齿轮疲劳试验Back-to-back_gear_testing

1 Back-to-Back Gear Testing Jishan Zhang Design Unit, Newcastle University 2 Typical Gear Failure Modes • Pitting (macropitting) • Micropitting • Case crushing • Bending • Scuffing 3 Typical Failure Modes Macropitting & micropitting Micropitting Macropits 4 Typical Failure Modes Micropitting • Grey or glitter in appearance by naked eyes • Small in size (5 ~ 10 µm in length) • Shallow, the depth is between 5 µm - 20 µm • Orienting against the direction of tractive force • occurs in the dedendum, or addendum, or both but seldom at the pitch line 5 Typical Failure Modes Macropitting 6 Typical Failure Modes Case Crushing 7 Typical Failure Modes Bending Fatigue 8 Typical Failure Modes Scuffing 9 Capacity of DU Gear Test Rig Gear test rig is capable of generating all typical gear failure modes and showing gear general performance: • Contact fatigue (macropitting, micropitting and case crushing) • Bending fatigue • Scuffing • Noise and vibration • Contact pattern • Efficiency • Others 10 Purpose of Gear Testing Gear test rig is mainly used for: 1. Contact fatigue S-N curve determination 2. Gear performance verification and comparison Variables • macro-geometry • micro-geometry • material • heat treatment • surface treatment • manufacturing process • surface engineering • lubrication oil • oil temperature • nozzle position •… 11 Generating Gear S-N Curve How to set load levels • Maximum Packing (5 load levels, at least 5 data points each load level) • Standard Packing (12 – 16 data points) • Minimum Packing (7 – 10 data points) 12 Gear Performance Verification and Comparison 1. Accelerated test Higher than designed load is usually used in order to generate results in a reasonable time, 20% increase in contact stress is common. However, be aware that the failure mode may change if the load is too high. 2. Refer to the widely recognised test procedures or standards: • Micropitting test FVA information sheet, July 1993 • Scuffing test Chinese national standard GB/T13672-1992 13 Back-to-back Gear Test Rig 75mm CENTRE DISTANCE TEST RIG • 4 test rigs installed • Centre Distance: 75mm Speed : 0 - 6000rpm • Gear Ratio : 1.5:1 Max. Torque : 400N • Facewidth : 10 & 15mm Max. Power at 6000rpm: 250kW • Module : 1 to 4mm Drive Motor : 5.5kW 14 Back-to-back Gear Test Rig 91.5mm CENTRE DISTANCE TEST RIG 2 test rigs installed, one being manufactured • Centre Distance: 91.5mm Speed: 0 to 6000rpm • Gear Ratio : 1:1 to1.5:1 Max. Torque: 1400N • Facewidth : 25mm Max. Power: 880kW • Module : 2 to 6mm Drive Motor: 30kW 15 Back-to-back Gear Test Rig 160mm CENTRE DISTANCE TEST RIG 3 Spur/Helical and 1 Spur Gear test rig installed. • Centre Distance: 160mm • Gear Ratio: 1:1 • Facewidth: 38mm • Module: 4 to 10mm • Speed: 0 - 4500rpm • Max. Torque: 6000N • Max. Power : 2800kW • Drive Motor : 75kW 16 Test Methodology Back-to-back gear test rig: • Configuration 1: One slave gearbox + one test gearbox • Configuration 2: Two test gearboxes 17 Test Methodology How to set motor rotation speed? • Higher than designed gear speed (accelerated test); or • Close to real application, equal pitch line speed • Avoid the resonance zone of the rig • To be economic, around 50 Hz motor speed • Be aware of the different rotation speed between pinion and wheel 18 Test Methodology • Torque direction determines which gear flank is to be loaded. For example, A direction: left flank; B direction: right flank • The combination of motor rotation and torque direction determines which gear is driving which gear is driven How to set motor rotation direction and torque direction? 19 Test Methodology How to set oil temperature? • Set to higher than designed oil temperature to accelerate the test, or • Set it close to real application 20 Test Methodology How to set oil flow rate? • 12 litter/minute/MW by default 21 Test Methodology Differences Between Two test gearboxes: • Driving or Driven • Speed increasing or speed reducing 22 Test Methodology How many data points can be obtained in one test? • One test gearbox: one data • Two test gearboxes: two data Note: • Normally testing one gear set (pinion and wheel) in one flank generates one data point • Slave gears are needed if one set of gear fails first 23 Test Methodology How many data points can be obtained in one pair of gear? • Maximum 2 (1 for left flank; 1 for right flank) 24 Inspection Techniques Before Test • Metrology (profile, lead and pitch), 4 teeth, 3 locations • Surface roughness, 4 teeth, 3 locations • Gear tapered bore dimensional measurement • Hardness profile • Residual stress profile • Micro-structure • Grinding burn/defects Before mounting gears on the rig, the following items should be checked: • Backlash • Contact pattern After mounting gears on the rig, the following items should be checked: 25 Inspection Techniques During Test Test rig needs to be stopped at regular intervals in order to carry out the following inspections: • Taking photos • Taking replicas • Microscopic check on replicas • On-site surface roughness measurement • Profile check by taking gears off • Gear flank temperature measurement • Sketching gear surface condition 26 Inspection Techniques Example - Sketching gear surface condition 775Nm (925MPa) 1100Nm (1097MPa) 2275Nm (1473MPa) 4400Nm (1924MPa) Pinion Wheel Progression of micropitting 27 Inspection Techniques After Test • Sectioning and sampling • Microscopic studies 28 Inspection Techniques Example – sectioning and sampling 29 Inspection Techniques Example – microscopic studies 30 Failure Criteria Macropitting Case hardened gears: • 4 % in one flank or 1% in all flanks • run out: 1×108 at pinion Through-hardened gears: • 2 % in all flanks • run out: 5×107 at pinion 31 Failure Criteria Micropitting Micropitting is found to be progressive and profile deviation is more than 20μm in either pinion or wheel Run out cycles: ≥ 5×107 at pinion 32 Failure Criteria Scuffing Moderate scuffing, total width of scuffing is more than one tooth width of the pinion Initial scuffing Severe scuffingModerate scuffing 33 Back-to-Back Gear Testing Any Questions ? Jishan Zhang Design Unit, Newcastle University Typical Gear Failure Modes Typical Failure Modes Typical Failure Modes Typical Failure Modes Typical Failure Modes Typical Failure Modes Typical Failure Modes Capacity of DU Gear Test Rig Purpose of Gear Testing Generating Gear S-N Curve Gear Performance Verification and Comparison Test Methodology Test Methodology Test Methodology Test Methodology Test Methodology Test Methodology Test Methodology Test Methodology Inspection Techniques Inspection Techniques Inspection Techniques Inspection Techniques Inspection Techniques Inspection Techniques Failure Criteria Failure Criteria Failure Criteria