Jeong-Hak Park

INSPECTION OF IMPACT DAMAGE IN HONEYCOMB COMPOSITE BY ESPI, THERMOGRAPHY AND ULTRASONIC TESTING

Honeycomb composites are now fairly widely used in civilian and military aircraft structures. Common defects found in these materials are delaminations by impact damage and their presence will lead to structural weaknesses which could lead failure of the airframe structures. It is important to develop effective non-destructive testing procedures to identify these defects and increase the safety of aircraft travel. This paper describes the detection technique of impact damage defect using thermography and ESPI. The results obtained with the two techniques are compared with ultrasonic C-scan testing. The investigation shows that both imaging NDT methods are able to identify the presence of artificial defect and impact damage. The adoption of the thermography allowed significant advantages in inspection condition, and gives smaller error in quantitative estimation of defects.

C/SiC Multilayer Coating for the Oxidation Resistance of C-C Composite by Low Pressure Chemical Vapor Deposition

Functionally graded materials (FGM) consisting of C and SiC were deposited between the carbon fiber reinforced carbon (C-C) composites and the SiC coating layer by low pressure chemical vapor deposition (LPCVD) method to reduce the thermal stress. The compositions of the graded layers could be easily controlled to various steps by manipulating the input ratio of CH3SiCl3 to C2H2. The residual stresses for the designed compositional distribution were calculated by finite element method (FEM). The designed FGM layers were coated experimentally on the C-C composites and the oxidation behavior of the composites was investigated.

Quantitative Defects Detection in Wind Turbine Blade Using Optical Infrared Thermography

Abstract A wind turbine blade is an important component in wind-power generation, and is generally exposed toharsh environmental conditions. Ultrasonic inspection is mainly used to inspect such blades, but it has beendifficult to quantify defect sizes in complicated composite structures. Recently, active infrared thermography hasbeen widely studied for inspecting composite structures, in which thermal energy is applied to an object, and aninfrared camera detects the energy emitted from it. In this paper, a calibration method for active optical lock-inthermography is proposed to quantify the size. Inclusion, debonding and wrinkle defects, created in a wind bladefor 100 kW wind power generation, were all successfully detected using this method. In particular, a 50.0φ mmdebonding defect was sized with 98.0% accuracy. Keywords: Wind Turbine Blade, Optical Infrared Thermography, Lock-in Method, Quantitative Defects Detection[Received: December 18, 2014, Revised: February 3, 2015, Accepted: February 17, 2015] *과 학기술연합 대원교(UST) ** ,항공기시스템공학 한국표준과학연구원 안전측정센터 Corresponding Author: Safety MeasurementCenter, Korea Research Institute of Standards and Science, Daejeon 305-340, Korea (E-mail: mychoi@kriss.re.kr)

The Study of Micro Crack Detection in Dissimilar Metal Weld Using a Variable Ultrasound Infrared Thermography

Abstract As a nondestructive inspection technology currently in use, infrared thermography has gradually expandedits application range to industry. The method detects only defect areas by grafting ultrasound on a technique ofdetecting infrared energy emitted from all objects with absolute temperature of 0 K and converting this energy intothermography for inspection. Ultrasound infrared thermography has merits including the ability to inspect a widearea in a short time without contacting the target object. This study investigated the applicability of the techniquefor defect detection using variable ultrasound excitation inspection methods on samples of Terfenol-D, amagnetostrictive material with a tunable natural resonant frequency. Keywords: Infrared Thermography, Absolute Temperature, Variable Ultrasound, Magnetostrictive Material, Terfenol-D[Received: June 2, 2015, Revised: June 22, 2015, Accepted: June 22, 2015] * ,한국표준과학연구원안전측정센터** ,한국스마트구조시스템연구원 Corresponding Author: Department of Research & Development, Korea ResearchInstitute of Smart Material and Structures System Association, Daejeon 302-852, Korea (E-mail: m55nring@naver.com)

Study on the Micro Crack Detection in Joints by Using Ultrasound Infrared Thermography

This study detected SCC defects of dissimilar metal welded(STS304 and SA106 Gr. b) pipes using the ultrasonic infrared thermography method and the lock-in image treatment method among infrared thermography method. The infrared excitement equipment has 250 Watt of output and 20 kHz of frequency. By using the ultrasound infrared thermography method, the internal defects of dissimilar metal weld joints of pipes used at nuclear power plants could get detected. By an actual PT test, it was observed that the cracks inside the pipe existed not as a single crack but rather as a multiple cracks within a certain area and generated a hot spot image of a broad area on the thermography image. In addition, UT technology could not easily defects detected by the width of fine hair cracks. but, ultrasound infrared thermography technique was defect detected.

Infrared Thermography Characterization of Defects in Seamless Pipes Using an Infrared Reflector

Infrared thermography uses infrared energy radiated from any objects above absolute zero temperature, and the range of its application has been constantly broadened. As one of the active test techniques detecting radiant energy generated when energy is applied to an object, ultrasound infrared thermography is a method of detecting defects through hot spots occurring at a defect area when 15~100 kHz of ultrasound is excited to an object. This technique is effective in detecting a wide range affected by ultrasound and vibration in real time. Especially, it is really effective when a defect area is minute. Therefore, this study conducted thermography through lock-in signal processing when an actual defect exists inside the austenite STS304 seamless pipe, which simulates thermal fatigue cracks in a nuclear power plant pipe. With ultrasound excited, this study could detect defects on the rear of a pipe by using an aluminium reflector. Besides, by regulating the angle of the aluminium reflector, this study could detect both front and rear defects as a single infrared thermography image.

Hansun ST Introduction: Intelligent Surveillance Leading Company, Korea

Hansun ST is a research institute spin-off company mutually invested by Korea Research Institute of Standards and Science (KRISS) and Hansun Engineering Co., Ltd. on the permission of the Korean government. Our major business model is consisted of intelligent CCTV system, high-performance pan-tilt device, and thermal image analysis. Our mission is dedicating to customers’ safety and future. http://dx.doi.org/10.21611/qirt.2017.056

Study on the Performance of Infrared Thermal Imaging Light Source for Detection of Impact Defects in CFRP Composite Sandwich Panels

Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the composite materials as well as deform the composite materials, resulting in various problems such as weakened rigidity of the composite structure and penetration of water into tiny cracks. In this study, experiments were conducted using a 2 kW halogen lamp which is most frequently used as a light source, a 2 kW near-infrared lamp, which is used for heating to a high temperature, and a 6 kW xenon flash lamp which emits a large amount of energy for a moment. CFRP composite sandwich panels using Nomex honeycomb core were used as the specimens. Experiments were carried out under impact damages of 1, 4 and 8 J. It was found that the detection of defects was fast when the xenon flash lamp was used. The detection of damaged regions was excellent when the halogen lamp was used. Furthermore, the near-infrared lamp is an effective technology for showing the surface of a test object.

Detecting the Honeycomb Sandwich Composite Material’s Moisture Impregnating Defects by Using Infrared Thermography Technique

Many composite materials are used in the aerospace industry because of their excellent mechanical properties. However, the nature of aviation exposes these materials to high temperature and high moisture conditions depending on climate, location, and altitude. Therefore, the molecular arrangement chemical properties, and mechanical properties of composite materials can be changed under these conditions. As a result, surface disruptions and cracks can be created. Consequently, moisture-impregnating defects can be induced due to the crack and delamination of composite materials as they are repeatedly exposed to moisture absorption moisture release, fatigue environment, temperature changes, and fluid pressure changes. This study evaluates the possibility of detecting the moisture-impregnating defects of CFRP and GFRP honeycomb structure sandwich composite materials, which are the composite materials in the aircraft structure, by using an active infrared thermography technology among non-destructive testing methods. In all experiments, it was possible to distinguish the area and a number of CFRP composite materials more clearly than those of GFRP composite material. The highest detection rate was observed in the heating duration of 50 mHz and the low detection rate was at the heating duration of over 500 mHz. The reflection method showed a higher detection rate than the transmission method.

The Study of detection of Micro Defect Using Multi Ultrasound Infrared Thermography

We tend to have increased utilization of the non-destructive inspection method using infrared thermography. Any ultrasonic methods of various tests , and are mainly used as a method of inspecting a defect of a small size infrared thermography. An infrared thermography is mainly used as a method for inspecting a defect of microscopic size. Existing ultrasound, infrared thermography method, was mainly used for one of the energy incident apparatus. However, the larger the size of the inspection object, a problem occurs to the defect detection . The utilizing plural ultrasound infrared thermography inspection techniques to the energy source into two or more in order to solve this problem. The results of the experiment, when the advancing a plurality of ultrasonic examination, the influence is present in the displacement of the actual specimen. It was possible to confirm the correlation between the defect detection with the displacement of the test specimen. 10.21611/qirt.2016.024