Finite Element Modal Analysis Research Articles

In Situ Testing and Finite Element Analysis of a Discontinuous Mortise and Tenon Stone Bridge Under Natural Excitation

To study the dynamic response of multi-span mortise and tenon stone bridges under natural excitation, a bluestone multi-span stone bridge with a main span of 2.56 m in southern China was taken as the research object. Based on the collected pulsating signals of bridge piers and slabs, the natural frequencies and damping ratios of the main span bridge slab and pier were analyzed using the half-power broadband method (HPBM) and random decrement technique (RDT). Modal analysis was conducted using ANSYS, and the results were compared with those obtained from on-site experiments for further performance analysis. The research results of this article indicate that the natural frequency range of the 2.56-m bridge slab identified by measured signals is 48–49 Hz, and the damping ratio range is 33.33–36.61%. The natural frequency of the central pier is 75–76 Hz, and the damping ratio range is 26.39–27.83%. Through finite element modal analysis, the natural frequency of the bridge slab is 54.401 Hz, with an error of 10.5%. The natural frequency of the overall stone bridge is about 82.2 Hz, with an error of about 8.2%. The validated finite element model was subjected to normal water flow impact and erosion simulation. The results indicate that under erosion with fewer particles and lower flow rates, the upstream pier bottom at the center receives the highest relative erosion mass and displacement per unit area. The bridge deck near the main span also experienced relative displacement. Therefore, in the subsequent protection work, special attention should be paid to these components.

Development and testing of a novel vibratory compaction instrument considering its natural frequency.

This study aims to develop a novel vibratory compaction instrument designed for the preparation of large triaxial soil specimens, offering an efficient alternative to the traditional manual specimen preparation process. However, when the motor frequency closely aligns with the natural frequency of the structure, severe resonance phenomena may occur. This paper employed finite element modal analysis, experimental modal analysis, and operational modal analysis techniques to conduct a multi-objective optimization of the structure, aiming to improve the dynamic characteristics. First, the natural frequency and mode shapes of the vibratory compaction instrument were determined via finite element technology. Subsequently, the optimization of this instrument was conducted by integrating the Kriging surrogate model with the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Finally, the steel column underwent a modal test using impulse stimulation to ascertain its natural frequency, and the stochastic subspace identification (SSI) approach was employed to conduct an operational modal analysis of the vibratory compaction instrument to determine its modal characteristics. The experimental findings corroborated the conclusions obtained from the finite element analysis, validating the precision of the finite element modal analysis and the rationality of the optimized structure. The research results are of significant importance for improving the preparation efficiency of large triaxial specimen, contributing to advancements in soil mechanics testing.

Finite element analysis of anatomic plate fixation for proximal clavicular fractures

To explore establishment and finite element analysis of personalized proximal clavicular anatomical plate screw fixation model. A 40-year-old male healthy volunteer was selected and the finite element analysis modules of 3D reconstruction software Mimics 15.01, Hypermesh 2019 and Abaqus 2020 were used. The finite element model of anatomic plate at the proximal clavicle was established, and a vertical load of 250 N was applied to the distal end of long axis of clavicle about 15 mm, then the overall structure, plate and screw displacement cloud image, Mises stress distribution were observed. The displacement distribution of the overall structure shows the maximum displacement was distributed on the distal clavicle. Under the four conditions of normal upper limb weight, longitudinal clavicle fracture, oblique fracture and shoulder impact violence during fall, longitudinal clavicle fracture and oblique fracture, the maximum displacement were 1.04 mm, 1.03 mm, 1.35 mm and 1.33 mm, respectively. The displacement cloud map of titanium alloy steel plate showed the largest displacement was distributed near the distal clavicular bone, and the maximum displacement were 0.89 mm, 0.88 mm, 1.10 mm and 1.09 mm, respectively. The displacement cloud map of titanium alloy screw showed the largest displacement was distributed at the root of the distal screw, and the maximum displacement were 0.88 mm, 0.87 mm, 1.08 mm and 1.06 mm, respectively. Mises stress distribution showed the maximum stress was mainly distributed on titanium alloy plates and screws, and the stress on the clavicle was very small. Mises stress distribution cloud showed the maximum Mises stress was distributed at the second row of screw holes near the clavicle, and the maximum Mises stress were 673.1, 678.1, 648.5, 654.4 MPa, respectively. The maximum stresses of titanium alloy screws were 414.5, 417.4, 415.8 and 419.7 MPa, respectively. The biomechanical changes of personalized proximal clavicular anatomical plates are demonstrated by using 3D finite element method to provide biomechanical data for personalized proximal clavicular anatomical plates.

Reliability polynomial chaos metamodel for the dynamic behaviour of reinforced concrete bridges

The approximation of complex engineering problems and mathematical regressions serves as the authentic inspiration behind the artificial intelligence metamodeling methods. Among these methods, polynomial chaos expansion, along with artificial neural networks, has emerged at the forefront and become the most practical technique. Previous studies have highlighted their robust capabilities in solving complex problems and their wide utilization across numerous applications, particularly in structural analysis, optimization design problems, and predictive models of uncertainty outcomes. The aim of this article is to present a methodology that introduces their implementation of for structural engineering, primarily focusing on reinforced concrete bridges. The proposed approach consists of demonstrating the applicability of the polynomial chaos to evaluate the dynamic behavior of two-span reinforced concrete bridges through a predictive model of natural vibration properties for eigenvalues modal analysis. Subsequently, response spectral method is conducted according to the Moroccan guide for bridge seismic design and the prescription of the EUROCODE 8 within the context of reliability assessment using Monte Carlo simulation. The efficacy of the proposed approach is illustrated by a comparison between the predicted vibration properties and the resulting values obtained through finite element modal analysis and artificial neural networks. The polynomial chaos process is based on a collected dataset of multiple reinforced concrete bridges sourced from technical studies offices and the Regional Administration of the East, affiliated with the Moroccan Ministry of Equipment and Water. Finally, this work contributes to the field by enhancing predictive modeling and reliability evaluation for bridge engineering using artificial intelligence metamodels.

Natural frequency informed finite element modal analysis method for estimating elastic properties of solid materials

Natural frequency informed finite element modal analysis method for estimating elastic properties of solid materials

Experimental and numerical analyses on the modal behaviour of an aluminium alloy sheet

Abstract The study of modal behaviour for vehicle body panels represents a field of interest for automotive engineering, having a major influence on automotive comfort, with respect to vehicle noise, vibration and harshness, but also concerning the durability of vehicle body. The investigation of natural frequencies and vibration mode shapes is crucial in the design phase, because essential information can be obtained concerning the behaviour of the components in dynamic conditions. The current paper focuses on the investigation of vibration modes and frequency response function on an aluminium alloy sheet. The aim of the paper is to perform the study of modal behaviour both experimentally and theoretically, through measurements using the impact hammer method and respectively through finite element analysis. The CAD model of the aluminium alloy sheet has been developed in Catia V5 environment in view of elaborating the finite element model, which has been used for investigation of modal behaviour, taking into account the case of free vibrations. Through the modal finite element analysis performed in Ansys Workbench, the natural frequencies of the aluminium alloy sheet, as well as the corresponding mode shapes have been obtained. Experiments have been performed on an aluminium alloy sheet, mounted on an elastic support with low natural frequency. The impact hammer method has been used for obtaining the natural frequencies, through frequency analysis of accelerations measured with two piezoelectric accelerometers mounted on the aluminium alloy sheet. The frequency response function has been computed from the response acceleration measured on the aluminium alloy sheet and the impact force measured using the force transducer of the impact hammer. Virtual instruments have been developed in LabVIEW environment for data acquisition, time domain and frequency analysis, as well as for determining the frequency response function using the measured signals. The natural frequencies obtained from the finite element analyses have been compared to the results of measurements and very good similarities have been ascertained. The experimental investigation of modal behaviour contributed to the validation of the finite element model, but further research is required to investigate the possibilities of improving the modal behaviour of the aluminium alloy sheet.

Design optimization and experimental verification of ultrasonic stack for micro hot embossing of polymers

Ultrasonic micro hot embossing (UMHE) is a prominent technique used in numerous sectors to produce micro parts since it is cheaper, faster, and more accurate. Amplitude uniformity is a crucial parameter in UMHE in order to manufacture micro parts with accurate dimensions and high-quality surfaces, even though limited research has been conducted on the uniformity of ultrasonic amplitude at the horn face during the embossing process. This paper presents an experimental and numerical study for designing an ultrasonic transducer and horn tailored to the micro hot embossing of polymer micro parts. A finite element (FE) simulation model combined with the Taguchi method has been developed to optimize the horn geometry and maximum amplitude uniformity. The Taguchi orthogonal array of 25 design runs has been generated and simulated using the developed FE modal analysis model, and then the optimized geometry was used to fabricate the horn. Applied torque and operating time calibrate and evaluate the transducer vibration characteristics. Experimental and simulation results revealed that the fabricated ultrasonic transducer and horn of a straight microfeature has a natural frequency of 28.8 kHz and has an 11 µm average peak-to-peak amplitude with 0.963 amplitude homogeneity along the microfeature face. The achieved frequency separation was greater than 0.85 kHz, whereas the gain ratio was 1.2. The design methodology developed in this paper showed great potential and has been numerically validated for various microfeature shapes across the horn face. Consequently, it can be applied to various ultrasonic applications beyond UMHE.

Determining stop band locations in periodic waveguides by conventional finite element modal analysis

Determining stop band locations in periodic waveguides by conventional finite element modal analysis

Structural Behaviour and Strength Evaluation of a Venetian Church through Finite-Element Analysis

The evaluation of the structural behaviour of a masonry Venetian church with a pointed barrel vault is presented in this paper through an analysis following the necessary steps of a monument study. With a detailed geometric model and material estimation, the finite-element method is used to investigate the influence of specific structural parts of the structure, like masonry buttresses and wall connections, on the structural behaviour. The operational modal analysis is used to identify the structure dynamically. The comparison of the eigenfrequencies, which are estimated by in situ measurements and finite-element modal analysis, is used to perform a model identification. The response spectrum analysis, the static analysis after the subsistence of some parts following strengthening proposals, and the transient analysis of specific seismic excitations are used for the evaluation of the structural behaviour. The purpose of the work is to highlight the need for an interdisciplinary approach to the study of a monumental complex structure, regardless of its scale. The coexistence of structural elements of different stiffnesses, such as vaults, elongated walls, buttresses, transverse walls with pediment and belfry, as well as the concha, affects the mechanical behaviour and the pathology of the structure, which is difficult to study with simplifying models. From the analysis, it is concluded that subsidence problems, combined with seismic actions, lead to the cracking of the masonry, while the existence of buttresses limits the extension of the damage and contributes to the stabilization of the structure.

Random Vibration Characteristics and Vibration Suppression of an Aero-engine Inlet Rake Fabricated by Laser Powder Bed Fusion

The inlet rake is generally installed in aero-engine during rig and flight test for flow field pressure and temperature measuring. There are usually complex flow channels and pipelines inside the rake to extract air flow to the sensor. The laser powder bed fusion(L-PBF) technique was applied in rake fabrication recently due to its progressive layer stacking molding procedure. However, the difference of thermoforming method between L-PBF and the traditional casting process leads to the mechanical property disparities of the material. In this work, the determinants of random vibration response of the inlet rake manufactured by L-PBF with GH4169 powder were studied individually. The stiffness and yield property of the material were investigated by the specimen tensile test, which indicates higher elasticity modulus and yield stress comparing to the ones by castling or forging process. The damping ratio of the inlet rake was obtained through stress attenuation characteristics experiment and analysis under stepwise excitation. The stress distribution and resonance margin of the inlet rake under the aero-engine random vibration spectrum were simulated by finite element modal and random vibration analysis. The results showed that the damping ratio of the L-PBF inlet rake is much smaller than engineering recommendations, and the resonance margin is insufficient. Thus, the stress level of the inlet rake was very high, especially in the blade root section, quite close to the yield limit of the material. To solve this problem, the vibration suppression methods of the inlet rake were studied from the perspective of structural design optimization and damping ratio increasing. Through the rational design of the resonance margin and addition of vibration damping structure, the vibration stress of inlet rake was significantly suppressed. As the result, the rake was installed in the inlet during the aero-engine rig test for flow field pressure and temperature measurement successfully.

Dynamic performance enhancement of machining center with epoxy granite base: Experiments and finite element simulations

Epoxy granite (EG) is used for machine building applications owing to excellent dynamic properties compared to cast iron (CI). Steel is preferred to reinforce with EG to improve the static stiffness of structures. The effects of addition of steel content on stiffness and damping properties of EG composite were assessed through a specimen level study. Subsequently, the base, which is a primary structure that affects the dynamics of the vertical machining center (VMC) was taken up for investigation. The novelty of the present work is the development of scaled down model of EG base with optimum reinforcement ratio to improve the dynamic response of VMC without compromising the static rigidity of the existing CI base. An experimental study was carried out to validate the assumption made in numerical analysis that EG is isotropic and homogeneous. The results of similitude relations revealed that the EG base exhibited sixteen times higher damping compared to CI base. The influence of EG base on the overall dynamics of VMC was assessed by performing pre-stressed finite element modal analysis and harmonic analysis. Upto seven-fold improvements in directional stiffnesses of VMC with the EG base were observed compared to VMC with CI base. The results of stability lobe diagram revealed a three-fold improvement in material removal rate for VMC with EG base compared to VMC with CI base. Thus, the proposed steel reinforced configuration of EG base has demonstrated a better dynamic performance of VMC without compromising static rigidity.

Integrating a Physical Model with Multi-Objective Optimization for the Design of Optical Angle Nano-Positioning Mechanism

In light of recent advancements in synchrotron radiation technology and nano-technology, there has been a marked increase in the need for ultra-precision nano-positioning mechanisms. This paper presents a method that integrates physical models with multi-objective optimization for developing an optical angle nano-positioning mechanism. We begin by examining the actual motion law of the mechanism, based on kinematic principles. The outcomes from this kinematic analysis facilitate a static analysis of the flexible hinge, identified as a critical component of the mechanism. Subsequently, we establish a dynamic model for the entire mechanism. By employing the physical model as a base and combining it with the optimization algorithm, we identify the optimal design parameters for the mechanism. The design achieves a resolution of 50 nrad and meets the specified requirements. The first-order inherent frequency of the mechanism is approximately 43.75 Hz. There is a discrepancy of 2.63% from the finite element modal analysis results and a 3.33% difference from the theoretical analysis results, validating the reliability of the design method proposed in this study.

Optimization of PMSM for EV based on Vibration and Noise Suppression

The key to the suppression of vibration and noise for PMSM is the optimization of electromagnetic excitation force. The method of motor body optimization can effectively reduce the radial excitation force of the motor, so as to suppress the vibration and noise of the motor. Firstly, the stator structure of the motor is optimized with V-shape skew slot based on the analytical modeling of the radial electromagnetic excitation force of the motor. Then, the structural parameters of the motor that affect the electromagnetic excitation force of the motor are determined, and the average torque, torque ripple and radial electromagnetic excitation force generated by tangential electromagnetic excitation force are taken as the optimization objectives. The sensitivity analysis and classification of the structural parameters of the motor are carried out. The multi-objective genetic algorithm and response surface method are combined to optimize the structural parameters of the motor. Finally, the finite element analysis, modal analysis, multi-speed vibration and noise analysis of the optimized motor are done. The performance comparisons before and after optimization have proved that the peak of equivalent sound power level have decreased by 8.65% after the optimization of V-shaped skewed slot structure. After the optimization of structural parameters, the power level of permanent magnet synchronous motor has been reduced by 9.22%. For the vibration noise caused by resonance and the main frequency of vibration noise harmonics, the suppression effects are also better than those of V-shape skewed slots optimization, and the ERPL values are reduced by 9.22% and 10.12%, respectively, in two cases. The results show that the vibration and noise of permanent magnet synchronous motor are effectively suppressed.

Seeing the piano sound Exploration on utilizing finite element analysis to visualize piano sound

The study aims to provide a way for impaired people to learn music better through music visualization. We established a relationship between piano key frequencies and Chladni patterns. Firstly, we performed modal analysis simulations using ANSYS, covering the full range of excitable modes in the frequency range of the piano keys. However, since the natural frequencies of the simulation results were slightly different from experimental results, we used the hammering method to validate the simulation results and to demonstrate that the finite element modal analysis was able to simulate the dynamic properties of the circular plate well. Subsequent studies have found that different excitation frequencies in the lower frequency range may also affect the generation of Chladni patterns. Using harmonic analysis in ANSYS, we confirmed that tones of similar frequency on the same plate can produce different Chladni patterns, thus greatly simplifying the previous problem of having to use multiple plates of different shapes and sizes in order to visualize most of the piano keys. Based on the graphical simulation of a single tone, we have successfully extended it to a melody. This result provides strong support for effectively helping the hearing impaired to learn to play musical instruments, makes it possible to present music in a visual form, and opens up new possibilities for the wider use of music education tools in the hearing-impaired community.

Robot Design of Underwater Building Surface Dredging - Structural Design

In order to improve the efficiency of dredging, reduce the cost of dredging and ensure the safety of operation, this paper designs an underwater building surface dredging robot (hereinafter referred to as "underwater dredging robot"), which mainly includes the following aspects. The structure of underwater dredging robot is planned and divided into dredging system, walking system, driving system and support system. According to the actual work situation and the characteristics of each system, the scheme selection and structure design are carried out, and the overall layout scheme is obtained. The materials of the support system are selected and its force under different working conditions is analyzed. Through finite element analysis and modal analysis, it is verified that its reliability meets the requirements and there is no resonance phenomenon in the work.

Research on the Multi-Angle Seismic Spectrum Response Law of Auxiliary Feedwater Electric Pumps

The auxiliary feedwater electric pump, which is vital in nuclear power units, demands exceptional seismic reliability. The impact of the seismic excitation direction on the seismic response of the complex auxiliary feedwater electric pump structure remains inadequately understood, thereby introducing uncertainties into seismic analysis and equipment installation procedures. To address this challenge, this study centers on a representative horizontal multi-stage centrifugal pump based on the finite element model and modal analysis. Utilizing the response spectrum method and the square root of the sum of the squares (SRSS) vibration pattern superposition principle, the research comprehensively explores the seismic response characteristics of individual pressure-bearing components and key rotor positions under seismic excitation from various angles. Findings reveal intricate variations in maximum stress and displacement responses for each pressure-bearing component under safe shutdown earthquake (SSE) level seismic excitation, corresponding to different input angles of seismic spectra. In assessing the seismic operability of the clearance between the impeller and the stator, the direction near 45° exhibits the maximum displacement response, highlighting the need for focused attention in testing and verification checks. The methodologies and conclusions presented in this paper offer valuable insights for designing, optimizing, and installing horizontal multi-stage centrifugal pumps, including auxiliary feedwater electric pumps, providing valuable guidance for future applications in the field.

Earthquake wonders: High school investigation in mortise tenon structures

Frequent global earthquakes lead to catastrophic property damage and casualties due to building collapses. However, the 1976 Tangshan Earthquake showcased an exception: the Forbidden City, constructed with wooden materials and featuring mortise-tenon structures, remained unscathed among surrounding destruction. This study investigates the earthquake-resilient attributes of wooden mortise-tenon joints utilizing economical high school equipment. An innovative low-cost sensor system, featuring custom instrumented hammer, is developed and validated. Calibration of the hammer's impact force employs correlation with acceleration data from a standardized scale weight during impact. The system's reliability is tested by comparing resonance frequencies from Finite Element modal analysis and experimental data for a cantilever beam. Impact hammer tests assess frequency response and damping across buildings with various joint configurations. Mortise-tenon joints display augmented frictional damping due to internal displacement. Through simulated vibration acceleration responses, a crucial finding emerges---integration of mortise-tenon joints translates to an impressive 11.0% reduction in earthquake vibrations. This research underscores the potential of accessible high school devices in advancing seismic engineering insights.

Study on Preload of Bolted Connections in Pitch Bearing Based on Vibration Modal Analysis

In wind turbine systems, bolted connections are frequently subjected to gravitational and centrifugal loads transmitted by the blades during operation. This can lead to the attenuation of bolt preloading, resulting in bolt loosening or uneven loading, which in turn affects the service life of the generator unit. Therefore, the study of bolt preloading variations is crucial. However, there are numerous factors influencing bolt preloading, and the existing techniques struggle to precisely assess bolt preloading. This paper proposed a bolt preloading evaluation technique based on the hammer modal method. Focusing on the 42CrMo4 bolted connection of a pitch bearing, a test platform for bolt preloading assessment is constructed. Hammer modal tests are conducted under various preloading forces. By combining finite element modal analysis, the correspondence between preloading changes and the bending frequencies and modes of the bolted connection is obtained. The research illustrated that with changes in bolt preloading, variations occur in coherence, phase, and natural frequencies of frequency response functions. The fundamental correlation between bolt preloading and the second-order bending frequency can be utilized to assess changes in preloading. Furthermore, the applicability of this method has been validated, offering a reference for evaluating bolt preloading.

Study on the Forced Torsional Vibration Response of Multiple Rotating Blades with Underplatform Dampers

Underplatform dampers (UPDs), a type of dry friction damper, are commonly used for vibration reduction of turbine blades. This study investigated the effect of UPDs on the forced torsional vibration response of turbine blades within a multi-blade system. Pre-stressed finite element modal analysis and the harmonic balance method were combined to calculate the forced torsional vibration responses of a system with and without UPDs. The experiments were then carried out on a rotating multi-blade system with and without UPDs, with a focus on the effect of mass stacking on damping performance. The results showed that the installation of underplatform dampers could increase the frequency corresponding to the maximum response of the blade torsional vibration and cause multiple peaks that varied in the vibration response based on the mass of the UPDs. With an appropriate normal force, the underplatform dampers could effectively reduce the blade torsional vibration by 68.9%. However, excessive normal force of UPDs could lead to multiple large vibration peaks, which should be avoided in engineering practice. Additionally, the numerical results for the forced torsional vibration response of the rotating multi-blade system with UPDs were relatively close to the experimental results, indicating that the calculation method could be effectively applied to the nonlinear prediction of forced vibrations of rotating blades with dampers.

Carbon fibre reinforced plastic for smartness car body design, practice and simulation

With the vigorous implementation of national policies and regulations such as energy-saving and emission reduction, lightweighting has become one of the trends in the development of the automotive industry, which is of great significance in reducing energy consumption and increasing the range of vehicles. This paper is based on a newly developed smartness car body designed for elderly users, which aims to solve the problem of mobility and companionship for the elderly, with a maximum speed of 20 km/h and a weight requirement of 45 kg or less. This paper focuses on the lightweight technology of the body of the smartness car, using carbon fibre composite material as the carrier, and using simulation analysis combined with experimental testing to systematically study the body material selection, structure and process, and to carry out force analysis, finite element analysis and modal analysis on the designed body, verifying that the body of the smartness car meets the lightweight design requirements.