This paper proposes intermittent feed high-speed grinding, which shows considerable advantages in terms of reducing grinding temperature, relieving grinding wheel blockage and improving workpiece surface integrity. In this grinding, the continuous feed mode of the workpiece is changed into the normal feed + fast retreat reciprocating feed mode by a fast linear feed worktable. By reasonably setting the normal feed distance of single grinding, the action time of the grinding wheel and workpiece is reduced, so that the grinding heat transfer process does not reach a stable state, reducing the grinding temperature during single grinding. Besides this, the surface temperature is cooled to nearly room temperature and the grinding wheel is flushed by the timely retreating of the grinding wheel to allow the grinding fluid to enter the grinding zone fully, which greatly reduces the phenomenon of heat accumulation and grinding wheel loading. An intermittent feed high-speed grinding experiment on Ti-6Al-4V (TC4) titanium alloy was systematically carried out, and the influence of the grinding parameters on grinding force and grinding temperature was deeply analyzed. The instantaneous grinding temperature field and thermal stress field of TC4 titanium alloy in intermittent feed high-speed grinding were constructed with the finite element method. The surface morphology of the grinding wheel and TC4 titanium alloy specimens after intermittent feed grinding were analyzed and were compared with those after traditional continuous grinding. It was found that the curves of the grinding force and temperature varied with time in the process of machining, consisting of many “pulse” peaks. Under the same grinding parameters, the magnitude of the grinding force is the same as that of continuous grinding. In a certain range, the grinding temperature is greatly affected by the single feed distance and the interval time. The numerical simulation results are in good agreement with the experimental results, and the error is controlled within 12%. Compared with traditional high-speed grinding, under the same process parameters, the grinding temperature is greatly reduced, the surface integrity of the workpiece is better, and the clogging of the grinding wheel is greatly reduced.

This paper presents a simplified model of misaligned-installing matched bearings, which is always constituted by two angular contact bearings in machine tools. Aiming at the effect of parallel misalignment arising in practical installing between two matched bearings, the nonlinear restoring force is derived and a matched bearings-rotor system model is established with Timoshenko elements. The Continued-Poincare–Newton–Floquet method is employed to analyze the global nonlinear characteristics with a varying clearance. Compared with the normally installed matched bearings-rotor system, it can be found that the amount of misalignment plays an important factor both on the global stability and vibration amplitude for a misaligned matched bearings-rotor system. The broadest unstable speed region always arise while the amount of misalignment equals to the initial clearance, and a slightly larger misalignment than the initial clearance can easily help the system from unstable dynamic behavior to periodic behavior. Meanwhile, a horizontal increasing misalignment will mainly affect the horizontal dynamic response by the way of magnifying and right shifting the vibration amplitude peak on speed axis obviously, but do a slight opposite effect on vertical normally installed direction. The results show that a proper amount of misalignment may be beneficial for the dynamic characteristic for the matched bearings-rotor system.

The rotor system supported by rolling bearings usually provides a resonance effect due to the nonlinearity of bearings. In this paper, the causes of these anomalous resonance effects are discussed by establishing coupling dynamic model of the flexible rotor-roller bearings system. The 4-degrees of freedom (DOF) Timoshenko finite element and the free interface modal synthesis technique are used to model the elastic rotor. Then, a piece-wise flexible rotor model coupling with a 5-DOF dynamic bearing model is obtained by fixing the inner race to rotor. And waterfall plots are mainly obtained using the method of adaptive Runge-Kutta. Comparisons are made between the simulated response of the rotor-simplified bearing and rotor-bearing coupling models. Firstly, the vibration of cage can cause supercritical anomaly vibration except for the subcritical vibration induced by the variable compliance vibration. Secondly, the vibration amplitude of the coupling model is lower than the rotor-nonlinear springs model.