Structural acoustics analysis of automobile parts by using finite element method

The vibrations developed during the work represent one of the main mechanical problems of the electric motors. Their frequencies and levels can cause large damages of different electrical motors parts. This is the reason why even in the design phase it is useful to be known the values of the natural frequencies of the parts. This can be made in two different ways: using modern capabilities of finite element method (FEM) or doing experimental modal analysis. The study developed in the present paper refers to the modal analysis of a three-phase squirrel cage induction of 1.5 kW, for both, for its elements and, for motor and the electric motor as an assembly. The FEM modal analysis was applied using ABAQUS software for assembly of the 7 elements of the motor. The 3D model was developed, mechanical connections being of screw type. The theoretical model was validated by experiments, with impact hammer test method. The validation confirms the assumptions made for the 3D model and the designed model can be use, as example, for other FEM based modal analysis. The natural frequencies obtained both by FEM and experimental method does not overlap on the working frequencies.

In engineering domains, modal analysis is a field that is studied extensively with the goal of better characterizingcomponents or structures. Themodal analysis produces modal parameters, which are essential properties of a system that can be employed for damage identification, vibration analysis, and structural health monitoring. Plated element’s relevance in variousapplications makes it an intriguing vibration study subject. In thisresearch, modal analysis was performed on a square steel plate in free ends condition. This work aimedto provide a complete anatomical description of this complex boundary condition and its implications on modal parameters. Before comparing modal parameters with experimental data, a primary modal analysis was performed using finite element (FE)method. Then experimental analysis was conducted under the operational modal analysis setup (OMA).As the results, six natural frequencies are retrieved and compared amongst the two methods, recording the maximum of 6% percentage difference from the readings. This implied a close values estimated between the methods used. For mode shapes, ninemodes are identified from FE method and discussed according to established free plate vibration studies, while threesimilarly identified modes successfully recognized by using OMA.

BModes is a finite-element code we developed to provide coupled modes for flexible blades, rotating or non-rotating, and for towers, onshore or offshore (supported either on floating platforms or on monopile foundations). Both the blade and the tower allow a tip attachment, which is modeled as a rigid body with mass, six moments of inertia, and a mass centroid that may be offset from the blade or tower axis. Examples of tip attachments are aerodynamic brakes for blades and nacelle-rotor subassemblies for towers. Allowable supports for the tower include tension wires, floating platforms, and shallow-water monopiles with elastic foundation. Coupled modes (implying coupling of flap, lag, axial, and torsion motions) have several applications. Examples are: modeling of major flexible components for modal-based aeroelastic codes such as FAST [1], validation of turbine models using experimental data, modal-based fatigue analysis, and understanding of aeroelastic-stability behavior of turbines. This paper presents verification of the blade modal analysis capability of BModes. Verification begins with simple uniform beams, rotating and non-rotating, and progresses to realistic blades. BModes-computed modes for all models are compared with analytical modes, if possible to obtain, and with modes generated by RCAS [2]. All results, presented in terms of frequencies and mode shapes, show excellent agreement. I. Introduction BModes is a finite-element code that allows high-fidelity modal analysis of a turbine blade or a tower. Both the blade, rotating or non-rotating, and the tower can have arbitrary distribution of structural properties along their length. Both allow tip attachment, which is assumed to be a rigid body with mass, six moments of inertia, and a mass centroid that may be offset from the blade or the tower axis. Examples of tip attachments are aerodynamic brakes for blades and nacelle-rotor subassemblies for towers. In addition, the blade may have precone and an arbitrary pitch-control setting. For the tower, BModes allows three configurations: a land-based tower, an offshore monopile-supported tower, or an offshore floating-platform-supported tower. The land-based tower may optionally have tension support wires. BModes yields coupled modes for both the blade and the tower. A coupled mode implies presence of flexural, axial, and torsion motions in a natural mode of vibration. For the blade, flexural motion means flap and lag bending, whereas for the tower it means fore-aft and side-to-side bending. Knowledge of coupled modes is crucial to several applications. Examples are: modeling of major flexible components for modal-based aeroelastic codes, validation of turbine models using experimental data, modal-based fatigue analysis, and in-depth interpretation of aeroelasticstability behavior of turbines, both onshore and offshore. Obtaining rotating-blade coupled modes involves solving a complex boundary-value problem, and only a few codes rigorously handle this. BModes is accurate because it uses a finite-element approach in conjunction with analytical linearization and a special finite-element assembly that properly captures Coriolis and centrifugal effects. The finite-element method (FEM) is based on a 15- degree of freedom (dof) element with three internal and two boundary nodes. Because BModes is a finite-element based, it has the capability to handle a complex range of boundary conditions. The structural properties along the blade length are specified in terms of the flap bending, lag bending, torsion, and axial stiffness; mass; section moments of inertia; and chordwise offsets of section shear center, tension center, and center-of-mass along the blade. These properties may be obtained from experimental tests, blade manufacturer, or a properties-extractor code, such as PreComp [3] or BPE [4]. Currently, BModes can handle only metallic or

가전분야에서의 전동기 효율향상을 통한 에너지 소비절감 효과는 상당히 크지만 이를 위한 전동기의 설계/해석 기술 확보가 아직은 미흡한 상태이다. 이에 따라 유도형 동기전동기가 제안되었지만, 유도형 동기 전동기는 유도전 동기와 동기전동기의 특성을 동시에 가지고 있어, 해석 및 설계가 쉽지 않다. 따라서 본 논문에서는 기존의 냉장고 압축기용 전동기인 단상유도전동기를 대처할 수 있는 단상 유도형 동기전동기를 이용해 파라미터에 따라 특성이 어떻게 바뀌는가에 대해 서술하였다. 그에 따라 단상유도전동기의 정상상태 특성을 해석하고 제안모델의 성능을 기존모델과 비교하고 실험하여 해석결과의 신뢰성을 검증한다. 또한 본 논문에서는 제안모델의 기존 고정자 형상이나 권선 스팩을 유지하고 회전자의 형상이나 구조만을 변경시켜 성능향상을 도모하였다. 해석방법으로는 전자장 수치 해석적인 방법으로 널리 이용되고 있는 유한요소법(Finite Element Method : FEM)을 이용하였다.

This study presents a novel and efficient modal analysis framework for thick cylindrical structures with complex geometry and material variability, subject to arbitrary boundary conditions. The methodology is applied to an electric motor (e-motor) stator assembly modelled as a thick cylindrical shell incorporating stator teeth, windings, and housing or cooling jacket effects. The model accommodates both continuous and piecewise variations in material properties and thickness. Based on First-Order Shear Deformation Shell Theory (FSDST), it accounts for shear deformation, rotary inertia, and trapezoidal stress distributions, enabling accurate prediction of axial, circumferential, torsional, and bending vibration modes. A segmentation approach is used along the axial direction, with artificial massless springs enforcing continuity and permitting general boundary conditions. Displacement fields are constructed using orthogonal Jacobi polynomials, and the eigenvalue problem is solved via the Rayleigh–Ritz method. Notably, the methodology allows accurate and efficient prediction of axisymmetric (breathing) modes in thick, non-uniform cylindrical shells – a capability rarely addressed in existing literature, despite its importance in Noise, Vibration, and Harshness (NVH) analysis. Validation against Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) on both generic cylindrical shells and a real Permanent Magnet Synchronous Machine (PMSM) stator shows excellent agreement, with natural frequency deviations typically below 5% and highly consistent mode shapes. The framework also achieves over 95% reduction in computational time compared to FEA, establishing it as a highly adaptable and practical tool for vibration analysis in electric motor design and NVH engineering applications.

In this master's thesis work, finite element method limitations are investigated in the dynamic analysis of reinforced panels. The panel was modelled using different meshes in order to show that, depending on the element length (or the number of degree of freedom) used in the model, the model does not properly stand for the real structure. In order to assess experimentally the model, an aluminum reinforced panel was built and, through experimental methods, a modal analysis was carried out. The finite element modelling limits were tested and compared to experimental results regarding mid-frequencies. A comparison between finite element and spectral element methods was carried out for computational cost reduction purposes. Due to uncertainties of some model input parameters, a statistical variation was performed using Monte Carlo and Surface Response methods. Results have shown that, at high frequencies the finite element method is not appropriete for dynamic analysis due to high computational costs in high frequency and it is highly sensitive to small variations of the input parameters.

The handling and control of towed cable and body systems onboard surface ships and submarines presents a significant technical challenge to design engineers in the defense and ocean industries. The current approaches rely heavily on the empirical methods and the time-consuming and costly prototype testing. Computer simulation provides a cost effective way to reduce the high risks associated with the towed cable/body system. However, the current dynamic analysis of towed cables is mostly done by the finite difference (FD) method in stead of the finite element (FE) method that is widely used in almost all engineering fields. This paper presents an alternative FE method to simulate the dynamics of towed cable and body system, in which the large rigid body motion is coupled with small elastic deformation. The newly derived FE method is formulated in terms of element nodal positions, which is different from the existing FE methods that use displacements. The alternative FE method solves for the cable position directly in order to eliminate accumulated numerical errors arising from existing FE methods that solve for displacements first in order to obtain the cable position over very long period of time. The alternative FE formulation is implemented and applied to real applications to demonstrate its robustness by comparing simulation results with the experimental and sea trial data.

Blind-Kriging based natural frequency modeling of industrial Robot

Machine tool vibrations have great impact on machining process. In this paper the dynamic behavior and modal parameters of surface grinding machine is presented. For this purpose, the CAD (computer aided design) model of the surface grinding machine structure is provided in catia and then Natural frequencies and mode shapes of the machine tool structure are carried out through FEM (finite element method) modal analysis under ansys. The model is evaluated and corrected with experimental results by modal testing on surface grinding machine. Finally, the natural frequencies and mode shapes obtained by both experimental and FEM modal analysis are compared. The results of two methods are in widely agreement.

Monitoring of structural vibrations and operational modal analysis are clearly essential to effectively control structural safety and the operational behavior of tidal current turbines. In order to satisfy industrial requirements, generally related to a mass gain problem, hybridization provides an excellent method to improve the breaking strength of composite materials, while keeping adequate mechanical performance for marine renewable energy applications. In this context, this work aims to study the structural modal analysis of a tidal turbine nozzle and the effect of hybrid materials (carbon/Glass) on the natural frequencies and corresponding mode shapes of the three laminates. The modal analysis was calculated by the Finite Element Method using ABAQUS software. According to the results, the stacking sequence has a considerable impact on the natural frequency of the nozzle. Furthermore, it is also found that the resonance effect does not appear for the three laminates under investigation.

The paper presents a finite element model of dual-rotor system with pedestal looseness stemming from loosened bolts. Dynamic model including bearing pedestal looseness is established based on the dual-rotor test rig. Three-degree-of-freedom (DOF) planar rigid motion of loose bearing pedestal is fully considered and collision recovery coefficient is also introduced in the model. Based on the Timoshenko beam elements, using the finite element method, rigid body kinematics, and the Newmark-βalgorithm for numerical simulation, dynamic characteristics of the inner and outer rotors and the bearing pedestal plane rigid body motion under bearing pedestal looseness condition are studied. Meanwhile, the looseness experiments under two different speed combinations are carried out, and the experimental results are basically the same. The simulation results are compared with the experimental results, indicating that vibration displacement waveforms of loosened rotor have “clipping” phenomenon. When the bearing pedestal looseness fault occurs, the inner and outer rotors vibration spectrum not only contains the difference and sum frequency of the two rotors’ fundamental frequency but also contains2Xand3Xcomponent of rotor with loosened support, and so forth; low frequency spectrum is more, containing dividing component, and so forth; the rotor displacement spectrums also contain fewer combination frequency components, and so forth; when one side of the inner rotor bearing pedestal is loosened, the inner rotor axis trajectory is drawn into similar-ellipse shape.

Analytical method for modal analysis of submerged electric motor stator

Numerical analysis and physical consideration of vocal fold vibration by modal analysis

This paper represents a modal analysis of electric motor in electric drive for determining the modal vibration of electric motor by using the modeling, finite element meshing and the computation of modal vibration for electric motor. Electric motor parts are created and assembled in Catia V5 which facilitated the easy assembly of the complex parts. Discretization of electric motor is carried out in hyper mesh as it converts the domain into mesh and easily shows the failure element. Computation of modal vibration is done by using the numerical method. To avoid the resonance rigid body and natural frequencies are calculated at different mode and shown.

A robot hand is used to transport the glass substrate in TFT-LCD manufacturing process. Carbon/epoxy composite is one of the best materials for this kind of robot hand application, due to their lightweight, high stiffness, and good damping characteristics. Major requirement of the robot hand is given as allowable deflection under weight loading of glass substrate and robot hand itself. In this thesis, a carbon/epoxy robot hand was analyzed using finite element method and beam theory to determine the deflection of the hand under the loading that is equivalent to actual weight. Because natural frequency is one of the major interests in robot hand design for TFT-LCD manufacturing process, modal analysis is also conducted using finite element method and beam theory. A robot hand was manufactured, and actual deflection and natural frequency were measured to verify the analysis results and compliance to requirement. The test results showed good agreement with analysis results.