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In the milling process, the spindle vibration response is an important factor affecting the machining quality and accuracy. In this article, the mechanism of cutting vibration coupling is analyzed, and the dynamic cutting thickness during the milling process is calculated to make the model more accurate and closer to the actual situation. The five degrees of freedom nonlinear vibration model is established to analyze the instantaneous dynamic behaviour under cutting force and unbalanced mass excitation. The linear stiffness and bearing contact force models of the spindle system are derived by Hertz's contact theory. On the basis of the established simulation model, the effects of unbalanced mass eccentricity, spindle speed, axial preload, milling condition parameters on the dynamic behavior are analyzed. The feasibility of the coupled dynamic model is confirmed through experiments. The motion behaviour of the spindle exhibits rich and complex non-linear phenomena due to the interaction of cutting force and vibration response. Therefore, the proposed model provides a theoretical basis for the prediction of cutting force and dynamic characterisatic during the milling process. [ABSTRACT FROM AUTHOR]

The sliding guide plays a crucial role in CNC (Computerized Numerical Control) machine tools, as its dynamic characteristics can significantly impact the machining quality and reliability. Therefore, this study focuses on the analytical modeling and analysis of the sliding guide system. Firstly, a static model of the sliding guide system is established based on fractal theory. The accuracy of the static model is verified through loading experiments. Utilizing the developed model, the influence of relevant parameters on the bond surface stiffness is analyzed. Subsequently, the concentrated mass method is applied to further develop a nonlinear dynamics model of the system based on the static model. The nonlinear dynamical equation is solved using the Runge–Kutta method. The vibration responses at various excitation frequencies are measured and compared with simulation results, which show good agreement. Lastly, based on the established dynamic model, the study investigates the effects of parameters such as external load, sliding guide material, excitation frequency, tilting surface angle, and slider mass on the dynamic characteristics of the sliding guide system. The main result of this research is to establish the static model of wedge sliding guide based on fractal theory, and further establish the dynamic model of wedge sliding guide on this basis. On the basis of the dynamic model, relevant parameters are discussed, and the effects of different parameters on the dynamic characteristics of the sliding guideway are obtained through the parameter discussion. Based on the results of parametric discussion, the performance of sliding guide can be enhanced by changing the parameters. This study helps to prevent resonance and instability in sliding guide systems. By investigating the analysis and modeling of the sliding guide system, this study aims to enhance the understanding of its dynamic behavior and improve the overall performance of CNC machine tools. [ABSTRACT FROM AUTHOR]

In order to accurately understand the dynamic behavior of the machine tool spindle, it is necessary to accurately model the interactions between thermal, nonlinear dynamics and nonlinear milling process for machine tool spindle. To this end, this paper establishes a real-time coupled model for the thermal–dynamics–milling process of spindle considering nonlinear characteristics, and the established model can be used to predict response evolution, including temperature distribution, thermal deformation, vibration, bearing support force and instantaneous milling loads. Using the thermal network method, a transient thermal model of the spindle system is established considering the time-varying characteristics of heat generation and thermal transfer during milling. The five degree of freedom (DOF) nonlinear dynamic model of bearing is established including thermal deformation and is coupled with spindle vibrations. The ten-DOF Timoshenko beam is used to model the spindle dynamics with the tool subjected to nonlinear dynamic milling load. The instantaneous load generated in milling process is calculated including the effects of tool vibration, cutting condition and the geometric errors of tool assembly. Besides, the coupling calculation of the established model is proposed with the application of the combined fourth-order Runge–Kutta and Newmark β methods. The process dynamic responses of the actual spindle are measured, and the measured results closely match the simulation results. Finally, in order to provide theoretical reference for designers, the changes in thermal behavior, vibration and cutting stability by varying rotation speed, thermal boundary conditions and operation conditions are investigated. [ABSTRACT FROM AUTHOR]

This paper proposes a new dynamic model of the aerostatic spindle, including radial and thrust bearing. The engineering calculation method of the hydrodynamic equation of the hydrostatic spindle is studied, and its validity is verified by comparing with the finite difference calculation results. Moreover, the dynamic model of the spindle is based on the lumped mass method, considering the gyroscopic effect, and through coupling with the bearing, a multi-degree-of-freedom fluid–structure interaction nonlinear dynamic model is constructed. This paper is the first to take the influence of the tilting motion of the spindle on the dynamic characteristics of the aerostatic bearing into consideration, and the engineering calculation method is used to solve the dynamic equation of the spindle in real-time. On the basis of the Runge–Kutta method, which is used to obtain the dynamic response of the spindle, this research studied the effects of air film thickness, radial bearing length, and air supply pressure on the motion response of the spindle system comprehensively. [ABSTRACT FROM AUTHOR]

The non-uniform load distribution of crowned roller along the contact line has a significant impact on the dynamic characteristics and fatigue life of the roller linear guideway workbench (RLGW). Moreover, the randomness in the design parameters due to unavoidable manufacturing errors will induce the uncertainty in the vibration prediction of RLGW, which will affect the machining accuracy of machine tool. To this end, this paper first establishes a novel five-DOF dynamic model considering the non-uniform load distribution of crowned roller to investigate the vibration characteristics of RLGW. The coordinate transformation method is used to obtain the vibrations at the four raceways of carriage by applying the workbench vibrations. The Hertz contact theory and the slicing method are applied to calculate the contact force and moment of crowned roller including the influence of roller profile, and a time-varying five-DOF restoring force model dependent on the workbench vibrations is established. Then, to improve the computing efficiency, a vibration reliability evaluation method of RLGW based on the active learning Kriging model and Monte Carlo Simulation (ALK-MCS) method is proposed. The developed dynamics modeling method is verified by some experiments on a CNC milling machine workbench system. The changes in the vibration characteristics and stiffness of RLGW are studied by varying the preload degree and number of loaded rollers. Furthermore, the vibration reliability and reliability sensitivity of RLGW are studied to provide theoretical foundation for the parameter optimization. [ABSTRACT FROM AUTHOR]

A dynamic model based on rotor dynamics was proposed to analyze the effect of workpiece-tool system vibration on the cutting accuracy of commercially pure titanium TA2. The proposed model considers the imbalance of mass and stiffness caused by material removal, regenerative chatter effect, the Johnson–Cook plastic material constitutive model of the workpiece, and coupled vibration between workpiece and tool. The differential equation of the rotating workpiece-tool system is derived by using D' Alembert's principle. The model's validity is verified by cutting tests and surface topography observation. Besides, the effects of different cutting parameters on cutting vibration characteristics and Processing quality are discussed. According to cutter-workpiece vibration response and the test results of surface roughness, chip morphology, and surface morphology, the causes of cutting vibration and the influence of cutting parameters on surface quality are revealed. [ABSTRACT FROM AUTHOR]

In cutting process, the insufficiency in grasp of the tool vibration characteristics of spindle system seriously hinders the improvement of machining quality and efficiency. Thus, this paper develops a novel dynamic model of spindle system in ball end milling process considering the nonlinear contact behavior of bearings. For the sake of coupling with the motion differential equations of spindle shaft, a general analytical expression for the nonlinear contact force of matched angular contact ball bearings is proposed. Then, dynamic cutting force model during ball end milling is established with consideration of the influence of tool vibration on the uncut chip thickness. Furthermore, the effectiveness and feasibility of the proposed model is confirmed by some cutting tests. Finally, the effects of rotation speed, bearing preload, and cutting parameters on the tool end vibration response of spindle system are analyzed in detail. The investigations reveal that the main resonance frequency increases and the corresponding resonance amplitude decreases as bearing preload increases. The larger bearing preload can improve cutting stability and machining quality. It is also concluded that the change regarding axial depth of cut considerably affects the vibration behaviors of tool end. The proposed dynamic model can be applied to predict the vibration of spindle system during ball end milling, especially the tool vibration. [ABSTRACT FROM AUTHOR]

It is industry tendency to accurately predict the dynamics of the mechanical systems with full consideration of errors. Based on the Hertz contact theory and general bearing modeling methods, this study proposed a more practical model using numerical method to investigate the influence of assembly error on the dynamics of linear guide slide platform. First, the modeling methods of five types of assembly errors are established, based on which, a nonlinear dynamic model is developed to investigate the influence of assembly error. In consideration of assembly error, the modeling method enables the sum of restoring forces and restoring moments equal to zero when no external load applied to the platform. Second, the simulation results indicate that the assembly error can cause uneven load distribution, change the dynamics of the system. In addition, different from previous research results, the stability of the system cannot be improved by simply increasing the preload. Last, in order to validate the proposed method, the proposed model is compared with previous fewer degrees-of-freedom model, and a series of experiments are conducted on a specialized platform to estimate the parameters of the system and verify the proposed model. [ABSTRACT FROM AUTHOR]

In this study, a five-degree-of-freedom dynamic model of variable lead preloaded single nut ball screw is proposed. The proposed model considers the effect of excitation amplitude, deflection angle, the number of balls, and the preload into consideration. Moreover, to study the effect of working parameters on nonlinear dynamics, bifurcation diagram, 3-D frequency spectrum, phase diagram, and Poincaré section with different system parameters are shown in the Discussion section. The numerical analysis indicates that the system can exhibit different motion states, and the continuous frequency component can be observed. Moreover, a series of experiments are conducted to estimate the dynamic parameters and validate the proposed dynamic model. [ABSTRACT FROM AUTHOR]

As an integrated application of modern information technologies and artificial intelligence, Prognostic and Health Management (PHM) is important for machine health monitoring. Prediction of tool wear is one of the symbolic applications of PHM technology in modern manufacturing systems and industry. In this paper, a multi-scale Convolutional Gated Recurrent Unit network (MCGRU) is proposed to address raw sensory data for tool wear prediction. At the bottom of MCGRU, six parallel and independent branches with different kernel sizes are designed to form a multi-scale convolutional neural network, which augments the adaptability to features of different time scales. These features of different scales extracted from raw data are then fed into a Deep Gated Recurrent Unit network to capture long-term dependencies and learn significant representations. At the top of the MCGRU, a fully connected layer and a regression layer are built for cutting tool wear prediction. Two case studies are performed to verify the capability and effectiveness of the proposed MCGRU network and results show that MCGRU outperforms several state-of-the-art baseline models. [ABSTRACT FROM AUTHOR]

Nonlinear factors existing in engineering structures have drawn considerable attention, and nonlinear identification is a competent technique to understand the dynamic characteristics of nonlinear structures. Therefore, in this paper, a novel nonlinear separation subspace identification (NSSI) algorithm based on subspace algorithm and nonlinear separation strategy is proposed to conduct nonlinear parameter identification of nonlinear structures. For the proposed NSSI algorithm, the low-level excitation test is firstly conducted to obtain the transfer matrix in the linear response formula. Then, the obtained transfer matrix is used in the high-level excitation test to calculate the nonlinear response part by the proposed nonlinear separation strategy, and the subspace algorithm is utilized to identify the nonlinear parameter on the modified state-space model including only the nonlinear part. The proposed NSSI algorithm can reduce the coupling error caused by simultaneously processing both the large number part (corresponding to the linear part) and small number part (corresponding to the nonlinear part) in the traditional nonlinear subspace identification (NSI) algorithm. At last, two numerical experiments are given to validate the effectiveness of the developed novel nonlinear identification method. Furthermore, some influence factors are discussed to show the stability of the identification algorithm, and some comparisons between the proposed NSSI method and traditional NSI method are also conducted to demonstrate the advantages of the novel method. [ABSTRACT FROM AUTHOR]

Anesthesia/surgery could be associated with cognitive impairment and Alzheimer’s disease neuropathogenesis. However, whether surgery under different anesthetics has different effects on cognitive function remains largely unknown. We therefore set out to compare effects of anesthetic isoflurane or desflurane plus surgery on cognitive function and hippocampus levels of synaptic marker (postsynaptic density-95 and synaptophysin) and ATP. Five-month-old AD Transgenic (Tg) (FAD5X) and wild-type male mice received isoflurane or desflurane plus abdominal surgery. We assessed cognitive function in Barnes maze and measured hippocampus levels of postsynaptic density-95, synaptophysin, and ATP in the mice. We determined whether vitamin K2 could mitigate these anesthesia/surgery-induced changes. Isoflurane, but not desflurane, plus surgery increased escape latency and escape distance in Barnes maze probe test and reduced postsynaptic density-95, synaptophysin, and ATP levels as compared to control condition in AD Tg mice. Vitamin K2 attenuated the anesthesia/surgery-induced changes in the AD Tg mice. These findings suggest that isoflurane, but not desflurane, plus surgery might induce cognitive impairment via causing brain energy deficits. Pending confirmative studies in both animals and humans suggest desflurane could be a better choice for AD patients when surgery is needed. Moreover, vitamin K2 could treat cognitive deficiency associated with anesthesia and surgery. [ABSTRACT FROM AUTHOR]