Multiphysics based Modal and Harmonic Analysis of Axial Turbines

Design and analysis of microelectromechanical system based displacement amplification mechanism (MDAM) using analytical and finite element method is presented in this paper. The mechanism consists of side masses, microflexures, and microhinges with one end constrained and the other free. The MDAM acts as a displacement amplification device in a direction perpendicular to the applied displacement direction. The mechanism is modeled and analyzed using the Kane’s approach for solving kinematics, which is then used with Castigliano’s approach to develop a modified kinetic model. Modal and dynamic analyses of the mechanism are carried out to predict the natural frequencies and behavior of mechanism under application of dynamic loads. The extended finite element method (XFEM-using commercial software IntelliSuite®) is used for validation of mathematical models developed. Kinematic sensitivity and performance analysis of the proposed mechanism is carried out to predict the behavior of MDAM. Analyses results demonstrate the viability of mechanism as a displacement amplification device. An amplification factor of 10 is achieved. Effect of different performance parameters like width, length, angle, and thickness of flexures upon the output force and displacement is also part of this research work. Results predicted by analytical model and numerical simulations were found to be in close agreement. The MDAM can be used independently or in combination with other compliant mechanisms to amplify displacements. This amplification mechanism can be integrated with any conventional actuation as well as sensing mechanism in a microsystem where amplified displacement is desired for improved sensitivity and performance.

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

Effect of Dynamic Loading on the Transport of Solutes into Agarose Hydrogels

Prediction of corrosion based damages in turbine blades using modal and harmonic analyses

BackgroundFor implant-supported hybrid prostheses, high mastication forces and reduced acrylic resin thickness over a metal substructure often cause failures arising from tooth or resin fractures. To assay fracture resistance of artificial teeth and resin in implant-supported hybrid prostheses in relation to the titanium structure and retention design supporting teeth.Material and Methods40 specimens bearing incisors were divided into four groups according to the titanium structure supporting the teeth and the type of load force applied: Group I (Control; n=10): Application of static loading to ten incisors set over a metal structure with internal retention. Group II (Control; n=10): Application of static loading to ten incisors set over a metal structure with external retention. The remaining study specimens (n=20) were subjected to 120,000 masticatory and thermal cycles in a chewing simulator. Afterwards, static loading was applied until the point of fracture using an Instron machine. Group III (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with internal retention. Group IV (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with external retention. Data obtained for the four groups was analyzed and compared, determining the type of fracture (cohesive or adhesive) using a reflected light microscope.ResultsStatistical analysis confirmed that there were significant differences in fracture resistance between the four groups. External retention was found to have more fracture resistance than the internal retention.ConclusionsHybrid prostheses with titanium substructures and external retention obtained significantly better results than samples with internal retention. Key words:Chewing simulator, thermocycler, fatigue, implant-supported hybrid prosthesis, acrylic teeth, fracture, metal structure design.

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 structural design for safety and durability, the primary concern is to reduce structural fatigue damages due to random dynamic loadings during the service life of locomotive vehicle system. Rolling stocks is facing new sever safety problems, such as bogie frame structure components fracture and safety-based design optimization to durability of locomotive. The objective of the current research is to find the most efficient approach to predict structure safety with Multi-Body Simulation (MBS) and Finite Element Method (FEM). The method is implemented to evaluate bogie frame fatigue damages under dynamic stochastic loadings. The time varying boundary conditions and dynamic load history acting on the large structure can be evaluated by applying the Multi-body Simulation technique in software SIMPACK. Stress/strain analysis technology with software ANSYS yields the danger stresses in the critical locations of the structure depending on the unite loads. And modal analysis is used to determine frequencies and mode shapes of structure. Based on these danger stresses distribution and dynamic load time history, fatigue life can be estimated with Palmgren-Miner theory. The standard time history method involves stress or strain cycle counting, damage prediction, and finally life estimation in Software FE-Fatigue with factor of safety technology.

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.

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.

IEC 61400-2 establishes the Simplified Load Method for designing low-power wind turbine blades without considering dynamic loads in the simplified load methodology. This paper analyzes the load hypotheses established by the standard, also considering the natural frequencies in a 900 W blade. The research methodology begins with the design parameters, the application of the BEM Method, and the use of the QBlade software. Then, the load hypotheses of the standard are defined. Finally, the structural design and the modal and structural analysis of the blade were conducted using FEM-based software. The results show that the minimum participation factors are found on the z-axis and the maximum on the x- and y-axis, and their magnitudes decrease when the natural frequency increases. In general, the principal maximum stresses are located in the middle section of the blade, in the external fiberglass layer, both on the intrados and extrados sides. In conclusion, structural scenarios were established to relate the participation factors of the modal analyses with the load hypotheses. The critical scenarios are at natural frequencies below 280 Hz.

The planetary transmission mechanism is the core component for realizing the maneuverability of high-speed tracked vehicles. The modal test can determine the transmission characteristics of the planetary transmission system structure, and can check whether the dynamic characteristics of the planetary transmission system meet the design requirements. It is the basis of studying the dynamic characteristics of planetary transmission mechanism. In this paper, the free mode of the planetary variable speed mechanism is tested by using the free modal test method, and the modal analysis is carried out by using the finite element method. The results show that the vibration modes of the planetary variable speed mechanism are consistent with the results of finite element simulation, and the deviation between the measured modal frequency and the simulated modal frequency is less than 2%. The modal test provides the basis for the verification of the structural dynamic model and the dynamic coupling analysis of the planetary transmission system.

Modal and Harmonic Response Analysis of Key Components of Ditch Device Based on ANSYS

We theoretically investigate a new type of piezoelectric actuator with tubular interdigitated electrodes. A partial model is adopted due to the axial symmetry of the actuator, which is divided into non-overlapping opposing electrode pairs on the center plane of the branch electrode. We present a finite element model of actuator and analyze its static-dynamic properties by using the commercially available finite element software ABAQUS. The length-to-diameter ratio of the tubular actuator can be as larger as necessary, so we are more concerned with the axial mechanical properties of the actuator. Thus we studied the influence of the electrode’s shape and structure size on the clamping stress and free strain of the partial models. We also analyzed an ordinary piezoelectric model of the same size. We demonstrated that the partial model displayed significantly improved axial performance over the ordinary one. The axial stress of the partial model can reach 2.75 times that of the ordinary one, and the axial free strain can reach 1.55 times that of the ordinary one. According to the results of the static analysis, appropriate electrodes and structural parameters were selected to establish a tubular actuator model, with which modal and harmonic response analysis were performed. A modal analysis was used to obtain the frequencies and the shapes of the axial vibration. Each pair of electrodes is shunted to a sinusoidal varying voltage. Using the results of the harmonic response analysis, we obtained the actuator’s axial resonance curve.

In the history of civil engineering, the structures were usually designed considering only static load factor. Later due to research in the civil engineering field, it was explored that the structures are also acted upon by several other loads which included seismic loads, wind loads, snow loads and many others depending upon the dimensions of the structure, location of the structure, type of the ground profile, etc. Hence this brought in the process of analyzing a structure for different types of loads and designing the structure for the critical load case of which dynamic load is considered as one of the important load for which the structure should be analyzed and designed. The main aim of this research work is to investigate the seismic performance of a multistoried reinforced concrete moment resisting framed building under static and dynamic loading as per Bangladesh National Building Code (BNBC, 2006). Static seismic load has been applied to the structure according to Equivalent static force (ESF) method. On the other hand, response spectrum (RS) method has been performed for the application of dynamic loading. The present study focuses on investigating the variation of storey-displacement and storey drift for each storey, base shear, bending moments and shear forces in columns at different storey level. Finally, a comparative study has been carried out between static and dynamic analysis. Based on computing modeling output data, it has been found that the base shear obtained from RS analysis is less compared to ESF method. Maximum storey-displacement obtained from dynamic RS analysis is about 78% of that of static analysis. At the same time, in case of maximum bending moment in an interior column, the dynamic value is approximately 87% of the static value.

All the forces in the real-world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are usually utilized with dynamic factors. Static loads are especially exploited well in structural optimization where many analyses are carried out. However, the dynamic factors are not determined logically. Therefore, structural engineers often come up with unreliable solutions. An analytical method based on modal analysis is proposed for the transformation of dynamic loads into Equivalent Static Loads (ESLs). The ESLs are calculated to generate an identical displacement field with that from dynamic loads at a certain time. The process is derived and evaluated mathematically by using the modal analysis. Since the exact solution is extremely expensive, some approximation methods are proposed. Error analyses have been conducted for the approximation methods. Standard examples for structural design are selected and solved by the proposed method. Applications of the method to structural optimization are discussed. Copyright © John Wiley & Sons, Ltd.