scholarly journals Ultrasonic Adaptive Detection for Aerospace Components with Varying Thickness

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Zhen Xiao ◽  
Chunguang Xu ◽  
Dingguo Xiao ◽  
Genyue Peng ◽  
Xinliang Li
Keyword(s):  
Turbine Blades ◽  
Threshold Function ◽  
Experimental Result ◽  
Calibration Coefficient ◽  
Equivalent Diameter ◽  
Adaptive Detection ◽  
Ultrasonic Signals ◽  
Varying Thickness ◽  
The Time Domain ◽  
Other Ndt Methods

Automatic inspection of microdefects located in the aerospace components is difficult due to the imprecise scanning trajectory, especially for those specimens with varying thickness. In this paper, a new ultrasonic nondestructive testing (NDT) system using the robotic scanning trajectory is constructed for inspecting turbine blades. Additionally, an approach based on the analysis of ultrasonic signals is proposed to calibrate the trajectory; the ultrasonic image based on the threshold function represents the distribution of inner defects when the following gate is used to track the flaw echo. Therefore, the characteristic parameters of the flaw echo signals are easy to be discriminated if the reflection waves are stable in the time domain. Experimental result verified the effective and feasibility of the proposed approach; the distribution of inner defects can be shown with a higher resolution than other NDT methods when robotic orientation is correct at each point of scanning trajectory. Furthermore, the feature signals can be tracked more accurately during the ultrasonic signal processing if the ultrasonic distance was considered as a calibration coefficient of positional matrix. The proposed ultrasonic adaptive detection is adapted to complex geometric structure with a minimum resolution of equivalent diameter of the inner flaw being 0.15 millimeters.

Ultrasonic Signals Generated by a Laser Source in Film/Substrate Systems

1999 ◽  
Author(s):  
T. W. Murray ◽  
Z. Guo ◽  
S. Krishnaswamy ◽  
J. D. Achenbach
Keyword(s):  
Mechanical Properties ◽  
Time Domain ◽  
Michelson Interferometer ◽  
Pulsed Laser ◽  
Laser Source ◽  
Laser Generation ◽  
Ultrasonic Signals ◽  
Acoustic Wave Generation ◽  
The Time Domain ◽  
Film Substrate

Abstract A model for the pulsed laser generation of ultrasound in an isotropic film on a semi-infinite substrate is presented. The model gives the time domain displacement of the system as a function of the density and mechanical properties of the film and substrate and the thermal properties of the film. Theoretical signals are calculated and analyzed for both a slow layer on a fast substrate and a fast layer on a slow substrate. The model has been verified experimentally using a 1 ns Nd:YAG laser source for acoustic wave generation and a stabilized Michelson interferometer for detection. Experimental and theoretical signals agree well for both fast on slow and slow on fast systems.

Transition Process From Contact to Floating State in a Squeeze Air Film

1998 ◽  
Vol 120 (1) ◽  
pp. 60-68 ◽  
Author(s):  
K. Kajiwara ◽  
Y. Harayama ◽  
R. Ueda ◽  
T. Sonoda
Keyword(s):  
Parallel Plate ◽  
Direct Detection ◽  
Transition Process ◽  
Experimental Results ◽  
Experimental Result ◽  
Test Material ◽  
Squeeze Film ◽  
The Time Domain ◽  
Dc Current ◽  
Air Film

This paper presents a series of trials of direct detection of the transition process of a squeeze film, from the contacting state into the floating one. The material was initially placed on the surface of a vibrator constituting a squeeze air film. Three electrical trials were performed to certify whether the material could be elevated after the vibrator was excited. When this is done, clearance is expected between the surfaces of the test material and the vibrator. This may be regarded as the equivalent of a change in electrical resistance from almost zero to infinity, with a kind of parallel-plate capacitor being formed. First, detection through DC current was carried out. The experimental result, however, reveals that the resistance never does become infinite, although the equivalent contacting area calculated from this value is very small. Second, detection through DC voltage was performed by terminating the clearance with parallel resistance. The experimental results verify the appearance of the floating state. Third, the average clearance could be detected by regarding it as a parallel-plate type capacitor. Here a Langevin type piezoelectric transducer was used as the vibrator. Through these experimental results an important fact was observed: the waveform of the voltage applied to the transducer is closely related to the movement of the clearance in the time domain.

Mechanical Properties According to Heat Treatment for Gas Turbine Blade Material

2007 ◽  
Vol 26-28 ◽  
pp. 209-212
Author(s):  
Moon Young Kim ◽  
Sung Ho Yang ◽  
Kuk Hyun Song
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Hot Isostatic Pressing ◽  
Experimental Result ◽  
Gas Turbine Blade ◽  
Post Heat Treatment ◽  
Gas Turbine Blades

This work was studied for the changes of thermal properties on GTD-111 DS (Directional Solidification) gas turbine blade. In this study, gas turbine blades with 24,000~34,000 firing hours was used to get more effective result, gradually applied hot isostatic pressing (HIP) and post-heat treatment for these samples. In the latter steps, we observed changes of γ´ phase affected in material properties, and microhardness test was carried out to evaluate mechanical properties according to changes of γ´ fraction and shape. Experimental result shows, changes of γ´ fraction and shape were affected by HIP and post-heat treatment. And also mechanical properties changes such as micro-hardness related to γ´ phase. In this study, we explained changing transition of microstructure according to γ´ fraction distribution.

Vibration Fatigue Analysis for the Frame of Vehicle Equipment

2014 ◽  
Vol 494-495 ◽  
pp. 142-145
Author(s):  
Chao Yang ◽  
Shou Ne Xiao ◽  
Tao Zhu
Keyword(s):  
Fatigue Failure ◽  
Time Domain ◽  
Intrinsic Property ◽  
Fatigue Analysis ◽  
Experimental Result ◽  
Frequency Domain Method ◽  
Time Domain Simulation ◽  
Simulation Approach ◽  
Vibration Fatigue ◽  
The Time Domain

Traditional fatigue analysis approaches could not solve the structure fatigue failure caused by resonances. The time domain simulation approach which took the structural intrinsic property into account was presented to solve vibration fatigue problems. The vibration fatigue failure of the frame of vehicle equipment was studied. Broadband vibration loads were put into the finite element model of the frame as excitations, the stress power spectral density of a dangerous point was calculated. At last, the Dirlik method and the time domain simulation approach were used to calculate the fatigue life. The results show that the damage caused by the first-order vertical flexural vibration is the largest; the result of the time domain simulation approach has a good agreement with the experimental result when compared with the frequency domain method.

Assessment of Surface-Based Aeroacoustic Noise From Blades of a Vertical-Axis Wind Turbine

2014 ◽  
Author(s):  
Robert Williams ◽  
Joana Rocha ◽  
Edgar Matida ◽  
Fred Nitzsche
Keyword(s):  
Wind Turbine ◽  
Acoustic Pressure ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Two Dimensions ◽  
Vertical Axis Wind Turbine ◽  
Noise Sources ◽  
Unsteady Panel Method ◽  
The Time Domain

Surface-based sources of aerodynamically-generated noise for the 17-m troposkien shape vertical-axis wind turbine are predicted using Farassat’s Formulation 1A of the Ffowcs Williams-Hawkings equation. By discretizing the three-dimensional turbine blades over the height of the turbine into constant-radius sections, the blades were aerodynamically modeled in two-dimensions in the horizontal plane by an unsteady panel method to obtain results for surface pressures and velocities. The acoustic pressure generated by the blades throughout their rotations was determined by the combination of loading and thickness noise sources on the surface of the blade sections in the time-domain. The simulation results were compared to experimental results for the acoustic pressure power spectral density. The sound pressure level around the turbine was found to have a slight dipole radiation pattern, caused primarily by the loading acoustic pressure on the blades.

scholarly journals Analysis and Compensation of Equivalent Diameter Error of Articulated Arm Coordinate Measuring Machine

2018 ◽  
Vol 51 (1-2) ◽  
pp. 16-26 ◽  
Author(s):  
Zai Luo ◽  
Hui Liu ◽  
Dong Li ◽  
Kun Tian
Keyword(s):  
Coordinate Measuring Machine ◽  
Maximum Error ◽  
Error Reduction ◽  
Experimental Result ◽  
Average Error ◽  
Equivalent Diameter ◽  
Error Source ◽  
Measuring Device ◽  
Measuring Machine ◽  
Measuring Force

As a key part of the articulated arm coordinate measuring machine, the probe can determine the measurement accuracy. Therefore, the error source and influencing factors of the equivalent diameter of the probe are studied. First, the influence of the primary factor of the measuring force on the equivalent diameter of the probe is studied by analyzing the influence degree of its error source. Second, a mathematical model of the relationship between the equivalent diameter and the measuring force of the articulated arm coordinate measuring machine is built to compensate for the equivalent diameter error caused by the measuring force by the simulated annealing method. To illustrate the application advantage of our proposed study, a simple force-measuring device is designed based on this model. The experimental result shows that the maximum error reduction is approximately 43 µm, while the average error reduction ranges from 33 to 4.0 µm, which represents an 87.7% improvement. Overall, our proposed method can effectively compensate for the equivalent diameter error caused by the measuring force. This method can improve the accuracy of the articulated arm coordinate measuring machines on both calibration and measurement.

Stick-Slip Motion of Frictionally Damped Turbine Airfoils: A Finite Element in Time (FET) Approach

1997 ◽  
Vol 119 (2) ◽  
pp. 236-242 ◽  
Author(s):  
Yu Wang
Keyword(s):  
Turbine Blades ◽  
Static Friction ◽  
Response Analysis ◽  
Stick Slip ◽  
System Equations ◽  
Structured System ◽  
The Time Domain ◽  
Turbine Airfoils ◽  
Stick Slip Motion ◽  
Slip Motion

A method is proposed for analyzing the periodic stick-slip motion of a single degree of freedom model of frictionally damped turbine blades. The method of finite elements in the time domain (FET) is based on a Hamilton’s weak principle, paralleling the variational methods in elastostatics. It permits a complete determination of the hysteretic friction force, and results in a set of highly structured system equations. The method has a number of unique features, which are utilized to provide a simple yet efficient approach for predicting the steady-state response. When applied to a number of example problems, including systems with static friction and the excitation of multiple discrete frequencies, the FET method is demonstrated to be an efficient and reliable alternative technique for nonlinear dynamic response analysis.

A New Method for Optimizing Friction Damping in Randomly Excited Systems

1989 ◽  
Author(s):  
T. M. Cameron ◽  
J. H. Griffin
Keyword(s):  
Time Domain ◽  
Turbine Blades ◽  
Single Mode ◽  
Random Excitation ◽  
Degree Of Freedom ◽  
System Response ◽  
Friction Damping ◽  
Single Mode Approximation ◽  
The One ◽  
The Time Domain

A method is developed that can be used to calculate the stationary response of randomly excited nonlinear systems. The method iterates to obtain the fast Fourier transform of the system response, returning to the time domain at each iteration to take advantage of the ease in evaluating nonlinearities there. The updated estimates of the nonlinear terms are transformed back into the frequency domain in order to continue iterating on the frequency spectrum of the staionary response. This approach is used to calculate the response of a one degree of freedom system with friction damping that is subjected to random excitation. The one degree of freedom system provides a single mode approximation of systems (e.g. turbine blades) with friction damping. This study investigates various strategies that can be used to optimize the friction load so as to minimize the response of the system.

scholarly journals Computer Modeling and Simulation of Ultrasonic Signal Processing and Measurements

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Y. B. Gandole
Keyword(s):  
Experimental Data ◽  
Testing Procedure ◽  
Simulation Tool ◽  
Virtual Design ◽  
Acoustic Wave Propagation ◽  
Actual Measurement ◽  
Ultrasonic Signals ◽  
The Time Domain ◽  
Design And Testing ◽  
Good Agreement

The system for simulation, measurement, and processing in Graphical User Interface implementation is presented. The received signal from the simulation is compared to that of an actual measurement in the time domain. The comparison of simulated, experimental data clearly shows that acoustic wave propagation can be modeled. The feasibility has been demonstrated in an ultrasound transducer setup for material property investigations. The results of simulation are compared to experimental measurements. The simulation result has good agreement with the experimental data which confirms the validity of the model. The simulation tool therefore provides a way to predict the received signal before anything is built. Furthermore, the use of an ultrasonic simulation package allows for the development of the associated electronics to amplify and process the received ultrasonic signals. Such a virtual design and testing procedure not only can save us time and money, but also can provide better understanding on design failures and allow us to modify designs more efficiently and economically.

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