AUTOMATIC CRACK DETECTION USING THE NATURAL FREQUENCY RESPONSE OF THICK -WALLED CYLINDERS

2010 ◽  
Author(s):  
M. A. Hussain ◽  
M. A. Johnson ◽  
Donald O. Thompson ◽  
Dale E. Chimenti
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Crack Detection

Vibration Characteristics of Rotating Thin Disks—Part I: Experimental Results

2012 ◽  
Vol 79 (4) ◽  
Author(s):  
Ramin M. H. Khorasany ◽  
Stanley G. Hutton
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Linear Theory ◽  
Lateral Force ◽  
Vibration Characteristics ◽  
Experimental Results ◽  
Rotating Disks ◽  
Critical Speeds ◽  
Applied Forces ◽  
Thin Disks

Analysis of the linear vibration characteristics of unconstrained rotating isotropic thin disks leads to the important concept of “critical speeds.” These critical rotational speeds are of interest because they correspond to the situation where a natural frequency of the rotating disk, as measured by a stationary observer, is zero. Such speeds correspond physically to the speeds at which a traveling circumferential wave, of shape corresponding to the mode shape of the natural frequency being considered, travel around the disk in the absence of applied forces. At such speeds, according to linear theory, the blade may respond as a space fixed stationary wave and an applied space fixed dc force may induce a resonant condition in the disk response. Thus, in general, linear theory predicts that for rotating disks, with low levels of damping, large responses may be encountered in the region of the critical speeds due to the application of constant space fixed forces. However, large response invalidates the predictions of linear theory which has neglected the nonlinear stiffness produced by the effect of in-plane forces induced by large displacements. In the present paper, experimental studies were conducted in order to measure the frequency response characteristics of rotating disks both in an idling mode as well as when subjected to a space fixed lateral force. The applied lateral force (produced by an air jet) was such as to produce displacements large enough that non linear geometric effects were important in determining the disk frequencies. Experiments were conducted on thin annular disks of different thickness with the inner radius clamped to the driving arbor and the outer radius free. The results of these experiments are presented with an emphasis on recording the effects of geometric nonlinearities on lateral frequency response. In a companion paper (Khorasany and Hutton, 2010, “Vibration Characteristics of Rotating Thin Disks—Part II: Analytical Predictions,” ASME J. Mech., 79(4), p. 041007), analytical predictions of such disk behavior are presented and compared with the experimental results obtained in this study. The experimental results show that in the case where significant disk displacements are induced by a lateral force, the frequency characteristics are significantly influenced by the magnitude of forced displacements.

Analysis Accuracy of Digital Image Correlation Technique to Monitor Natural Frequency Response of Building under Dynamic Excitation

2011 ◽  
Vol 71-78 ◽  
pp. 3904-3908
Author(s):  
Ming Hsiang Shih ◽  
Wen Pei Sung ◽  
Feng Jen Tsai
Keyword(s):  
Digital Image Correlation ◽  
Frequency Response ◽  
Natural Frequency ◽  
Digital Image ◽  
Correlation Method ◽  
Cost Effective ◽  
Image Correlation ◽  
Correlation Technique ◽  
The People ◽  
External Forces

Strong typhoon and earthquake seriously threaten the safety of the life and property of the people. A cost-effective and reliable method is proposed to monitor the natural frequency response of building under excitation of external forces based on the applying digital image correlation method, DIC. The analysis accuracy of this dynamic DIC method is tested and verified by comparing with numerical analysis program, accelerometers, ACC and fast Fourier Transform, FFT. The test results reveal that the analysis accuracy of this DIC method near to the ACC and FFT traditional experimental methods. They demonstrate that using this DIC method to detect dynamic response of building under the excitation of external force has high practicability.

Pipeline Vibration Analysis and Control for the First Booster of Ethylene

2013 ◽  
Vol 313-314 ◽  
pp. 777-784 ◽  
Author(s):  
Wei Yi Zhang ◽  
Yong Ming An ◽  
Shu Feng Wang ◽  
Hang Wu ◽  
Jun Yong Lei
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Pressure Pulsation ◽  
Exhaust Valve ◽  
Pipeline System ◽  
Exhaust Pipe ◽  
Pulsation Frequency ◽  
Suction Pipe ◽  
The Law ◽  
Pipeline Vibration

For existing local severe vibration problems on the pipeline system of conveying ethylene booster in ethylene cracking system of a petrochemical company, the detailed analysis by CAESARII was carried out to its pipeline system natural frequency and vibration modal; The flow of ethylene gas within the booster pipeline from the suction pipe to exhaust pipe inside including the buffer tank was analyzed using fluid analysis software--FLUENT, the pressure field and velocity field of the flow was obtained. According to the law of the suction and exhaust valve open-closed mouth, dynamic boundary conditions was set on the suction valve and exhaust valve. The ethylene flow non-steady-state analysis calculations was carried out within the pipeline from the suction tube inlet to suction valve and from the exhaust valve to the exhaust tube outlet , the law of the pressure pulsation frequency response was obtained on the suction pipe inlet and the exhaust pipe outlet. The results show that ethylene gas pipeline pressure pulsation frequency response was basically equal to the frequency of the suction and exhaust valve open-closed mouth; The actual pipe vibration modals of the pipeline system on the scene and the pipeline vibration modals a few corresponding to the natural frequencies of the pipeline system close to the pulsation frequency in flow pressure are very similar, indicating that the vibration of the pipeline system is due to the pressure pulse frequency of the ethylene gas internal pipeline close to the natural frequency of the local pipeline, caused due to local resonance. Changing the form of hangers in vibration system can change the natural frequency of pipeline to avoid resonance. Tube fluid dynamic pressure caused by the stress of the pipeline is limited and will not cause damage to the tube material. Mass flow rate does not match with the tube diameter will cause too large flow velocity, the inertia force caused by the larger on the suction valve and exhaust valve before and after, resulting in the forced vibration of the compressor body.

Crack Detection in Cantilever Shaft Beam Using Natural Frequency

2017 ◽  
Vol 4 (2) ◽  
pp. 1366-1374 ◽  
Author(s):  
Dinesh Satpute ◽  
Prasad Baviskar ◽  
Pritesh Gandhi ◽  
Mayur Chavanke ◽  
Tejas Aher
Keyword(s):  
Natural Frequency ◽  
Crack Detection ◽  
Cantilever Shaft

Dynamic Analysis and Parameter Identification of a Single Mass Elastomeric Isolation System Using a Maxwell-Voigt Model

2006 ◽  
Vol 128 (6) ◽  
pp. 713-721 ◽  
Author(s):  
Jie Zhang ◽  
Christopher M. Richards
Keyword(s):  
Parameter Identification ◽  
Dynamic Analysis ◽  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Response Spectra ◽  
Isolation System ◽  
Single Mass ◽  
Voigt Model ◽  
Stiffness And Damping

Dynamic analysis and parameter identification of a single mass elastomeric isolation system represented by a Maxwell-Voigt model is examined. Influences that the stiffness and damping values of the Maxwell element have on natural frequency, damping ratio, and frequency response are uncovered and three unique categories of Maxwell-type elements are defined. It is also shown that Voigt and Maxwell-Voigt models with equivalent natural frequencies and damping ratios can have considerably different frequency response spectra. Lastly, a parameter identification method is developed for identifying Maxwell-Voigt models from frequency response spectra. The method is based on constant natural frequency and damping ratio curves generated from modal analysis of potential Maxwell-Voigt models.

scholarly journals Constrained Tibial Vibration in Mice: A Method for Studying the Effects of Vibrational Loading of Bone

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Blaine A. Christiansen ◽  
Philip V. Bayly ◽  
Matthew J. Silva
Keyword(s):  
Soft Tissue ◽  
Frequency Response ◽  
Natural Frequency ◽  
Lower Leg ◽  
Bone Strain ◽  
Fe Model ◽  
Loading Method ◽  
Vibrational Loading ◽  
Controlled Conditions

Vibrational loading can stimulate the formation of new trabecular bone or maintain bone mass. Studies investigating vibrational loading have often used whole-body vibration (WBV) as their loading method. However, WBV has limitations in small animal studies because transmissibility of vibration is dependent on posture. In this study, we propose constrained tibial vibration (CTV) as an experimental method for vibrational loading of mice under controlled conditions. In CTV, the lower leg of an anesthetized mouse is subjected to vertical vibrational loading while supporting a mass. The setup approximates a one degree-of-freedom vibrational system. Accelerometers were used to measure transmissibility of vibration through the lower leg in CTV at frequencies from 20Hzto150Hz. First, the frequency response of transmissibility was quantified in vivo, and dissections were performed to remove one component of the mouse leg (the knee joint, foot, or soft tissue) to investigate the contribution of each component to the frequency response of the intact leg. Next, a finite element (FE) model of a mouse tibia-fibula was used to estimate the deformation of the bone during CTV. Finally, strain gages were used to determine the dependence of bone strain on loading frequency. The in vivo mouse leg in the CTV system had a resonant frequency of 60Hz for ±0.5G vibration (1.0G peak to peak). Removing the foot caused the natural frequency of the system to shift from 60Hzto70Hz, removing the soft tissue caused no change in natural frequency, and removing the knee changed the natural frequency from 60Hzto90Hz. By using the FE model, maximum tensile and compressive strains during CTV were estimated to be on the cranial-medial and caudolateral surfaces of the tibia, respectively, and the peak transmissibility and peak cortical strain occurred at the same frequency. Strain gage data confirmed the relationship between peak transmissibility and peak bone strain indicated by the FE model, and showed that the maximum cyclic tibial strain during CTV of the intact leg was 330±82με and occurred at 60–70Hz. This study presents a comprehensive mechanical analysis of CTV, a loading method for studying vibrational loading under controlled conditions. This model will be used in future in vivo studies and will potentially become an important tool for understanding the response of bone to vibrational loading.

Mitigation of Vortex-Induced Vibrations of a Pivoted Circular Cylinder Using an Adaptive Pendulum Tuned-Mass Damper

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Sina Kheirkhah ◽  
Richard Lourenco ◽  
Serhiy Yarusevych ◽  
Sriram Narasimhan
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Tuned Mass Damper ◽  
Single Frequency ◽  
Fundamental Frequencies ◽  
Transverse Vibrations ◽  
Synchronization Region ◽  
Vortex Induced Vibrations ◽  
Mass Damper

A novel adaptive pendulum tuned-mass damper (TMD) was integrated with a two degree-of-freedom (DOF) cylindrical structure in order to control vortex-induced vibrations of the structure. The natural frequency of the TMD was adjusted autonomously in order to control the vortex-induced vibrations. The experiments were performed at a constant Reynolds number of 2100 and for four reduced velocities, 4.18, 5.44, 6.00, and 6.48. Two TMD damping ratios, 0 and 0.24, were investigated for a constant TMD mass ratio of 0.087. The results demonstrate that tuning the natural frequency of the TMD to the natural frequency of the structure decreases the amplitudes of transverse and streamwise vibrations of the structure significantly. Specifically, the transverse amplitudes of vibrations are decreased by a factor of ten and streamwise amplitudes of vibrations are decreased by a factor of three. Depending on the value of the TMD damping ratio, the frequency of transverse vibrations is either characterized by the natural frequency of the structure or by two other fundamental frequencies, one higher and the other lower than the natural frequency of the structure. The results demonstrate that, independent of the TMD damping and tuning frequency ratios, the frequency of streamwise vibrations matches that of the transverse vibrations in the synchronization region, and the cylinder traces elliptic trajectories. A mathematical model is proposed to gain insight into the frequency response of the structure and fluid-structure interactions. The model shows that, for low TMD damping ratios, the frequency response of the structure equipped with the TMD is characterized by two fundamental frequencies; whereas, for relatively high TMD damping ratios, the frequency response of the structure is characterized by a single frequency, i.e., the natural frequency. In both cases, the fluid forcing within the synchronization region is linked to the fundamental frequency/frequencies of the structure. Thus, the classical definition of synchronization applies to multiple DOF structures undergoing vortex-induced vibrations.

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