Nondestructive Evaluation of Composite Structures Using System Identification Technique

1988 ◽  
Vol 110 (2) ◽  
pp. 134-139 ◽  
Author(s):  
W. H. Tsai ◽  
J. C. S. Yang
Keyword(s):  
System Identification ◽  
Nondestructive Test ◽  
Nondestructive Evaluation ◽  
Fatigue Damage ◽  
Composite Structures ◽  
Impact Damage ◽  
Epoxy Ring ◽  
System Parameters ◽  
Identification Technique

A system identification technique is presented for nondestructive test to detect and to characterize the existence and location of cracks and other damages in composite structures. Various composite structures, including Kevlar-epoxy plate, graphite epoxy ring, and graphite-epoxy coupon have been tested for different damages such as crack, delamination, impact damage, fatigue damage, etc. In addition, the correlation between severity of any type of the damages mentioned above and changes in identified system parameters has also been systematically studied.

Dual-energy wave subtraction imaging for evaluation of barely visible impact damage with an ultrasonic propagation imaging system

2017 ◽  
Vol 29 (17) ◽  
pp. 3411-3425 ◽  
Author(s):  
Yunshil Choi ◽  
Jung-Ryul Lee
Keyword(s):  
Laser Beam ◽  
Nondestructive Evaluation ◽  
Composite Structures ◽  
Imaging System ◽  
Impact Damage ◽  
Dual Energy ◽  
Ultrasonic Waves ◽  
Excitation Energies ◽  
Ultrasonic Signals ◽  
Ultrasonic Propagation

Barely visible impact damage from low-velocity impacts have been studied as critical design factors of composite structures. In this article, a dual-energy wave subtraction algorithm using an ultrasonic propagation imaging system is proposed to evaluate barely visible impact damage as a strategy of fast in situ nondestructive evaluation or structural health monitoring (SHM). The ultrasonic propagation imaging system is a type of nondestructive evaluation or SHM system and is based on scanning laser-induced guided ultrasound and fixed sensors. The amplitude of ultrasonic signals generated by the ultrasonic propagation imaging system increases with the increasing energy of the laser beam. Two ultrasonic signals generated by different excitation energies of the laser beam can be equalized by multiplying a constant factor to one of them. Therefore, the residuals after subtraction of two signals may be close to zero. However, the two different energy induced signals in the damaged area will be nonzero due to the change in material conditions regarding the laser ultrasonic generation mechanism. The dual-energy wave subtraction algorithm eliminates most of the incident ultrasonic waves and amplifies anomalous waves. A composite wing skin including two barely visible impact damages as well as a composite sandwich panel, including a single barely visible impact damage, were inspected to validate the proposed algorithm.

Nonlinear Model for Sub- and Superharmonic Motions of a MDOF Moored Structure, Part 2—Sensitivity Analysis and Comparison

2005 ◽  
Vol 127 (4) ◽  
pp. 291-299
Author(s):  
S. C. S. Yim ◽  
S. Raman ◽  
P. A. Palo
Keyword(s):  
Sensitivity Analysis ◽  
System Identification ◽  
Nonlinear System ◽  
Nonlinear System Identification ◽  
Detailed Comparison ◽  
Identification Procedure ◽  
System Parameters ◽  
Nonlinear Responses ◽  
Identification Technique ◽  
Single Set

The nonlinear R-MI/SO system identification procedure and the parameters of the MDOF system identified in Part 1 are examined in detail in this paper. A parametric study is conducted and the results are presented on the sensitivity of the system parameters for two key nonlinear responses—subharmonic and superharmonic resonances. The parameters are compared to determine the appropriateness of using a single set of system parameters for both response regions. A detailed comparison of the MDOF and the corresponding SDOF system results is performed. The knowledge gained from the SDOF and MDOF studies on the applicability of the R-MISO technique for the system identification of MDOF submerged moored structures is discussed. The results show that the MDOF extension of the R-MI/SO nonlinear system identification technique works well; the resulting system parameters are relatively constant and can be applied to the both the sub- and superharmonic regions.

A System Identification Method for Excitation-Frequency Dependent Rotordynamic Coefficients

2012 ◽  
Author(s):  
Timothy W. Dimond ◽  
Amir A. Younan ◽  
Paul Allaire
Keyword(s):  
System Identification ◽  
Measurement Uncertainty ◽  
Excitation Frequency ◽  
Frequency Dependent ◽  
Rotordynamic Coefficients ◽  
Adjoint Systems ◽  
Dynamic Coefficients ◽  
Backward Whirl ◽  
Identification Technique ◽  
Damped Systems

Experimental identification of rotordynamic systems presents unique challenges. Gyroscopics, generally damped systems, and non-self-adjoint systems due to fluid structure interaction forces mean that symmetry cannot be used to reduce the number of parameters to be identified. Rotordynamic system experimental measurements are often noisy, which complicates comparisons with theory. When linearized, the resulting dynamic coefficients are also often a function of excitation frequency, as distinct from operating speed. In this paper, a frequency domain system identification technique is presented that addresses these issues for rigid-rotor test rigs. The method employs power spectral density functions and forward and backward whirl orbits to obtain the excitation frequency dependent effective stiffness and damping. The method is highly suited for use with experiments that employ active magnetic exciters that can perturb the rotor in the forward and backward whirl directions. Simulation examples are provided for excitation-frequency reduced tilting pad bearing dynamic coefficients. In the simulations, 20 and 50 percent Gaussian output noise was considered. Based on ensemble averages of the coefficient estimates, the 95 percent confidence intervals due to noise effects were within 1.2% of the identified value. The method is suitable for identification of linear dynamic coefficients for rotordynamic system components referenced to shaft motion. The method can be used to reduce the effect of noise on measurement uncertainty. The statistical framework can also be used to make decisions about experimental run times and acceptable levels of measurement uncertainty. The data obtained from such an experimental design can be used to verify component models and give rotordynamicists greater confidence in the design of turbomachinery.

scholarly journals Effect of Multi-Impact on QIQH Carbon/Epoxy Composite Laminate

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 511
Author(s):  
Adadé Seyth Ezéckiel Amouzou ◽  
Olivier Sicot ◽  
Ameur Chettah ◽  
Shahram Aivazzadeh
Keyword(s):  
Composite Structures ◽  
Epoxy Composite ◽  
Impact Damage ◽  
Ultrasonic Control ◽  
Impact Tests ◽  
Post Impact ◽  
Testing Techniques ◽  
Force Time ◽  
The Relationship ◽  
Force Displacement

This work is motivated by increasingly used of composite structures under severe loading conditions. During their use, these materials are often subjected to impact as for example, in the aeronautical field the fall of hailstone on structure composites. In fact, the low energy traditional impact tests don’t allow to see the evolution of the damage and don’t permit also to compare the best tolerance to impact between different stratifications. The multi-impact tests made it possible to find a solution to this problem. In this work, multi-impact tests are performed on three carbon/epoxy stratifications. The final goal is to predict the durability of the composite structures during impact loading for their design. This study brings to light the response of multi-impact tests through force-time and force-displacement curves obtained experimentally. On the other hand, a parameter D has introduced following the experimental results. This made it possible to rank the three stratifications from their tolerance to multi-impact tests. To evaluate the post impact damage, ultrasonic testing techniques are used. The results allow to find the relationship between the damaged surface obtained by the ultrasonic control and the parameter D and to rank the three laminates configurations.

Multiparameter Real-World System Identification using Iterative Residual Tuning

2021 ◽  
pp. 1-12
Author(s):  
Adam Allevato ◽  
Mitch W Pryor ◽  
Andrea L. Thomaz
Keyword(s):  
System Identification ◽  
Robot Control ◽  
Tracking Error ◽  
Nonlinear System Identification ◽  
Visual Observation ◽  
Free System ◽  
Proposed Model ◽  
Derivative Free ◽  
Identification Technique ◽  
Using Data

Abstract In this work we consider the problem of nonlinear system identification, using data to learn multiple and often coupled parameters that allow a simulator to more accurately model a physical system or mechanism and close the so-called reality gap for more accurate robot control. Our approach uses iterative residual tuning (IRT), a recently-developed derivative-free system identification technique that utilizes neural networks and visual observation to estimate parameter differences between a proposed model and a target model. We develop several modifications to the basic IRT approach and apply it to the system identification of a 5-parameter model of a marble rolling in a robot-controlled labyrinth game mechanism. We validate our technique both in simulation—where we outperform two baselines—and on a real system, where we achieve marble tracking error of 4% after just 5 optimization iterations.

Feasibility of PZT ceramics for impact damage detection in composite structures

2015 ◽  
Author(s):  
Gerges Dib ◽  
Ermias Koricho ◽  
Oleksii Karpenko ◽  
Mahmood Haq ◽  
Lalita Udpa ◽  
...  
Keyword(s):  
Damage Detection ◽  
Composite Structures ◽  
Impact Damage ◽  
Pzt Ceramics
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