Determination of the Vibration Frequency in Nondestructive Testing

Danilov, V. N.; Ermolov, I. N.; Щербаков, А. А.

doi:10.1023/b:runt.0000009069.19618.0b

Cited by 9 publications

(4 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4a) and a duration of 3 to 10 periods [12][13][14]. Since different methods can be used to detect high-frequency ESs, the sensitivity can be calculated from the ES magnitude.…”

Section: Acoustic Methodsmentioning

confidence: 99%

Estimating the characteristics of piezoelectric transducers

Senyutkin

Chineikina

2005

Russ J Nondestruct Test

View full text Add to dashboard Cite

A method for estimating the sensitivity of piezoelectric transducers (PETs) is proposed. It is based on normalizing the amplitude of the PET-exciting voltage and calculating the sensitivity with respect to a conventional unit level. The results obtained from measuring PETs produced by well-known foreign manufacturers and at our factory are presented. Attention is also given to measuring the duration of echo signals. The described technique for evaluating the characteristics of echo signals can also be applied to contact angle PETs. The results obtained and proposals put forward in this study can be considered when correcting the Russian Standard for measuring the PET characteristics.Analyzing the EN 12668-2 European Standard and the GOST (State Standard) 23702-90 Russian Standard has shown that measurement of the sensitivity of piezoelectric transducers (PETs) and estimation of the shape of PET signals must be refined [1]. In accordance with the above standards, the PET sensitivity is defined by the formula [1][2][3] (1)where A is the PET sensitivity (the pulse conversion coefficient) (in dB), U ES is the echo-signal (ES) magnitude (in V), and U PET is the amplitude of voltage from a generator applied to the PET (in V).However, virtually no requirements are imposed upon the conditions for exciting a PET. Value A determined from (1) does not give consumers of PETs any information on the conditions under which the PET characteristics were measured nor does it allow the PET operation to be predicted in particular applications. Since the PET excitation conditions may appreciably affect the ES characteristics [4-6], a concept of the standard PET excitation must be introduced.A standard excitation is successfully used in measuring the characteristics of electroacoustic radiators and sound detectors. Normalizing the exciting voltage and estimating the radiation with respect to a certain adopted value ensures good reproducibility of the measurement results at a level provided by domestic and foreign manufacturers [7].The characteristics of PETs excited under standard conditions are measured more simply in a pulsed mode using the echo method. Most present-day flaw detectors and ultrasonic thickness gages also utilize the echo method, which is implemented using a shock-excitation generator producing short video pulses [8]. As a rule, these are exponential or rectangular pulses with amplitudes of 25-400 V and durations of 50-500 ns [9]. RF pulses are not very often used to excite PETs; this type of excitation is applied in a limited number of fields of ultrasonic testing, such as resonance thickness measuring, studying the ES spectra, and testing materials with high damping [10,11]. In traditional applications of the echo method, the ES spectral characteristics are usually unnecessary. In addition, during PET excitation by an RF pulse, evaluation of the sensitivity of a PET with short ESs (1-1.5 periods) may significantly distort the shape of the ES.Hence, we can formulate the following requirements for a standard generator...

show abstract

“…4a) and a duration of 3 to 10 periods [12][13][14]. Since different methods can be used to detect high-frequency ESs, the sensitivity can be calculated from the ES magnitude.…”

Section: Acoustic Methodsmentioning

confidence: 99%

Estimating the characteristics of piezoelectric transducers

Senyutkin

Chineikina

2005

Russ J Nondestruct Test

View full text Add to dashboard Cite

show abstract

“…The probe's operating frequency determined from the spectral peak in Fig. 3 is 2.18 MHz, and from two oscillation periods with the highest positive amplitudes in the pulse (as recommended in [4]), the frequency is somewhat higher-2.25 MHz. Measuring the signal level from a flat-bottom reflector of 10.2-mm 2 area in a specimen with the ACOUSTIC METHODS DANILOV same dimensions has shown that it is 5.8 ± 0.3 dB lower than that from a reflector of 20.4-mm 2 area.…”

mentioning

confidence: 99%

“…2 4 6 f, MHz Echo-signal spectrum (4) which was obtained earlier in [6] (see formula (17)). Hence, the effect of a flat-bottom hole on the bottom-signal level is determined not only by the relative size of the hole (i.e., by the hole-to specimen-radius ratio, b fb /b) but also by the relative size of the specimen itself, b/h.…”

mentioning

confidence: 99%

Effect of the Size of a Flat-Bottom Hole in a Cylindrical Specimen on the Bottom-Signal Level

Danilov¹

2005

Russ J Nondestruct Test

Self Cite

View full text Add to dashboard Cite

The effect of a change in the size of a flat-bottom hole on the level of a bottom signal measured with a normal probe at an end surface of a cylindrical specimen is considered. It is shown that this effect depends on the specimen's radius-to-length ratio. It is established that the difference in the levels of a bottom signal and a signal from a hole in the specimen is in good agreement (within 0.5 dB) with the corresponding difference obtained from the calculated DGS diagram.During ultrasonic inspection of forged pieces, rods, etc., with normal probes aimed at the tuning of the sensitivity of flaw detectors and evaluation of the equivalent area of flaws, a common practice is to use cylindrical calibration blocks with artificial reflectors in the form of flat-bottom holes, the planes of which are oriented perpendicularly to the ultrasonic-beam propagation [1]. Such reflectors are manufactured in the form of holes with flat profiles at different depths, axially symmetric with respect to the specimens. Reliable time selection of signals from flat-bottom reflectors against the background of a bottom signal from the specimen's surface, which is opposite to the surface of emission, and reception of a longitudinal wave can be achieved at typical distances from the reflectors to the former surface (the depth of the hole) of 15-20 mm. An example of specimens with such reflectors is a KCO-2 kit of calibration blocks (GOST (State Standard) 21397-81) used in ultrasonic testing of intermediate products and articles from aluminum alloys [2]. Analogous specimens are also produced from steel with allowance for the requirements of the above standard [1]. Specimens undergo primary and periodic certification (upon production and during service, respectively) to check the correspondence of their parameters to the required standards. In order to ensure the uniformity of measurements in the determination of the echo-signal amplitudes from the specimen's flatbottom reflectors, it is necessary to choose a reference signal, the amplitude of which must be compared to the signal amplitudes from the reflectors. For a KCO-2 kit, it was proposed to use an echo signal from a steel ball in an immersion bath as the reference signal, which is used to adjust the bath's elements and calibrate the flawdetector's sensitivity [3]. The normalized signal levels obtained are compared to the rated values, the tolerable deviations from which are ± 2 dB at most. The necessity of performing rather laborious measurements using a special-purpose setup makes the monitoring of signal levels from the reflectors impracticable not only during operation but also during periodic certification of specimens by metrological agencies.One of the methods for substantially simplifying the determination of the correspondence of signals from flat-bottom reflectors to the rated values is their comparison with the levels of the bottom signals in the same specimens, which are measured at such a position of a normal probe in which the maximum signal from a given reflector is achi...

show abstract

“…Note that some papers (e.g., [5,6]) point to the fact that the aforementioned procedures for determining the frequency are not always adequate for practical situations and the results obtained through them may be different from each other. In our opinion, the techniques currently employed to determine the vibration frequencies during ultrasonic NDT do not adequately take into account the peculiarities of real echo pulses reflected by [7,8].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Frequency Features of Pulse Echoes from Different Reflectors

Ринкевич

Nemytova

Перов

2011

ISRN Mechanical Engineering

View full text Add to dashboard Cite

Correspondence should be addressed to Dmitry V. Perov, peroff@imp.uran.ru The analysis of interaction of ultrasonic pulses with different reflectors which are located in elastic media is carried out. A parameter which allows estimating the form of reflector is instantaneous frequency of pulse-echo. This parameter is an unsteady pulse echo characteristic. Instantaneous frequency determination algorithm is to use wavelet transformation which has increased noise immunity. It is shown that the instantaneous frequency value for a pulse echo is often shifted from a rated frequency of piezoelectric transducer. Difference between the frequencies extensively depends on the reflector form.

show abstract

Determination of the Vibration Frequency in Nondestructive Testing

Cited by 9 publications

References 1 publication

Estimating the characteristics of piezoelectric transducers

Estimating the characteristics of piezoelectric transducers

Effect of the Size of a Flat-Bottom Hole in a Cylindrical Specimen on the Bottom-Signal Level

Comparison of Frequency Features of Pulse Echoes from Different Reflectors

Contact Info

Product

Resources

About