Tendenze attuali nei metodi di calcolo per progettare gearboxDr. Ulrich KisslingKISSsoft AG, Bubikon, Svizzera

- Standardized Gear Calculation Procedures (for Gear Failure Modes)

- Actual trends: ‘Old’ and ‘new’ Gear Types

- Non-conventional Gear Calculation Procedures

- Bearings, Shafts, Screws, Connections, …

- System view: Gearboxes, Power Transmission

Tendenze attuali nei metodi di calcolo per progettare gearbox

Standardized Gear Calculation Procedures

(for Gear Failure Modes)

Predicting Gear Failure Modes of Cylindrical Gears by Classic Calculation Methods in Standards

Year Method (DIN 3990-3) First ISO

edition

published

in

1970 Bending (DIN 3990-3) 1996

1970 Pitting (DIN 3990-2) 1996

1985 Scoring (DIN 3990-4) 2000

2003 Subsurface fatigue (DNV 41.2) - 2003 by DNV

2010 Micropitting (ISO 15144) 2010

2113 Wear (VDI 2736) - 2014 by VDI

2015 Flank breaking (Draft, WG6)

???? Next phenomena …

‘Old’ and ‘new’ Gear Failure Modes

Failure by fatigue- Bending fatigue / Tooth (root) breakage (ISO6336-3)- Pitting (ISO6336-2)- Micropitting (ISO TR 15144)- Tooth flank fracture (TFF) (ISO DTS 19042) - Tooth interior fatigue fracture (TIFF)

Failure by overload- Scoring (ISO TR 13989)- Static tooth root breakage

Gear Failure Modes

Consequences of failure by fatigue- Tooth (root) breakage Breakdown- Pitting Increased noise/vibrations- Micropitting Slightly increased vibrations- Tooth flank fracture (TFF) Breakdown- Tooth interior fatigue fracture Breakdown

Can failure be prevented by inspection ? - Tooth (root) breakage Crack can be seen, Magnaflux- Pitting Easy to see- Micropitting Easy to see- Tooth flank fracture (TFF) Not detectable (only by Ultrasonic)- Tooth interior fatigue f. (TIFF) Not detectable (only by Ultrasonic)

Gear Failure Modes: Tooth Flank Fracture

What is TFF?

Only in surface hardened gears;

Tooth fracture due to a crack located in the active flank area, often at approximately half the height of the tooth;

Primary crack initiation is at a considerable depth below the surface of the loaded gear flank, typically at or below the case-core interface;

The primary crack starter is often but not always associated with a small non-metallic inclusion;

Gear Failure Modes: Tooth Flank Fracture

What is TFF?

The primary crack propagates from the initial crack starter in both directions – towards the surface of the loaded flank and into the core towards the opposite tooth root section;

Due to the high hardness in the case, the crack propagation towards the surface is smaller as through the core;

Angle between primary crack and flank surface is approx. 40-50°;

Gear Failure Modes: Tooth Flank Fracture

What is TFF?

Final breakage of the tooth is due to forced rupture; typically developing according to local bending stress;

Fractured surfaces show typical fatigue characteristics with a crack lense around the initiation point and a residual zone of forced rupture;

In many cases no indications of surface related failures such as pitting or micro-pitting are observed on the gear flanks.

Gear Failure Modes: Tooth Interior Fatigue Fracture

Similar phenomena, not to be confounded with TFF

Tooth Interior Fatigue Fracture (TIFF):Occurs (mostly) on idler gears; caused by alternating bending; crack is horizontal

TIFF (from Diss. Witzig)

Gear Failure Modes: Wear

- Dry running Gears in plastic- Big low speed Gears in steel

VDI 2736:

Wear distribution on Flank

Actual trends

‘Old’ and ‘new’ Gear Types

Gear pairs

External gears Internal gears Bevel gearsSpiral bevel gears

Cylindrical gears

Face gears

Intersect axesParrallel axes

Worm gearsCrossed helical gearsHypoid gears

Skewed axes

Beveloid gears Face gears

Special Gear Geometry:

Low loss gears, Cycloid Gears, ...

Low Loss Gearsmn smallz1, z2 high

ea 1.0-1.1

Non-conventional

Gear Calculation Procedures

Contact Analysis

Non loaded contact pattern analysis (TCA)

Loaded Tooth Contact Analysis (LTCA)

Contact pattern analysis (Non loaded)

Easy to handle, if a true 3D model is available!

Produce a ‘skin’-model of both gears Rotate one gear against the other The contact pattern shows up Considering shaft alignment and mounting position error

Loaded Tooth Contact Analysis (LTCA)

by specific semi-numeric approach by FEM(as RIKOR, … since 1977) (as ANSYS, NASTRAN,…)

Helical gear contact analysis

Main results: Stress distribution, Transmission error, Losses, ….

Bevel gear contact analysis

- For straigth, helical and spiral bevel gears - For Klingelnberg and Gleason bevel gears- Allows the analytical evaluation of flank contact with TE, H. Pressure, ..

Klingelnberg, with profile modification Gleason, without profile modification

Bevel gear contact analysis

Comparison of modification (Klingelnberg 11:54, D2=360mm)

Modification:LB=150mmHB=60mm

Contact Analysis

Flank and Profile Modification Optimization:Transmission Error and KHb at 60, 80, 100% load with different modifications.

Contact Analysis in Gear Configurations

Deformation of planet carrier

Shafts are calculated (including bearing stiffness) using conventional methodsCarrier deformation (torsion) by FECarrier 3D is builded and processed automatically

FE softwareCode-Aster used

Bearings, Shafts, Screws,

Connections, …

Bearing calculation methods

Conventional method Non-conventional methodISO 281 ISO 16281

Generally used in:Industrial gear drives

Generally used in:AutomotiveWind

System view:

Gearboxes, Power Transmission

System view

Power flow definitionDuty cyclesLifetime analysisRunning virtual tests

Damage Calculation of all Components

> Finding the weakest element

Total Power Losses: Automotive

Reduce losses in Gear meshing, clutches, synchronization,

lubrication system, sealing

Double Clutch

Transmission

Thermal Capacity: Industrial Gear Reducers

(ISO 14179 and others)

Contact Analysis including Housing Stiffness

Stiffness Matrix

Bearing Loads

sH-distribution from LTCA:

Eigenfrequencies on System level

(Torsional and bending)

System: Integration with

Multibody Dynamic Simulation

Gear Calculation Dynamic Simulation

Gear meshing stiffness >> Simulation

Stresses, Lifetime << Torque behavior

ADAMS

Noise Prediction

Transmission Error

is known

Vibration propagation

is hard to predict

Noise (dB(A)) prediction

is not yet possible

dB(A) ??

Who we are

Company KISSsoft AG1980: Software development for personal use from Kissling Gear AG

1986: Sale of the first KISSsoft license to company Saurer AG, Switzerland

1998: KISSsoft AG Switzerland, Founder Dr. Kissling

2005: KISSsoft USA LLC, Chicago

2015: Partners in Korea, China, India, South Africa, Italy, France,Germany, Argentina, Turkey, Belarus, Czech Republic,Slovakia, Russia, BrazilOver 2700 clients worldwide, 30 members of staff

For over 30 years KISSsoft AG has been the driving force behind developments in the machine elements sector.

Its activities in committees that define international calculation standards ensure first-hand knowledge.

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