The Computational Method of Estimating Vibration Stress Levels for GTE Compressor Blades

At present, the process of designing a GTE involves a large amount of computational modeling. With the help of computational modeling, it is possible to predict a behavior of an engine part during engine operations before conducting experimental studies. For example, the numerical dynamic behavior analysis of compressor blades and prediction of dynamic stress levels during fluctuations in free modes are urgent problems. A high level of dynamic stress in the compressor blades in resonant modes can break a blade and stop an engine. In this paper, we propose a simple vibration stress estimation method for the compressor blades based on the calculation of natural frequencies and vibration forms. The method is based on a comparative analysis and scaling of stresses by the value of the total potential or kinetic energy. This estimation method is valid for local changes in the blade geometry, which do not lead to changes in the natural frequencies and vibration forms of the blades, assuming that the geometry change does not change the level of the aerodynamic excitation of the blade or its damping. At the stage of development or revision of the blade, a large number of variants of the blade geometry needs to be analyzed in order to reduce dynamic stresses. The proposed vibration stress estimation method has shown its high efficiency in developing and refining the geometry of the compressor blade. The vibration stress estimation method was tested using the rotor blade of a high-pressure compressor. As a result of the experimental study of the rotor blade, a high level of vibration stresses exceeding the permissible level was found for natural frequencies and vibration forms. To reduce the vibration stresses, measures were proposed to modify the geometry of the blade. For the modified blade geometry, the vibration stress estimation was performed with a prediction of the vibration stress values based on the manifested vibration forms. In order to verify the estimated vibration stress change, an experimental study of the modified blade was conducted. The vibration stress estimation method for the compressor blades was successfully verified.

Investigation of Twist Waves Distribution along Structurally Nonuniform Yarn

This paper presents the features of yarn structure formation on spinning machine, i.e. yarn twist change when winding. It was considered that the twist distribution was one of the reasons for its decrease along the formed yarn. In this paper, based on analysis of changes in thickness and twist due to axial deformation, we consider a yarn moving at constant speed. Moving dynamics of yarn are studied here by using Euler variables. The correspondences of forward and reverse twist waves’ distribution speeds on presented frequency at various vibration forms are obtained. The parameters of Doppler effect for the waves distributed along the yarn are determined.

Crack modeling of metal rod eigen-frequencies

The paper presents the development of approaches to the crack detection in metal rod structures based on the analysis of the lowest eigen-frequency modes. Full-scale experiments and numerical calculations are carried out, and the obtained results are compared. A vibration analyzer is used for full-scale experiments, and numerical calculations are performed by using Autodesk Inventor. With regard to the internal friction, the antinodes of various vibration forms were identified using a specially developed program. The model includes sensors for the the field experiment as masses affecting the frequency-response characteristics. The dependences are obtained for eigen-frequencies in the presence of cracks and for the crack locations. The polynomial dependences of the crack location on the lowest eigen-frequency modes of the rod can be used to analyze the crack position of in cantilever beams.

ACOUSTIC MODELS OF THE MAIN SOURCES OF NOISE OF MULTI-SPINDLE DRILLING WOODWORKING MACHINE

The harmful factors in the woodworking industry include the increased noise level in the workplace. This is especially true when working with multi-spindle drilling woodworking machines. The main sources of noise include the constant speed of drills, the geometric shape of the motor and the body of the cutting units, as well as the pneumatic feed mechanism of the cutting units or workpieces. The article presents a theoretical justification of noise sources, which allowed us to obtain the equation of sound power of noise sources in general form. The acoustic calculation of the main noise sources was performed using the obtained formulas. The obtained acoustic models of the main noise sources showed that the practical calculation of sound pressure levels or sound power is actually reduced to determining the vibration rates on the natural vibration forms of the sources.

The verification of a piezoelectric vibration-suppression system with a multimode basic RLC shunt circuit and its comparison to a multi-mode current-flowing shunt circuit

One of the modern methods of reducing vibrations of plates and beams is using piezoelectric materials in the form of distributed elements or patches (applied in a passive or an active system). However, for the multimodal response of a structure, there is no possibility to place the actuators in exactly the areas with maximum curvature values for each mode. Additionally, in the case of passive multimodal suppression systems – in which energy is needed to be supplied to the system – there is the necessity to create a complicated electrical circuit. The particular electrical shunts of the circuit are tuned to the specifi c vibration forms which require damping. The main objective of this article is to show the possibility of creating a multimodal vibration suppression system with typical resonant shunts and proposed second slightly modifi ed.

Load test of new European record holder in span length among extradosed type bridges

The article presents acceptance load tests of a newly built extradosed MS-3 bridge located along the national road DK-16 near Ostróda (Poland). The structure features significant dimension in European reference scale. It is a new record holder in span length regarding this distinct bridge category. Its length ranges 206 m. Static and dynamic load tests were performed here. The program was extended by entire structural laser scanning and identification of natural vibration forms.

The Bridge Wind Tunnel Test Based on the Digital Image Correlation Method

Based on mark points on the surface of bridge pneumatic model, adopting the DIC-Digital image correlation method to handle the pictures captured by CCD Video Camera in the high frequency get the displacement values of the mark points in the time series and thus obtaining the vibration forms of the bridge. The fundamental principles of the DIC-Digital image correlation method and its application were introduced in this paper and the reliability and stability of the method was testified by the comparison to the results measured by the laser displacement sensor

Modal Analysis of the Hydraulic Retarder Shell

The 3D model of THB40 hydraulic retarder shell was established which was based on the Pro/E modeling software. The model was simplified and was introduced to ANSYS Workbench as FEA model by ANSYS-Pro/E data interface. The constraints were imposed on the FEA model for the preceding six modal analysis. The former 6 order natural frequencies and the biggest resonance deformation is obtained to determine whether there are some vibration forms which have unfavorable effects on the vehicle and to avoid resonance phenomenon to appear. At the same time, it provides the reference for the further research of the vibration mechanism of the structure and the vibration suppression technique for practical application.