Practice for Immersed Ultrasonic Testing by the Reflection Method Using Pulsed Longitudinal Waves

On the basis of the previously developed model for estimating the attenuation coefficient of elastic longitudinal waves in cast iron due to their Rayleigh scattering on graphite inclusions, the influence of such attenuation for cast iron with globular graphite on the characteristics of signals with frequency spectra of different widths depending on the nominal pulse frequencies, cast iron models and the distance traveled by the ultrasonic wave is studied. Computer modeling acoustic channel for environment – cast iron with globular graphite for standard normal probes of two types for studying influence of such environment on characteristics real transmitting and registered signals at the ultrasonic testing. Comparison of results of calculations of spectrums and pulses of registered bottom signals with their experimental values for two samples of cast iron with globular graphite has shown an opportunity of use of the applied settlement model for description of the actual physical phenomena quite adequate for practice. Influence of attenuation of longitudinal waves in cast iron with globular graphite on the directivity characteristic of their radiation is shown on model of cast iron and duration of a pulse. The estimation of the relation of levels of a registered signal and structural noise for various reflectors and characteristics of controllable cast iron has shown performance of recommendations by I. N. Ermolov on reliable detection of a useful signal on a background of noise for thickness, before established experimentally. Features of DGS-diagrams for cast iron with globular graphite, caused by higher, than in steel, attenuation of longitudinal waves and a little smaller speeds of their distribution are marked.

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Ultrasonic testing of steel flat product of thickness equal or greater than 6 mm (reflection method)

10.3403/01685801 ◽

1999 ◽

Keyword(s):

Ultrasonic Testing ◽

Reflection Method

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Ultrasonic Testing for Vulcanization Inspection of Natural Rubber

Nondestructive Evaluation ◽

10.1115/imece2003-41782 ◽

2003 ◽

Author(s):

Mongkol Seenawat ◽

Asa Prateepasen ◽

Cherdpong Jomdecha

Keyword(s):

Natural Rubber ◽

Longitudinal Wave ◽

Frequency Spectrum ◽

Ultrasonic Testing ◽

Ultrasonic Attenuation ◽

Longitudinal Waves ◽

Transmission Technique ◽

Frequency Domains ◽

Novel Method ◽

Pulse Echo

This paper presents a novel method to inspect the levels of vulcanization of natural rubber by ultrasonic testing. In the research, test specimens are natural rubbers of type ‘cis-1,4-polyisoprene’ vulcanized at different durations. Piezoelectric contact transducers were used to transmit and receive ultrasonic to/from each sample. Longitudinal waves at nominal frequency of 2, 2.25 and 5 MHz were used to investigate the samples. Experiments were conducted using two techniques: pulse echo and through transmission. The pulse echo technique was applied to inspect the ultrasonic attenuation and the velocity of longitudinal wave of natural rubber. The through transmission technique was implemented to identify the shape and amplitude of the frequency spectrum. The results from both time and frequency domains can be employed to classify the levels of the vulcanization. From the experiments, this ultrasonic testing provides an effective way to inspect the vulcanization of natural rubber with repeatability and allows faster inspection rate than other methods.

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