Quantitative Nondestructive Testing Research Articles

3210 ステップ加熱時の温度変動解析による減肉欠陥検出(OS13 貯槽の防災と設計IV)

Thermographic NDT techniques based on transient temperature distribution after active heating have been developed by many researchers as one of effective quantitative nondestructive testing techniques. The interest of the researchers has been focused on how to process transient temperature data after active heating i.e., pulse heating or step heating, to conduct successful identification of defect parameters such as its depth, shape and size. In this paper, a data processing technique based on the Fourier analysis is proposed. When a step heat flux is applied to the surface of material containing a defect inside, characteristic temperature change is observed on the surface due to the heat insulation effect of the defect. Especially defect depth influences the time profile of the transient temperature change after active heating. In this study, experimental investigations were carried out to demonstrate the feasibility of the proposed technique for identification of material loss corrosion defect in steel plates.

Quantitative Analysis on Parameters of a Defect with Speckle Interferometry and Finite Element Optimization Method

Quantitative nondestructive testing (QNDT) is required for the in-service inspection of high-cost structures whose failure could lead tragic consequences. The optical methods are widely used for NDT and NDE. However, most of them base on the qualitative detection of the partial fringes induced by the defects. The defect characteristic parameters (DCPs), such as coordinates and types, are easily obtained, but it is difficult to obtain other parameters, e.g. the defect size and embedded depth due to the non-unique relation between the DCPs and the deformation of detected defects. In this paper, the optical method, design optimization and FEM are combined to accomplish QNDT. Three types of defects are inspected and their DCPs values are obtained quantitatively. Moreover, factors that influence detection accuracy of the DCPs are also discussed.

Quantitave Alternative Method of Determining Hardness of Carburized Steel Annealed or Quenched by a CO2-Laser on the Basis of Carbon-Dependent Correlation Between Hardness and Thermal Diffusivity

A quantitative nondestructive testing method is proposed for imaging thermally treated steel. A theoretical model and experimental data on visualizing an optical beam deflected by a metal sample heated by a Gaussian beam are given. An analytic solution of heat equations obtained in the corresponding approximation gives a theoretical expression for the surface temperature, important for understanding the experimental process. Attention is concentrated to measurements which make it possible to clarify correlation between mechanical parameters and local thermal characteristics of the sample. For the purpose of establishing a simple theoretical correlation between the steel microhardness and the thermal diffusivity in accordance with variations of the structure and composition of steel, a theoretical procedure of inverting the dependence between the thermal diffusivity and the photothermal de ection observed experimentally is proposed and a methodological comparison of the results is carried out.

349 低サイクル疲労微小表面き裂の超音波非破壊評価 : 検出限界と周波数の関係(OS2-1 欠陥検出)(OS2 超音波と材料評価)

This present study was done with the aim of improving the reliability of quantitative ultrasonic nondestructive testing. The water immersion ultrasonic method, using an oblique longitudinal wave with large incidence angle (over the critical angle), was applied to measure small surface fatigue crack due to low-cycle loading. Surface fatigue crack initiation process, beginning from persistent slip band initiation, was measured using ultrasonic microscope. To estimate the precision of measurement, four transducers with different frequency, they are 5,10,20 and 50MHz, respectively, were used to make clear the relation between the ultrasonic frequency and its minimum detectable size of surface fatigue crack.

Modeling tools for ultrasonic inspection of welds

Developments in quantitative ultrasonic nondestructive testing (NDT) of welds require simulation tools for cost-effective research and engineering works. The present paper reviews the specific developments in modeling of weld inspection at the French Atomic Energy Commission (CEA), made in keeping with the general pattern of CEA in simulation studies of ultrasonic examination. Two models have been developed for several years at CEA for this purpose. One is dedicated to the computation of the ultrasonic field radiated by arbitrary transducers into pieces (possibly anisotropic and heterogeneous) under examination. We specifically discuss how the metallurgical structure and associated elastic properties of welds is taken into account. The other simulates a testing experiment. It accounts for the interaction of the beam with defects (within a piece made of isotropic material) and specimen boundaries and simulates the transducer scan over the piece for synthesizing images comparable with measurements. We specifically discuss the influence of the possible complex geometry of the back-wall of a weld. Examples of application are given. They demonstrate the usefulness of such modeling tools in ultrasonic NDT of welds to study and optimize testing configurations, and to help NDT experts to interpret actual data.

Noise analysis of digital ultrasonic nondestructive evaluation system

Being one of the five most commonly used nondestructive testing (NDT) routines, ultrasonic testing (UT) is under fast development in recent years, with more attention being focused on quantitative testing and nondestructive evaluation (NDE). In the evaluation of pressure vessels and piping, UT is utilized not only in manufacturing quality controlling, but also in-service monitoring and residual life prediction, such as the inspection of welded joints, monitoring of crack propagation, evaluation of materials property deterioration. In ultrasonic NDE and quantitative NDT, one of the main factors disturbing the reliability and accuracy of test is noise encountered during inspection. At present, a digitized instrument is increasingly preferred in practice. Considering every step, from wave emitting to digitalization of analog signal, the following noises usually emerge—the electronic circuit noise of instrument; structure noise caused by grain boundaries of material under testing; ringing noise due to oscillation of probe; digital noise of finite-word digital system; pulse noise by virtue of fluctuation of inspection circumstance. Among these, the most serious is the structure noise encountered in the testing of coarse-grained austenite stainless steel, which affects the defect signal, making the least detectable defect size increase. In the present paper the characteristics, detriment and elimination algorithms of electrical noise, pulse noise, ringing noise and structure noise in a digital ultrasonic NDE system are discussed. A physical model of the digital ultrasonic NDE system is established, and noises are classified into different categories from the viewpoint of the model. The characteristics of electrical noise are analyzed; an algorithm of extremum filtering constructed to eliminate the pulse noise; high-pass filter and wavelet packet are employed to process ringing noise; the features of structure noise are studied and it is de-noised by wavelet transform (WT) and wavelet packet transform (WPT). The results obtained from real-world signal show that the electrical noise can be taken approximately as white noise with a Gaussian distribution. The algorithm of extremum filtering can filter the pulse noise without any effect on other information in the signal. Wavelet packet algorithm is more suitable for the elimination of long-term ringing noise than high-pass filter under the condition of less loss of defect echo. Processing the signals of coarse-grained austenite stainless steel samples with defects by use of WT and WPT concludes that as structure noise can be divided into certain frequency bands, generally different from those of defect echoes by WT and WPT, the defect can be pointed out, and the signal-to-noise ratio enhanced substantially after the threshold processing of frequency components of signals followed reconstruction.

Novel quantitative non-destructive testing method for composite structures

A novel QNDT (quantitative non-destructive testing) method is developed that is combined with a phase-shifting shearing speckle and thermograph, and, it aims at the detection of faults such as cracks, voids, delamination and weak areas. The technique is immune to ambient noise and is suitable for measuring the in situ environment. Some different depth defects that would produce deformation differing from other positions could be found with shearing speckle when the sample is loaded, however, a thermograph based on the thermal resistance effect of a defect can detect only those varisized defects embedded deeply in the composite structure by measuring the surface temperature distribution. The resolution is examined for artificial delaminated defects in carbon-fiber composite structures using a phase-shifting shearing speckle and thermograph. The experimental results have demonstrated that the technique is effective for revealing defects in composite structures.

Models for the computation of ultrasonic fields and their interaction with defects in realistic NDT configurations

Developments in quantitative ultrasonic non-destructive testing (subsequently denoted by NDT) require simulation tools for cost-effective research and engineering works. The present paper reviews the two models developed for several years at the French Atomic Energy Commission (CEA) for this purpose. The first one is dedicated to the computation of the ultrasonic field radiated by arbitrary transducers into pieces under examination. The second simulates actual testing configurations, that is, includes beam/defect interaction as well as the transducer scan over the piece so as to synthesise images typical of those actually measured in NDT experiments. Examples of their application in the context of nuclear engineering are given. They demonstrate the usefulness of such modelling tools in ultrasonic NDT either to study and optimise testing configurations, including transducer design or to help NDT-experts to interpret actual data, possibly by means of model-based automatic data inversion.

Review of quantitative nondestructive testing

Review of quantitative nondestructive testing

Prediction of eddy current probe signal trajectories

Development of computer based defect characterization schemes in quantitative eddy current nondestructive testing (NDT) requires an adequate mathematical model capable of describing the complicated interactions between the impressed and induced currents, primary and secondary fields and the flaws in materials. This paper describes a finite element model which predicts the apparent changes in the normalized complex impedance of a differential eddy current probe in axisymmetric NDT configurations. Using this 'numerical model' differential eddy current probe, signal trajectories (as obtained on an eddy-scope screen in actual testing) are predicted for three axisymmetric geometries associated with nuclear power plant steam generators - circumferential I.D. and O.D. slots in an INCONEL tube, and a carbon steel support plate encircling a defect-free tube. Comparison is made between the theoretical and experimental results at a probe excitation frequency of 100kHz. Finite element analysis techniques appear to be well suited to the modeling of eddy current NDT phenomena and for predicting the eddy current probe signal trajectories.