Papers by Author: Jian Fu Zhang

Abstract: This paper presented a real-time measuring method of temperature fields and thermal deformations in vertical machining center. And a FEA model including the thermal contact resistance at interface for evaluating the temperature distribution and tools deformation in vertical machining center (VMC) was established. Compared with the experiment results, it is shown that the new model is much more accurate than the traditional model without considering thermal contact resistance at interface.

Abstract: High volume fraction silicon carbide particulate reinforced aluminum matrix (SiCp/Al) composite are new class of difficult-to-machine materials due to their high strength. This paper presents an experimental investigation on the machinability of 60 vol% SiCp/Al composites by comparing the rotary ultrasonic milling method with the conventional machining method. The test scheme is designed, and the measurement method of the cutting force, surface roughness and morphology are illustrated. Based on the constructed experimental platform, the influences of machining parameters, such as cutting speed, feed rate and cut depth, on the cutting force and surface roughness are discussed. The experimental results show that ultrasonic machining is an effective method for machining high volume fraction SiCp/Al.

Abstract: Material constitutive equation plays an important role in Finite Element Analysis (FEA) of metal cutting process. This paper proposes a method to obtain parameters for Power Law model of a Japanese type of alloy steel (SCM440H) for 3-D FEA of face milling process, involving pressure bar experiments and orthogonal metal cutting experiments. Since pressure bar test cannot reach the high strain rate occurred in cutting process, orthogonal cutting experiment was combined to obtain parameters for material model. By this method, the ideal parameters for FEA of the face milling process were finally determined. Face milling experiments were performed to verify the accuracy of the model built.

Abstract: This study introduces rotary ultrasonic face milling (RUFM) process into flat surface machining of K9 glass. The effective cutting velocity, and cutting length of single diamond particle were presented in RUFM. The model of material removal for RUFM was developed through examining indentation fracture mechanics theory and material removal characteristics of brittle materials, and analyzing kinematics properties of diamond grits in RUFM. With a view of comparative researches, the cutting force of RUFM and diamond milling of K9 glass are compared. The experimental results tell that the relationship between the cutting depth (dc) and the ultrasonic amplitude (A) of the cutter has remarkable effects on cutting force, which was also discussed in the kinematic characteristics analysis section. The results also show that RUFM process can significantly reduce cutting force and the effects of process variable changes on cutting force in RUFM are weaker as dc is smaller than A. However, the reduction trends of the cutting forces in RUFM are very small and even increased in some process conditions, as dc is larger than A. It suggests that the cutting depth should be smaller than the ultrasonic amplitude of the cutter with RUFM process to obtain better processing performance.

Abstract: Aiming at the problem of the influence of joints on machine structure static performance, this paper presents a method of modeling and experiment on static characteristic of BT tool holder-spindle interface. A FEA model of tool holder-spindle interface is established by setting several equivalent springs, whose parameters are identified through experiment. The effectiveness of the proposed method is tested and verified by building finite element model and applying the spring parameters to it. The comparison between the emulational result and experimental result shows that the simulation accuracy has improved tremendously, which the relative error reduces to less than 10% under different axial forces.

Abstract: This paper analyzed the dynamic performances of vertical machining center and investigated the problems of dynamiccharacteristics. The modal analysis in both experiment and simulation wascarried out to obtain the modal parameters. The vibrations of the machine spindle were tested to obtain the vibration spectrum under different spindle speeds. It synthesized and compared with the vibration and modal characteristic in order to investigatethe weak parts of the structure. It is concluded that modal characteristic has something to do with the vibration, and there is eccentric between the active rotor and driven rotor. This comprehensive comparison method for dynamic analysis is very effective.

Abstract: Stiffness analysis plays an important role in the optimization of the machine tool. By analyzing the static stiffness, dynamic stiffness and natural frequency of the key components, we discussed how to improve static and dynamic performance of the whole machine. Through the finite element analysis method, weak parts of the vertical machining center are firstly identified based on static stiffness analysis. Due to the purposes of increasing the stroke in Y-direction, improving the whole machine stiffness and without increasing the whole machine weight, optimal designs are carried out mainly on the structures of the spindle box and the column. And the performance of the parts and the whole machine before and after optimization is compared by testing whether the stiffness is improved or not. We also conducted experiments, and the results are consistent with the results of finite element analysis.

Abstract: The plastic-coated slideways have been widely used for form-generating movement in machine tools. Its dynamic behavior plays an important role in the vibration properties of the whole machine. In this work, according to the situation that researches on this subject were rather insufficient, a theoretical research was analyzed concerning the stiffness and damping characteristics of rectangle-shaped plastic-coated slideways. The mathematical model was firstly suggested especially based on the assembly of the saddle and worktable. Both stiffness and damping characteristics on vertical and horizontal directions were theoretically determined. To derive the governing motion equation of the slideway system, the carriage and rail were considered as rigid bodies and connected with a series of spring and damping elements at the joint face. Moreover, through the Lagrange’s approach, the frequencies of the carriage at vertical, pitching, yawing and rolling vibration mode were identified.