Analysis and Research on the Modal Experiment of Series-Parallel Hybrid Grinding and Polishing Machine
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In order to improve the dynamic performance of the grinding machine and improve the machining precision of the machine tool, a modal experiment is conducted on the complete machine and main sub-structures of the series-parallel hybrid grinding and polishing machine tool according to the basic theory of experimental modal analysis. Also, hammer impulse excitation and varied-time-based sampling methods are adopted to perform experimental modal analysis. Meanwhile, the eigensystem realization algorithm (ERA) is utilized to identify modal parameters, so that the low-order natural frequency, damping ratio and modal shape of the complete machine and its main substructures can be obtained. Based on the analysis of frequency and vibration mode, the beam is a weak link of the machine tool, while an approach to improve the dynamic characteristics of the machine tool structure is proposed to provide a basis for the optimized design of dynamics.Keywords:
Machine tool
Natural frequency
Hammer
Modal analysis is the study of dynamic characteristic of structures induced by vibrational excitation. Under modal excitation, three important parameters namely natural frequency, damping ratio and mode shape associated with the structural properties are acquired. This paper presents an experimental investigation of glass by experimental modal analysis. The specimen is excited by an impact hammer to perform resonant vibration where the characteristics of the resonance are acquired. One most important characteristic is the natural frequency where it is known that different material having undergone resonant vibration exhibit different specific natural frequencies to it. The natural frequencies are used as the parameters of determining the structural properties of the glass. The modal analysis is done using the LMS instruments and software where Frequency Response Function (FRF) measurement technique is employed in determining the natural frequencies. The structural properties are established based on the obtained natural frequencies and geometries of the materials using the expression from available literature. The results are then compared with the theoretical values for verification.
Natural frequency
Characterization
Damping ratio
Hammer
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A number of different structures in industrial facilities are installed on supports. There is the case that the damage occurs by the coupled vibration. The response magnification is obtained from the modal natural frequency and the modal damping ratio of the coupled system in the seismic design. Therefore, the modal natural frequency and the modal damping ratio of the coupled system are required. The natural frequency and the damping ratio of the support and the structure are abtained during the initial design process or by a shaking test. However, the modal natural frequency and the modal damping ratio of the coupled system are not easily obtained. The modal natural frequency of the coupled system can be calculated from theoretical equation, but the modal damping ratio cannot be easily calculated. In the present study, an equation to calculate the modal damping ratio of the coupled system with classic damping is presented. In addition, a simple equation to calculate the modal damping ratio with a non-classic damping system is proposed. This equation is evaluated theoretically. The proposed equation is useful for obtaining the modal damping ratio without performing eigenvalue analysis or a shaking test.
Damping ratio
Natural frequency
Damping torque
Thermoelastic damping
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The quality of machining is dependent on the machine’s dynamic behavior throughout the operating process. Because of the loads or vibration during operation, the rigidity of the machine structure can be reduced. Therefore, the study of advances in the dynamic characteristics has great significance for the development of machine tools, especially for high-speed machines. This paper presents the design and analysis of a rigid gantry structure with a spindle speed in the range of (6.000 ÷ 24.000)rpm, corresponding to the natural frequency of the machine structure more than (100 ÷ 400)Hz. Use CAE (computer-aided engineering) analysis software to analyze the natural frequency of machine structure. The research results show that the machine structure will have good stiffness, high vibration resistance and avoid resonance to achieve the best machining surface. In addition, it is the basis for selection of cutting mode suitable for the machining process in order to improve the reliability and efficiency of work of the machine structure and the accuracy of the processed products.
Machine tool
Natural frequency
Rigidity (electromagnetism)
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Fence (mathematics)
Picketing
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Natural frequency
Damping ratio
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The Modal Punch is a variable length shai? with an impact tip and load cell attached to one end. It is held against the surface of the test structure and struck with a hammer. The force input spectrum of the Modal FTmch is controlled by the combination of the stiffness of the tip on the punch and the hammer that used to strike the punch. Considerations of the force window used with the Modal Punch will be discussed. The application of the Modal Punch to test an automotive axle in its housing will bc described, Sometimes during the course of an impact modal test, the need arises to impact at locations that are inaccessible to a conventional impact hammer. The Modal Punch has been developed to give the test engineer an option to overcome the limitations of this situation. ln the past, uninstmmcntcd punches have beat used out of necessity to impact on these locatmns. Xx punch was struck with an instrumented hammer, and the output of the impact hammer load cell was meawed and assumed to be the force imparted to the structure, However, the force imparted to the structure through the punch is not the same as the striking force. IJnderstanding the differences between these two force chwacteristics is paramount to the need for and proper “se of the Modal Punch.
Hammer
Impact
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With the purpose of realizing the analysis of mechanical structure dynamic characteristics and inhibit vibration and noise, combined with the analysis of a certain type of high speed sewing machines vibration characteristics, we carry on the concrete experimental modal analysis, and compare the results of the experimental modal analysis with the results of spectrum analysis. The analysis results show that the second order natural frequency of the shell is close to two octaves under the normal working speed of sewing machine and it will lead to resonance. Enhancing the structural rigidity and the natural frequency under this modal to avoid resonance frequency is the key to improve vibration resistance of the structure.
Natural frequency
Rigidity (electromagnetism)
Structural Dynamics
Frequency analysis
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Hammer
Repeatability
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A number of different structures in industrial facilities are installed on supports. There is the case that the damage occurs by the coupled vibration. The response magnification is obtained from the modal natural frequency and the modal damping ratio of the coupled system in the seismic design. Therefore, the modal natural frequency and the modal damping ratio of the coupled system are required. The natural frequency and the damping ratio of the support and the structure are obtained during the initial design process or by a shaking test. However, the modal natural frequency and the modal damping ratio of the coupled system are not easily obtained. The modal natural frequency of the coupled system can be calculated from theoretical equation, but the modal damping ratio cannot be easily calculated. In the present study, an equation to calculate the modal damping ratio of the coupled system with classic damping is presented. In addition, a simple equation to calculate the modal damping ratio with a non-classic damping system is proposed. This equation is evaluated both theoretically and experimentally. The proposed equation is useful for obtaining the modal damping ratio without performing eigenvalue analysis or a shaking test.
Damping ratio
Natural frequency
Damping torque
Thermoelastic damping
Magnetic damping
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Citations (7)