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1

Evaluating the Attenuation in Ultrasonic Testing of Castings

Boháčik M., Mičian M., Sládek A.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

151--156

EN

This paper considers the assessment of attenuation in aluminium alloys castings and in cast iron prepared by gravity casting method and by casting under pressure. The issue of ultrasound attenuation is important in setting the conditions of non-destructive (NDT) testing, especially in casted materials. The characteristics of the ultrasonic technique and ultrasonic attenuation and the calculation of the attenuation and the velocity of ultrasound are presented in the theoretical part of this paper. For experimental measurements, cylindrical castings from AlSi alloy (a hypoeutectic alloy with a silicon content of about 7% - AlSi7 and a eutectic alloy with a silicon content of about 12% - AlSi12) and from grey and ductile cast iron were made. The ultrasonic records of the casting control, the calculation of ultrasound attenuation for individual samples are listed and described in the experimental part. The evaluation of measurements and comparison of calculated ultrasound attenuation is at the end of this article.

2

Assessment of vacuum bag pressure impact on porosity of laminates made with VBO prepregs

Czarnocki P., Katz T., Koperniak P.

Composites Theory and Practice

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2015

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R. 15, nr 3

141--145

EN

Vacuum bag only (VBO) prepregs allow for manufacturing composite airframe parts without the need for expensive autoclaves since such prepregs can be cured in ovens with the help of vacuum bags. However, the vacuum pressure must be kept at an acceptable level to obtain low porosity products. One of such prepregs is Cytec MTM46/HTS(12K)-150-35% RW carbon/epoxy VBO prepreg designed for airframe applications. The aim of the presented research was to determine an acceptable level of vacuum pressure in vacuum bags, in particular, and the effect it exerts on the porosity of laminates made with the aforementioned prepreg. For this purpose, UD laminate plates were manufactured under 10, 40, 60, 80 kPa and 96kPa vacuum pressure. Next, ultrasound attenuation displayed by every single plate during ultrasound C-scanning was defined in terms of the so-called full screen height percentage and presented in the form of coloured contour plots. Upon counting the pixels corresponding to each colour, it was possible to determine plate area fractions for each attenuation level. Next, a certain number of specimens was cut out of the plate regions that differed in their attenuation and these specimens were x-rayed with the help of a tomograph, then specialized software was used to determine their porosity. Finally, an experimental relationship between the ultrasound attenuation and specimen porosity was determined.

PL

Tak zwane „vacuum bag only” (VBO) preimpregnaty umożliwiają wytwarzanie struktur lotniczych bez potrzeby stosowania autoklawów. Prepregi takie mogą być utwardzane w piecach, z wykorzystaniem worków próżniowych. Jednakże, by uzyskać porowatość na akceptowalnym poziomie, ciśnienie w worku próżniowym musi być utrzymywane na odpowiednio niskim poziomie. Przedstawione badania dotyczą wpływu, jakie wywiera podciśnienie w worku próżniowym na porowatość wyrobu. W celu zbadania tej zależności wykonano jednokierunkowo wzmocnione płyty z wykorzystaniem prepregu VBO MTM46/HTS(12K)-150-35% RW firmy Cytec. Płyty utwardzano, stosując podciśnienia 10, 40, 60, 80 i 96 kPa, a następnie, wykonując C-skany, wyznaczono tłumienie sygnału ultradźwiękowego dla każdej z płyt. Jako miarę tłumienia przyjęto wielkość amplitudy odbitego sygnału wyrażoną w procentach wysokości ekranu skanera (w funkcji tzw. FSH). Uzyskane wyniki przedstawiono w formie kolorowych map warstwicowych. Licząc pixele odpowiadające każdej z barw, wyznaczono stosunki pól o wyselekcjonowanych wartościach tłumienia w odniesieniu do całkowitej powierzchni analizowanych płyt. Następnie, wykorzystując tomografię komputerową i specjalistyczne oprogramowanie, wyznaczono porowatości próbek wyciętych z wytypowanych obszarów badanych płyt. Umożliwiło to uzyskanie doświadczalnej zależności między tłumieniem fali ultradźwiękowej w badanym laminacie a jego porowatością.

3

Effect of magnetic field on ultrasonic elastic oscillation decrement in Fe-Si-Al soft magnetic alloy

Ashmarin G.M., Naimi E.K., Kaputkin D.E.

Inżynieria Materiałowa

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2004

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R. XXV, nr 3

253-256

EN

A new method to measure ultrasonic elastic oscillation decrement (USEOD) in ferromagnetic magnetic materials under both direct and alternating magnetic fields is developed. An influence of frequencies and magnitudes of these fields on USEOD in sendust-type soft magnetic alloy in two states with different structural defect densities was studied. The magnitude of elastic oscillations was up to 10^-4. Amplitude-dependent USEOD component is higher in high-defective state but amplitude- independent component is higher in low-defective state. Direct magnetic field with H < or = 1050 A/m does not affect USEOD, but alternating magnetic field with frequency of 50-1350 Hz decreases the amplitude-depending USEOD component significantly. These results were discussed basing on the theory of the interaction between mechanical oscillations and magnetic domain structure.