Vibrations In Engineering Structures Research Articles

A multi-band elastic metamaterial for low-frequency multi-polarization vibration absorption

The vibration of engineering structures in actual practice occurs across numerous frequency ranges and includes diverse polarization modes such as bending, torsion, and expansion. Nevertheless, most reported elastic metamaterials are designed for a single frequency range or a single elastic wave mode, thereby making it challenging to simultaneously suppress the propagation of vibrational energy across multiple frequency ranges and polarization modes. To address this limitation, we propose a two-degree-of-freedom elastic metamaterial exhibiting a multi-frequency range elastic band gap and multi-polarization mode elastic wave band gap. By incorporating periodic vibration-absorbing units, gradient parameter vibration-absorbing units, and different polarization mode vibration-absorbing units to the actual equipment support structure, we achieve respective vibration attenuation enhancement, broadband vibration absorption, and multi-polarization mode vibration absorption. We systematically verify the effectiveness of our design through kinetic theoretical analysis, full-wave field simulations, and experimental tests. This metamaterial vibration absorption device can effectively meet the application requirements of complex vibration reduction involving multi-frequency ranges and modes in practical engineering, providing novel insights into equipment vibration and noise reduction design that holds significant reference value for engineering applications.

Dynamic properties of large amplitude nonlinear oscillations using Hamiltonian-based frequency formulation

In the present work, we present a detailed investigation into the large amplitude vibration of nonlinear engineering structures by means of the Hamiltonian-based frequency formulation (HBFF), extracted from the Hamiltonian theory and residual equation method. Compared to the variational method, the frequency amplitude formulas have an excellent agreement. In addition, the compared curves between the HBFF, variational method and exact solution indicate that the HBFF is more accurate. The ideas in this research are expected to shed a new light to the exploration of the nonlinear oscillation problems arising in physics and engineering.

Laser additive manufacturing of Miura-origami tube inspired quasi-zero stiffness metamaterial with prominent longitudinal wave propagation

ABSTRACT Origami metamaterials have become frontiers of research in many disciplines due to their infinite design space, simple size variation, and topologically variable properties. In this study, a novel metamaterial inspired by Miura-origami tubes with a complex quasi-zero-stiffness (QZS) structure was fabricated via laser powder bed fusion (LPBF). The unit of the QZS metamaterial consists of a two-layer quadrilateral frame and two vertical springs attached to its diagonal points. The geometric accuracy, densification level and mechanical properties of the QZS parts fabricated at various processing conditions were investigated and the optimised processing parameters were determined. The displacement response of the QZS parts was analysed by experiments in conjunction with simulation analysis. The results show that the LPBF-fabricated QZS metamaterials form four extra-wide longitudinal wave band gaps under low frequencies from 660 Hz to 2500 Hz. The proposed LPBF-fabricated QZS metamaterial shows great potential in impeding the longitudinal vibration of engineering structures.

Experimental and numerical analysis of interface cohesive behavior on the viscoelastic damper under shear loading

The viscoelastic (VE) damper has been widely employed in isolation technology to mitigate the vibrations of engineering structures induced by earthquakes or winds. The VE damper is composed of steel plates and VE material which are chemically adhesive at contact surfaces and vulcanized through a high temperature. The performance degradation at the interface between the steel plate and VE material has a great impact on the mechanical properties of the VE damper at finite shear displacement and deserves more in-depth studies. In this work, the three-dimensional refined numerical model of the VE damper based on the bi-linear cohesive constitutive law is developed using the finite element software Abaqus. Experimental validations indicate the high feasibility of the developed model to represent the stiffness degradation behaviors of the VE damper under shear loading. The present work demonstrates the effectiveness of bi-linear cohesive constitutive law in dealing with the interface characteristics of the VE damper, and the wide application perspective of the developed model in engineering practice.

Application of Parametric Forced Tuned Solid Ball Dampers for Vibration Control of Engineering Structures

In this paper, parametric forced tuned solid ball dampers (TSBD) are considered for vibration control of engineering structures in an untypical way. The special feature of the presented investigation is to evaluate the potential application of parametric forcing of the rolling cylindrical or spherical body in the runway for reducing the vertical vibrations of a vibration-prone main system. Typically, tuned solid ball dampers are applied to structures that are prone to horizontal vibrations only. The coupled nonlinear differential equations of motion are derived and the phenomenon of parametric resonance of the rolling body in the runway is analyzed. A criterion for avoiding parametric resonance is given to achieve the optimal damping effect of the TSBD. In the second part of the article, a method for the targeted use of parametric resonance to reduce the vertical vibrations of engineering structures is presented and verified, considering a biaxially harmonic excited pedestrian bridge. It is shown that, with a suitable choice of damper parameters, a stable vibration of the rolling body in the runway is formed over the course of the vibration despite the occurrence of parametric resonance and that the maximum vertical vibration amplitudes of the main system can be reduced up to 93%. Hence, the here presented untypical application of parametric forced TSBD for reducing the vertical forced vibrations of vibration-prone main systems could be successfully demonstrated.

Influence of inter-panel connections on vibration response of CLT floors due to pedestrian-induced loading

Long-span cross-laminated timber (CLT) floors are typically an assembly of prefabricated CLT panels connected together on the site. The actual connections are commonly neglected in design calculations. Hence, a CLT floor is modelled either as a monolith slab or more frequently as a set of CLT panels with no connections at all. This paper presents a numerical study designed to examine the influence of two most common inter-panel connections, i.e. single surface spline and half-lapped joint, on vibration modes and vibration responses of a range of different CLT floors due to pedestrian-induced loading. Although the inter-panel connections are relatively complex in reality, they are modelled here as an equivalent 2D elastic strip between the CLT panels. This relatively simple yet robust model can be used with ease in design practice, regardless finite element (FE) software used to extract vibration modes of a CLT floor. The corresponding monolith floors and floors without inter-panel connections are studied for the comparison of the results. Vertical vibration responses are simulated for low-frequency and high-frequency floors using the corresponding walking force models given in a popular design guideline for footfall induced vibrations of civil engineering structures. Vibration responses were calculated for single pedestrian occupants and their walking paths parallel and perpendicular to the line of connection. The results showed that including the inter-panel connections in a FE model resulted in up to 2.5 higher RMS acceleration levels. Hence, the common practice of modelling CLT floors as monolith slabs or as a set of panels without connections should be left behind.

On the understanding of damping capacity in SMA: From the material thermomechanical behaviour to the structure response

Superelastic Shape Memory Alloys (SMAs) provide a high damping capacity due to the hysteretic motion of the inter-phase boundaries during the martensitic transformation. They have demonstrated their ability to control vibrations of SMA-based Civil Engineering and Aerospace structures. In order to improve existing damping devices, characterization of SMA damping capacity is necessary, despite the lack of a standard procedure. Classical characterizations such as tensile or torsion tests on SMA samples are very attractive, the fact that they are common and simple to process. Furthermore, environment and loading conditions are quite easy to control. Different energy-based formulations have been proposed in the literature to explicitly predict SMA damping capacity from the hysteretic mechanical behaviour. The aim of this paper is to classify commonly used formulations from the literature, using a new thermomechanical vibration numerical model of a SMA beam structure. Thus, three energy-based predictions of SMA intrinsic damping ratio measured at the material scale are compared to the damping ratio measured from the free vibration signal at the SMA beam structure scale, taken as the objective reference. The formulation proposed by Piedbœuf and Gauvin provided a better match in three study-cases.

Experimental Study of High Axial Damping Rubber (HADR) in New Viscoelastic Dampers

Abstract In the last few years, dampers with viscoelastic material as passive energy dissipation devices have been considered, with their dual behavior, in the modern methods of seismic performance-based design. In these new dampers, energy dissipation of viscoelastic material, unlike ordinary viscoelastic dampers obtained by shear strain, is provided by amplified axial strain. Hence, the production of a High Axial Damping Rubber (HADR) is required in these dampers. This article presents the results of experimental work carried out to characterize the mechanical response of a HADR to be used in the design and construction of new viscoelastic dampers for controlling strong vibrations in civil engineering structures. The experimental results showed that the HADR behavior is better than that of styrene butadiene rubber, leading to improved mechanical properties in the range of standard rubber. The hardness, tensile strength, elongation at break, compressive strength, and rate of resilience of this rubber are obtained as, respectively, 60 durometer (shore A), 16.56 MPa, 519 %, 1,730 kPa, and 50 %. Finally, the uniaxial tension and compression data of HADR for its modeling in the finite element program are discussed.

Influences of ground motion parameters and structural damping on the optimum design of inerter-based tuned mass dampers

Tuned mass dampers (TMDs) are widely adopted to control the adverse vibrations of engineering structures. To further improve the effectiveness of TMD, inerter was introduced into TMD recently to form inerter-based TMD systems. Similar to TMD, inerter-based TMDs should be carefully designed (optimized) in order to get their best control performances. In the previous studies on using inerter-based devices for seismic induced vibration control, the external excitation was normally simplified as a white noise and the inherent structural damping was ignored. However, it is well known that seismic excitation cannot be simply assumed as a white noise and damping always exists in the structure. The parameters obtained by the previous optimization procedures thus do not necessarily result in the best performance of the device. In the present study, the equations of motion of a single-degree-of-freedom (SDOF) structure equipped with three types of inerter-based TMDs subjected to seismic excitation are firstly developed. Instead of using a white noise as input, the filtered Kanai-Tajimi spectrum, which is characterized by the site damping and frequency, is adopted to model seismic ground motion. Then the effects of site damping, site frequency and structural damping on the inerter-based TMDs are comprehensively investigated and formulas are proposed to estimate the optimal parameters. Lastly, the responses of a structure without control and controlled by an inerter-based TMD under simulated and recorded earthquake ground motions are analysed by using MATLAB/Simulink. Numerical results show that the optimal parameters of inerter-based TMDs are significantly dependent on the site frequency and structural damping, while the site damping has little influence. Moreover, the accuracy of the proposed formulas is validated, and the control effectiveness of the inerter-based TMD is confirmed.

Equivalent model and parameter analysis of non-packed particle damper

A non-packed particle damper (NPPD) is an advantageous passive damping device with a wide frequency band and good robustness. However, its damping mechanism remains unclear, and its application for controlling vibrations in civil engineering structures is being explored. By analysing the particle motion state, this paper proposes a double inertia mass equivalent model (DIMEM) to reflect the interaction between particles. The effect of inertia was introduced in the DIMEM to consider the rolling effect of particles on the damping performance of the NPPD. An electromagnetic vibration table test of a single-storey frame structure with an NPPD was designed and performed. The parameter determination method and applicability of the DIMEM were also evaluated based on experimental and theoretical analyses. Furthermore, the effects of the parameters on the damping performance of the NPPD were systematically analysed. The results confirm that the equivalent model can reflect the damping performance and mechanism of the NPPD. The particle group inertia is an inherent property of the NPPD. With an increase in the ratio of inertance to particle mass, the optimal vibration damping performance deteriorates under harmonic excitation, and the corresponding equivalent connection stiffness gradually increases. The equivalent connection stiffness, additional mass ratio, recovery coefficient, and acceleration normalised collision distance significantly affect the damping performance and mechanism. However, the effects of the equivalent connection damping coefficient and rolling friction coefficient are negligible. The proposed DIMEM and the corresponding parameter analysis can provide an important reference for the application of NPPDs in civil engineering.

The Multiple Tuned Mass Damper for Passive Control of Structures by Cuckoo Algorithm

Adjustable mass dampers are recently used to reduce seismic vibrations of engineering structures. Function of these types of systems requires a suitable setting of their parameters. In this study, a practical method to design Multiple Tuned Mass Dampers (MTMD) has been proposed to minimize the maximum displacement of roof, acceleration of roof and TMDs displacement to reduce the seismic response of structures. To solve the problem Cuckoo Optimization Algorithm (CMOA) has been used. The results of numerical simulations for a shear frame of ten floors exposed to earthquakes demonstrate that CMOA is able to present appropriate solutions in the form of Parato charts for setting optimal parameters of MTMD, caused by creating a proper compromise between the objective functions in conflict with each other. Eventually, MTMD desirably reduces seismic responses of structures. Also, MTMD performance depends on input quake, TMD mass ratio and the number of TMDs.

Virtual Engine In-Cylinder Pressure Sensor for Automobiles and Agricultural Tractors

The cylinder pressure signal is a very useful indicator for advanced high-performance internal-combustion engines equipped in modern automobiles and agricultural tractors. In this paper, a previous framework for the cylinder pressure estimation is conducted based on a transfer path model (between the cylinder pressure signal and the vibration signal) identified in frequency domain. The main idea behind the previous framework is based on the Kalman filter (of which the input is the engine structure vibration) for the augmented model formed by augmenting the cylinder pressure signal model with delay blocks and the transfer path model identified in time domain. Two combustion metrics, pressure peak Pmax and peak location Ploc, are used for evaluating the estimation framework under the transfer path identified in frequency domain. The estimation results are compared with both experimental data collected from a four-cylinder diesel engine and previous work results, and illustrate the effectiveness of the newly identified transfer path.

Combustion Ionization for Detection of Misfire, Knock, and Sporadic Preignition in a Gasoline Direct Injection Engine

Detection of combustion-related phenomena such as misfire, knock, and sporadic preignition is very important for the development of electronic controls needed for the gasoline direct injection engines to meet the production goals in power, fuel economy, and low emissions. This paper applies several types of combustion ionization sensors, and a pressure transducer that directly senses the in-cylinder combustion, and the knock sensor which is an accelerometer that detects the impact of combustion on engine structure vibration. Experimental investigations were conducted on a turbocharged four-cylinder gasoline direct injection engine under operating conditions that produce the above phenomena. One of the cylinders is instrumented with a piezo quartz pressure transducer, MSFI (multi-sensing fuel injector), a stand-alone ion current probe, and a spark plug applied to act as an ion current sensor. A comparison is made between the capabilities of the pressure transducer, ion current sensors, and the knock sensor in detecting the above phenomena. The signals from in-cylinder combustion sensors give more accurate information about combustion than the knock sensor. As far as the feasibility and cost of their application in production vehicles, the spark plug sensor and MSFI appear to be the most favorable, followed by the stand-alone mounted sensor which is an addition to the engine.

Development of stiffness-adjustable tuned mass dampers for frequency retuning

Tuned mass damper is an attractive strategy to mitigate the vibration of civil engineering structures. However, the performance of a tuned mass damper may show a significant loss due to the frequency detuning effect. Hence, an inerter-induced negative stiffness (apparent mass effect) and magnetic-force-induced positive/negative stiffness are proposed to integrate a stiffness-adjustable vertical tuned mass damper and pendulum tuned mass damper for frequency retuning, respectively. Based on the established differential equations of motion for a vertical tuned mass damper coupled with an inerter and a pendulum tuned mass damper integrated with a magnetic-force-induced positive-/negative-stiffness device, the frequency retuning principles of a vertical tuned mass damper and a pendulum tuned mass damper are, respectively, demonstrated. The frequency retuning strategies for both the vertical tuned mass damper and the pendulum tuned mass damper are confirmed and clarified by model tests. Furthermore, the performance of a retuned vertical tuned mass damper for mitigating vibration of a linear undamped single-degree-of-freedom primary structure is discussed, and the effects of the amplitudes of the pendulum tuned mass damper on magnetic-force-induced stiffness as well as the frequency of the pendulum tuned mass damper are also investigated. Both theoretical analysis and experimental investigations show that the proposed frequency tuning methodologies of tuned mass dampers are efficient and cost-effective with relatively simple configurations.

Recursive Engine In-Cylinder Pressure Estimation Using Kalman Filter and Structural Vibration Signal

The cylinder pressure signal is a very useful indicator for modern high-performance internal-combustion (IC) engines. Unfortunately, direct measurements of the cylinder pressure are impractical because installing cylinder transducers is difficult and conditions in IC engine cylinders are adverse. Therefore, different methods have been investigated to reconstruct the cylinder pressure from externally measured signals, such as the engine structure vibration and the crank angular speed. In this paper, some of existing methods are reviewed firstly. Then a novel recursive cylinder pressure estimation method based on using the Kalman filter with the engine structure vibration signal as input is proposed. Two combustion metrics, pressure peak (Pmax) and peak location (Ploc), were used for evaluating the proposed method. The estimation results were compared with the experimental data collected from a four-cylinder diesel engine and showed the effectiveness of the proposed method.

Modeling, design, and testing of a proof-of-concept prototype damper with friction and eddy current damping effects

Friction is considered as one of the most reliable mechanisms of energy dissipation that has been utilized extensively in passive damping devices to mitigate vibration of civil engineering structures subjected to extreme natural hazards such as earthquakes and windstorms. However, passive friction dampers are well-known for having a highly nonlinear hysteretic behavior caused by stick-slip motion at low velocities, a phenomenon that is inherent in friction and increases the acceleration response of the structure under control unfavorably. The authors have recently proposed the theoretical concept of a new type of damping device termed as “Passive Electromagnetic Eddy Current Friction Damper” (PEMECFD) in which an eddy current damping mechanism was utilized not only to decrease the undesirable effects of stick-slip motion, but also to increase the energy dissipation capacity of the damping device as a whole. That study was focused on demonstration of the theoretical performance of the proposed damping device through numerical simulations. This paper further investigates the influence of eddy current damping on energy dissipation due to friction through modeling, design, and testing of a proof-of-concept prototype damper. The design of this damper has been improved over the design in the previous study. The normal force in this damper is produced by the repulsive magnetic force between two cuboidal permanent magnets (PMs) magnetized in the direction normal to the direction of the motion. The eddy current damping force is generated because of the motion of the two PMs and two additional PMs relative to a copper plate in their vicinity. The dynamic models for the force-displacement relationship of the prototype damper are based on LuGre friction model, electromagnetic theory, and inertial effects of the prototype damper. The parameters of the dynamic models have been identified through a series of characterization tests on the prototype damper under harmonic excitations of different frequencies in the laboratory. Finally, the identified dynamic models have been validated by subjecting the prototype damper to two different random excitations. The results indicate that the proposed dynamic models are capable of representing force-displacement behavior of the new type of passive damping device for a wide range of operating conditions.

Toward an adaptive vibration absorber using shape-memory alloys, for civil engineering applications

This article explores the capabilities of a novel adaptive vibration absorber for civil engineering structures, with regard to frequency self-tuning, based on the temperature modulation of shape-memory alloy restitution elements. This real-time temperature modulation of shape-memory alloys, through Joule effect, enables to control the elastic modulus of these elements, by inducing thermal martensitic transformations, and allows for the adaptation of the stiffness of the absorber, in order to be continuously tunable for a wide frequency range. A series of simulations are performed, using numerical models of a lively footbridge, to give an additional insight into the high potentialities of this adaptive control approach in the mitigation of vibrations in civil engineering structures.

Numerical analysis using state space method for vibration control of car seat by employing passive and semi active dampers

In passenger cars the vibrations developed at the ground are transmitted to the passengers through seats. Due to vibrations discomfort is experienced by the passengers. Dampers are being successfully utilized to reduce the vibrations in civil engineering structures. Few dampers are used in passenger cars as well. In the present study viscous dampers and semi-active variable friction dampers are used in passenger cars. The car and car seat are modeled together as two degrees of freedom system. The study is carried out for two cases namely car moving on sagged bridges and car moving on road humps. The paper also presents the comparison of performance of both the dampers for the two cases. State space method has been employed for the numerical analysis of the study. It is found that the amplitude of displacements is reduced considerably by the employment of dampers and resonance is avoided. Performance wise viscous damper is found to be slightly better than semi-active variable friction damper.Keywords: Car seat, viscous damper, semi-active variable friction damper, two degrees of freedom, state space method

Measuring human-induced vibrations of civil engineering structures via vision-based motion tracking

We present a novel framework for measuring the body motion of multiple individuals in a group or crowd via a vision-based tracking algorithm, thus to enable studies of human-induced vibrations of civil engineering structures, such as floors and grandstands. To overcome the difficulties typically observed in this scenario, such as illumination change and object deformation, an online ensemble learning algorithm, which is adaptive to the non-stationary environment, is adopted. Incorporated with an easily carried and installed hardware, the system can capture the characteristics of displacements or accelerations for multiple individuals in a group of various sizes and in a real-world setting. To demonstrate the efficacy of the proposed system, measured displacements and calculated accelerations are compared to the simultaneous measurements obtained by two widely used motion tracking systems. Extensive experiments illustrate that the proposed system achieves equivalent performance as popular wireless inertial sensors and a marker-based optical system, but without limitations commonly associated with such traditional systems. The comparable experiments can also be used to guide the application of our proposed system.

Potential of Acoustic Emission in Unsupervised Monitoring of Gas-Fuelled Engines

Abstract: The aim of this paper is to scrutinise closely information that contains in the acoustic emission of a gas-fuelled engine and to define the potential of knock condition detection. The recently introduced technique of nonstationary system identification is investigated. At first, it utilises the wavelet transform to reveal time-frequency energy density of data. Then the modified version of singular value decomposition is applied to extract dominant frequency components from the data buried in background noise. The efficacy of knock feature extraction is investigated using three sources of data: in-cylinder pressure, engine structure vibration and engine noise sensed by a microphone.