Papers by Keyword: Ultrasonic Testing (UT)

Abstract: In the present investigation a batch of impellers made of 319S aluminum alloy with about 300 pieces and produced by semi-solid thixocasting process were subjected the ultrasonic testing (UT). The experimental results revealed that the equivalent size of the defects in the impellers was not more than φ0.4mm FBH+12dB. And there were two main types of defects in 12 mm depth area from the machined surface, where defect was apt to form. One type was single defect and the other was intensive defect. Moreover, other nondestructive testing (NDT) was used to test some impellers containing typical defect, and the result suggests that UT was more sensitive than x-ray testing. The defects existed in the impellers were investigated by Optical Microscope (OM) and Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS). The observation showed that the both types of defects existed in eutectic zone. The single defect derived from billet and the intensive defect came from die casting process.

Abstract: The article describes the use of ultrasonic testing methods for examining slabs made from cement based materials. For the detection of cracks, in full-scale slabs before and after the explosion, ultrasonic pulse method was used. Data obtained before the explosion confirm the high quality of the cement based material. Another set of data taken after the explosion shows the scale of cracks in the slabs. The article compares material characteristics of the unreinforced concrete, steel fibre concrete and high performance fibre reinforced concrete on the basis of materials tested by using the passage ultrasonic method after the explosion.

Abstract: In the ultrasonic detection of small-diameter steel pipe with thick wall, the quality of ultrasonic echo signals is the foundation for the pipeline flaw identification and feature extraction. In this paper,a de-noising method of wavelet packet based on threshold is proposed for the limitation of soft and hard thresholds. The ultrasonic wave pipeline detection signal contaminated by noise is de-noised by this method. Moreover, the contrastive analysis is performed among the wavelet packet transform based on adjusted threshold, original ultrasonic echo signal and the wavelet packet transform based on default threshold. Experiment results show that the noise reduction effect of the wavelet packet based on the adjusted threshold is obvious and the SNR of signals is also improved.

Abstract: This paper introduced the design of a portable ultrasonic TOFD imaging and detecting system, and developed the hardware and application software based on embedded system. We accomplished multi-channel ultrasonic transmission and acquisition, real time A-scan signal or TOFD image display, ultrasonic data storage and analysis of large capacity and automatic quantitative calculation of cracks in this system. This system offered rapid speed and high accuracy that could be used to locate and size cracks in both weld joint detection and field structure examination.

Abstract: The paper presents advanced ultrasonic and eddy current NDE techniques developed in the authors laboratory for nondestructive evaluation of austenitic stainless steel welds. The paper discusses the performance and comparison of 2D discrete wavelet transform (DWT) and de-noising methods applied on eddy current images obtained from stainless steel weld pad with machined longitudinal notches and a systematic approach for eddy current defect characterisation in weld pads by neural network. The simulation and experimental results on the effect of elastic anisotropy on ultrasonic phased array inspection in austenitic stainless steel weld are also discussed. A guided wave based ultrasonic method developed for detection of defects in stainless steel welds and its validation with complimentary techniques such as radiography and in-situ metallography are also presented.

Abstract: When matching pursuits (MP) method was used for noise suppression of ultrasonic testing signals, the number of matched atoms affects the denoising performance. The relationship between the number of the matched atoms and denoising capability was analyzed, using the root mean square error (RMSE) and improvement of signal-to-noise ratio (SNR) to evaluate denoising performance. The simulated signals with white noise at different SNR and experimental signal with white noise and grain noise were analyzed respectively, and the results show that the MP method can remove the white noise and grain noise effectively. Moreover the best denoising performance can be arrived if the number of matched atoms is appropriate. At last, the selection principle of atoms number is given.

Abstract: The ultrasonic flaw reflected signal of the thin-diameter rod was acquired by the general ultrasonic C-scan testing device. And synthetic aperture focusing technique be used in ultrasonic imaging of thin-diameter rod. Respectively, Comparing B-scan imaging and Conventional synthetic aperture focusing technique imaging as well as Frequency domain synthetic aperture focusing technique imaging . The final results show that both time domain and frequency domain synthetic aperture method could obtain a higher signal-to-noise ratio and testing resolution.

Abstract: Bonding quality is the key factor that affects the safety of concrete-filled steel tube (CFST) structure, so it is a very important research that how to judge the bonding quality. This paper expounded the theory of three methods used in nondestructive testing of CFST, and introduced the combined application of the methods of artificial tapping, ultrasonic testing, and strain analysis in a large simulation test.

Abstract: The ranging greater than 3m is not accorded with china engineering construction standardization association standard TECHNOLOGICAL SPECIFICATION FOR INSPECTION OF CONCRETE DEFECTS BY ULTRASONIC METHOD[CECS 21:200 (Transducer spacing is 2~3m). This paper studied large ranging of ultrasonic test mass concrete structure, and analyzed a project instance that was inspected the internal defects of mass concrete structures with various test methods, compared of those results. As detection is shown, first, with the test distance increased to 5.1m, the velocity of sound shows a linear trend of continuous development trend. Second, responds to improve of concrete strength, the velocity of sound increases, but not shows a linear trend. In addition, with the test distance increasing, concrete strength increases, but the velocity is down. A large ranging of ultrasonic test method was developed based on these observations.

Abstract: Water content is one of key effect factors on the dynamic elastic modulus, which is an important damage assessment index of concrete structures induced by freeze-thaw cycles, fire and chemical attacks. Through the ultrasonic and bending vibration test, the regularity of dynamic elastic modulus changed with the water content of concrete specimens was analyzed in this paper. The results show that the ultrasonic velocity has a low sensitivity to water content when it is below 1.5%. The bending vibration method can better reflect the effect of water content change on dynamic elastic modulus. The regression equation of dynamic elastic modulus and water content was set up by introducing the index function. The research results offer technical reference for the predicting of actual concrete dynamic elastic modulus in different humidity environment.