Study On Multi-Field Coupled Modeling And Wear Debris Deposition Law Of Ferrogram Making Device Of Analytical Ferrograph

Wear is a common phenomenon in the operation of mechanical equipment.Ferrography analysis is one of the main methods of equipment wear detection,which is widely used in condition monitoring and fault diagnosis of mechanical equipment.Analytical ferrograph is a commonly used ferrograph analysis instrument.It determines the wear state of the equipment through ferrographic image analysis,which has the prominent problems of low ferrographic image preparation efficiency and poor ferrogram quality.Therefore,this paper takes the analytical ferrograph as the research object,establishes the magnetic fluid solid multi-field coupled analysis model of its ferrogram making device,and deeply studies the deposition law of wear particles on the ferrogram slide by using the finite element numerical simulation method,and carries out the experimental verification of the ferrogram making effect.(1)The establishment of high gradient and strong magnetic field of ferrogram making device is the primary key problem in the design of analytical ferrograph.In this paper,the analytical calculation,numerical simulation and magnetic field test methods for magnetic field design of analytical ferrograph are proposed.The magnetic circuit model is established based on Ohm’s law and Gauss’s law,the flux leakage coefficient of the magnetic field device is obtained,and then the theoretical value of the magnetic induction intensity at the working air gap is obtained,which provides a theoretical basis for numerical calculation.A 2-D finite element model of the magnetic field device is established,the influence law of the magnetic circuit parameters on the magnetic induction intensity at the ferrogram is studied,and the reasonable value range of the parameters is obtained.Further establish a 3-D finite element model of the magnetic field device,study the influence law of the position parameters of the ferrogram on the magnetic induction intensity,and obtain its reasonable value range.The magnetic field measurement scheme of the ferrogram making device is developed formulated,and the Gauss meter is used to measure the magnetic induction intensity.The results show that the experimental results are consistent with the numerical results,which proves the correctness of the finite element model and analysis method.(2)Revealing the flow law of wear particles in oil samples is an important basis for the numerical simulation of wear particle deposition behavior.The expression of oil sample velocity is obtained by analytical method,and the finite element model of oil sample flow field of ferrogram making device is established.The laminar flow model is selected according to Reynolds number for numerical simulation under different flow field parameters,and its influence law on oil velocity is obtained.Then,metal wear particles are added,and the fluid solid coupling numerical simulation of oil sample containing wear particles is carried out by using Euler-Lagrange discrete phase model.The influence laws of wear particles,virtual mass force and initial velocity on oil sample velocity are obtained.The sensitive factors of different physical conditions and flow field parameters are obtained,which lays a foundation for the magnetic,fluid and solid multi-field coupled analysis of ferrogram making device.(3)Based on the magnetic field and flow field analysis model of the ferrogram making device,a magnetic,fluid and solid multi-field coupled model of the ferrogram making device is established to study the motion and deposition law of wear particles in the coupled field.The force of wear particles in the process of deposition is analyzed,and the theoretical law of wear particle deposition is obtained.The magnetic field,flow field and wear particle parameters are set in turn,and the coupled field numerical simulation based on flow particle tracking is carried out.According to the natural process of wear particles flowing out of the oil pipe and depositing on the ferrogram slide,the influences of oil sample pressure,viscosity,density,ferrogram slide inclination,the distance between the oil pipe and the ferrogram slide,and the release mode of wear particles on the deposition behavior of wear particles are analyzed in turn.Based on the law of wear deposition velocity and displacement,the reasonable value range of each parameter is obtained,and the sensitive factors are determined,which provides a theoretical basis for the regulation of wear deposition process.(4)In order to verify the deposition law and ferrogram making effect of wear particles on the ferrogram,the laboratory gearbox and shearer rocker arm gear box are selected for oil sample collection respectively,and the analytical ferrograph is used for ferrogram preparation and wear particle image acquisition.According to the morphology of different types of wear particles,the area and perimeter of wear particles are selected to verify the law of wear particle distribution.The test proves that the large wear particles deposit first and the small wear particles deposit later,which is consistent with the numerical simulation results.The oil sample viscosity and the distance between the tubing and the ferrogram are selected as the regulation parameter of the ferrogram making process to verify the ferrogram making effect.The influence of oil sample viscosity and the distance between the tubing and ferrogram on wear particles deposition is verified,that is,the wear particle movement displacement is large at low viscosity and small at high viscosity.When the tubing is far from the ferrogram,the wear particle displacement is large,while when the tubing is close to the ferrogram,the wear particle displacement is small.Through the ferrograph test under two different oil viscosities,it is proved that the accumulation and adhesion of wear particles can be effectively reduced under low viscosity.Through two groups of oil samples with different tubing height and distance from the ferrogram,it is verified that the distance between the tubing and the ferrogram has little effect on the accumulation and adhesion of wear particles.