Torsional Vibration Amplitude Research Articles

Experimental study of the effect of the properties of motor oils on the level of torsional vibrations of the shaft line of the Yaroslavets type vessel

The article presents the results of an experimental study of the influence of motor oil properties on the level of torsional vibrations of the propeller shaft of a Yaroslavets-type vessel. The tests were carried out on mooring lines to create the maximum load on the 3D6 main engine using standard MS20 motor oil and oil with copper additives. Torsional vibrations were measured using a certified verified strain gauge complex “Astech Electronics” (Great Britain) installed on the propeller shaft. The study found that the use of oil with copper additives and MS20 oil does not significantly affect the amplitudes of torsional vibrations of the ship’s propeller shaft in the range of crankshaft speeds of the 3D6 main engine from the minimum stable to nominal. It was found that during the startup of the main engine with oil with copper additives, the level of torsional vibrations decreases, which requires research on more powerful marine diesel engines and an assessment of this effect. When using oil with copper additives, a reduction in the overall spectrum of harmonic component amplitude oscillations is achieved, which leads to a positive effect of reducing stress in the crankshaft and gearbox. Torsional vibrations in the elements of the machine-propulsion complex of a Yaroslavets-type vessel when used as a tug do not exceed the permissible values calculated according to the RCO rules, so additional measures to reduce them are not required. Additional experimental studies are needed to assess the effect of lubricating oil with copper additives on the vibroacoustic characteristics of marine diesel engines — vibration level and external noise.

Multi-Band Torsional Vibration Amplitude Demodulation for Planetary Gearbox Fault Diagnosis Under Time-Varying Speed Conditions

Multi-Band Torsional Vibration Amplitude Demodulation for Planetary Gearbox Fault Diagnosis Under Time-Varying Speed Conditions

Безразборная диагностика технического состояния модельного силиконового демпфера крутильных колебаний по результатам лабораторных исследований

The results of laboratory studies on the non-dismountable assessment of the technical condition of a model torsional vibration damper conducted at the MTS testing center of the Astrakhan State Technical University are presented. The relevance lies in the practical application of the obtained research results for a non-dismountable assessment of the technical condition of silicone dampers of marine diesel engines and improving the effectiveness of the existing methodology. The assessment is proposed to be carried out using an in-depth analysis of the torsional oscillation function using wavelet analysis and window Fourier transform methods for dynamic modes of operation of a marine power plant with a rapid change in the rotational speed of the shaft line – start, set the rotational speed and stop. These modes can be dangerous for marine propulsion systems, which is confirmed by a number of facts of shaft destruction and loss of propellers during start-up and reverse of the main power plant. As criteria for evaluating the technical condition of the damper are adopted both traditional ones (the magnitude of stresses in the shafts, the amplitude and frequency of torsional vibrations) and the author's ones (the characteristics of the waveform analysis and windowed Fourier transform methods of the torsional vibration function) as well as the magnitude of vibration along three measuring axes. The data were obtained as a result of the use of the author's experimental samples of the torsional vibration monitoring system and a measuring device based on accelerometers in research. As a result of the study, the dependence of the voltage changes in the shafts, the frequency of vibrations, vibration and the characteristics of the waveform of the wavelet analysis of the Morlet function and windowed Fourier transform diagrams of the torsional vibration function on three simulated situations of the technical condition of the silicone damper – during silicone leakage, flywheel mass sticking and normal operation.

Longitudinal-Torsional Frequency Coupling Design of Novel Ultrasonic Horns for Giant Magnetostrictive Transducers.

The use of advanced brittle composites in engineering systems has necessitated robotic rotary ultrasonic machining to attain high precision with minimal machining defects such as delamination, burrs, and cracks. Longitudinal-torsional coupled (LTC) vibrations are created by introducing helical slots to a horn's profile to enhance the quality of ultrasonic machining. In this investigative research, modified ultrasonic horns were designed for a giant magnetostrictive transducer by generating helical slots in catenoidal and cubic polynomial profiles to attain a high amplitude ratio (TA/LA) and low stress concentrations. Novel ultrasonic horns with a giant magnetostrictive transducer were modelled to compute impedances and harmonic excitation responses. A structural dynamic analysis was conducted to investigate the effect of the location, width, depth and angle of helical slots on the Eigenfrequencies, torsional vibration amplitude, longitudinal vibration amplitude, stresses and amplitude ratio in novel LTC ultrasonic horns for different materials using the finite element method (FEM) based on the block Lanczos and full-solution methods. The newly designed horns achieved a higher amplitude ratio and lower stresses in comparison to the Bezier and industrial stepped LTC horns with the same length, end diameters and operating conditions. The novel cubic polynomial LTC ultrasonic horn was found superior to its catenoidal counterpart as a result of an 8.45% higher amplitude ratio. However, the catenoidal LTC ultrasonic horn exhibited 1.87% lower stress levels. The position of the helical slots was found to have the most significant influence on the vibration characteristics of LTC ultrasonic horns followed by the width, depth and angle. This high amplitude ratio will contribute to the improved vibration characteristics that will help realize good surface morphology when machining advanced materials.

Nonlinear characteristics and radial-bending-torsional vibration of a blade with breathing crack

Rotor failures due to cracked blades are frequently observed in rotating machinery. The identification of cracking state of rotating blade based on vibration characteristics has garnered a lot of attention. However, nonlinear characteristics and vibration combining in radial, bending and torsional directions of a rotating blade induced by the crack breathing is yet not clear. This paper proposes a radial-bending-torsional dynamic model of rotating blade with breathing crack. A time-varying integration method is proposed for determining the crack state based on the strain energy release rate. The crack breathing behavior is described by Boolean operation and the numerical integration are applied to open or close the crack. The model is validated through modal analysis, vibration responses and contact state of crack surface. Frequency veering is changed between the 2nd flap and 1st edgewise frequency due to the existence of crack. Strong nonlinear behaviors are found in the radial and torsional vibrations because of the crack breathing. Nonlinearities are also found in the combined vibrations between the radial-bending and the bending-torsional directions. Radial and torsional vibration amplitude levels can be used as an indication of blade crack failure, but the applicability depends on the absolute response decided by the aerodynamic excitation and resonant vibration. These findings can serve as guidance in crack identification and cracking state monitoring of rotating blades.

Torsional vibration analysis and fuzzy adaptive PID control optimization of underwater vector propulsion shaft systems

To examine the torsional vibration of vector propulsion shaft system (VPSS), a four-degree-of-freedom vibration model of the VPSS is established by concentrated mass approach, and the torsional vibration differential equation of the VPSS is deduced based on the Lagrange approach. The vibration differential equations is addressed numerically applying the Runge-Kutta algorithm to investigate the effect of various working shaft angles β on the free and forced vibration of the VPSS under the excitation conditions. To further reduce the torsional vibration amplitude and avoid fatigue damage of the system, and considering the nonlinear relationship within the system, this study develops a fuzzy adaptive PID approach to control the VPSS. The results show that the maximum torsional vibration amplitude of the VPSS is reduced by more than 70% and the transient response time is shortened by more than 90% with this control approach, which effectively reduces the torsional vibration amplitude of the VPSS and thereby significantly improves the safety performance of the underwater vehicle. This may provide technical references for the vibration control theory of the VPSS as well as engineering applications.

Optimized design of silicone oil torsional damper for diesel generator

Abstract Due to the high cylinder pressure and high-performance requirements, the silicone oil damper of an inline six-cylinder diesel generator needs to be optimized to reduce the crankshaft stress. The centralized mass method was used to simplify the crankshaft system. A multi-body dynamic model was established, and the crankshaft stress and torsional vibration amplitude were simulated. The results show that the excessive shear stress at generator crank pin 5 is due to the resonance between the first-order intrinsic frequency of the shaft system and the 3rd harmonic torsional vibration. The shear stress was analyzed for different damper thicknesses and stiffnesses, and it was found that the shear stress at crank pin 5 was minimized when the damper thickness was 60 mm and the torsional stiffness was 250,000 N·m/rad. The torsional amplitudes at different speeds and frequencies were measured in the bench test, and the results were consistent with the calculations. The designed silicone oil torsional damper meets the requirements of the 2000-hour bench test.

Study on heat dissipation of torsional vibration damper for engine crankshaft

Abstract High temperatures in torsional vibration dampers can cause silicone oil to fail, increasing crankshaft vibration and shortening component fatigue life. Accurate prediction of the damper temperature field is key to the manufacture of highly reliable torsional vibration dampers. This study establishes the relationship between temperature, torsional vibration amplitude, silicone oil viscosity, rotational speed, housing and inertia ring clearance, and heat generation power based on Comsol. A bench test was carried out on a 6-cylinder inline diesel engine. The simulated temperature profile matched the tested result in terms of trend and relative value, and the established model could accurately predict the temperature field of the engine crankshaft torsional vibration damper.

РЕМОНТ КОРЕННЫХ И ШАТУННЫХ ШЕЕК КОЛЕНЧАТЫХ ВАЛОВ ДИЗЕЛЬНЫХ ДВИГАТЕЛЕЙ ПРИ ПОМОЩИ ДИСКРЕТНОГО УПРОЧНЕНИЯ

Studies to assess the effect of discrete hardening of the crankshaft journals on its fatigue strength have been carried out. For this purpose, fatigue tests were carried out on two control parts of the D80 type crankshaft. It was established that the destruction of control part No. 1 occurred after 322,000 cycles, control part No. 2 after 201,000 cycles. The destruction zone of both control parts passes along the R8 mm transition fillet of the connecting rod journals. This allows us to conclude that the discrete hardening factor is not associated with fatigue failure of the control parts. In order to determine the service life of the crankshaft of the KamAZ 740 engine, strengthened in a discrete way (shaft of the fourth repair size), it was installed on a KamAZ 5320 vehicle. As a result of the tests, it was found that during the entire testing cycle the vehicle's mileage was 109,000 km. Moreover, at the time of completion of the tests, all parameters of the car’s engine met the technical requirements. The KamAZ 5320 vehicle is in operation to this day. Its mileage was 269,000 km without stopping for major repairs. To conduct operational tests of a cast iron crankshaft with discrete hardening of a D80 type engine, a 1D80B diesel generator engine was taken, which after assembly was subjected to full-scale testing. These tests included a 100-hour engine run-in, determination of the vibration level and amplitudes of torsional vibrations of the diesel generator shaft line in the operating speed range. The analysis of the vibration state of the engine showed that in all test modes the vibration level at the points under study does not exceed the norms (0.350 mm on the turbocharger housing and 0.150 mm on the generator foot). The maximum stresses from torsional vibrations were: 8, about 17.5 MPa; 4, 5 order 10.5 MPa; 1.5 order 10.0 MPa. The resulting stress levels are significantly lower than permissible. Tests of the 1D80B diesel generator showed its full compliance with the technical requirements for the operation of this engine.

Ultrasonic complex vibration source equipped with a step horn with a welding tip and its welding characteristics

We have developed a different type of ultrasonic complex vibration source that can generate planar vibrations. The ultrasonic complex vibration source is equipped with a step horn with a hollow part that incorporates a welding chip to improve practicality for industrial applications. The hollow portion in the step horn attached to the ultrasonic complex vibration source enables the adjustment of the longitudinal and torsional vibration amplitude. In this work, we performed finite element method analysis to develop the ultrasonic complex vibration source equipped with a step horn containing a hollow part and a welding tip. The ultrasonic complex vibration source was manufactured and the vibration characteristics and welding properties were measured. The same welding strength was obtained under similar experimental conditions to conventional ultrasonic complex vibration sources. Our results demonstrate that ultrasonic complex vibration sources can be miniaturized and are practically useful.

Dilatant-Fluid Torsional Vibration Damper for a Four-Stroke Diesel Engine Crankshaft

Abstract This paper presents a study of a viscous torsional vibration damper for a crankshaft of a four-stroke diesel engine. The reliable operation of a widely used silicone-type viscous damper depends on the ability of the silicone oil to absorb the energy of torsional vibrations. The non-Newtonian shear flow of the silicone oil interlayer, characterised by a reduction in the shear-rate-dependent viscosity and a moment of the drag forces, negatively affects damping characteristics. A torsional vibration damper, filled with a shear-thickening fluid, was considered and a rheological approach, based on viscosity growth with the shear rate increase, was applied. For such a damper, larger velocity gradients correspond to the higher values of a viscous force, which decreases torsional vibration. The parameter of damper effectiveness (defined by the fluid flow index, values of the damper gaps, torsional vibration amplitude and frequency) was implemented. It has been established that the efficiency of the torsional vibration damper filled with a dilatant fluid does not depend on the damper dimensions and gaps and significantly increases when a shear-thickening fluid is used instead of silicone oil or a Newtonian fluid. At higher values of the flow index, when the non-Newtonian flow becomes distinct, torsional vibrations are damped more effectively. Critical vibration amplitudes at high-velocity gradients, in turn, increase the damping effect as the moment of the drag forces and flow index are power-law related.

Mathematical modeling of torsional vibrations of the wheel-motor unit of mains diesel locomotive UZTE16M

The article considers methods for studying torsional vibrations of the wheel-motor block of a diesel locomotive UZTE16M. The diesel locomotives in question were modernized at the structural enterprise “O’ztemiryo’lmashta’mir” (Machine building and repair in Uzbekistan Railways company) under the joint-stock company “O’zbekiston temir yo’llari” (Uzbekistan railways). The authors of the article developed a dynamic model for the analysis of torsional vibrational movements that occur in the traction transmissions of the UZTE16M diesel locomotive, taking into account the geometric dimensions of the electric traction motors of the main locomotives and the degree of their wear. Based on the model of the wheel-motor block of mainline locomotives, differential equations of the torsional-vibrational motion of traction gears are obtained in the form of Lagrange equations of the 2nd kind. The results of numerical studies of the amplitudes of torsional vibrations of the wheel-motor block of the UzTE16M locomotive at different frequencies are presented. All calculations were performed in the MATHCAD 15 environment.

Impact of shafting angle of F5 cold rolling mill on the dynamics of main drive system

In view of the torsional vibration problem of the main drive system of the F5 rolling mill in a steel plant, two sets of torque monitoring sensors were installed on the cross universal joint shaft on site. Through online monitoring, it is found that the torsional vibration frequency of the cross universal joint shaft is twice the rotational frequency of the drive system, and the vibration amplitude of the upper shaft is greater than that of the lower shaft. Considering the influence of the inclination angle of the cross universal joint shaft, the transmission system can be simplified as a multi-body dynamic model of a five-inertia spring-mass system. Combined with the effect of the rolling torque of the strip and the electromagnetic torque of the main motor on the main drive system, a simulation model considering multi-physics coupled torsional vibration was established MATLAB/Simulink. The simulation shows that the torsional vibration frequency changes linearly with the rolling speed, which is always twice the rotational frequency of the transmission system, and the vibration amplitude also changes with the rolling speed, consistent with the field test results. As the diameter of the work roll increases, the angle of inclination of the universal joint shaft decreases, and the value of the torsional amplitude of the system also decreases. When the inclination angle is not considered at all, the torsional vibration of the system disappears, it shows that the inclination angle of the cross universal joint shaft is the root cause of the double rotational frequency torsional vibration of the main drive system. Since the inclination of the cross universal joint cannot be eliminated, the simulation results show that the torsional vibration of the transmission system can be effectively reduced by using large-diameter work rolls and reducing the stiffness of the upper cross universal joint while increasing the stiffness of the lower universal joint. When the lower shaft stiffness increases to 1.3 times, the upper shaft stiffness decreases to 0.8 times, and the work roll diameter is 425 mm, the torsional vibration amplitude of the upper connecting shaft decreases by 22.3 % at the rolling speed of 1200 m/min.

Semi-active control of crankshaft skyhook based on magnetorheological torsional damper

The purpose of this study was to solve the problem that the damping of rubber or silicone oil torsional dampers used in crankshafts is not adjustable and cannot effectively control torsional vibration at different resonant frequencies. Based on the controlled rheological properties of magnetorheological (MR) smart materials, this study designed a new type of variable damping MR torsional damper (MRTD) and proposed a semi-active control method to effectively control the torsional vibration of the crankshaft under multiple harmonic resonances. First, a mechanical model of the MRTD and a lumped parametric mass model of the crankshaft system were developed, and the resonance frequency harmonic range of the crankshaft system operation was determined by the torsional vibration characteristics analysis. Then a semi-active skyhook control method for the MRTD was proposed, and a joint control simulation analysis was performed using Amesim and Matlab software. The torsional vibration control effects of the crankshaft system with no damper, MRTD with different damping coefficients, and MRTD with skyhook control under acceleration and uniform speed conditions were comprehensively investigated. The simulation results indicated that the skyhook damping control significantly reduced the torsional vibration amplitude under both acceleration and uniform speed conditions, verifying the effectiveness of the skyhook-based control strategy for MRTD.

Self-Sensing WS2 Nanotube Torsional Resonators.

We demonstrate self-sensing tungsten disulfide nanotube (WS2 NT) torsional resonators. These resonators exhibit all-electrical self-sensing operation with electrostatic excitation and piezoresistive motion detection. We show that the torsional motion of the WS2 NT resonators results in a change of the nanotube electrical resistance, with the most significant change around their mechanical resonance, where the amplitude of torsional vibrations is maximal. Atomic force microscopy analysis revealed the torsional and bending stiffness of the WS2 NTs, which we used for modeling the behavior of the WS2 NT devices. In addition, the solution of the electrostatic boundary value problem shows how the spatial potential and electrostatic field lines around the device impact its capacitance. The results uncover the coupling between the electrical and mechanical behaviors of WS2 and emphasize their potential to operate as key components in functional devices, such as nanosensors and radio frequency devices.

Nonlinear analysis of axial-torsional vibration of drill string based on a 3 DOF model

Based on a model with three-degree-of-freedom, the nonlinear coupled axial-torsional vibration of drill string is numerically studied considering a modified contact model of bit-rock interaction. The effects of driving angular velocities, nominal drilling pressures, and formation stiffness on response are discussed. The simulation results show that response can be periodic, quasi-periodic or chaotic motion with the variation of system parameters. Increasing driving angular velocity is helpful to reduce the duration of sticking and even make the system stick-slip free. However, bit-bounce may occur if driving angular velocity is too large. Increasing nominal drilling pressure can cause the system to be more prone to stick-slip, but it has dampening effect on bit-bounce. The larger the formation stiffness is, the smaller the amplitude of the axial vibration response of the system is, and the driving angular velocity corresponding to the maximum amplitude of the axial vibration response is also larger, whereas the variation of the amplitude of torsional vibration is smaller. Compared with the results from two-degree-of-freedom model, the amplitude of torsional vibration of the present model is remarkable greater. Meanwhile, the present model is more prone to stick-slip than the one with two-degree-of-freedom, and it is not easy to bit bounce.

Effect of vibration on the aerodynamic behavior of a 5:1 rectangular cylinder

Synchronized surface pressure measurements and forced motion techniques are performed in a wind tunnel to investigate the aerodynamic characteristics of an oscillatory rectangular cylinder with a 5:1 benchmark section. The effects of the vertical and torsional vibration amplitude and the Reynolds number (Re) on the streamwise surface pressure are studied. The results show that the impact of vertical motion on the streamwise correlation of surface pressure is relatively smaller than that of torsional motion. It is also found that the effect of input energy from the forced motion and vortex shedding on the surface pressure does not remain constant along streamwise direction versus vibration amplitude. A method of estimating the flow structure around an oscillatory cylinder is proposed in terms of phase difference between the separation point and downstream pressure taps at vortex-shedding frequency, as well as the standard deviation, correlation coefficient and pressure contours. The Proper Orthogonal Decomposition (POD) technique is also introduced to lead to a better physical understanding and analyzing three-dimensional (3D) features of the pressure field structure around an oscillatory cylinder. Finally, the non-Gaussian features of the fluctuating surface pressure versus the vibration amplitudes are also investigated. This paper is intended to be a supplement to the 5:1 benchmark framework.

ВЫБОР ПАРАМЕТРОВ ДЕМПФЕРА КРУТИЛЬНЫХ КОЛЕБАНИЙ 4-ЦИЛИНДРОВОГО ДИЗЕЛЯ

Torsional vibration dampers in modern internal combustion engines are used to reduce alternating shear stresses leading to fatigue failure of the crankshaft, as well as to diagnose the crankshaft, reduce oil consumption, increase the mechanical efficiency of the engine, and reduce noise. Torsional vibration dampers are suggested to be used at OJSC “MINSK MOTOR PLANT” Holding Managing Company” to improve the technical level of four-cylinder diesel engines. Damper parameters choice is based on torsional system model research, which is equivalent to the torsional diesel system of a 4ЧН (4ChN) 11×12.5 diesel engine. The amplitudes of the crankshaft nose torsional vibrations with the engine running are calculated according to the full-load curve. It was found that the maximum amplitude of vibrations corresponds to the diesel engine operation at a rated speed of 1000 rpm. In this case the amplitude of twisting of the crankshaft nose is 0.123 deg. For this diesel engine operating mode, the moment of inertia of the liquid damper flywheel and the damping coefficient were determined. They ensure a decrease in the torsional vibrations amplitude by more than three times. The calculation determined the expected decrease in the torsional vibrations amplitude for other modes of engine operation according to the full-load curve. In the entire research of crankshaft rated speed, the amplitude of nose torsional vibrations when using a damper is three times lower than without it. For experimental refinement of the damper parameters, a damper design with a variable moment of the flywheel inertia, as well as the possibility of replacing the polymethylsiloxane fluid are proposed.

Laminar flow-induced vibration of a three-degree-of-freedom circular cylinder with an attached splitter plate

Splitter plates are widely used for drag reduction and vibration control or enhancement of circular cylinders. The effects of a splitter plate on the vertical flow-induced vibrations of a circular cylinder have been well studied. However, its effects on the vertical-torsional coupled vibrations require further investigation. In this paper, the three-degree-of-freedom (TDoF) flow-induced vibrations of a circular cylinder with an attached splitter plate are numerically investigated at a Reynolds number of 100. The ratio between the torsional and vertical natural frequencies is varied within fθ,0/fh,0 = 6, 4, 3, 2, and 1. Numerical results show that the flow-induced vibrations of a TDoF cylinder-plate assembly, depending on the frequency ratio, may differ significantly from those of a single-degree-of-freedom (SDoF) vertical or torsional assembly. For cylinder-plate assemblies with fθ,0/fh,0 = 6–2, the vibrations can be divided into a vertical vibration-dominated branch (V branch), a torsional vibration-dominated branch (T branch), and a coupled vibration-dominated branch (C branch). The V branch vibration of a TDoF assembly is similar to that of an SDoF vertical assembly at the same reduced flow velocity, while the difference increases with decreasing the frequency ratio. The T branch vibration of a TDoF assembly is almost identical to the vibration of an SDoF torsional assembly at the same reduced flow velocity. The ratio between the torsional and vertical vibration amplitudes increases with decreasing the frequency ratio in the C branch. For the assembly with fθ,0/fh,0 = 1, vertical-torsional coupled vortex-induced vibrations are observed with the largest torsional amplitude as high as 46.3°. The vibrations of TDoF assemblies with all considered frequency ratios may be more severe than those of SDoF vertical and torsional assemblies within specific ranges of reduced flow velocities. The mean drag coefficients for the fθ,0/fh,0 = 6–2 assemblies are lower than a stationary circular cylinder but often higher than a stationary cylinder-plate assembly. The mean drag coefficients for the fθ,0/fh,0 = 1 assembly in the lock-in range are considerably larger than that of a stationary circular cylinder. For TDoF assemblies with fθ,0/fh,0 = 6–2, the V branch and C branch vibrations are mainly driven by the interaction between the assembly and the shear layers, while the T branch vibrations are excited by the typical 2S mode of vortex shedding. The 2S vortex shedding mode is also observed in the lock-in range of the fθ,0/fh,0 = 1 assembly.

Experimental investigations on post-flutter performance of a bridge deck sectional model using a novel testing device

This paper studies the flutter performances of a streamlined bridge deck sectional model using a recently developed testing device for large-amplitude free vibration test. The reported torsional vibration amplitude of the sectional model exceeds 15°, and higher vibration amplitudes can be achieved if desired. The flutter performances at various initial angles of attack α0, the hysteresis behavior, and the energy budget property of the flutter response are analyzed. Experimental results show that the sectional model exhibits divergent vibrations right after the critical flutter velocities for α0 = 0°, −3°, and −5°, while it performs limit cycle oscillations (LCO) after the critical flutter velocities for α0 = +3° and +5°. Hysteresis phenomena are observed for all tested angles of attack. Both the critical flutter velocity and the vibration amplitudes around the critical velocity may be affected by the initial impulse excitation exerted on the bridge deck. The vertical-to-torsional amplitude ratio decreases with increasing the vibration amplitude for a coupled LCO, while the opposite rule is observed for a divergent vibration. The energy dissipated by the mechanical damping accumulates continuously while the total mechanical energy varies non-monotonously with increasing time. This study is expected to deepen the understanding of the flutter responses of a bridge deck in the presence of nonlinear aerodynamic effects. The experimental results can also serve as a database for validating computational fluid dynamics procedures and nonlinear self-excited force models.