Papers by Author: Ding Wen Yu

Abstract: In this study the influence of tool inclination angle on deformation of thin wall cantilever shape part has been analyzed using finite element numerical simulations. Polycrystalline diamond, PCD tool has been chosen as a tool material in this study because PCD tool has given better results in terms of surface roughness, tool life and productivity in end milling of titanium alloy Ti-6Al-4V. Firstly, in this study, the effect of tool inclination angle on tool contact geometry, cutting speed and cutting forces has been discussed. Then, finite element numerical simulations (FEM) have been carried out in AdvantEdge® for the prediction of cutting forces with PCD tool at four different tilt angles viz. 70°, 75°, 80° and 85° and the results have been compared to the coated carbide tool. Then the maximum magnitude of the forces which occurred in tangential direction (F_Y) were input in the Abaqus® software as a load acting on the thin long cantilever part and deformation results were analyzed. Results show that PCD tool due to its high hardness, strength and better wear resistance produce lower cutting forces at all angles studied and at an angle near the perpendicular to the surface being machined both tools have lower values of the deformation. The FEM simulation results match well with the theoretical study as theoretical analysis also shows that at angles nearer to perpendicular to the surface being machined, the tool will have lower effective cutting speed & forces and hence proved as the key to achieving better accuracies for long thin wall parts.

Abstract: To investigate factors affecting contact interface pressure distribution in bolted joint, a parametric model was established by ANSYS APDL language in this paper. The contact pressure distribution on bolted joint interface was obtained through interpolating and revising contact interface forces. It is observed that the position of peak interface pressure is between the edge of bolt hole and the edge of bolt head. The contact pressure linearly changes with the bolt load while the distribution trend and radius remain unchanged. When the total thickness of clamped members is fixed, the contact pressure distribution varies from concentrated to uniform with the increasing member thickness ratio, and the maximum contact radius is reached while the member thickness is equal. When one clamped member thickness is fixed, increasing the other’s thickness can also reduce the contact pressure concentration, but the effect gradually weakens. Increasing bolt diameter can slightly increase the absolute contact radius but decrease the normalized contact radius. The inclusion of a washer under the nut can slightly promote interface clamping.

Abstract: Finite element simulation is an effective method to study the thermal characteristics of high-speed motorized spindle, how to improve the simulation accuracy has become the key point of this research field. This paper presents a FEA method using ANSYS to precisely predict the thermal characteristics of high-speed spindle. Firstly, the heating and cooling characteristics of high-speed spindle are analyzed, main heating source, convective heat transfer coefficient, and thermal contact resistance are calculated. Secondly, FEA model of the machine center is built, the temperature field and thermal deformation of the spindle system are simulated. Thirdly, an experimental system to test thermal characteristics is designed, simulation results are compared with the experimental results. The result shows that the simulation errors are controlled in a relative low range, the FE modelling method can precisely predict the thermal characteristics of the motorized spindle.

Abstract: This paper proposes a method to simulate residual stress induced by end milling process via 3-D FEM. First, Johnson-Cook material model parameters for a Japanese type of alloy steel (SCM440H) were extracted by a combination method. With the material model parameters, symmetrical end milling process for plate of SCM440H was simulated by FE software to get the residual stress distribution in the machined workpiece. Residual stress measurement experiment was carried out after end milling process to be compared with simulation result to verify the method, which proved that high simulation accuracy can be obtained by extracted material model parameters.

Abstract: To improve the vibration isolation performanceof an air spring system,the characteristics of the dynamic stiffness and damping of adual chamber air springwere first analyzed. A theoretical model ofa four dual chamber air springs system wasthen constructed,and through experimental verification,the theoretical and experimental curves showedthe same change trend.Based on the theoretical models, anobjective function used to optimize the structural parameters of an air springwas constructed. It was demonstrated that the vibration isolation performance of the air spring system was improved with the optimized parameters.

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 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.

Abstract: With increasing spindle speed the cutting will be easy to enter into micro-feed cutting region. In the paper, the chip thickness and shape of high-speed and micro-feed cutting was researched in orthogonal milling. The cutting times in different fz was analyzed. We calculate the effective rake angle, friction angle and shear angle Furthermore, we measure cutting edge arc wear and tool flank wear of micro-feed cutting. Shown as the research results, the phenomenon of empty cutting and pure extrusion is very obvious as the feed rate per tooth is lower than 0.011mm/z. As the feed rate per tooth is lower than 0.005mm/z, the tool wear form is mainly cutting edge arc wear. As fz achieves 0.015mm/z, tool wear will decrease obviously and the tool appears the self-sharpening phenomenon.