Xiaoliang Jin

Chatter Stability Model of Micro-Milling With Process Damping

This paper presents the prediction of cutting forces and chatter stability of micro-milling operations from the materials constitutive flow stress and structural dynamics of the micro-end mill. The cutting force coefficients are identified either using previously presented slip-line field or finite element methods by considering the effects of chip size, cutting edge radius, rake angle and cutting speed. The process damping caused by the plowing of round edge is modeled by finite element method. The frequency response function of the fragile micro-mill is measured through specially devised piezo actuator mechanism. Dynamic model of micro-milling with the velocity dependent process damping mechanism is presented, and the chatter stability is predicted in frequency domain. The proposed models have been experimentally verified in micro-milling of AISI 1045 steel.

A Frequency-Shift Synchrosqueezing Method for Instantaneous Speed Estimation of Rotating Machinery

Instantaneous speed (IS) measurement is crucial in condition monitoring and real-time control of rotating machinery. Since the direct measurement of instantaneous rotating speed is not always available, the vibration measurement has been used for indirect estimation methods. In this paper, a novel indirect method is proposed to estimate the IS of rotating machinery. First, a frequency-shift synchrosqueezing transform is proposed to process the vibration signal to obtain the time–frequency (TF) representation. Second, the Viterbi algorithm is employed to extract the shifted instantaneous frequency (IF) from the TF representation. Finally, the extracted IF is used to recover the IF of the measured vibration signal. The IS of rotating machinery can be calculated from the estimated IF. The proposed method is validated with both numerical simulations and experiments. The results show that the proposed method could provide much higher frequency resolution, better TF concentration results, and more accurate IF estimation of the considered signal compared with the synchrosqueezing method. Furthermore, the proposed method was confirmed to be less sensitive to noise, especially for high-frequency components. [DOI: 10.1115/1.4029824]

A General Method for the Dynamic Modeling of Ball Bearing–Rotor Systems

A general dynamic modeling method of ball bearing–rotor systems is proposed. Gupta’s bearing model is applied to predict the rigid body motion of the system considering the three-dimensional motions of each part (i.e., outer ring, inner ring, ball, and rotor), lubrication tractions, and bearing clearances. The finite element method is used to model the elastic deformation of the rotor. The dynamic model of the whole ball bearing–rotor system is proposed by integrating the rigid body motion and the elastic vibration of the rotor. An experiment is conducted on a test rig of rotor supported by two angular contact ball bearings. The simulation results are compared with the measured vibration responses to validate the proposed model. Good agreements show the accuracy of the proposed model and its ability to predict the dynamic behavior of ball bearing–rotor systems. Based on the proposed model, vibration responses of a two bearing–rotor system under different bearing clearances were simulated and their characteristics were discussed. The proposed model may provide guidance for structural optimization, fault diagnosis, dynamic balancing, and other applications. [DOI: 10.1115/1.4029312]

Identification of Process Damping Coefficient Based on Material Constitutive Property

The contact between the tool flank wear land and wavy surface of workpiece causes energy dissipation which influences the tool vibration and chatter stability during a dynamic machining process. The process damping coefficient is affected by cutting conditions and constitutive property of workpiece material. This paper presents a finite element model of dynamic orthogonal cutting process with tool round edge and flank wear land. The process damping coefficient is identified based on the energy dissipation principle. The simulated results are experimentally validated.Copyright

Mechanics and dynamics of micro-cutting process

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Material Behavior in Micro Milling of Zirconium Based Bulk Metallic Glass

Bulk metallic glasses (BMGs) are a group of metallic materials with amorphous microstructure. BMGs have been increasingly used in various applications such as optical molds, sport equipment and biomedical components. The machining mechanism for the BMGs is distinct from that of the crystalline metal alloys due to the differences in their microstructures and mechanical properties. This paper presents experimental investigations on the material behavior in micro milling of zirconium based bulk metallic glass (Zr-based BMG) . Micro milling of the BMG with high spindle speed up to 105,000 rpm was conducted. Surface morphology, microstructural evolution and crystallization of the machined surface were characterized by optical and scanning electron microscopy, X-Ray diffraction and energy dispersive X-Ray spectroscopy. The results detailed the responses of the Zr-BMG to the milling conditions which enables the machining conditions to be optimized to achieve an improved surface quality and machining efficiency.

Assessment of high and low frequency vibration assisted turning with material hardness

Vibration assisted turning (VAT) is a process to implement external vibrations in conventional turning (CT) process in order to improve overall machining performance. In this paper, the machinability of both high frequency vibration assisted turning (HVAT) and low frequency vibration assisted turning (LVAT) is investigated in machining typical engineering materials, including AISI 52100, AISI 4340, IN-100, Ti6Al4V, AISI 1050 and Al-2024-T-351. Both HVAT and LVAT are assessed in terms of effective stresses, forces, temperature and residual stresses and compared to CT. A 3D finite element model is developed for machining Ti6Al4V, with simulated temperature and cutting force experimentally validated. This model is used to perform the evaluation of machining processes for other materials. In addition, surface finish and tool wear analyses are performed for AISI 4340 and Al 2024-T-351 to evaluate the applicability of LVAT compared to CT. It is found that HVAT and LVAT are able to achieve significant improvements compared to CT. Reduction of cutting forces, stresses and temperature is observed in the VAT process. The applicability of LVAT is found to be limited by hardness of the material.

Prediction of Coupled Torsional-Axial Vibrations of Drilling Tool With Clamping Boundary Conditions

Coupled torsional-axial vibrations of the drilling tool play a significant role in the machining dynamics of the drilling process. In this paper, the torsional-axial vibrations of the drilling tool due to the warping deformation of the pretwisted flute is modeled. An enhanced receptance coupling model is developed to predict the coupled torsional-axial vibrations of the drilling tool considering the dynamics of fixture and clamping conditions. Rigid and flexible receptance coupling methods are used, with the simulation results verified through modal experiments. The proposed model is able to provide optimum drilling tool configurations to avoid undesired tool vibrations and improve hole quality.Copyright