Numerical Simulation And Experiments On Ball End Milling Hardened Steel With Sandwich Structure

Hardened steel has the characteristics of low plasticity and low elongation,and easily forms a high-quality surface finish,for these reasons it is widely used in the production of moulds.Traditionally,large-scale hardened steel moulds are produced via an overall milling process.The structure of the large-scale hardened steel moulds is complex and there are many complex structures on the surface,such as grooves,bulges and the like.To reduce processing and material costs,the moulds are usually manufactured in sections and then integrally joined.In the actual production of large-scale automotive single-piece moulds,mould components of varying hardness are joined by welding.A sandwich structure is formed between those components of different hardness and the weld in between.If the variation in hardness is large and the welding zone material is different from the parent material,the precision milling of the die becomes very difficult.At present,research into the milling of hardened steel moulds only involves the case of direct contact between a single hardness region or two hardness regions,without considering the influence of the interlayers between adjacent hardness regions caused by welding.Therefore,it is of great theoretical value and engineering significance to study hardened steel milling processes that exhibit this hardness sandwich structure.The main content of this article is:1.The modal analysis of the ball-end milling cutter was carried out using ANSYS,and its 5th order natural frequency and mode of vibration were obtained.The modal experiment of the ball-end milling cutter was carried out by means of a hammer test,and the steady-state diagram of its modal parameter signature was obtained as well as the experimental modal frequency and damping ratio of the milling cutter.By comparison with the simulation results,the tool’s optimum overhang length was determined.This was used in the milling experiment in the next chapter2.A milling numerical analysis model of the hardened steel sandwich structure was established,and the milling process of the hardened steel sandwich structure was numerically simulated based on ABAQUS finite element software,physical failure chip separation criterion and the Johnson-Cook constitutive model.By changing the cutting processing parameters in the simulation process,the distribution of cutting temperature and cutting force for the hardened steel sandwich structure was obtained.The influence of the variation of workpiece hardness on the magnitude of the cutting force and the temperature were analysed,and the influence of tool parameters on the milling process was explored.3.The milling experiment was performed on the hardened steel sandwich structure.The milling force,milling vibration,chip morphology and the surface quality of the interlayer zone after machining the workpiece were studied.During experimental processing,the sandwich structure was explored using univariate analysis.The relationship between milling force and depth of cut,spindle speed and feed rate in the interlayer zone,and the milling force across the whole workpiece under specific parameters was compared with the simulation results,thus verifying the accuracy of the simulation results.A roughness tester was used to assess the surface roughness of the workpiece after machining.The relationship between surface roughness and processing parameters was analysed as well as the relationship between each parameter and the milling force via an orthogonal test of three factors and three levels.The vibration signal at each measuring point was analysed in terms of both the time domain and frequency domain.