Papers by Author: Min Li Zheng

Abstract: Geometry constraint and physical constraint change because the structure is complex, tonnage is large, and assembly load is complex on heavy duty machine tool, assembly relation is changed for repeated assembly, then, the assembly accuracy reproducibility and assembly accuracy retentivity decline, which results in the decrease of assembly reliability. According to this problem, the interaction of geometry constraint and physical constraint is discussed in this paper, the influence factors of assembly accuracy reproducibility and assembly accuracy retentivity are respectively analyzed, the establishing, demolition and re-establishing of assembly relation effects assembly accuracy reproducibility, and evolution of assembly relation with time effects assembly accuracy retentivity, which are respectively revealed. Using margin method to evaluate assembly accuracy reliability, the criterion and evaluation method of assembly accuracy reliability is proposed, in order to provide reliable and quantitative criterion for assembly process design, and reasonably set safety margin of geometry constraint and physical constraint, form reliable assembly process, realize that the assembly accuracy is controlled and improved by assembly.

Abstract: Based on the experiment of high speed ball-end milling hardened steel, investigated the distribution characteristics of cutting force and cutting heat and wearing character of cutter, and set up analysis model of cutter physical field. Using failure criterion and safety margin of cutter, founded physical field evaluation model of high speed ball-end milling cutter. By means of physical field analysis and experiment, explored the influence of cutting parameters on cutting property during cutter wear. Results indicate that the method of safety margin and physical field evaluation model can evaluate cutting property of cutter effectively, the impact of feed per tooth on physical field and safety margin is noticeable, and high speed and small feed are helpful to improve safety margin and cutting performance of cutter.

Abstract: For the instability of ball-end milling cutter in high speed milling, instantaneous cutting process of high speed milling hardened steel was studied. The model of instantaneous cutting layer parameters of high speed ball-end cutter was established, and the influence of cutting speed and inclination angles on instantaneous cutting layer parameters were obtained. Using the model, instantaneous cutting force was studied, and high speed milling experiment was processed. Results show that the increase of cutting speed makes the change rate of cutting layer parameters increasing, leads to the energy concentration in cutting process, and increases the impact on milling cutter. The increase of inclination angle makes the instantaneous cutting layer parameters show a trend of decrease and the decrease of cutting thickness more rapidly, which caused instantaneous unit cutting force to increase and the instantaneous main cutting force appears increasing trend, and the cutting process become unstable.

Abstract: Aim at the uncertainty of vibration behavior in high speed ball-end milling hardened steel, carried out the experiment of high speed milling hardened steel and modal analysis of cutter, studied vibration behavior of cutter and workpiece, and established vibration behavior sequence of high speed milling hardened steel. Using gray system theory, did gray cluster analysis of vibration characteristics, explored the correlation among cutter vibration, workpiece vibration and surface roughness characteristics, put forward the method of characterizing vibration characteristics in high speed ball-end milling hardened steel. The results show that high frequency vibrations of cutter and workpiece are caused by the interaction of centrifugal and dynamic cutting force, the increase of cutter overhang enhances high frequency vibration of cutter, the characteristic of cutter vibration changes from low frequency vibration to interaction of low frequency vibration and high frequency vibration. Using cutters with different overhang, surface roughness of high speed milling hardened steel has similar characteristics, surface roughness in row spacing direction can characterize low frequency vibration of cutter, and surface roughness in feed can characterize resonance characteristic of cutter caused by high frequency vibrations of cutter and workpiece.

Abstract: In order to depress cutter vibration caused by high hardness and periodic change of cutting force in high speed milling complex surface, investigated the modal characteristics of ball-end milling cutter through the modal analysis and transient analysis. Using the models of dynamic cutting force and cutting vibration, acquired dynamics characteristics of high speed ball-end milling cutter by the spectrum analysis of dynamic cutting force, simulation analysis of cutting vibration and experiment of high speed milling hardened steel. Results indicate that high speed ball-end milling energy concentrates in few special frequencies, the rotational speed and the numbers of cutter teeth determine the fundamental frequency. High speed ball-end milling cutter easily makes radial bending vibration by the lower modal characteristics, the overhang and inclination angle of cutter affect its dynamics characteristics significantly, and the modal parameters and vibration model of cutter acquired by step response method have higher credibility.

Abstract: High speed milling cutter is a representative cutter for high efficiency cutting, there is the indeterminacy induced by small sample and lacking information in evaluating its performance. By the analysis of cutter characteristics, acquires the data of structure, material and cutting parameter affecting the performance of cutter, and constructs structural levels model of performance behavior in designing cutter. Using the theory of axiomatic design, investigates mapping approach among structural domain, material domain and functional domain, and propounds collaborative design method of multilevel high speed milling cutter. Results of performance analysis and high speed milling experiment show that the model indicates the interaction among structural levels of cutter, and the design method makes the performance of cutter satisfy the requirements of safety, stability and high efficiency cutting.

Abstract: This work explored the process of safety decline based on stress field and deformation analysis of cutter, founded vibration models of centrifugal force and cutting force, and investigated the effect of dynamic balance precision and natural frequency on safety and stability of cutter. Using the model of maximal residue height on machining surface based on the vibration of cutter and experiment results, characterized safety decline behavior of high speed milling cutter. Experiment results verified that safety decline caused by the vibration of centrifugal force was much higher than the vibration of cutting force. The results indicate that the deformation of cutter and relative displacement of subassembly change mass distribution of cutter with rotational speed increasing in unimpaired state of cutter’s integrity, direct results are dynamic balance precision decline, the safety and stability state of cutter gradual deterioration because of the vibration, the safety of cutter occurs a dynamic decline in high speed milling.

Abstract: Using the theory of axiomatic design, the optimization method of high speed milling cutter was investigated, and the optimization designs of teeth distribution and dynamic balancing were created by means of function decomposition and grey cluster analysis. Results showed that the method solved effectively the problem of parameters interaction and functions coupling in optimization design of cutter, the effects of simplifying design process and improving collaborative design were validated in development of cutter. Experiments indicated that the vibration in high speed machining aluminum alloy was depressed, the cutter held higher cutting stability, and its cutting performance met the optimization design requirement of high speed milling cutter.

Abstract: This work investigated safety and stability of high speed milling cutter using FEM and Penghuanwu discriminance, propounded safety and stability criterion of cutter, and analyzed absolute degree of incidence on safety and stability of cutter using grey system theory, the influence laws of structure parameters and their interaction on safety and stability of cutter were acquired. Experiments of idling and high speed milling were carried out, analyzed the impact degree of structural parameters on safety and stability of cutter, and results validated the dependability and validity of safety and stability cutting criterion.

Abstract: Based on the milling force testing experiments on machining the carbon structural 45 steel, the study on the distributing principle of force density function for complex three-dimension groove milling insert with the waved-edge milling insert (the curve rake plane) developed by Harbin University of Science and Technology is studied. On the basis of the milling force mathematical model, the force density function of the curve rake plane is built by the milling force experiments and tool-chip contact area experiments. Having quantitative calculation on the force density function and programming, the distributing model of force density function is shown with 3D figure, so to analyze its distributing principle. All these studies will provide a theoretic base for the stress field analysis and solving the cutter disrepair which is the key problem in the automatization production and groove optimization.