Wyniki wyszukiwania - Biblioteka Nauki

1

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

100%

Praunseis Z. , Virtič P.

Przegląd Elektrotechniczny

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2013

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tom 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.

2

Verification of brittle fracture criteria for bimaterial structures

100%

Mieczkowski G. , Molski K.

Acta Mechanica et Automatica

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2014

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tom 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.

3

Experimental investigations of ultra-lightweight-concrete encased cold-formed steel structures: local stability behavior of C-section profiles subjected to eccentric compression

84%

Alabedi A. , Hegyi P.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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tom Vol. 72, nr 6

art. no. e151044

EN

Nowadays, cold-formed steel (CFS) has become widely used in the field of lightweight structures. In 2016, the Budapest University of Technology and Economics initiated a research study on a unique structural system using CFS and utilized ultra-lightweight concrete as an encasing material. This material serves as continuous bracing that improves CFS element resistance, stability behavior and performance, while also manifesting heat insulation capabilities, thus helping achieve sustainability goals. This paper is considered a continuation of previous research conducted by the authors. An experimental investigation was carried out on encased CFS columns subjected to eccentric loading. A total of fourteen stub-columns, with two distinct thicknesses, were subjected to various loading conditions for testing. The test results showed that local failure controlled the behavior of all the tested elements. The reduction in capacity resulting from eccentricity with respect to centric resistance varied between 20% and 52%, depending on the load position applied and on the core thickness of the tested steel elements. Moreover, the test outcomes were compared to the Eurocode analytical solution of pure steel elements. The overall load increment ranged from 46% to 18%, with a more noticeable bracing impact observed in the case of slender elements. Material tests also supplement the results.

4

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

84%

Więckowski D.

Journal of KONES

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2017

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tom 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.

5

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

84%

Zima B. , Moll J.

Archives of Civil and Mechanical Engineering

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2023

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tom 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.

6

Experimental and theoretical investigation of the shear lag effect in the novel non‑prismatic prestressed CSW-UHPC composite box girders

67%

Li H. , Li L. , Yoo D.-Y. , Ye M. , Zhou C. , Shao X.

Archives of Civil and Mechanical Engineering

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2023

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tom Vol. 23, no. 2

art. no. e132, 2023

EN

Due to their featured mechanical and structural merits, such as the light self-weight, excellent prestressing efficiency, appealing appearance, and optimal shear force and bending moment distributions in corrugated steel webs (CSWs) and concrete flanges, the prestressed concrete composite box girders with CSWs (CCBGCSWs) are popularly applied in highway bridges nowadays. To further enhance the cracking resistance of the concrete flanges of conventional prestressed CCBGCSWs, by replacing the regular concrete flanges with that made by ultra-high-performance concrete (UHPC) (i.e., with the much superior mechanical properties), this paper proposed a novel non-prismatic prestressed CSW-UHPC composite box girder to achieve the lighter dead weight, superior spanning capacity, and more rapid and cost-efficient construction for highway bridges. Owing to the differences in both the geometric dimensions and material properties, shear lag behavior of the proposed novel non-prismatic prestressed CSW-UHPC composite box girder could significantly differ from that of conventional prestressed CCBGCSWs. The shear lag effect refers to the non-uniform distributions of the longitudinal bending normal stress within the flanges caused by shear interaction between the webs and flanges, and the improper consideration of the shear lag behavior would impair the safety of thin-walled CCBGCSWs, especially the proposed novel non-prismatic prestressed CSW-UHPC composite box girder. Therefore, to investigate the shear lag behavior of the proposed novel nonprismatic prestressed CSW-UHPC composite box girder during different construction stages, a representative test specimen (5.55 m in length) with different boundary conditions (e.g., simply supported and cantilever) was designed and investigated under five different loading cases using the experimental tests and finite element (FE) analyses. In addition, a modified bar simulation method was proposed for the theoretical analysis of the shear lag behavior of the girder, and its feasibility and effectiveness were demonstrated through the comparisons to the experimental and numerical results. Finally, the results indicated that (i) the shear lag effect of UHPC flanges in the stress concentration region of the proposed novel non-prismatic CSW-UHPC composite box girder was more pronounced than that in the non-stress concentration region under different loading conditions; (ii) the shear lag coefficient (λ) of UHPC flanges in the non-stress and stress concentrated regions of the girder could be conservatively recommended not less than 1.1 and 1.25, respectively; and (iii) the boundary conditions and loading forms had significant influences on the shear lag behavior of the girder. The results of this study could serve as the experimental, numerical, and theoretical references for the shear lag behavior of the novel non-prismatic prestressed CSW-UHPC composite box girders.

7

Buckling resistance assessment of a slender cylindrical shell axially compressed

67%

Marcinkowski J.

Mechanics and Mechanical Engineering

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2010

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tom 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.