Research On Contact Thermal Resistance Of Machine Tool Fixed Interface

There is a fixed combination of the bed body-column,bearing seat-column,bearing seat-bed and other fixed CNC machine tool structure,due to the presence of micro-surface roughness,incomplete contact interface lead to contact thermal resistance.The thermal contact resistance between the bonding surfaces has an important influence on the heat transfer of CNC machine tools,the deformation of the bed rails and the machining accuracy.Therefore,it is necessary to further study its formation mechanism and influencing factors.In order to achieve the above goal,the theoretical modeling and simulation calculation of the contact surface thermal resistance are carried out.Based on this,a set of contact thermal resistance test equipment is designed to study the influence factors of contact thermal resistance.At last,the suitable value of the contact thermal resistance required by the machine tool thermal analysis is put forward.The main research contents are as follows:A contact thermal resistance model based on geometric-mechanical-thermal analysis was established.The rough surface morphology was characterized by the Weierstrasse-Mandelbrot fractal function.The fractal parameters were identified by power spectrum method.The model of contact heat transfer coefficient was obtained by integrating the elastic,elastic-plastic and plastic contact mechanics models,and the reciprocal of the model was obtained.Based on Ansys,a finite element model of the joint surface was set up,some boundary conditions were set,the contact heat transfer coefficient calculated by the theoretical model was applied to the contact surface of the joint surface,and the simulation analysis was carried out.The temperature field and the deformation field of the standard specimen are obtained and the temperature difference of the bonding surface is obtained.A set of standard specimen combined with surface contact thermal resistance measuring device was designed and a contact resistance measurement system was set up to measure and analyze the contact heat transfer coefficient at different temperature,pressure,material and surface shape.Synthetical comparison of heat transfer coefficient at interface with theoretical modeling and temperature difference at the interface of simulation.Based on the above,the simulation of the bed column assembly model of CNC machine tool was made with the consideration of the thermal contact resistance of the contact surface.The temperature field and deformation field of machine tool under different heat transfer coefficient of bed-column contact surface are contrasted in detail,and the deformation of the guide rail is extracted respectively.From the point of view of reducing the deformation of the guide rail,the contact heat transfer coefficient between the bed and the pillar can be reduced.At the same time,the thermal characteristic experiment was carried out on the machine tool,and the temperature resistance value was obtained,which provided a reference for improving the precision of the machine tool design stage.