Research On Dynamic And Static Characteristics About Hydrostatic Bearing Oil Film Of Heavy Vertical Lathe

Heavy duty NC vertical lathe is the main processing equipment that makes large size rotary parts, which is also one of the core equipment in the heavy manufacturing industry, and hydrostatic bearing is a core component in heavy duty vertical lathe. At present, the researches on hydrostatic bearing that scholars at home and abroad have done mostly are focused on its static characteristic, which is focused on experimental devices, cavity type, structure optimization and so on. But there is not much research on dynamic performance of hydrostatic bearing, so the writer will begin an intensive study on dynamic performance of oil film of open type hydrostatic bearing to reveal its transition process and change rule of dynamic stiffness, and to contrast its static stiffness. This research will provide fundamental basis for research and development of hydrostatic bearing, operational stability and machining precision of machine tool. The main work that has been done is as follows.1. Derive mathematical model. Utilize laminar flow equation of parallel plates to derive flow equation, pressure equation, bearing capacity equation and static stiffness equation of oil film of a single fan cavity oil pad about static characteristics. According to Newton's second law, static cha racteristic mathematical model and vibration mechanics, derive dynamic characteristics mathematical models of oil film of a single fan cavity oil pad.2. Analyze static characteristics. Use MATLAB to draw the static characteristic curves, such as the theoretical relation curve of carrying capacity and oil film thickness and the relation curve of stiffness and oil film thickness. Use CFX to compute the pressure field of oil film when the oil film thickness respectively is 0.06 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.14 mm and 0.16 mm, and use these results to contrast with the theoretical values. And then, carry on numerical simulation to compute the pressure field of oil film when the oil film thickness is 0.06 mm under different loading conditions, such as 15 t, 30 t, 45 t, 60 t, 75 t, 90 t, 105 t, 120 t, 135 t and150t, which will provide a basis for comparatively analyzing theoretical results, numerical simulation results and experimental results.3. Analyze dynamic characteristics. Use MATLAB to analyze the step response of oil film when the oil film initial thickness is 0.06 mm under 0.1t, 0.2t, 0.3t, 0.4t, 0.5t, 0.6t, 0.7t, 0.8t, 0.9t, 1.0t loading, and gain their response curves, the response time curve and the displacement curve. And respectively analyze the step response of oil film when the oil film initial thickness is 0.06 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.14 mm and 0.16 mm under 1.0t loading. Analyze the response of oil film whose thickness is 0.06 mm when it is acted by sine wave loading which is respectively 0.1t, 0.4t, 0.7t, 1.0t, and get response curves under different sine wave loading. Meanwhile, analyze the relation of dynamic stiffness and frequency when the oil film thickness is respectively 0.06 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.14 mm and 0.16 mm, and get the relation curve of the two. Use formula transformation to analyze the relation of dynamic stiffness, static stiffness and damping.