| Ball screw pair is the key transmission component of CNC machine tools,precision instruments,aviation aircraft,shipbuilding industry,weapon industry,etc.Its performance has great influence on the overall performance of the whole machine.Especially in recent years,with the rapid development of modern equipment manufacturing industry,the development trend of high speed,high precision,high efficiency,intelligence and automation have put forward higher requirements for the precision and dynamic performance of ball screw pair.High speed and heavy load will inevitably bring about the high temperature rise,high wear,vibration and noise;meanwhile,friction and wear are the main reasons for temperature rise and wear,vibration and noise,low life,so the research of ball screw friction,wear,and thermal characteristics is crucial for improving performance of ball screw.Ball screw pair is selected as the research object,and this paper analyzes some main parameters and structure parameters on the contact characteristics of ball screw,friction and wear properties,thermal properties and thermal structure coupling characteristics,the main research work:(1)The literatures on friction and wear,thermal characteristics analysis and fractal theory of ball screw pairs at home and abroad are reviewed.A summary of the current research status and development trend at home and abroad is completed.The related literature on friction and wear characteristics,thermal characteristics analysis,fractal theory and other related literature is analyzed,and existing problems are found.Finally,according to research direction of project group,the research content,research idea and specific work arrangement are made.(2)The contact characteristics of ball screw are analyzed,and the mathematical model of axial contact deformation and normal contact stress is established.Based on Hertz contact theory and considering the influence of spiral angle,axial contact deformation and normal contact stress of ball screw pair under different working conditions and structural parameters are studied.The influence of the axial working load,contact angle,spiral angle,working ball number and curvature ratio on contact characteristics is analyzed.(3)The friction torque model of the ball screw pair was established,and the influence of different working conditions on the friction torque was analyzed.First,the friction mechanism of ball screw pair is studied,and the influence of main factors on the friction torque is analyzed,including roller cycle mode,raceway parameter,pre tightening mode and pre tightening force,working load,speed,lubrication and material.Finally,the friction torque model of ball screw pair is established,and the influence of main working parameters on it is simulated.The analysis results are compared with previous studies.(4)Based on the Archard wear theory,the macro wear model and precision loss model of ball screw pair are established,and the influence of different structural parameters and different working conditions on the wear volume and accuracy loss is analyzed.The wear mechanism of ball screw pair is analyzed,and the Archard macro wear model is established.Combined with the axial deformation model of the contact analysis section,the precision loss model of the ball screw pair is established.The influence ruleof the working condition parameters and structural parameters on the wear amount and loss of precision is analyzed.(5)The micro fractal wear prediction model of ball screw pair was established,and the influence of fractal parameters on the micro wear model was analyzed.Based on the three-dimensional fractal theory,the fractal contact analysis is carried out,and the microscopic wear prediction model is established based on the adhesive wear mechanism.The influence rule of fractal dimension and fractal scale parameter on wear rate is analyzed.(6)The analytical calculation,finite element analysis and experimental verification of the temperature characteristics of ball screw are completed,and the precision loss model of ball screw considering the temperature rise is established.A three-dimensional fractal contact thermal conductivity model is established,and thermal boundary conditions of ball screw pair are solved.The influence of each parameter on temperature rise and thermal deformation is analyzed,a precision loss model considering the temperature rise is established,and the influence of temperature rise on accuracy loss is analyzed.Then finite element simulation and temperature rise experiment are completed,and the temperature variation rule of the screw was further obtained. |
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