Tendenze attuali nei metodi di calcolo per progettare gearbox Dr. Ulrich Kissling KISSsoft AG, Bubikon, Svizzera

Tendenze attuali nei metodi di calcolo per progettare gearbox Dr. Ulrich Kissling KISSsoft AG, Bubikon, Svizzera

Tendenze attuali nei metodi di calcolo per progettare gearbox - 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

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 gears Spiral bevel gears Cylindrical gears Face gears Parrallel axes Intersect axes Hypoid gears Crossed helical gears Worm gears Skewed axes

Beveloid gears Face gears

Special Gear Geometry: Low loss gears, Cycloid Gears,... Low Loss Gears mn small z1, 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 (as RIKOR, since 1977) by FEM (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=150mm HB=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 methods Carrier deformation (torsion) by FE Carrier 3D is builded and processed automatically FE software Code-Aster used

Bearings, Shafts, Screws, Connections,

Bearing calculation methods Conventional method Non-conventional method ISO 281 ISO 16281 Generally used in: Industrial gear drives Generally used in: Automotive Wind

System view: Gearboxes, Power Transmission

System view Power flow definition Duty cycles Lifetime analysis Running 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 ADAMS Gear Calculation Dynamic Simulation Gear meshing stiffness >> Simulation Stresses, Lifetime << Torque behavior

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 AG 1980: 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, Brazil Over 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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