacement of ISO 4964 which has been withdrawn and similar information can be found in
ISO 18265;
— replacement of some bibliography entries which were withdrawn, and changes from dated to
undated references;
— subclause 5.2, wording harmonized with the ISO 14635 series;
— Table 1, description "pitch line circumferential speed (v )" has been replaced by "circumferential
w
velocity at the pitch line" to harmonize the wording with the ISO 6336 series;
— Table 4, insertion of lines "Direction of rotation" and "Test lubrication volume" to conform to the
information in the ISO 14635 series.
A list of all parts in the ISO 14635 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
1) Cancelled and replaced by ISO 1328-1:2013.
iv
Introduction
The types of gear failures which can be influenced by the lubricant in use are scuffing, low-speed wear
and the gear-surface fatigue phenomena known as micro- and macropitting. In the gear design process,
these gear damages are taken into consideration by the use of specific lubricant and service-related
characteristic values. For an accurate, field-related selection of these values, adequate lubricant test
2)
procedures are required. The FZG test procedures described in this document, ISO 14635-2 and
ISO 14635-3 can be regarded as tools for the determination of the lubricant-related characteristic
values to be introduced into the load-carrying capacity calculation of gears.
FZG test method A/8,3/90 for the relative scuffing load-carrying capacity of oils described in this
document is typical for the majority of applications in industrial and marine gears. ISO 14635-2 is
related to the relative scuffing load-carrying capacity of oils of very high extreme pressure (EP)
properties, as used for the lubrication of automotive driveline components. Other FZG test procedures
for the determination of low-speed wear, micro- and macropitting load-carrying capacity of gears are
intended to be added to the ISO 14635 series as further parts.
2) FZG = Forschungsstelle für Zahnräder und Getriebebau, Technische Universität München (Gear Research
Centre, Technical University, Munich).
v
INTERNATIONAL STANDARD ISO 14635-1:2023(E)
Gears — FZG test procedures —
Part 1:
FZG test method A/8,3/90 for relative scuffing load-
carrying capacity of oils
1 Scope
This document specifies a test method based on a FZG four-square test machine to determine the
relative load-carrying capacity of lubricating oils defined by the gear-surface damage known as
scuffing. High surface temperatures due to high surface pressures and sliding velocities can initiate
the breakdown of the lubricant films. This test method can be used to assess such lubricant breakdown
under defined conditions of temperature, high sliding velocity and stepwise increased load.
NOTE This method is technically equivalent to ASTM D 5182-19 and CEC L-07-A-95.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
3)
ISO 1328-1:1995 , Cylindrical gears — ISO system of accuracy — Part : Definitions and allowable values of
deviations relevant to flanks of gear teeth
ISO 18265, Metallic materials — Conversion of hardness values
ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms,
definitions and surface texture parameters
ASTM D 235, Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
scuffing load-carrying capacity
(of a lubricant) maximum load which can be sustained under a defined set of conditions
Note 1 to entry: For examples of failure see Figure 1.
3) Cancelled and replaced by ISO 1328-1:2013.
Note 2 to entry: Scuffing is a particularly severe form of damage to the gear-tooth surface in which seizure or
welding together of areas of tooth surface occur, due to absence or breakdown of a lubricant film between the
contacting tooth flanks of mating gears, typically caused by high temperature and high pressure. Scuffing is
most likely when surface velocities are high. Scuffing can also occur at relatively low sliding velocities when
tooth-surface pressures are high enough either generally or, because of uneven surface geometry and loading, in
discrete areas.
Note 3 to entry: Risk of scuffing damage varies with the properties of gear materials, the lubricant used, the
surface roughness of tooth flanks, the sliding velocities and the load. Consequences of scuffing of high-speed
gears include a tendency to high levels of dynamic loading due to increase of vibrations, which usually leads to
further damage by scuffing, pitting or tooth breakage.
3.2
FZG test condition A/8,3/90
test condition where A is the particular tooth form of the test gears, according to Table 1, 8,3 is the
speed at the pitch circle, in metres per second, and 90 is the initial oil temperature in degrees Celsius,
from load stage 5 and onward in the oil sump
Note 1 to entry: The direction of the rotation of the gears is shown in Figure 3.
3.3
failure load stage
load stage in which the summed total width of scuffing damage on the active flank area of the 16 pinion
teeth exceeds one gear-tooth width, i.e. 20 mm
Note 1 to entry: Examples of flank damages for the purpose of the test method are shown in Figure 1.
4 Brief description of method
4.1 General principle
A set of test gears as defined in Clause 5, Tables 1 and 2, is run with the test lubricant at constant speed
for a fixed number of revolutions using dip-lubrication mode. Loading of the gear teeth is increased in
steps outlined in Table 3. Beginning with load stage 5, the initial oil temperature is controlled between
(90 ± 3) °C. During the test run of each load stage, the oil temperature is allowed to rise freely. After
load stage 4, the pinion tooth flanks are inspected for surface damage a
...