Experimental analysis of vibrator baseplate dynamics

Brook, Robert A.; Crews, Gary A.

doi:10.1190/1.1888909

Cited by 6 publications

(3 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the weighted sum method is very practical, the disadvantages are also exposed with the development of the seismic exploration. Researchers have verified that weighted sum method just provides a representation of the ground force in a narrow frequency bandwidth, because the model cannot describe the interaction between the baseplate and the ground as the frequency increases (Brook and Crew, 1991; Lebedev and Beresnev, 2005; Liu et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

A model for the vibrator–ground coupling vibration and the dynamic responses under excitation of sweep signal

Huang

Lian

et al. 2019

Advances in Structural Engineering

View full text Add to dashboard Cite

To analyze the behavior of the vibrator–ground coupling vibration, a model containing equivalent dynamic stiffness and equivalent dynamic damping to describe the interaction between the vibrator and the ground is established based on half-space theory. According to load cell test, this model shows a good agreement with the experimental data. Dynamic responses of the structure are analyzed on displacement, velocity, acceleration, and ground force. Results show that the stroke and pump displacement are main constraints that limit the bandwidth of vibrator toward low frequency, and the stroke of conventional vibrator is not long enough to achieve lower frequency. Analysis of velocity response indicates that with the increase of frequency, a larger mass results in a lower velocity under external force. The influence of the ground acting on the baseplate is limited, and the acceleration of the baseplate is determined by its own mass beyond 80 Hz. Analysis of ground force shows that the response of the structure can be divided into three stages. The reaction mass, the baseplate, and the ground play different roles in dominating the ground force at different frequency bands.

show abstract

Section: Introductionmentioning

confidence: 99%

A model for the vibrator–ground coupling vibration and the dynamic responses under excitation of sweep signal

Huang

Lian

et al. 2019

Advances in Structural Engineering

View full text Add to dashboard Cite

show abstract

“…To improve the performance of vibrator, some studies focus on the response of vibrator. Brook and Crew 6 conducted field tests to analyze the baseplate dynamics and found that structural problems could introduce errors in the higher frequencies. Martin and Jack 7 used a down hole string of cemented geophones to monitor the seismic signal generated by vibrator, and found that the vibrator response changed with different force level.…”

Section: Introductionmentioning

confidence: 99%

Modal characteristics and phase response of vibrator under excitation of sweep frequency

Wen

Huang

et al. 2020

Advances in Mechanical Engineering

View full text Add to dashboard Cite

To analyze the dynamic responses of vibrator, a vibrator-ground coupling vibration model considering sweep frequency is proposed based on half-space theory, and modal characteristics and phase response of the structure are investigated. Results show that the sweep frequency has a significant effect on the dynamic responses of the vibrator. The natural frequency of the vibrator changes with sweep frequency, and the resonance may occur at 2.071 Hz and 53.12 Hz. The vibrator has two mode shapes. The first-order mode shape is that the reaction mass and the baseplate move in the same direction and the structure is dominated by the reaction mass. At the second-order resonance, the reaction mass and the baseplate move in opposite directions and the baseplate dominates the system. The phase of the vibrator also changes with the frequency and varies greatly. The phases of reaction mass acceleration, baseplate acceleration and ground force suffer abrupt changes at about 2 Hz and 50 Hz. Especially, the phase of the baseplate acceleration experiences a 180° jumping at about 50 Hz. The abrupt change/jumping frequencies of the phase are basically the same as the natural frequencies, indicating that the resonance has significant effect on the vibrator output.

show abstract

“…In a 1984 paper, Sallas introduced weighted sum method which was based on measuring the acceleration of reaction mass and baseplate to calculate the ground force [11]. Unfortunately, researchers have verified that the weighted sum method does not provide a true representation of the ground force [12][13][14], because the acceleration measured by the sensors is not reliable as the baseplate suffers unpredictable deformation at high frequencies [15][16][17]. Hendrix analyzed the response of baseplate at high frequencies using multiple accelerometers mounted on the baseplate [18].…”

Section: Introductionmentioning

confidence: 99%

Study on dynamics of vibrator baseplate at low and high frequencies

Huang¹,

Li²,

Lei³

2017

J. vibroeng.

View full text Add to dashboard Cite

In order to figure out the dynamics response of vibrator baseplate and why baseplate performs poorly at high frequencies, a finite element model of vibrator-ground is developed to analyze acceleration, deformation and decoupling of the baseplate at low and high frequencies. Results show that the acceleration at low frequencies is in accordance with the function of hydraulic pressure. On the contrary, the acceleration at high frequencies is irregular and fluctuant. Within the bandwidth, the maximum deformation locates in the central area, and the baseplate deformation in long-axis direction is greater than that in minor-axis direction. Compared to low frequencies, dynamics response at high frequencies suffers response delay, and the vibrator structure is very sensitive to asymmetry, resulting in warping and waveform deformation. Baseplate experiences decoupling at both low and high frequencies, however, the decoupling at high frequencies occurs more frequently, which leads to more serious distortion. It is also found that symmetrical structure is helpful for reducing negative deformation. In conclusion, high fluctuation of acceleration, response delay and harmonic caused by complicated deformation and decoupling distortion reduce the quality of output signal and block the bandwidth towards high frequencies.

show abstract

Experimental analysis of vibrator baseplate dynamics

Cited by 6 publications

References 6 publications

A model for the vibrator–ground coupling vibration and the dynamic responses under excitation of sweep signal

A model for the vibrator–ground coupling vibration and the dynamic responses under excitation of sweep signal

Modal characteristics and phase response of vibrator under excitation of sweep frequency

Study on dynamics of vibrator baseplate at low and high frequencies

Contact Info

Product

Resources

About