Reliability Of Ultrasonic Testing Research Articles

Frequency-dependent reliability of ultrasonic testing based on numerical model with consideration of coarse aggregates in concrete

Frequency-dependent reliability of ultrasonic testing based on numerical model with consideration of coarse aggregates in concrete

Ultrasonic Testing of Welded Joints in Polyethylene Pipe

The reliability of ultrasonic testing (UST) of the quality of welded joints of polyethylene pipelines, made end-to-end with а heated tool, is considered in comparison with mесhапiсаl tests and radiography. The greatest detection of solid defects is provided bу u|trasonic inspection with the use of chord transducers (not less than 90%). When detecting defects translucent for ultrasound (lack of penetration, lack of fusion, etc.), the reliability decreases to 70–80%.

Features of ultrasonic control of butt welded joints of polyethylene pipes

The reliability of ultrasonic testing (UT) of the quality of welded joints of polyethylene pipelines, made end-to-end with a heated tool, is considered in comparison with mechanical tests and radiography. The greatest detection of solid defects is provided by ultrasonic inspection with the use of chord tipe probes (not less than 90 %). When detecting defects translucent for ultrasound (lack of penetration, lack of fusion, etc.), the reliability decreases to 70÷80 %. Keywords: welding, polyethylene pipeline, quality control, ultrasonic testing, chord tipe probe. aleshin@bmstu.ru

Applying Special Spatiotemporal Signal Processing Algorithms to Ultrasonic Testing of Large Antique Cast Bells

Original spatiotemporal signal processing algorithms have been developed to improve the reliability of ultrasonic testing of unique antique cast bronze articles. In particular, to inspect large bells on the grounds of the Moscow Kremlin, with numerous relief images that limit the surface available for mounting piezoelectric transducers, various spatiotemporal signal processing algorithms have been designed, including the ones based on rotating a double-crystal transducer with the summation of partial defectograms.

Application of Empirical Mode Decomposition for Ultrasonic Testing of Coarse-grained Materials

In ultrasonic testing of coarse-grained materials, signal to noise ratio (SNR) of testing signals is reduced seriously for the structure noise, and echoes from defects are difficult to be identified. In order to improve the SNR and the reliability of ultrasonic testing of coarse-grained materials, empirical mode decomposition (EMD) is introduced to process the testing signal here. Signal envelope can be formed by using cubic spline interpolation, and nonlinear and non-stationary signal can be decomposed self-adaptive into the sum of several intrinsic mode functions (IMF) by using characteristic time scale of the signals, and then higher order and tendency of the original signals can be obtained. The denoising experiment with low SNR simulated signal are achieved according to the feature of EMD, and SNR is enhanced more by comparison with the wavelet analysis method. And testing signal collected from coarse-grained materials is used to finish denoising experiment, and it is shown from the experiment result that the EMD has better adaptive ability in decomposing noise-polluted signals and less empirical information is required in the denoising process. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.3286

Research on Ultrasonic Testing of Coarse-Grain Materials with Hilbert-Huang Transform

In ultrasonic testing of coarse-grain materials, signal to noise ratio (SNR) is so poor because of the serious structure noise, and reflected wave from defects is difficult to be identified. In order to improve SNR and increase the reliability of ultrasonic testing for coarse grain materials, Hilbert-Huang Transform (HHT) is introduced to analyze and process the testing signal here. Firstly, detected signals from the coarse grain material can be collected by using ultrasonic test system; And then many Intrinsic Mode Function (IMF) can be obtained according to Empirical Mode Decomposition (EMD), and marginal spectrum of different mode can be gotten by Hilbert transform; And finally, the noise should be removed after analyzing the time-frequency information, and SNR is able to be enhanced and the reflection wave from defect is being more obvious. It was shown from the experimental result that the ineffective structure noise could be removed after HHT, and SNR could be improved and the defect reflection is more outstanding.

Development of an Ultrasonic Performance Demonstration System for Dissimilar Metal Welds in Korean Nuclear Power Plants

To work towards better reliability of ultrasonic testing systems, the Korean Ministry of Science and Technology (MOST) published Bulletin 2004-13 in June 2004. This was replaced by the Ministry of Education and Science Technology (MEST) Bulletin 2009-37 published in September 2009, which directed that all nuclear power plants in Korea shall implement performance demonstration of dissimilar metal welds. Meeting the MEST bulletin requirements and increasing the reliability of ultrasonic testing require the development of a dissimilar metal weld performance demonstration system for ultrasonic testing. The present paper describes the development of a performance demonstration system for dissimilar metal weld ultrasonic testing for nuclear power plants, which meets the requirements of ASME Code Section XI, Appendix VIII and MEST Bulletin 2009-37 and details some of the results obtained for the system.

Modern approaches to the certification of ultrasonic testing techniques

Algorithms intended for certifying ultrasonic testing techniques and based on the complex application of reliability and accuracy indices, which are constructed taking into account the character of techniques, specific features of their use, and the objectives of their certification (comparison of techniques, introduction of a new technique involving measurement procedures, etc.) are proposed. On the basis of the main regulations of GOST (State Standard) R ISO 5725-1, 5725-2, the reproducibility and repeatability of determining the measured characteristics of artificial reflectors and actual flaws and the reliability of ultrasonic testing of welded joints have been assessed.

The W1 Issue. I: Extent of Weld Fracturing during Northridge Earthquake

Ultrasonic indications in the roots of complete penetration welds (W1's) were the most common of the unexpected conditions identified after the 1994 Northridge earthquake in welded steel moment frame (WSMF) buildings. Widely treated by the engineering profession as earthquake-caused damage requiring repair, and characterized as such by the SAC, W1's have not previously been subjected to systematic study either to factually establish their ostensible relationship to earthquake ground motions or to debunk it. In this first part of a two-part paper, the conclusions from several studies that were generally directed toward accurately characterizing W1's, identifying their origins, clarifying the extent and distribution of earthquake damage to WSMF buildings caused by the Northridge event, and developing recommendations for cost-efficient post-earthquake damage surveying of WSMF buildings are presented. In a companion paper, the reliability of ultrasonic testing (UT) of WSMF buildings during construction is also investigated as a possible explanation for the widespread presence of W1's in existing WSMF buildings. The studies found that W1's are not related to earthquake ground motion, that the extent of Northridge earthquake damage to WSMF buildings is substantially less than previously published accounts suggest, and that UT as normally implemented by testing lab personnel is an unreliable inspection technique for the roots of complete penetration T-joints with backing.

The W1 Issue. II: UT Reliability for Inspection of T-Joints with Backing

Ultrasonic indications in the roots of complete penetration welds (W1's) were the most common of the unexpected conditions identified after the 1994 Northridge earthquake in welded steel moment frame (WSMF) buildings. Widely treated by the engineering profession as earthquake-caused damage requiring repair, and characterized as such by the SAC, W1's have not previously been subjected to systematic study either to factually establish their ostensible relationship to earthquake ground motions or to debunk it. In this paper, the reliability of ultrasonic testing (UT) of full-penetration welded joints with backing in WSMF buildings is investigated. A study involving verification of the findings of UT via destructive investigation, a study of the influence of operator variability, and studies delineating some of the limitations of ultrasonics are described. In the first part of this two-part paper, several studies that were generally directed toward accurately characterizing W1's, identifying their origins, clarifying the extent and distribution of earthquake damage to WSMF buildings caused by the Northridge event, and developing recommendations for cost-efficient post-earthquake damage surveying of WSMF buildings were presented. Those studies found that W1's are not related to earthquake ground motion, and that the extent of Northridge earthquake damage to WSMF buildings is substantially less than previously published accounts suggest. In the present paper, it is shown that, as normally implemented by testing lab personnel, UT is an unreliable inspection technique for complete penetration T-joints with backing, which provides a plausible explanation for the widespread occurrence of W1's in existing buildings.

Characterisation and quantification of defects in rotors and casings of steam turbines

The loading situation of components in modern fossil-fired power plants is characterised by higher cyclic service in comparison to older plants. This leads in combination with larger units to increased stresses in the relevant components. To evaluate the risk of failure due to natural defects, life time approaches have been developed on the basis of advanced methods of fracture mechanics. The assessment of natural defects using fracture mechanics is, however, based on the following preconditions:• knowledge and data on the behaviour of such defects in terms of damage mechanism taking into account crack initiation and crack propagation under loading situations comparable to those in service,• data on the real size and geometry of defects,• data on the exact location of the defects.To create such a database an extensive joint research programme was started in the early eighties by German turbine manufacturers, steel makers and research institutes. The paper provides an overview of the results of these efforts. Special emphasis is placed on describing the improvements in ultrasonic testing techniques. The results of feature tests are reported. They have been performed to obtain information and data on the behaviour of natural defects under creep, creep fatigue and fatigue load. Subsequent metallographic investigations determine the real size and location of the defects but also the relevant damage mechanisms. Comparison of metallographic data and NDT data prove the reliability of ultrasonic testing. Thus an improved rating of the permissible ultrasonic indications in turbines and castings was obtained.