Infrared Thermography and Acoustic Emission in 2D Plain Woven C/Sic Composites under Tensile-Tensile Fatigue Loading

2010 ◽  
Vol 118-120 ◽  
pp. 251-255 ◽  
Author(s):  
Bin Li ◽  
Xiao Yan Tong ◽  
Zi Yang Feng ◽  
Lei Jiang Yao
Keyword(s):  
Acoustic Emission ◽  
Applied Stress ◽  
Infrared Camera ◽  
Wide Band ◽  
Fatigue Loading ◽  
Thermal Dissipation ◽  
Tensile Fatigue ◽  
Ae Signal ◽  
Sic Composites ◽  
Non Destructive

Plain plate specimens of 2D plain woven C/SiC composites were performed on Instron8801. Infrared (IR) thermography was recorded using an infrared camera. Acoustic emission (AE) signal was detected by two AE wide band sensors attached on specimen. They were measured synchronously and real-timely. Thermal dissipation Q was deduced based on the first law of thermodynamics. When the applied stress was lower than fatigue endurance limit, Q rose in the early cyclic loading stage and then the rate of Q accumulation gradually approached a steady value as the proceeding cycles, conversely, Q rose quickly until led to failure of the composites. AE accumulated energy was discussed based on the AE data. Higher applied stress would cause more damage within the composites, and more AE signals were detected. Compared with damage calculated from modulus, Q and AE accumulated energy had fairly well agreement with the damage. It can be concluded that it is possible to employ these non-destructive evaluation methods as in-situ damage evolution indicators for 2D C/SiC composites.

Study of Initial Stages of Fatigue Process Using Non-Destructive Testing Methods

2013 ◽  
Vol 592-593 ◽  
pp. 553-556
Author(s):  
František Vlasic ◽  
Josef Volák ◽  
Libor Nohál ◽  
Pavel Mazal ◽  
Filip Hort
Keyword(s):  
Acoustic Emission ◽  
Crack Nucleation ◽  
Electrical Potential ◽  
Fatigue Loading ◽  
Non Destructive Testing ◽  
Testing Methods ◽  
Destructive Testing ◽  
Fatigue Process ◽  
Cyclic Damage ◽  
Non Destructive

This paper deals with the basic research of cyclic damage during the initial stages of fatigue process using the non-destructive testing methods. The acoustic emission method was used for monitoring of the microstructure changes during fatigue loading. The electrical potential measurements of specimen and microscopic observation were used mainly to detect the first short cracks and their propagation. The fatigue tests at room temperature were conducted on titanium alloy and creep-resistant steel specimens under bending and tension loading. The aim of the study was to compare the acoustic emission signal at different types of loading until fracture and to analyze in detail the signal changes in initial stages of fatigue process. This analysis was primarily based on the waveform similarity and division into classes. The results show the high sensitivity of the acoustic emission technology in the transition from the stage of surface relief evolution to the stage of crack nucleation and propagation.

scholarly journals DAMAGE PROPAGATION AND THERMOGRAPHY IN DISCONTINUOUS CARBON FIBER COMPOSITE (DCFC) UNDER TENSILE (FATIGUE) LOADING

2019 ◽  
Vol 82 (1) ◽  
Author(s):  
Jefri Bale ◽  
Emmanuel Valot ◽  
Olivier Polit
Keyword(s):  
Fatigue Life ◽  
Carbon Fiber ◽  
Fiber Composite ◽  
Thermal Response ◽  
Fatigue Loading ◽  
Carbon Fiber Composite ◽  
Damage Propagation ◽  
Initial Damage ◽  
Tensile Fatigue ◽  
Non Destructive

The discontinuous carbon fiber composite (DCFC) has a different damage behaviour due to non homogenuous sub structure. Consequently, monitoring and diagnosis of DCFC damage mechanisms require the application of a contactless method in real-time operation, i.e., non destructive method of thermography. The aim of this study is to investigate the damage propagation of DCFC material under tensile (fatigue) condition with non destructive testing (NDT) thermography method. Under fatigue testing, temperature evolutions were monitored by an Infra-Red (IR) camera. The results show that damage propagation and thermal response indicated the similar behaviour which consists of three stages. At the beginning, low temperature increased until ≈ 10% of fatigue life due to the initial damage. The initial damage propagated and the temperature reached the stable thermal state due to the saturation in the damage appearance of micro cracking of matrix and chip until ≈ 80% of fatigue life. At the last ≈ 20% of fatigue life, damage continued to propagate and provoked the occurrence of macro damage that induced the final failure indicated by highest peak of temperature. The analysis from the experiment results concluded that thermal response relates with the damage propagation of DCFC under fatigue loading.

Detection and Monitoring of Fatigue Cracks in Metallic Structures Using Acoustic Emission: Routes to Quantification of Probability of Detection

2014 ◽  
Vol 891-892 ◽  
pp. 1268-1274 ◽  
Author(s):  
Daniel Gagar ◽  
Peter Foote ◽  
Phil E. Irving
Keyword(s):  
Acoustic Emission ◽  
Fatigue Crack ◽  
Fatigue Cracks ◽  
Failure Process ◽  
Probability Of Detection ◽  
Metallic Structures ◽  
Final Failure ◽  
Ae Signal ◽  
Non Destructive ◽  
Ae Signals

The performance and reliability of Structural Health Monitoring (SHM) techniques remain largely unquantified. This is in contrast to the probability of detection (POD) and sensitivity of manual non destructive inspection methods which are well characterised. In this study factors influencing the rates of emission of Acoustic Emission (AE) signals from propagating fatigue cracks were investigated. Fatigue crack growth experiments were performed in 2014 T6 aluminium sheet to observe the effects of changes in crack length, loading spectrum and sample geometry on rates of emission and the probability of detecting and locating the fatigue crack. Significant variation was found in the rates of AE signal generation during crack progression from initiation to final failure. AE signals at any point in the failure process were found to result from different failure mechanisms operating at particular stages in the failure process.

scholarly journals Analysis of the results of acoustic emission diagnostics of a structure during helicopter fatigue tests

Aviation ◽  
2018 ◽  
Vol 21 (2) ◽  
pp. 64-69 ◽  
Author(s):  
Aleksandrs URBAHS ◽  
Kristine CARJOVA ◽  
Jurijs FESCUKS
Keyword(s):  
Acoustic Emission ◽  
Measurement Data ◽  
Fatigue Tests ◽  
Parameter Analysis ◽  
Inspection Method ◽  
Characteristic Structure ◽  
Ae Signal ◽  
Diagnostic Measurement ◽  
Non Destructive ◽  
Ae Signals

The study is devoted to a perspective diagnostic method, which makes it possible to deal with diagnostic tasks – the acoustic non-destructive inspection method based on acoustic emission (AE) signal parameter analysis. The practical use of this method is related to the interpretation of diagnostic measurement data. The parameters of acoustic emission (AE) signals were measured during bench tests of the tail boom structure and fin, as well as the joint areas of the fin, tail boom, and fuselage of the helicopter (joint area No.1 and No.19, frames of the tail boom and fuselage respectively).The analysis of fatigue damage kinetics was carried out in several stages for groups of bolts and for characteristic structure loading intervals. Bolt fracture was predicted at least 26 to 44 flight hours before the actual collapse. Using the AE parameters, the micro crack origin intervals identified when the bolt bearing capacity after the occurrence of the damage reached 96%.

Fractal Theory Based Damage Assessing Method of Acoustic Emission Test

2009 ◽  
Vol 413-414 ◽  
pp. 335-342 ◽  
Author(s):  
Yong Huang ◽  
Hui Li ◽  
Xin Yan ◽  
Jin Ping Ou
Keyword(s):  
Acoustic Emission ◽  
Development Process ◽  
Fractal Theory ◽  
Damage Index ◽  
Damage Development ◽  
Ae Signal ◽  
Static Experiment ◽  
Acoustic Emission Test ◽  
Assessing Method ◽  
Non Destructive

Acoustic emission (AE) test monitoring is an effective non-destructive technique. In the paper, a new damage assessing method which is damage acuteness index for AE signal of PZT patches based on fractal theory was proposed. The damage index was deduced by the character of signal analysed by fractal theory. It is deduced that both the curve length and the fractal dimension (FD) of signal are related with damage development. The AE test of Pseudo-static experiment of a concrete-filled GFRP tubes (CFFT) was performed for validation. The results show that the damage acuteness index can assess damage development process effectively. So the damage acuteness index is a promising method to apply in AE test monitoring.

Damage Progression and Residual Strength Evaluation in Sandwich Panels Loaded at the Center

2011 ◽  
Vol 465 ◽  
pp. 527-530 ◽  
Author(s):  
Amir Refahi Oskouei ◽  
Milad Hajikhani ◽  
Mehdi Ahmadi Najaf Abadi ◽  
Amir Sharifi ◽  
Mohammad Heidari
Keyword(s):  
Acoustic Emission ◽  
Residual Strength ◽  
Mechanical Energy ◽  
Sandwich Panels ◽  
Static Test ◽  
Loading Level ◽  
Out Of Plane ◽  
Ae Signal ◽  
Diamond Saw ◽  
Non Destructive

This paper addresses damage evaluation of loaded sandwich panels by using acoustic emission (AE) as a non-destructive method. The specimens were loaded monotonically out-of-plane in control of displacement and the tests were stopped at three different damage levels. Each loading level activates different failure mechanism that can influence on residual strength of material. After each quasi-static test, the damaged plate was cut by a diamond saw to obtain tensile specimens. After cutting, compression test carried out by using acoustic emission to monitor the process. Depend on loading level the damage value was variant as it caused different residual strength that was related to acoustic emission signals activities. There is a relation between AE signal energy and mechanical energy that can follow to evaluate the residual strength of panels in different loading level in sandwich panels. Results show that the using AE method having mechanical results can be effective in residual strength and progressive damage evolution.

Characterization of Tensile Damage for 3D-C/SiC Composites by Acoustic Emission

2010 ◽  
Vol 97-101 ◽  
pp. 834-837
Author(s):  
Yan Jun Chang ◽  
Ke Shi Zhang ◽  
Hui Juan Hu ◽  
Gui Qiong Jiao
Keyword(s):  
Acoustic Emission ◽  
Average Frequency ◽  
Relative Energy ◽  
Uniaxial Tensile ◽  
Damage Mechanisms ◽  
Tensile Process ◽  
Relative Stress ◽  
Ae Signal ◽  
Felicity Ratio ◽  
Sic Composites

The various damage mechanisms in 3D-C/SiC composites are identified using acoustic emission (AE) signal parameters, and the Felicity effect is studied on different unloading stress. As a result, the damage mechanisms in 3D-C/SiC composites can be identified successfully by the amplitude, average frequency and relative energy, and there are several damage modes together during uniaxial tensile process. The Kaiser effect is almost absent and the Felicity ratio fluctuates at 0.95 on lower stress stage and drops when the relative stress is above 65%.

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