Impact Damper Research Articles

Suppressing vibration of structures using nonlinear single unit impact dampers via Taguchi method

This paper investigates a vibratory system that employs Hertzian contact theory in terms of free vibration. Nonlinear impact dampers are created by using a spring, mass, and viscous damper model. The model is simulated in MATLAB software using the DAS method as a proper simulation framework. The Taguchi method is used to examine the efficacy of impact dampers for controlling structural vibrations of the structure. It is demonstrated that the optimal factors obtained can effectively suppress the structure’s unwanted vibrations. The analysis of variance is also used to indicate the most influential factor of dampers to demonstrate their ability to quench vibrations.

Development of a new magnetorheological impact damper with low velocity sensitivity

The velocity sensitive characteristic of the conventional linear magnetorheological (MR) damper is undesirable in the application of impact protection. It will induce large damping forces when the damper suffers high velocity impacts, whilst comprising the energy dissipation efficiency of the damper and posing a serious threat to occupants and mechanical structures. This work reports a new MR impact damper (NMRID) with low velocity sensitivity. Unlike the conventional MR impact damper (CMRID) in which MR fluids (MRFs) flow from one chamber to the other through a small annular gap between the piston and cylinder, the NMRID has a whole annular gap between the shaft and cylinder that is filled with MRFs, and the MRFs work in a pure shear mode without any liquid flow. In this work, a NMRID and a CMRID were prototyped. The velocity sensitivities of these two impact dampers were compared via numerical analysis and experimental impact tests. The analysis and test results indicate that NMRID possesses a much lower velocity sensitivity than the CMRID; the dynamic range of the NMRID decreases less than CMRID with the increase of nominal impact velocity. Then, to demonstrate the controllability of NMRID, impact tests with a bang–bang control were implemented, and the peak force of NMRID was successfully controlled around a target force under different levels of nominal impact velocity. This research proves that the designed NMRID is less sensitive to velocity than the CMRID and the NMRID has good controllability, demonstrating that the NMRID can serve as a better candidate than CMRID in applications with high impact velocity.

Developments on auxetic closed cell foam pressure vessel fabrications

Auxetic foam can have higher indentation resistance, better protection under impact and higher vibration damping than conventional foam. Unlike auxetic open cell foam, with established, commercially viable options for manufacturing, methods for making auxetic closed cell foam are not established. We revisited pressure-vessel methods, proposed in 1996, for making auxetic closed cell foam. We processed low-density polyethylene foam for 6 h at 400–700 kPa and 100 °C, causing foams to shrink by a factor of two to five. The volumetric compression kinked cell walls, producing negative Poisson’s ratios as low as −0.2 and Young’s moduli from 0.2 to 1.2 MPa. Trends between applied volumetric compression and Poisson’s ratio agree with those for open cell foam—initially decreasing to negative values as volume reduced by a factor of two after processing, then plateauing or slightly increasing as volume decreased by a factor of two to five. Foams of different sizes and shapes (15–75 mm sides) processed in the same conditions (700 kPa, 6 h, 100 °C) shrank evenly in all three axes and had similar final volume ratios. We noticed a long settling period, of up to three months, where foams slowly shrank. Placing foam in a vacuum after processing reduced the settling period to within 24 h.

Multi-objective optimization and seismic performance verification of multiple tuned impact dampers for nonlinear benchmark building

This paper presents a type of multiple tuned impact damper (MTID), endowed with the wide frequency band of vibration attenuation and effectiveness for multi-mode control, to mitigate the vibrations of the seismically excited high-rise buildings. Focusing on multi-objective optimization, the concept of the multi-objective multi-verse optimizer (MOMVO) is utilized for developing the design procedure for MTID towards the best parametric solutions. Moreover, a series of analytical comparisons are conducted between the optimally and conventionally designed MTIDs on a 20-story nonlinear benchmark building to verify the superiority of the proposed multi-objective optimization method. The optimal control effects of the MTID system are systematically evaluated from basic response indexes to nonlinear behaviors of the benchmark building. Furthermore, the performance of optimal distributed MTID systems with various placement strategies is also investigated for effective installations of TIDs. Finally, the damping mechanism of various distributed MTIDs is clarified based on the evaluation of energy comprising seismic input energy, structural energy, and the energy of the damping systems. The results show that the optimal MTID systems provide good reduction effects on dynamic responses and nonlinear damage of the primary structure with hyposensitivity to the uncertainty of seismic excitations. The proposed design algorithm for MTID systems can be an attractive alternative to effectively obtain optimal parameters of the controllers. In addition, a reasonable installation strategy allows for an increase in energy transfer speed and energy transfer amplitude, thus improving the damping capacity of the MTID system.

Comparative modal analysis of B70 and LCR-6 type railway sleepers after repeated impact loads

Due to today's high-frequency trainloads and wheel or rail irregularities, the railway system is more exposed to impact loading conditions. In this study, laminated carbon fiber reinforced polyurethane (L-CFRPU) products were used, with a new non-pre-stressed production process, to improve the impact damping characteristics of concrete railway sleepers. New designed LCR-6 type sleepers were compared with standard B70 type pre-stressed concrete sleepers by performing modal analysis before and after a 50 times repeated-330 kN impact loading procedure. This is the first study to compare new LCR-6 type sleepers with prestressed competitors after impact loads. According to the analysis results, FRF magnitude values ​​decrease up to 83% lower in impacted LCR-6 type sleepers compared to impacted B70 type sleepers. After the impact loading procedure, the cracks formed in LCR-6 type sleepers closed and remained below 50-µm width, and according to the simultaneous mechanical test results, these few hairline cracks do not cause a significant mechanical capacity loss, while increasing the damping ratios by 274%. This advantage will be beneficial in extending the service life of sleepers and protecting other railway components from vibration and impact damage. Therefore, while the pre-stressed concrete sleepers have a negative course during their service life, the non-pre-stressed LCR type sleepers show a positive acceleration.

Nonlinear Dynamics of an Elastic Stop System and Its Application in a Rotor System

Impact dampers or vibration systems with gaps are common in engineering applications, and the impact effects introduced by the gaps make such systems strongly nonlinear. In this paper, a model with an elastic stop is established, considering the stiffness and damping characteristics of the stop, which is a novel kind of impact damper and can be applied in a rotor system. The amplitude–frequency and phase–frequency response of the system at different gaps are obtained by the harmonic balance method with the alternating frequency–time scheme (HBM-AFT). The stability of the periodic solution is analyzed by the Floquet theory, and the time history and frequency spectra of the unstable point are analyzed by the numerical integration method. In the results, there can be more than one steady-state response at unstable points for a given excitation frequency, and the jump phenomenon occurs. The elastic stop is effective in the vibration amplitude suppression if its stiffness has been designed properly. This study provides an insight into the dynamic responses and its applications of the system with gaps, which is guidance for the analysis of pedestal looseness faults and vibration suppress methods.

In-operation performance evaluation of damped light poles using fatigue life estimations

This study demonstrates the practical application of vibration-based monitoring for the health evaluation of slender structures. The subject structures are the light poles installed on the Confederation Bridge in eastern Canada. The unique nature of this 12.9 km bridge and its location in the Northumberland Strait provides an opportunity to study light pole vibrations in harsh environmental conditions. In a previous study, a prototype impact damper using two lead balls within a pipe cylinder added to the top of the pole was developed to attenuate the large amplitude first-mode vibrations. In this current study, an extended full-scale vibration monitoring program of two bridge light poles under actual wind loading conditions is carried out over a period of several months to evaluate the in-operation performance of the custom prototype pole-top impact damper. An analysis method for calculating the cumulative fatigue damage (cFD) from vibration data and for estimating the remaining fatigue service life of in-operation bridge light poles is presented. With these methods, it is found that the pole-top impact dampers increase the remaining fatigue service life of the original Confederation bridge light poles by approximately 2.5 years. From fatigue modeling, it is also found that if the dampers had originally been installed with the light poles during construction in 1997, the cumulative fatigue damage could have been reduced by an average of 25% with a projected service life increase of 48%, which represents an additional 12 years of service above the actual estimated service life of 25 years.

Study on Energy Dissipation Mechanism of an Impact Damper System

Abstract The objective of this paper is to investigate how higher damping is achieved by energy dissipation as high-frequency vibration due to the addition of impact mass. In an impact damper system, collision between primary and impact masses cause an exchange of momentum resulting in dissipation of energy. A numerical model is developed to study the dynamic behavior of an impact damper system using a multi-degree-of-freedom (MDOF) system with augmented Lagrangian multiplier contact algorithm. Mathematical modeling and numerical simulations are carried out using ansysfea package. Studies are carried out for various mass ratios subjecting the system to low-frequency high amplitude excitation. Time responses obtained from numerical simulations at fundamental mode when the system is excited in the vicinity of its fundamental frequency are validated by comparing with experimental results. Magnification factor evaluated from numerical simulation results is comparable with those obtained from experimental data. The transient response obtained from numerical simulations is used to study the behavior of first three modes of the system excited in vicinity of its fundamental frequency. It is inferred that dissipation of energy is a main reason for achieving higher damping for an impact damper system in addition to being transformed to heat, sound, and/or those required to deform a body.

An experimental evaluation of particle impact dampers applied on the tool for milling of hardened steel complex surface

In the manufacturing of dies and molds, vibrations may represent serious problems, since the finishing tool used is usually slender (high length/diameter ratio) in order to machine deep cavities with complex geometries, typical of these products. Vibration is an undesirable phenomenon in any machining operation as it can lead to poor surface finish, low material removal rate, and high tool wear rate. Impact dampers have been put into the tools as a method for reducing vibration in machining processes. Damping occurs through energy dissipation and linear momentum exchange during intermittent collisions between the main structure (in this case the milling tool) and a free mass (spheres or cylinders placed within a tool cavity). Although efficient, these types of dampers are highly nonlinear. Thus, the aim of this work is to analyze the effect of different materials and geometries (steel spheres, tungsten spheres and steel cylinders) acting as impact damper elements inside a ball nose end milling tool. To perform this task, a comparison of commercial tool holders and dampened tool holders was done in the milling of a convex D6 steel surface, comparing commercial tool holders with dampened ones. The results showed that the tools with impact dampers generated lower values of roughness in the workpiece (around 30% of the value observed in the conventional steel tool holder for the case of steel cylinders and around 40% for both spheres) and presented lower levels of vibration when compared to the same tool without the impact damper, mainly in the machining of workpiece regions where radial and tangential forces are predominant. The tool which used tungsten spheres as damper elements generated roughness surfaces similar to those obtained with steel spheres, while the tool which used steel cylinders only generated lower roughness in the regions where the axial force component is not predominant, which shows that its performance is highly dependent on the resulting force direction.

Railway noise reduction by periodic tuned particle impact damper with bounce and pitch-coupled vibration modes

In this study, a two-dimensional TPID (tuned particle impact damper) was proposed for reducing vibration via the interactions between the bounce and pitch vibration modes of the mass damper. To reduce the broadband vibration energy, the inelastic particle impact was utilized. The influence of the inelastic impacts on the rail vibration was investigated by the wave approach. To analyze the wave propagation characteristics, the periodic structure comprising the track and TPID was considered. The effects of the damper types, width, and loss factor on the complex wave propagation constant were investigated. The proposed TPID was applied to the actual rail. The track decay rate in the vertical direction increased by 3.2 dB/m. Accordingly, the proposed TPID effectively reduced the broadband rail vibration and allowed the tuning for optimal performance at multiple frequency ranges. With this actual installation on the track excited by the operating trains, the noise reduction performance both for moving passenger compartments and nearby residential area was verified. The sound levels in the residential area and in the passenger compartment decreased by 5.7 and 3.4 dBA, respectively. The proposed damper utilized the metallic components with advantages on rapid attachment and detachment. The proposed noise-control methodology is a cost effective vibration treatment to assure environment-friendly rail system.

Optimal design of passive momentum exchange impact damper using mechanical singularity

Optimal design of passive momentum exchange impact damper using mechanical singularity

New discrete mass model examining the dynamics of multiple-element-pendulum impact dampers for bridge stay-cables

A new discrete multi-degree-of-freedom model is presented to examine the behavior of a multiple-element-pendulum impact damper for mitigating aeroelastic vibration of bridge stays. An earlier model, previously derived to study vibrations, did not consider simultaneous multi-mode stay response and non-distributed load cases. The new, discrete multi-degree-of-freedom model is calibrated using data derived from a field experiment on a 31.2 m long stay with integrated damper. Experiments are performed at Vienna University of Technology. Both free-vibration tests and forced-vibration tests are used to calibrate the new model and examine its adequacy. Identification of model parameters is discussed. The new model enables design and implementation of the damping apparatus on a standard stay-cable under various external loads.

Interval of restitution coefficient for chattering in impact damper

Based on the impact damper, a dynamic model of a non-fixed constrained collision system was established. The coefficient of restitution is used as the main control parameter to analyze the system’s periodic movement and its bifurcation region. The chattering movement characteristics of the system were revealed. The interval of restitution coefficient for the chattering of collision system under various mass ratio and frequency ratio was obtained. The results show that the chattering phenomenon occurs in the collision system when the coefficient of restitution is greater than 0.5; as the mass ratio decreases, the interval of restitution coefficient for chattering continues to expand; as the frequency increases, the interval of restitution coefficient for chattering narrows.

The Possibility of Using a System with an Inertial Element as an Impact Damper

The Possibility of Using a System with an Inertial Element as an Impact Damper

Impact damping and vibration attenuation in nematic liquid crystal elastomers

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems. One of their most celebrated properties is the ‘soft elasticity’, leading to a wide plateau of low, nearly-constant stress upon stretching, a characteristically slow stress relaxation, enhanced surface adhesion, and other remarkable effects. The dynamic soft response of LCE to shear deformations leads to the extremely large loss behaviour with the loss factor tanδ approaching unity over a wide temperature and frequency ranges, with clear implications for damping applications. Here we investigate this effect of anomalous damping, optimising the impact and vibration geometries to reach the greatest benefits in vibration isolation and impact damping by accessing internal shear deformation modes. We compare impact energy dissipation in shaped samples and projectiles, with elastic wave transmission and resonance, finding a good correlation between the results of such diverse tests. By comparing with ordinary elastomers used for industrial damping, we demonstrate that the nematic LCE is an exceptional damping material and propose directions that should be explored for further improvements in practical damping applications.

Experimental and analytical investigation of impact dampers in free vibration reduction with coulomb friction

The presence of vibration in structures and machines can establish failures and reduce the efficiency. Passive dampers have been used extensively for vibration control because of their simple concept. One of these dampers is impact damper (ID). Impact dampers are suitable to operate in harsh environments and effective over a wide range of frequencies. In this paper, the experimental and theoretical investigation on the effect of the ID in free vibration of a cantilever beam is done. The lateral motion of the free end of the cantilever beam is modeled as one degree of freedom (1-DOF) system. The motion of the 1-DOF system equipped with the ID with Coulomb friction is studied analytically. Free vibration of cantilever beam investigated experimentally. The experimental results are presented and discussed. The damping inclination of the ID in various experimental and theoretical studies is proposed. The results show the validation between the experimental and the theoretical studies.

The influence of stacking sequence on the low-velocity impact response and damping behavior of carbon and flax fabric reinforced hybrid composites

With the wide application of fiber reinforced polymer (FRP) composites, the impact resistance and damping properties of FRP have been considered as the essential properties of many applications. In this paper, the hybrid composites (FCFCF, where C represents carbon fiber layer and f represents flax layer) and sandwich structure (CFFFC) alternately laminated with carbon fiber and flax fabric were studied by vacuum-assisted resin pouring (VARI) process, and the effects of stacking sequence of carbon fiber and flax fabric layers on low-speed impact response and damping properties were studied. The better impact response and higher energy absorption of hybrid composites with the sandwich structure are attributed to the higher strength of the skin layer and better adhesion between core layers. Furthermore, affected by the types of surface fibers, FCFCF has lower vibration frequency and higher energy consumption, and its damping coefficient is 26.4% higher than that of CFFFC.

Polymer foams as advanced energy absorbing materials for sports applications—A review

AbstractThe use of polymer foams is becoming increasingly important due to the attainable weight reduction and value‐added properties. The development of foam structures is a popular research area as they have outstanding energy absorbing capability, which is related to the special deformation mechanisms of the cell structure (cell wall buckling and collapse of the cells). This property is exploited by the sports industry, where the main task of such products is to protect the health of the athlete and to ensure safe sports conditions. This review provides a comprehensive presentation of the advanced energy absorbing applications of polymeric foams in sports. The article presents in detail the processing technologies of polymer foams, as well as the sports‐specific regulations which contain the requirements for sports products. The impact damping of polymeric foams is typically determined by falling weight impact tests, which were used in several previous studies. However, it is a great challenge to compare the published results, as the test parameters and the tested materials are different. Currently, an unexplored field of research is the detailed study of multilayer sandwich foam structures. Understanding the effect of layer order on mechanical properties would help researchers achieve a major improvement in this field.

Design and FEA of Impact Damper for Four-wheeler car

Abstract: The problem of over speeding vehicles in highway transportation is one of major problem faced in the current scenario of Indian traffic. The issue of over speeding not only damages the vehicle but the serious consequence of this is there due to loss of precious life. In real life scenario accidents in are totally unavoidable we can only have counter measures to prevent them and avoid the fatalitiesinvolved. Safety impact guard is one of the real-time counter measures which reduce the impact when the vehicle is involved in high speed impact. The proposed design which is being discussed in detail throughout this paper is for design of a re-usable safety impact damper with pressure relief valve. This design discusses the force of energy or impact that is dampened due to the action of the impact damper with the pressure relief valve. The entire objective of the project is to reduce the fatalities by designing an impact damper which provides safety against the front and rear end collisions. Keywords: Impact, Pressure relief valve, Damper

Stochastic bifurcation analysis of a friction-damped system with impact and fractional derivative damping

Stochastic bifurcation analysis of a friction-damped system with impact and fractional derivative damping