Study On The Mechanism Of Influence Of Early Defects And Three-Body Abrasive On Gear Wear Evolution Under Variable Load

Wind turbine gearboxes are inevitably operating under harsh working conditions such as strong gusts of wind and dust,and the unstable external load and hard three-body abrasives such as sand and dust are mixed in,which will aggravate gear wear to varying degrees,and fatal failures such as broken teeth will occur in serious cases,resulting in huge safety hazards to mechanical equipment.In order to explore the friction and wear evolution mechanism of gears under such harsh working conditions,the wear life and failure characteristics of gears with early defects under variable load are explored,and the wear evolution law of gears in the whole life cycle of gears mixed with three-body abrasives in lubricating oil liquid is explored.In this paper,a gear friction and wear test bench for variable load loading was built by force flow closed quantitative loading system and controlled magnetic powder brake alternating loading,and the oil samples in the wear process were monitored by thistle analytical ferrospectrometer and ferromagnetic particle counter,and the dynamic wear characteristics of the gear running process were obtained,and the wear scar morphology of the damaged tooth surface before and after the experiment was observed by scanning electron microscope,and the distribution and wear mark characteristics of the wear materials on the tooth surface were analyzed.The specific work content is as follows:（1）In this paper,the strength check analysis of the tooth root and tooth surface of the meshing gear was carried out,and the fixed loading and variable load capacity of the gear variable load wear test were determined.Based on the gear wear failure theory under variable load,the theoretical model of tribody abrasive wear is analyzed,and the mathematical calculation model of the wear amount of tribody abrasive on solid surface is given,the factors affecting abrasive wear are analyzed,and the hard particles of Al₂O₃ are selected as the initial abrasive in gear oil,and the form and cause of gear failure under early single pit defects and tri-body abrasive wear are analyzed.（2）The gear wear test bench that can realize variable load loading was constructed by force flow closure mode,and the wear characteristics and operating status of 20Gr Mn Ti helical gears mixed with three-body abrasives in the early single pit defect and oil were analyzed and studied.Variable loads were applied by semi-couplings and magnetic powder brakes to simulate realistic working conditions,and particle counters,thistle analytical ferrospectrometers and scanning electron microscopes（SEM）were used to observe the damage morphology of oil abrasive particles and gear tooth surfaces.In this experiment,the wear mechanism of 20Gr Mn Ti helical gears mixed with early single pit defects and three-body abrasives was studied from four aspects:gear wear amount,tooth surface wear morphology analysis,abrasive particle detection and vibration analysis.（3）Qualitative and quantitative analysis of experimental results.The results show that the defect shortens the service life of the gear,and the concentration of abrasive particles in the late stage of wear reaches 70,000 pieces/ml.Single-pit defective gears in the stable wear stage,the concentration of abrasive particles in the oil sample is low and the fine flake abrasive particles of1-15μm are the mainstay;In the later stage of gear wear,due to severe wear of the tooth surface,the spectral pattern amplitude reached 10.5 Hz and 11.763 Hz.In a group of experiments with three-body abrasives,the concentration of abrasive particles soared to 17000/ml within 0-20h,and then rapidly decreased and stabilized at 2000/ml for a long time,entering a stable wear period.By designing experiments to explore the influence mechanism of early defects and three-body abrades on wear evolution of helical gear under variable load conditions,the following conclusions can be drawn:the existence of single pit defects obviously shortens the normal life of gear;A large number of abnormal abrasive particles and large abrasive chains are produced under the contact condition of heavy load and high speed.By comparing with the wear particle data of the control group,it is found that the three-body abrasives have great influence on the wear state of the gear at the initial stage of wear.In the group adding three-body abrasives,the second run-in phenomenon occurs and the severe wear stage is advanced,and the number of large abrasive particles increases rapidly.The vibration of gear in the early stage of wear is greatly affected by impact load,and the variable load condition has a great effect on the early wear of gear.The initial three-body abrasive in gearbox oil will accelerate gear wear.The macro-morphology analysis of the worn gear teeth shows that under the repeated action of the impact load,the parts above the pitch line of the gear teeth surface have serious material loss and serious deformation.