Modal Analysis of High-Speed Face Milling System Based on Composite Structure System Analysis Method

This paper describes the modal analysis of a thick cylinder with both ends free, based on Mindlin's thick plate theory. The equations of vibration of the thick cylinder were derived in consideration of shearing deformation and rotatory inertia, and were simplified and solved under assumption of the axial and circumferential deformations of the neutral cylindrical surface. Except for some low modes, the calculated natural frequencies agreed well with the values obtained by experimental modal analysis and with the modal analysis by use of Finite Element Method. Also, the calculated mode shapes compared well with those obtained by FEM modal analysis.

This study carried out an experimental and numerical modal analysis of the Turkish traditional instrument 'Bendir' by an acoustical excitation source. In experimental modal analysis, Bendir was excited acoustically for specified frequencies and elastic deformations of different areas of Bendir due to the excitation were observed with a laser vibrometer. Using the Fourier series handled gained data, modal analysis was done. The first six natural frequencies obtained experimentally and numerically were compared. In addition, other hits in Bendir, symbolizing three fundamental voices such as 'dum', 'te', 'ke' were used to excite the instrument. As a result, time dependent deformation & velocity data were determined and different responses of Bendir were compared.

As an alternative to operational modal analysis and classical experimental modal analysis (EMA), a novel method was introduced previously, namely impact-synchronous modal analysis (ISMA). The effectiveness ISMA on rotor and structural dynamic systems has been proven in previous literature. More recently, an automated impact device (AID) was introduced which utilized tachometer pulse as initiation signal and its effectiveness on ISMA was proven. An attempt to further enhance this device in term of equipment and cost is then proposed by replacing the tachometer with the in-use tri-axial accelerometer through utilizing the filtered response of cyclic load component as an initiation signal to control the impact device, which is also the primary aim for this study. Prior to modal testing, accuracy of this device is illustrated at desired phase angles of 0 deg, 90 deg, 180 deg, and 270 deg. Subsequently, frequency response function (FRF) estimations obtained for ISMA using enhanced AID has demonstrated the suppression capabilities of this device on disturbances, i.e., reduction of 93.58% at 30 Hz and 57.78% at 60 Hz, resulting in a high correlation for signature assurance criterion (SAC) and cross signature assurance criterion (CSAC). Modal parameters extracted from the EMA and ISMA using impact device are presented and compared, for the first three natural modes of the test rig. It is found that natural frequencies are deviating by less than 6%, whereas modal assurance criterion (MAC) values between the mode shapes of the two tests are found to be above 0.9.

Application of Sherman–Morrison–Woodbury formulas in instantaneous dynamic of peripheral milling for thin-walled component

The dynamic characteristics of a machine tool structure used for machining engineering components at the microscale requires minimising the effects of vibrations. This requires a machine tool to be rigid and to be able to dissipate heat and vibrating waves in a symmetrical fashion. The idea for the structure comes from the structural stability afforded by using a tetrahedral geometry. The tetrahedral structure is a stable structure and it is considered that the geometry could minimise vibrations than conventional machine tool designs. The reason lies in the way that the structure is kinematically balanced. To explore the hypothesis, an experimental modal analysis established the vibration characteristics of the structure and of a conventional machine tool. Modal analysis consisted of measuring the Frequency Response Functions (FRFs) from impact tests to determine the natural frequencies, damping and mode shapes of the machine tool structures. A finite-element model was compared with the experimental data, thus validating the model so that it may be used for modelling future changes to the design of mesomachine tools.

As all experimental procedures, Experimental Modal Analysis (EMA) is subject to a wide range of potential testing and processing errors. The modal identification methods are sensitive to these errors, yielding modal results which are uncertain up to certain error bounds. The question hence is what these error bounds on test data and modal parameters are. In this paper, the studied source of uncertainty is related to the variance (noise) on the Frequency Response Function (FRF) measurements. Under the H1 assumptions and in single-input cases, the FRF variances can be computed from the coherences and the FRFs. In multiple-input cases, some more measurement functions are required. Advanced system identification methods like the Maximum Likelihood Estimator (MLE) and PolyMAX Plus have the possibility to take the uncertainty on the measurement data into account and to propagate the data uncertainty to (modal) parameter uncertainty. This paper will review FRF variance estimation techniques, including some pragmatic approaches. The basic concepts of Maximum Likelihood Estimation and the calculation of confidence bounds will be discussed. Some typical structural testing and modal analysis cases will be used as illustration of the discussed concepts.

MODAL ANALYSIS OF A LIGHTWEIGHT STRUCTURE—INVESTIGATION OF THE EFFECTS OF THE SUPPORTS ON THE STRUCTURAL DYNAMICS

An alternative approach to measure similarity between two deterministic transient signals

Laminated rubber bearing is a significant device found in structures such as bridges and buildings. It is used to isolate the foundation and the superstructure from seismic loads. Since it is made up from a combination of rubbers and steel plates in alternate layers which make the laminated rubber bearing a complex material, the measurements of damping of the laminated rubber bearing is difficult in practice. Damping is a dissipation of energy or energy losses in the vibration of the structure when the structures are excited with external dynamic loading. An accurate value of damping is very important as damping plays a crucial role in fixing the borderline between stability and instability in many structural systems. Therefore, it is essential to determine the accurate value of damping in structural analysis. Finite element and experimental modal analysis is one of the methods that can be used to determine dynamic properties including damping in any structures. Hence, the main objectives of this research are to determine the natural frequencies, mode shapes, Rayleigh’s damping coefficients, α and β and to evaluate the performance of the laminated rubber bearing components i.e. steel and rubber plates using finite element and experimental modal analysis. Based on the finding, the finite element modal analysis with the added Rayleigh’s damping coefficients α and β shows a good agreement with the experimental modal analysis in term of natural frequencies and mode shapes. The value of natural frequencies reduces after the Rayleigh’s damping coefficients are added into the finite element modal analysis and the minimum and maximum displacement are found to be unaffected by the Rayleigh’s damping coefficients for rubber plate. It can be concluded that modal analysis method can be used to estimate the accurate values of damping ratio and to determine the Rayleigh’s damping coefficients α and β as well.

In this paper, construction of finite element analysis based on DEFORMTM 3D four-blade face milling cutter aluminum 6061 cutting, explore the finite element analysis of face milling cutter rotating in a circle cutting of aluminum alloy 6061.Tool types used WC milling cutters, cutting speed, feed rate as fixed process parameters. The study analyzed four rotations of the blade face milling chip formation, effective stress, effective strain and material changes in temperature and tool wear.

Output-only (or operational) modal analysis (OMA) has proven to be a desirable tool for a wide range of applications for identifying dynamic modal parameters while structures are in service. It is especially useful for machine tools because evident changes will occur in dynamic properties between the working state and the static condition. However, the absence of input measurements obstructs OMA from assembling the frequency response function (FRF), which is necessary for many applications. Recently, a random cutting technique was proposed to excite the machine tools in order to extract the dynamic parameters through OMA. The present study is an extension of that work to estimate the FRF of machine tools. In this paper, the random cutting process is modeled to predict the cutting forces according to available information, such as the cutting parameters, the tool geometry, and the workpiece material, which are all known before machining. A function is introduced into the model to evaluate the influence of the variation of spindle speed on the cutting forces. Then, the calculated cutting forces are employed to replace the missing input measurement to estimate the FRF. The proposed method was experimentally validated and showed satisfactory agreement between the measured and estimated results in magnitude, although the phase is not that desirable. Finally, the approximation error of the method was analyzed and some error reduction strategies were presented.

This paper presents an application of the Experimental Acoustic Modal Analysis (AMA) on a vintage 10 M Conn tenor saxophone. This technique originates from the traditional Modal Analysis which is commonly adopted to determine the dynamic behaviour of solid structures. The methodology is based on the measurement of Frequency Response Functions (FRFs) as a ratio of the acoustic pressure, measured by means of a set of microphones positioned along the saxophone body, and the volume velocity produced by an acoustic source and measured at the instrument input. The microphones are housed on the stripped saxophone keys by means of tailored three-dimensional printed adapters. The AMA makes use of the FRFs to extract modal parameters, such as resonance frequencies, loss factors, and mode shapes. These parameters pertain to the cavity modes of the saxophone passive resonator. The analysis has been performed for three different notes (B ♭, B, and C) and for two registers of the instrument in order to show the potential of the technique. Moreover, the influence of the mouthpiece volume on the cavity modes has been shown. The information obtained by AMA can find useful application in the validation of analytical or numerical models of this kind of musical instruments.

This study investigated the dynamic properties of a spherical sandwich composite structure made of carbon fiber face sheets and a Nomex honeycomb core. The structure was produced using the hand lay-up method. The results from Experimental Modal Analysis (EMA) and the numerical model created in ANSYS showed high consistency. The natural frequency difference was only 0.73% for the second mode, with the largest discrepancy of 6.5% was observed in the first mode. These differences are thought to be related to structural variations from the manufacturing process, such as resin distribution, carbon fiber fabric stacking, and air voids and the experimental challenges such as double hit errors, measurement resolutions related to force sensor and accelerometer and environmental noise. The vibration damping capability of the sandwich structure was investigated. Some modes exhibited high damping, while others had relatively lower values. The highest and the lowest damping ratios were obtained as 0.83% for the third mode and 0.23% for the fourth mode. A numerical equivalent model of the structure was created in ANSYS to determine its natural frequencies and vibration modes, confirming its effectiveness in modeling complex structures.

The paper deals with an experimental and a numerical investigation of dynamic properties of the structure. Object of interest is a steel rod with circle section. The modal parameters, such as mode shapes and natural frequencies, are obtained by two different ways: experimentally by using experimental modal analysis and numerically by finite element analysis which were computed in NX Nastran solver. The results from both methods are compared in NX through the correlation function. A relation between measured mode shapes and computed mode shapes is expressed by Modal Assurance Criterion. This process of comparing is appropriate for verification of experimental approaches.

<p>This report consists of experimental and Finite element-based numerical modal analysis of a 3D printed PLA cantilever beam with a nonuniform delamination of 0.5mm, carried out as part of an MEng project. Experimental modal analysis is performed on four different samples of different delamination thicknesses, including the one with a delamination of 0.5mm, to obtain the system's bending fundamental frequency. Numerical analysis, however, is focused and conducted on only the defective specimen with a non-uniform delamination of 0.5mm. In this case, the delamination is sketched with the help of an electronic microscope which takes the images of the delamination zone. These images are then used to plot the non-uniform delamination on the 3D model, focusing on obtaining the model that is as close as possible to the manufactured specimen. The experimental frequencies are subsequently compared with the numerical values obtained from the Finite Element Analysis (FEA) of the 3D model. In numerical analysis, a progressive approach was used to create two sophisticated models referred to as refined and further refined models. The numerical fundamental frequency obtained from these last models are compared with that of the PLA beam with uniform delamination of 0.5mm. It is observed that by applying progressive refinement in the FEM model, the numerical fundamental bending frequency increasingly converges to the experimental one. Appendix A consists of the images taken by the microscope, which show the non-uniform geometry of the delamination zone.</p>