SOME FEATURES OF ULTRASONIC TESTING OF CAST IRON OBJECTS WITH FLAKE AND GLOBULAR GRAPHITE USING NORMAL LINEAR PROBES WITH PHASED ARRAYS

2020 ◽  
pp. 4-19
Author(s):  
V. N. Danilov ◽  
L. V. Voronkova
Keyword(s):  
Cast Iron ◽  
Longitudinal Wave ◽  
Attenuation Coefficient ◽  
Computer Modelling ◽  
Signal Spectrum ◽  
Flake Graphite ◽  
Longitudinal Waves ◽  
Globular Graphite ◽  
The Difference ◽  
Directivity Characteristics

Computer modelling of the acoustic characteristics of signals of direct normal probe with phased array (PFR) in the cast iron with flake and globular graphite was performed. As a result the form of acoustic pulses of a longitudinal wave, depending on the passed by wave distance and the values of attenuation coefficient for different models of cast iron was calculated. The main modeled characteristics of the probe include the directivity characteristic and the change in the amplitude of the signal along the acoustic axis. It is shown that the difference in the PFR directivity characteristics for cast iron with flake graphite of different models and steel is due to two factors – significantly lower longitudinal wave velocities in cast iron compared to steel and a decrease in its operating frequency due to attenuation. In this case, for cast iron with globular graphite, a small change in the width of the diagrams is due only to the lower speed of longitudinal waves in cast iron compared to steel. For cast iron with flake graphite model 3, the phenomenon of nonlinear attenuation due to a decrease in the frequency of the maximum of the signal spectrum during the propagation of a longitudinal wave in cast iron with a corresponding decrease in the frequency – dependent attenuation coefficient is established. Evaluation of the nonlinearity of attenuation for cast iron with globular graphite showed that it is very small. The influence of calculation of initial signal delays on the velocity of longitudinal waves in steel on the directivity characteristics in cast iron, decreasing with increasing focus distance, is established. It is shown that for cast iron with flake graphite there are cases when the direction of transmitting of PFR in cast iron is practically absent.

ON THE INFLUENCE OF THE SIZE OF FLAKE GRAPHITE INCLUSIONS AND ITS VOLUME CONTENT ON THE ACOUSTIC PARAMETERS OF CAST IRON AND THE CHARACTERISTICS OF ULTRASONIC LONGITUDINAL WAVE SIGNALS

2021 ◽  
pp. 4-15
Author(s):  
V. N. Danilov ◽  
L. V. Voronkova
Keyword(s):  
Computer Simulation ◽  
Cast Iron ◽  
Longitudinal Wave ◽  
Attenuation Coefficient ◽  
Volume Content ◽  
Phased Array ◽  
Flake Graphite ◽  
Layered Model ◽  
Linear Probe ◽  
Graphite Inclusions

Algorithms have been presented for calculating the velocity (in the approximation of a fine-layered model) and the attenuation coefficient of a longitudinal ultrasonic wave in cast iron, depending on the average size of graphite elements and its volume content, the calculation results for which are qualitatively confirmed experimentally. The calculation was performed using a fine-layered model of the structure, the graphite inclusions were described in the form of plane-parallel layers placed in an isotropic elastic medium (metal base). Computer simulation of acoustic paths for a mediumcast iron with flake graphite for standard direct converters is carried out in order to study the influence of such a medium on the characteristics of transmitted and received signals during ultrasonic testing. In the course of the research, a previously developed model was used to calculate the attenuation coefficient of longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions. Computer simulation of the acoustic characteristics of the signals of a direct linear probe with a phased array in cast iron with flake graphite was carried out, during which the shape of the acoustic pulses of the longitudinal wave was calculated, depending on the distance traveled by the wave and the value of the attenuation coefficient for various models of cast iron. The main modeled characteristics of the transducer include the directivity characteristic and the change in the signal amplitude along the acoustic axis. It is shown that for cast iron with flake graphite, there are cases when the directivity of the probe with a phased array transmitted into the cast iron is practically absent.

INVESTIGATION OF THE EFFECT OF ATTENUATION OF ELASTIC LONGITUDINAL WAVES IN CAST IRON WITH FLAKE GRAPHITE ON THE CHARACTERISTICS OF SIGNALS DURING ULTRASONIC TESTING

2019 ◽  
pp. 18-33 ◽  
Author(s):  
V. N. Danilov ◽  
L. V. Voronkova
Keyword(s):  
Cast Iron ◽  
Mean Value ◽  
Flake Graphite ◽  
Metal Base ◽  
Longitudinal Waves ◽  
The Mean ◽  
Average Size ◽  
Graphite Inclusions ◽  
Bulk Elasticity ◽  
Directivity Characteristics

The model of estimation of damping coefficient of elastic longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions, considering the deviation of the modulus of bulk elasticity of the phases of cast iron (metal base and graphite) from the mean value, is developed according to the theory of Mason. At the same time, the characteristics of cast iron used for calculations include the value of the longitudinal wave velocity, the mass content of graphite inclusions and their average size. In the process of studying the effect of attenuation of elastic longitudinal waves in cast iron with flake graphite on the characteristics of signals with narrow, medium width and wide spectra, a difference in the nature of the spectra changes due to frequency-dependent attenuation depending on the nominal pulse frequencies, cast iron models and the distance traveled by the ultrasonic wave is established. It is shown that the shorter the pulse, the greater the shift of the spectrum maximum in the frequency range less than the nominal. The effect of attenuation of longitudinal waves in cast iron with flake graphite on the impulse directivity characteristic of the round piezoplate depending on the cast iron model and pulse spatial length is established. The expansion of pulse directivity characteristics with increasing of the distance traveled by the wave in cast iron is shown, the greater the wider the pulse spectrum.

INVESTIGATION OF THE SPECIFICITY OF ULTRASONIC TESTING OF CAST IRON WITH GLOBULAR GRAPHITE USING LONGITUDINAL ELASTIC WAVES

2020 ◽  
pp. 6-25 ◽  
Author(s):  
V. N. Danilov ◽  
L. V. Voronkova
Keyword(s):  
Cast Iron ◽  
Ultrasonic Testing ◽  
Rayleigh Scattering ◽  
Frequency Spectra ◽  
Longitudinal Waves ◽  
Globular Graphite ◽  
Useful Signal ◽  
Two Samples ◽  
Standard Normal ◽  
Experimental Values

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.

Oxidation of Plain, Alloyed And Ductile Irons at 1300 Degrees F★

CORROSION ◽  
1954 ◽  
Vol 10 (9) ◽  
pp. 295-298 ◽  
Author(s):  
J. A. CAMERON
Keyword(s):  
Cast Iron ◽  
Ductile Iron ◽  
Spheroidal Graphite ◽  
Flake Graphite ◽  
Alloyed Cast ◽  
Resistance To Oxidation ◽  
Alloyed Cast Iron ◽  
The Difference ◽  
Better Than

Abstract Oxidation tests of up to 4000 hours duration at 1300 degrees F were made on ordinary flake graphite gray irons, ductile iron, and on highly alloyed cast iron having both flake and spheroidal graphite. It is concluded that ductile irons possess resistance to oxidation markedly better than that of flake graphite irons. In highly alloyed irons the difference is less pronounced at this temperature. Specimens exposed in atmospheric tempering furnace equipped with fan for circulation of air.

Analysis of the Common Causes of Papermaking Cast Iron Dryer's Defects and the Study of Test On-Line

2014 ◽  
Vol 936 ◽  
pp. 1851-1856
Author(s):  
Wen Wei Li ◽  
Qing Du ◽  
Wei Zhong Li
Keyword(s):  
Cast Iron ◽  
Longitudinal Wave ◽  
Transition Zone ◽  
Safety Assessment ◽  
Large Angle ◽  
Online Testing ◽  
Destructive Testing ◽  
Double Crystal ◽  
Testing Technology ◽  
Shrinkage Cavities

The existing researches only put forward the stress concentration portion and design improvements from the perspective of stress analysis, or conducts safety assessment on dryers with the methodology of fracture mechanics, without non-destructive testing methods. Based on over 3,400 tests on cast iron dryers in Hangzhou, an ultrasonic testing technology with longitudinal wave double crystal probe is developed in the present investigation. This study illustrates how to identify the volume defects through testing on the air holes, shrinkage cavities and inclusions in the dryer cylinder and small R transition zone with longitudinal wave double crystal probe at a small angle (5°), as well as plane defects with deep cracks through testing on the dryer cylinder and small R transition zone with longitudinal wave double crystal probe at a large angle (42°). It addresses the issues of how to measure the thickness in regular online testing for cast iron dryers, to calculate the intensity or compare with the design value, to identify low hardness value, to determine the key parts in online testing, and how to conduct safety assessment on the cast iron dryers with small cracks. This technique may resolve various problems in cast iron dryer testing.

scholarly journals The Morphology Analysis of Plasma-Sprayed Cast Iron Splats at Different Substrate Temperatures via Fractal Dimension and Circularity Methods

2019 ◽  
Vol 38 (2019) ◽  
pp. 692-698
Author(s):  
Qiulan Wei ◽  
Li He ◽  
Zhang Liu ◽  
Xiao Feng ◽  
Ya-Zhe Xing
Keyword(s):  
Fractal Dimension ◽  
Cast Iron ◽  
Substrate Temperature ◽  
Solidification Rate ◽  
Molten Droplet ◽  
Characterization Methods ◽  
Different Temperatures ◽  
Molten Droplets ◽  
The Difference ◽  
Plasma Sprayed

AbstractPlasma-sprayed cast iron splats were deposited onto polished aluminum substrates preheated to different temperatures ranging from 25°C to 250°C. The morphology of single splat was observed by a field emission scanning electron microscope. Quantitative characterization methods, including fractal dimension (FD) and circularity analyses of the splat profile, were employed to identify the difference in morphology of the splats with the change of the substrate temperature. The results showed that the substrate temperature has a significant effect on the spreading of molten droplets and the morphology of resultant splats through changing the solidification rate of the droplets. With the increment of substrate temperature, the homogeneous and sufficient spreading of the droplets resulted from low solidification rate reduces the splashing of the droplets. In addition, the evaporation of adsorbed moisture on the substrate improves the wettability between the spreading droplet and the substrate, then benefits the homogeneous spreading of the molten droplet. As a result, a distinct decline in the FD value was observed. It was also suggested that the FD analysis could be used to characterize the morphology of the splat more effectively while the circularity method was heavily dependent on the area of the splat.

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