Indirect online tool wear monitoring and model-based identification of process-related signal

Tool wear monitoring using vibrations is a complex task, due to various simultaneously occurring vibration sources and due to distortion of the signals acquired. This work investigates the mechanism by which tool wear information is concealed within acquired process-intrinsic vibration signals. Excluding other sources of vibration, such as machine-related, is attempted utilizing process simulations. As a case study, face milling is performed for three different cutting speeds. At first, the resulted simulated wear curves have been compared with experimental ones resulted under the same cutting conditions. Then, a quantification of the effect of tool wear on the acquired signals is presented.

Effect of the Aero-Engine Mounting Stiffness on the Whole Engine Coupling Vibration

A finite element (FE) model of the rotor tester of an aero-engine, having a thin-walled casing structure, mounted with the way of an actual engine, is developed to simulate the intrinsic vibration characteristics under actual engine-mounting condition. First, a modal experiment of the rotor tester for the whole aero-engine is conducted, and the FE model is modified and validated based on the modal experimental results. Second, the first three orders of natural frequencies and the modal shapes are evaluated using the modified FE model under three different types of mounting stiffness, namely, a fixed mounting boundary, a free mounting boundary, and a flexible mounting boundary. Subsequently, the influences of the mounting stiffness on the coupling vibration of the rotor and stator are studied via a new rotor–stator coupling factor, which is proposed in this study. The results show that the higher the rotor–stator coupling degree of the modal shape, the greater the influence of the mounting condition on the modal shape. Moreover, the influence of the mounting stiffness on the rotor–stator coupling degree is nonlinear. The coupling phenomena of the rotor and stator exist in many modal shapes of actual large turbofan engines, and the effect of mounting stiffness on the rotor–stator coupling cannot be ignored. Hence, the mounting stiffness needs to be considered carefully while modeling the whole aero-engine and simulating the dynamic characteristics of the whole aero-engine.

Criteria of Equality of Modal Frequency of Micromechanical Gyroscopes-Accelerometers Sensitive Elements

<p class="zhengwen"><span lang="EN-GB">In this work the topology of the integrated micromechanical sensor of LL-type is developed. Using the condition of equality of modal frequencies of sensitive elements of the micromechanical sensor in both modes along the one axis the criterion of the coincidence is obtained, the criterion of modal frequencies of sensitive elements of the micromechanical sensor in a sense mode along the two axis is obtained, dependences of the ratio of beam length on thickness of a structural layer are showed, the results of numerical simulation of modal frequencies of the micromechanical sensor sensitive element in a drive mode or a sense mode is obtained using the criterion. Using the criterion, it is possible to achieve coincidence of intrinsic vibration frequencies of a sensitive element in a sense mode that provides the same sensitivity to the angular velocities. Coincidence of frequency of forced vibrations in a drive mode with vibration frequencies of a sense mode along both axis of sensitivity can be achieved by using electrostatic elasticity.</span></p>

The Frequency-Domain Analysis of the Rheological Data Acquired with Multi-Function and All-Electric Rheometer

The key parts of multi-function and all-electric rheometer (MAR) designed by the authors were introduced. The data processing method based on frequency-domain analysis were established. Intrinsic vibration displacement is defined to eliminate the effect of steady velocity displacement and extract the useful information of vibration displacement. The actual frequency, amplitude and phase of the superimposed vibration displacement and the entrance pressure were obtained by the frequency-domain analysis of the intrinsic vibration displacement and the entrance pressure. The control precision of the superimposed vibration displacement frequency and amplitude of MAR proved to be high. The direct current component of entrance pressure can be seen as the mean entrance pressure which stands for the flow resistance. The study of mean entrance pressure is useful in discovering the energy consumption mechanism of the polymer processing introduced vibration energy. Loss angle can be calculate according to the phase of entrance pressure and superimposed vibration displacement. The higher order harmonic of the entrance pressure can be used to characterize the nonlinear viscoelasticity of polymer melts. The factors which depend on the shear rate and influence the viscoelasitic properties can be studied by test the loss angle based on MAR.

Loss Angle Testing of Polymer Melts at High Shear Rate

Theoretical and experimental study of loss angle of polymer melts at high shear rate was done based on multi-function and all-electric rheometer (MAR) designed by the authors. The phase difference of the dynamic components of shear strain and shear stress at the capillary wall proved to be as same as the phase difference of superimposed vibration displacement and the entrance pressure. In order to get the loss angle, the intrinsic vibration displacement was defined and original signal was transformed from time domain representation to frequency domain representation by DFT. The experiment results show that the loss angle increases greatly with the increase of the superimposed vibration displacement frequency. It indicates that the viscous losses increase while the elastic properties decrease with the increase of the superimposed vibration displacement frequency. The loss angle didnt change notably with the increase of the piston steady velocity and the superimposed vibration displacement amplitude. This indicates that the viscoelastic properties keep consistence when the shear rate and piston amplitude changes.