Identification of dynamic characteristics of nonlinear joint based on the optimum equivalent linear frequency response function

2010 ◽  
Vol 329 (9) ◽  
pp. 1460-1479 ◽  
Author(s):  
H. Kashani ◽  
A.S. Nobari
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Dynamic Characteristics ◽  
Frequency Response Function ◽  
Linear Frequency ◽  
Equivalent Linear ◽  
Nonlinear Joint

Structural Damage Identification Based on Strain Frequency Response Functions

2018 ◽  
Vol 18 (12) ◽  
pp. 1850159 ◽  
Author(s):  
Fariba Shadan ◽  
Faramarz Khoshnoudian ◽  
Akbar Esfandiari
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Dynamic Characteristics ◽  
Structural Damage ◽  
Frequency Response Function ◽  
Damage Identification ◽  
Model Updating ◽  
Measurement Data ◽  
Sensitivity Equation ◽  
Strain Frequency

Damage identification using the sensitivity of the dynamic characteristics of the structure of concern has been studied considerably. Among the dynamic characteristics used to locate and quantify structural damages, the frequency response function (FRF) data has the advantage of avoiding modal analysis errors. Additionally, previous studies demonstrated that strains are more sensitive to localized damages compared to displacements. So, in this study, the strain frequency response function (SFRF) data is utilized to identify structural damages using a sensitivity-based model updating approach. A pseudo-linear sensitivity equation which removes the adverse effects of incomplete measurement data is proposed. The approximation used for the sensitivity equation utilizes measured natural frequencies to reconstruct the unmeasured SFRFs. Moreover, new approaches are proposed for selecting the excitation and measurement locations for effective model updating. The efficiency of the proposed method is validated numerically through 2D truss and frame examples using incomplete and noise polluted SFRF data. Results indicate that the method can be used to accurately locate and quantify the severity of damage.

scholarly journals STUDYING THE DYNAMIC CHARACTERISTICS TO LENGTHEN THE OPERATING LIFE FOR A DIESEL ENGINE USING FREQUENCY RESPONSE FUNCTION (FRF) MEASUREMENT

SINERGI ◽  
2018 ◽  
Vol 22 (3) ◽  
pp. 161
Author(s):  
Subekti Subekti
Keyword(s):  
Diesel Engine ◽  
Frequency Response ◽  
Response Function ◽  
Dynamic Characteristics ◽  
Frequency Response Function ◽  
Natural Frequencies ◽  
Vibration Mode ◽  
Valve Train ◽  
Operating Life ◽  
Local Vibration

This research was conducted on Diesel engine single cylinder which aims to study the dynamic characteristics of Diesel engine type HATZ 1D 80 made in Germany. The test was performed by measuring the Frequency Response Function (FRF). In this study, the vibration response was measured at three points: point A which was situated below the engine shaft and in line with the stinger. Point A indicated the FRF point. Point B was located in the valve train component, while point C was situated above the cap of the valve train component. The range of frequencies applied was 0 - 3200 Hz, 3200 - 6400 Hz, 6400 - 9600 Hz, and 9600 - 11200 Hz. This research indicates that the natural frequencies arose because of the global vibration mode. The global vibration mode occurred at natural frequencies of 3118, 4805, 4821, 5021, 7129, 8601, and 11107 Hz. While other natural frequencies were associated with the local vibration mode because it appears only at one point of measurement.

A Novel Variable Impedance Hydrodynamic Oil-Film Bearing: Part 2: Experimental Identification of the Steady State and Dynamic Characteristics

1996 ◽  
Vol 210 (1) ◽  
pp. 65-74 ◽  
Author(s):  
P J Ogrodnik ◽  
M J Goodwin ◽  
Y Fang ◽  
M P Roach
Keyword(s):  
Steady State ◽  
Frequency Response ◽  
Response Function ◽  
Dynamic Characteristics ◽  
Frequency Response Function ◽  
Binary Sequence ◽  
Inversion Method ◽  
Oil Film ◽  
Generalized Matrix ◽  
Curve Fitting Method

A novel form of hydrodynamic oil-film bearing has been examined experimentally to establish both steady state and dynamic characteristics. The novel bearing design is based on a 120° partial arc bearing but contains two recesses to which are attached accumulators. The facility to open or close a valve located between the accumulator and the recesses enables the engineer to effectively tune the bearing in situ. This bearing also has the benefit of being similar in cost to a standard bearing. The oil-film coefficients were obtained from the frequency response function obtained when the system was excited by a pseudo random binary sequence signal. The use of the generalized matrix inversion method to determine the oil-film coefficients from the frequency response function was found to be some 10 per cent faster than the least squares curve-fitting method. Both methods were shown to produce reliable estimates to extract oil-film coefficients.

Effect of a Nonlinear Joint on the Dynamic Performance of a Machine Tool

2007 ◽  
Vol 129 (5) ◽  
pp. 943-950 ◽  
Author(s):  
Jaspreet S. Dhupia ◽  
Bartosz Powalka ◽  
A. Galip Ulsoy ◽  
Reuven Katz
Keyword(s):  
Machine Tool ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Performance ◽  
Stability Lobe ◽  
Receptance Coupling ◽  
Nonlinear Joint ◽  
Stability Lobe Diagrams ◽  
Machine Structure

This paper presents the effect of experimentally evaluated nonlinearities in a machine joint on the overall machine tool dynamic performance using frequency response functions and stability lobe diagrams. Typical machine joints are very stiff and have weak nonlinearities. The experimental evaluation of the nonlinear joint parameters of a commercial translational guide has been discussed in Dhupia et al., 2007, J. Vibr. Control, accepted. Those results are used in the current paper to represent the connection between the column and the spindle of an idealized column-spindle machine structure. The goal is to isolate and understand the effects of such joints on the machine tool dynamic performance. The nonlinear receptance coupling approach is used to evaluate the frequency response function, which is then used to evaluate the stability lobe diagrams for an idealized machine structure. Despite the weak nonlinearities in the joint, significant shifts in the natural frequency and amplitudes at resonance can be observed at different forcing amplitudes. These changes in the structural dynamics, in turn, can lead to significant changes in the location of chatter stability lobes with respect to spindle speed. These variations in frequency response function and stability lobe diagram of machine tools due to nonlinearities in the structure are qualitatively verified by conducting impact hammer tests at different force amplitudes on a machine tool.

Sign in / Sign up

Export Citation Format

Share Document