Investigation of Mechanical Properties and Failure Behavior of CFRP Filament-Wound Composites Using an Acoustic Emission-Based Methodology and Numerical Simulation

Sajad Alimirzaei,Mehdi Ahmadi Najafabadi,Ali Nikbakht 한국섬유공학회 2023 Fibers and polymers Vol.24 No.2

Filament wound composites have a continuous structure, and to improve the mechanical behavior of these structures, it isnecessary to identify the damage mechanisms. The focus of this study is to investigate the mechanical properties and failureanalyses of filament-wound carbon/epoxy composite samples under three-point bending using the acoustic emission technique. To investigate this, first, using a filament winding machine, composite plates and composite structures with a squarecross section were fabricated. Afterward, composite specimens were tested and most independent elastic constants, strengthproperties, and shear properties were obtained. Then, a three-point bending testing of filament-wound composite specimenswas performed, and to identify the damage mechanisms the analysis of acoustic emission signals recorded during loadingwas also implemented. The acoustic emission signals of composite samples were classified using hierarchical and wavelettransform methods and the evolution of different damage mechanisms was investigated. Eventually, composite samples weresimulated in ABAQUS software, and to consider the damage mechanisms, the continuum damage mechanics model wasconsidered as a user material subroutine in simulation. The experimental results showed that the received acoustic emissionsignals matched very well with the mechanical behavior, and the acoustic response of the composite samples to the loadingincludes three regions. The amplitude range of the first, second, and third clusters was obtained between 35–74, 51–100, and55–84 dB, respectively. Finally, in the clustering method, the frequency range of fiber/matrix debonding and fiber breakagewere characterized between 200 and 250 and over 380 kHz, respectively.

음향방출을 이용한 금속의 피로 균열성장 패턴인식 기법

이수일(Soo Ill Lee),이종석(Jong-Seok Lee),민황기(Hwang-Ki Min),박철훈(Cheol Hoon Park) 대한전자공학회 2009 電子工學會論文誌-SP (Signal processing) Vol.46 No.3

음향방출 기법은 작동중인 상태에서 기계 설비를 비파괴 검사할 수 있는 기법이며, 균열성장 같은 장애의 신뢰성 있는 감시를 위해서 순간적인 균열신호뿐만 아니라 동특성을 이용하는 것이 중요하다. 균열성장을 검출하기 위해 널리 사용되는 물리적 파괴 3단계는 음향방출 현상이 시간에 따라 서로 겹치는 문제점이 있어 정확한 균열성장 시간을 추정하기 어렵다. 제안한 패턴인식 기법은 오경보와 미탐지를 최소화하기 위해서 음향방출 동특성을 입력으로 사용하고, 균열성장 시간을 정확히 추정하기 위해 시간에 따른 클러스터링 기법을 사용한다. 실험결과는 제안한 패턴인식 기법이 압력의 변화에 의한 음향방출의 변화의 강인함 때문에 실용화에 효율적임을 보여준다. Acoustic emission-based techniques are being used for the nondestructive inspection of mechanical systems used in service. For reliable fault monitoring related to the crack growth, it is important to identify the dynamical characteristics as well as transient crack-related signals. Widely used methods which are based on physical phenomena of the three damage stages for detecting the crack growth have a problem that crack-related acoustic emission activities overlap in time, therefore it is insufficient to estimate the exact crack growth time. The proposed pattern recognition method uses the dynamical characteristics of acoustic emission as inputs for minimizing false alarms and miss alarms and performs the temporal clustering to estimate the crack growth time accurately. Experimental results show that the proposed method is effective for practical use because of its robustness to changes of acoustic emission caused by changes of pressure levels.

항공용 복합재료에 대한 음향방출의 활용

이상호 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.3

본 연구에서는 복합재료에 적용 가능한 음향방출 비파괴 시험 평가 기법의 정립을 목표로, 복합재 표준 시험 용 평가 시편(STEB), 금속재 압역용기 내부의 복합재 내열튜브, 추진기관 토출관 등의 수압 보증 시험에서 음향방출 시험법을 적용하였다. 복합재 표준 시험용 평가 시험용 평가 시편의 경우 음향방출 hit rate parameter를 이용하여 파열압력이 낮은 시편(2100psi이하)과, 파열압력이 높은 시편(2100psi이상)과의 구분이 가능하였으며, 파열압력이 낮은 시편은 파열압력의 50%범위내에서 파열위치의 탐지가 가능하였다. 금속재 압력용기 내부의 복합재료 내열튜브 및 추진기관 토출관의 시험 결과, 수압시험 중 크랙의 발생 압력, 초기 발생 위치, 및 진전과정의 탐지가 가능하였다. To establish nondestructive test method for aerospace composite materials, various composite specimens were tested and analyzed using acoustic emission. The hit rate of acoustic emission closely was related with crack initiation and propagation. This report also presents detection capability of crack initiation pressure, initial crack active location, and crack propagation using acoustic emission.

Acoustic emission analysis of the compressive deformation of iron foams and their biocompatibility study

Park, Hyeji,Hong, Kicheol,Kang, Jin Soo,Um, Teakyung,Knapek, Michal,Miná,rik, Peter,Sung, Yung-Eun,Má,this, Kristiá,n,Yamamoto, Akiko,Kim, Hyun-Kyung,Choe, Heeman Elsevier 2019 Materials Science and Engineering C Vol.97 No.-

<P><B>Abstract</B></P> <P>We synthesized Fe foams using water suspensions of micrometric Fe<SUB>2</SUB>O<SUB>3</SUB> powder by reducing and sintering the sublimated Fe oxide green body to Fe under 5% H<SUB>2</SUB>/Ar gas. The resultant Fe foam showed aligned lamellar macropores replicating the ice dendrites. The compressive behavior and deformation mechanism of the synthesized Fe foam were studied using an acoustic emission (AE) method, with which we detected sudden localized structural changes in the Fe foam material. The evolution of the deformation mechanism was elucidated using the adaptive sequential <I>k</I>-means (ASK) algorithm; specifically, the plastic deformation of the cell struts was followed by localized cell collapse, which eventually led to fracturing of the cell walls. For potential biomedical applications, the corrosion and biocompatibility characteristics of the two synthesized Fe foams with different porosities (50% vs. 44%) were examined and compared. Despite its larger porosity, the superior corrosion behavior of the Fe foam with 50% porosity can be attributed to its larger pore size and smaller microscopic surface area. Based on the cytotoxicity tests for the extracts of the foams, the Fe foam with 44% porosity showed better cytocompatibility than that with 50% porosity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Iron foam synthesized from water suspension of Fe<SUB>2</SUB>O<SUB>3</SUB> powder under 5% H<SUB>2</SUB>/Ar gas. </LI> <LI> Compressive deformation mechanism of iron foam is analyzed using an acoustic emission. </LI> <LI> Not porosity but pore size is a dominant factor for corrosion behavior of iron foams. </LI> <LI> Concentration released Fe<SUP>n+</SUP> controls cytotoxicity of iron foam extracts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Experimental Study on Flame-Vortex Interactions in Turbulent Hydrogen Non-premixed Flames with Coaxial Air

김문기(Munki Kim),오정석(Jeong-suk Oh),최영일(Young-il Choi),윤영빈(Youngbin Yoon) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-

This paper investigates the effects of acoustic forcing on NOx emissions and mixing process in the near field region of turbulent hydrogen nonpremixed flames. The resonance frequency was selected to force the coaxial air jet acoustically, because the resonance frequency is effective to amplify the forcing amplitude and reduce NOx emissions. When the resonance frequency is acoustically excited, a streamwise vortex is formed in the mixing layer between the coaxial air jet and coflowing air. As the vortex develops downstream, it entrains both ambient air and combustion products into the coaxial air jet to mix well. In addition, the strong vortex pulls the flame surface toward the coaxial air jet, causing intense chemical reaction. Acoustic excitation also causes velocity fluctuations of coaxial air jet as well as fuel jet but, the maximum value of centerline fuel velocity fluctuation occurs at the different phases of Ф=180° for nonreacting case and Ф=0° for reacting case. Since acoustic excitation enhances the mixing rate of fuel and air, the line of the stoichiometric mixture fraction becomes narrow. Finally, acoustic forcing at the resonance frequency reduces the normalized flame length by 15 % and EINOx by 25 %, compared to the flame without acoustic excitation.

Acoustic excitation effect on NO_x reduction and flame stability in a lifted non-premixed turbulent hydrogen jet with coaxial air

Oh, J.,Heo, P.,Yoon, Y. Pergamon Press ; Elsevier Science Ltd 2009 International journal of hydrogen energy Vol.34 No.18

The effects of acoustic excitation on the reduction in nitric oxidant (NO<SUB>x</SUB>) emission were experimentally investigated in non-premixed lifted hydrogen jet flames with coaxial air. The purpose of the present work was to analyze the acoustic forcing effect on the flow field, the reaction zone, and NO<SUB>x</SUB> emission, and to study the mechanisms of NO<SUB>x</SUB> reduction and flame stabilization. To analyze of the flow field, a PIV method was used that incorporated two Nd-YAG lasers and a CCD camera. The reaction zone was visualized by taking OH* chemiluminescence images with a 307.1 +/- 5 nm narrow band pass filter and an ICCD camera. A flow condition was carefully selected at u<SUB>F</SUB> = 150, 200, 250 m/s and u<SUB>A</SUB> = 12, 16, 20 m/s, which was sustainable for acoustic excitation in a lifted flame region. The frequency was swept from 150 to 1000 Hz in 5 Hz steps. From the measurements of the flow field, the reaction zone, and NO<SUB>x</SUB> emission, we concluded that NO<SUB>x</SUB> emission was reduced and minimized at the resonance frequency. The vortex that was generated by acoustic forcing promoted air entrainment and enhanced the fuel-air mixing rate. This premixing effect resulted in a lower flame temperature, and thus lower NO<SUB>x</SUB> emissions. In addition, the liftoff height periodically fluctuated due to the stretch effect as the vortex interacted with the flame base.

부상된 수소난류확산화염에서 동축공기의 음향가진에 의한 NOx 저감

허필원(Pilwon Heo),오정석(Jeongseog Oh),윤영빈(Youngbin Yoon) 한국연소학회 2009 한국연소학회지 Vol.14 No.1

The effects of acoustic excitation of coaxial air on mixing enhancement and reduction of nitrogen oxides (NOx) emission were investigated. A compression driver was attached to the coaxial air supply tube to impose excitation. Measurements of NOx emission with frequency sweeping were performed to observe the trend of NOx emission according to the fuel and air flow conditions and to inquire about the effective excitation frequency for reducing NOx. Then, Schlieren photographs were taken to visualize the flow field and to study the effect of excitation. In addition, phase-locked particle image velocimetry (PIV) was performed to acquire velocity field for each case and to investigate the effect of vortices more clearly. Direct photographs and OH chemiluminescence photographs were taken to study the variation of flame length and reaction zone. It was found that acoustic forcing frequencies close to the resonance frequencies of coaxial air supply tube could reduce NOx emission. This NOx reduction was influenced by mixing enhancement due to large-scale vortices formed by fluctuation of coaxial air jet velocity.

음향방출기법을 이용한 전로베어링 안전진단 기술개발

박경조 한국안전학회 2003 한국안전학회지 Vol.18 No.2

A method is presented for diagnosing the converter bearings by using acoustic emission. The flaking mechanism causing the large-scale bearing for furnace to flaw is investigated and a possibility of defect is verified by Finite Element method. he diagnosis logic is proposed for detecting the flaw of a non-continuous rotating machine. It is proved that the acoustic emission energy can be used as a representative parameter for an acoustic event. Applying the method to the tilting bearings for steel mill in operation, the effectiveness of this logic is evaluated. It is shown that AE signal is generated only when the bearing is tilting, and the trend analysis can be focused upon this process.

Visualization and acoustic emission monitoring of nucleate boiling on rough and smooth fuel cladding surfaces at atmospheric pressure

Baek, Seung Heon,Shim, Hee-Sang,Kim, Jung Gu,Hur, Do Haeng Elsevier 2018 Nuclear engineering and design Vol.330 No.-

<P><B>Abstract</B></P> <P>The purpose of this work is to evaluate nucleate boiling phenomena occurring on as-received rough and chemically etched smooth fuel claddings in water at atmospheric pressure using the visualization method and the acoustic emission technique. The onset of nucleate boiling on the smooth cladding surface occurred at higher temperature than on the rough cladding surface. The visible boiling phenomena remarkably decreased on the smooth cladding surface compared with those on the rough cladding surface. The density and energy of AE signals emitted from vapor bubbles on the smooth cladding surface decreased than those on the rough cladding tube. The variation trend of AE signals was in good agreement with the visualization results. Therefore, it is expected that the AE technique can be effectively utilized to monitor the boiling behaviors on the heated surfaces even under non-visualized conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nucleate boiling on a rough and smooth fuel cladding surface is observed visually. </LI> <LI> Nucleate boiling on the two different surfaces is monitored using acoustic emission. </LI> <LI> Nucleate boiling occurs more actively on a rough cladding surface. </LI> <LI> Acoustic emission data are in good agreement with the visualization results. </LI> </UL> </P>

음향방출기법을 이용한 경동, 대형회전체 안전진단 기술개발

박경조 여수대학교 2002 論文集 Vol.17 No.-

A method is presented for diagnosing a large-scale, tilting machine by using acoustic emissions. First of all, the flaking mechanism causing the large-scale bearing for furnace to defect is investigated and verified by Finite Element method. The dagnosis logic is proposed for detecting the flaw of a non-continuous rotating machine. It is proved that the acoustic emission energy can be used as a representative parameter for an acoustic event. Applyig the method to the tilting bearings for steel mill in operation, the effectiveness of this logic is evaluated. From the results, it is shown that AE signal is generated only when the bearing is tilting, and the trend analysis can be focused upon this process.