Manyong Choi

Detection of delamination defect inside timber by sonic IR

In ultrasound excitation thermography, the injected ultrasound to an object is transformed to heat by thermo-structure effect and internal friction. The advantage of this technique is selectively sensitive to thermally active defects. The appearance of defects, which can be visualized by thermography camera, depends strongly on the method of excitation. In preliminary studies, ultrasonic excitation horns of ultrasonic manufacturing process are widely adopted for a polymer structure. However, it is needed that these horns are modified for improving the defect detection capability. This paper proposes a new ultrasonic excitation horns with tuning fork shape in NDT of wood material. Geometric conditions are optimized by FEA and application results by the developed horn are described and compared with those by a previous horn.

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.

Thermal stress analysis of a circular holed specimen

Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Although the operating frequency is designed at more than resonance frequencies, the structure, when a vibrating structure starts or stops, has to pass through a resonance frequency, which results in large stress concentration. This paper applies thermography to analyze transient stress variation of a circular holed plate. In experiment, the finite element modal (FEM) analysis of the specimen was performed and the surface temperature measured by infrared camera is calculated to the stress of the nearby hole, based on thermoelastic equation. Stress distributions between 2nd and 3rd vibration mode are investigated with thermography and also dynamic stress concentration factors according to the change of vibration amplitude are estimated at resonance frequency.

Quantitative Evaluation of a Crack Inside of Pressure Pipeline by Shearography and ESPI

Electronic Speckle Pattern Interferometry (ESPI) and Shearography for quantitative analysis of a crack inside of pipelines are described. Shearography is used widely for non‐destructive inspection because of less sensitivity to environmental disturbance and simple interferometer. However, it is difficult to determine the defect size quantitatively because there are so many effect factors‐ shearing distance, shearing direction, and induced load, which depend on operator’s skill and crack information. These effective factors in Shearography are optimized for quantitative analysis and the size of crack is determined. And also, ESPI is used for determination of crack size quantitatively. In ESPI only induced load play an important role and the effective factor is independent on information of a crack. The displacement of object surface is obtained three‐dimensionally and differentiated numerically, which is same to result of Shearography so that crack size can be determined quantitatively without any informat...

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

Reference specimen for detectability evaluation of thermographic NDT system

Thermographic nondestructive testing techniques have been receiving increasing attentions as one of the effective NDT techniques, because of its non-contact, remote sensing, time-saving, and cost-saving vision techniques. However, the defect detecting ability of this technique basically depends on environmental condition such as surrounding temperature, initial temperature of inspection target, emissivity and so on. Most of thermographic NDT engineers have been concerned about this problem, also. This paper proposes two reference specimens, aluminum alloy and stainless steel for evaluating detecting ability of photothermal thermography nondestructive inspection system. This paper will improve on the reliability of thermographic NDT technique.

TUNING FORK HORN DESIGN FOR ULTRASOUND EXCITATION THERMORAPHY

In ultrasound excitation thermography, the injected ultrasound to an object is transformed to heat by thermo-structure effect and internal friction. The advantage of this technique is selectively sensitive to thermally active defects. The appearance of defects, which can be visualized by thermography camera, depends strongly on the method of excitation. In preliminary studies, ultrasonic excitation horns of ultrasonic manufacturing process are widely adopted for a polymer structure. However, it is needed that these horns are modified for improving the defect detection capability. This paper proposes a new ultrasonic excitation horns with tuning fork shape in NDT of polymer material. Geometric conditions are optimized by FEA and application results by the developed horn are described and compared with those by a previous horn.

Evaluation of elastic modulus of cantilever beam by TA-ESPI

The paper proposes an evaluation technique for the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of a thin film are the Nano indentation test, Buldge test, Micro-tensile test, and so on. They each have strength and weakness in the preparation of the test specimen and the analysis of experimental results. ESPI is a type of laser speckle interferometry technique offering non-contact, high-resolution and whole-field measurement. The technique is a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI can be used to find the resonance frequency for each vibration mode shape. And the elastic modules of a test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique can be used to find the elastic modulus of a material requiring simple preparation process and analysis.