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1

Theoretical and experimental analysis of guided wave propagation in plate-like structures with sinusoidal thickness variations

Zima Beata, Moll Jochen

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e34, 2023

EN

Guided waves have attracted significant attention for non-destructive testing (NDT) and structural health monitoring (SHM) due to their ability to travel relatively long distances without significant energy loss combined with their sensitivity to even small defects. Therefore, they are commonly used in damage detection and localization applications. The main idea of incorporating guided waves in NDT and SHM is based on processing the received signals and appropriate interpretation of their characteristics. A great amount of research devoted to diagnostics of plate-like structures considers specimens with constant thickness, which significantly facilities the diagnostic process. In such a case the velocity is also assumed to be constant. However, the developed diagnostic methods should be applicable, especially for the structures exposed to an aggressive environment, excessive load, or unfavorable weather conditions, etc., when the probability of damage occurring is much higher. In such cases, the assumption about the uniform thickness alongside the propagation path cannot be applied in every case. Thus, the present study is focused on wave propagation in metallic plates with variable thickness. The results of theoretical, numerical and experimental investigations of antisymmetric Lamb mode propagation in aluminum plates with a sine-shaped surface are presented. In the first step, the influence of non-uniform thickness distribution on wave velocity has been described. Next, the inverse problem aimed at shape reconstruction based on time of flight (ToF) analysis and spatially varying wave velocity was solved and compared with the standard dispersion curve-fitting method.

2

Experimental verification of the use of dummies for tests in empirical research

Więckowski D.

Journal of KONES

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2017

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Vol. 24, No. 1

357--362

EN

The issues related to the use of test dummies for experimental research in the field of automotive engineering have been addressed. The article discusses the historical introduction and development of the dummies in the biomechanical tests, which have contributed to the replacement of, previously conducted tests on corpses or volunteers. The evolution of dummies development Evolution of the dummies construction development to the present times has been presented. Question was raised: what is the “similarity” between the dummy living human being. Contemporary dummies reflect very well features of the human body are made of good quality materials and can be equipped with numerous sensors performing various measurements. Comparative empirical tests carried out with an adult dummy and a living adult of similar parameters such as: size (weight and height) body proportions have been presented. The impact of vibrations on the human occupant riding a motor vehicle was examined, with road tests being carried out of realized driving on various road surfaces within that work and with the data recorded being analysed in the time domain and frequency domain. In the time domain, time histories of the accelerations recorded were analysed and the root-mean-square (RMS) acceleration values were calculated. In the frequency domain, the power spectral density (PSD) values and the absolute transmittance (amplification) values were determined for the acceleration signals recorded. The analysis of the measurement results for the ability to absorb vibration by living human being and the dummy has been done. The differences and similarities between the living human subject and the test dummy have been presented from the point of view of utilizing such subjects for experimental tests.

3

Verification of brittle fracture criteria for bimaterial structures

Mieczkowski G., Molski K.

Acta Mechanica et Automatica

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2014

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Vol. 8, no. 1

44--48

EN

The increasing application of composite materials in the construction of machines causes strong need for modelling and evaluat-ing their strength. There are many well known hypotheses used for homogeneous materials subjected to monotone and cyclic loading conditions, which have been verified experimentally by various authors. These hypotheses should be verified also for composite materials. This paper provides experimental and theoretical results of such verifications for bimaterial structures with interfacial cracks. Three well known fracture hypotheses of: Griffith, McClintock and Novozhilov were chosen. The theoretical critical load values arising from each hy-potheses were compared with the experimental data including uni and multi-axial loading conditions. All tests were carried out with using specially prepared specimens of steel and PMMA.

4

Evaluation of mechanical properties of soft magnetic materials for axial flux permanent magnet synchronous machines

Praunseis Z., Virtič P.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 2b

35--37

EN

Accurate determination of real material mechanical properties is important for safe servicing of energy components. The aim of the paper is systematic experimental approach for determination of mechanical properties of high strenght low alloyed steels and mild carbon steel in the rolling, thickness and width direction.

PL

W artykule przedstawiono metodę eksperymentalnej i systematycznej oceny właściwości mechanicznych stali niskostopowej i niskowęglowej o wysokiej wytrzymałości. Precyzyjne określenie tych parametrów pozwala na zwiększenie bezpieczeństwa użytkowania i serwisowania elementów.

5

Buckling resistance assessment of a slender cylindrical shell axially compressed

Marcinkowski J.

Mechanics and Mechanical Engineering

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2010

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Vol. 14, nr 2

309-316

EN

The paper deals with some considerations focused on resistance assessment of slender cylindrical shells subjected to the axial compression. The load carrying capacity of such shells is determined by stability criterion. It is not enough to determine the critical load in order to assess the load carrying capacity. It is necessary to apply the whole procedure recommended by designing codes and other design recommendations. Details of this procedure were presented in the paper. The correctness of the resistance assessment was verified experimentally on segments of cylindrical shells made of stainless steel.