Inconel 718 alloy was tested. A new type of specimens of variable cross-sectional area measuring part was used for the tests. This provided a continuous distribution of plastic strain in that part of the sample. The proposed method enables to replace a series of specimens by one specimen. The degradation of the material was obtained by static tensile test and the creep test. The permanent deformation that varies along the specimen axis allows for an analysis of damage induced by a plastic deformation. The degradation of the alloy corresponds with the changes of acoustics properties of the material - attenuation of ultrasonic waves. It allows to detennine the degree of damage to the material using a non-invasive - ultrasonic method. Using the damage parameter proposed by Johnson allows to obtain correlation between the non-destructive results and a damage degree of the material. The presented testing method delivers information about changes in the material structure caused by permanent deformation.
The article presents the results of tests aimed at detecting discontinuities in the subsurface layer of elements intended for further processing. For the initial identification of discontinuities, the method of computed tomography was used. Based on the tomographic images of selected typical defects and measurements of the electrical conductivity of the material, the parameters for the eddy current tests were determined. A series of discontinuities in the subsurface layer to a depth of about 0.48 mm were detected. This allowed, at a given stage of machining, relevant elements to be selected for further processing.
This paper presents the results of the quantitative evaluation of the degree of damage caused by plastic strain accumulated in static tensile tests and creep tests. To detect changes in the structure of the material and in order to determine the degradation of the materials, nondestructive methods were used, namely the ultrasonic and eddy current methods. In ultrasonic testing, attenuation and acoustic birefringence were used as damage indicators. In the case of the eddy current method, changes in the phase angle of impedance were observed in the material. The material tested was Inconel 718 alloy. Inconel alloys are often find application in extreme working conditions including in the power engineering industry, aviation and aerospace. A new type of specimen with the variable cross-sectional area of the measuring part was used in the tests. This allowed researchers to obtain a continuous distribution of plastic strain and enabled analysis of the material with respect to different damage degrees. The correlation between the degree of damage, expressed by the measure of deformation, and the value of nondestructive indicators was determined. On the basis of it, the dependence indicating the ability to nondestructive evaluation of the degradation degree of the material, subjected to loads exceeding the yield limit was obtained.
Structural materials under various mechanical loads are damaged as a result of their plastic deformation and subsequent nucleation and propagation of cracks. Detection of damage in its initial phase is crucial to ensure safety and durability of construction elements. In this work, we proposed contact stiffness (
S
S
) determined using the instrumented indentation technique as the damage indicator. New procedure for deformation-induced damage investigation is proposed and the indentation tests were performed in the specially designed specimens made from Inconel 718 alloy, which was previously subjected to mechanical loads. Damage parameter (
D
ε
{D}_{\varepsilon }
) determined on the basis of Johnson–Cook damage model was used as a reference measure of damage degree. Fracture analysis was carried out to investigate the early stage of damage development in the tested specimens. The value of contact stiffness determined from the instrumented indentation shows linear correlation with the value of damage parameter. This innovative approach was used in the presented investigation.
This work is focused on the checking of the correctness of the brazing process of honeycomb seals to stationary elements of aircraft turbine engines. It describes this process, paying attention to the aspects that have a fundamental impact on whether the seal will be brazed to the base as required, or whether unacceptable areas of non-brazing will appear. The aim of the study was to check the possibility of using the ultrasonic method to check the correctness of the brazing process of honeycomb seals and to compare the tests carried out using this method with the mostly used visual tests. The research carried out as part of the work showed very well that there are reasons to use the ultrasonic defectoscopy method to test the correctness of the brazing process of honeycomb seals in the elements of aircraft engines. This method also makes it possible to automate the checking process, fully document it and objectively assess the correctness of the connection. The results obtained in the study provide a very good starting point for further research, the aim of which will be to implement the ultrasonic defectoscopy method for testing the correctness of brazing honeycomb seals into practice in industrial conditions.
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