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1

The use of computational contact mechanics approaches to assess the performance of parts bearing stress concentrators

Lyashenko B. A., Stotsko Z. A., Kuzin O. A., Kuzin M. O.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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Vol. 103, nr 1

25--32

EN

Purpose: The purpose of this work is to build new computational schemes for assessing the strength parameters of parts with inhomogeneous properties of surface layers in the presence of stress concentrators. Design/methodology/approach: Using the developed approaches of mathematical modeling and open software for calculating the structures of the FEM - FEniCS, the required thickness of the hardened zones of parts has been established, which ensures their minimum softening during operation, depending on the characteristics of the stress concentrator. Findings: It is shown that for each size of the surface stress concentrator there is a critical value of the hardening thickness, the excess of which does not affect the operational strength of the parts, but increases the cost of technological operations. Research limitations/implications: In this article proposes a method for calculating the influence of the dimensional characteristics of hardening zones on the contact strength of parts with stress concentrators under conditions of prevailing power loads. Practical implications: The results obtained in this work were used to determine the technological modes of plasma hardening, which ensure an increase in the contact strength of parts with stress concentrators, depending on their dimensional characteristics. Originality/value: Using the approaches of computational mechanics and mathematical and computer modeling, methods for controlling the contact strength of parts with inhomogeneous non-local properties in the presence of a surface stress concentrator are proposed for the first time.

2

The analysis of stress distribution in tempered structural glass with stress concentrators under tension and compression

Šaučiuvėnas Gintas, Gečys Tomas, Mudrov Andrej, Ustinovichius Leonas, Miedzialowski Czesław

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

62--77

EN

The paper describes the results obtained from the tensile and compression experimental tests of the structural tempered glass plates with three different types of stress concentrators and without them. The types of stress concentrator have been chosen as close as possible to those usually found in practical situations and also taking into account the cases known from the literature. All tests are performed under the same conditions and with the step of loading 1.0 kN for tension and compression tests up to the limit of 8.0 kN. The stress gradients are measured with an optical device by birefringence. The research is aimed at determining the distribution and the values of stress gradients under tension and compression. The paper considers the problems of determining the stress values and their distribution in the glass plates with various stress concentrators, based on the results of non-destructive measuring, analytical calculations and the numerical simulation.

3

Analysis the state of stress in a stainless steel plate with stress concentrator in the form of circular hole

Konieczny Mateusz, Achtelik Henryk, Gasik Grzegorz

Inżynieria Materiałowa

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2019

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Vol. 40, nr 6

146--153

EN

The paper presents an analytical, numerical and experimental analysis of the state of stress in a plate with stress concentrator in the form of circular hole subjected to uniaxial tension. This type of the plate have found wide spread applications in the field of aerospace, marine and automobile engineering. The maximum difference in the values of reduced stresses calculated analytically in relation to the results obtained experimentally was δσa red = –19.74%. However, the maximum difference in the values of reduced stress calculated numerically using the finite element method (FEM) with the ANSYS program in relation to the results obtained experimentally δσn red = –31.86%, The study showed that the analytically calculated and numerically determined stresses are lower than the stresses obtained experimentally, which results in less operational safety of the structural element. However, the numerical method in the form of the finite element method becomes, in the case of a very complicated element shape, the only method for determining the magnitude and distribution of stresses near the notch in the designed element.

PL

Celem pracy jest analityczna, numeryczna oraz eksperymentalna analiza stanu naprężenia w tarczy z koncentratorem naprężeń w postaci otworu kołowego o średnicy d poddanej jednoosiowemu rozciąganiu siłą Pi i na tej podstawie zlokalizowanie stref spiętrzenia naprężeń.

4

Zastosowanie próbek cylindrycznych z karbami do wyznaczania parametrów odporności betonu na pękanie

Kazberuk A., Kosior-Kazberuk M.

Inżynieria i Budownictwo

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2011

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R. 67, nr 6

332-334

PL

Zaproponowano metodę wyznaczania krytycznego współczynnika intensywności naprężeń w betonie z wykorzystaniem ściskanych próbek o przekroju kołowym, z centralnie umieszczonym otworem w postaci rombu. Metoda może być stosowana do analizy procesu pękania w otoczeniu koncentratorów naprężeń w dowolnym elemencie konstrukcyjnym.

EN

The method of determination of the critical stress intensity factor for concrete was proposed. The compressed cylindrical sample with central diamond-shaped hole was used. The approach presented can be applied to the analysis of the fracture process in the vicinity of the stress concentrators such us sharp and round notches formed in the structural elements.

5

Badanie prędkości pękania zmęczeniowego w stali 18G2A przy wahadłowym zginaniu

Gasiak G., Rozumek D.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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1999

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Z. 68, t. 1

105--112

PL

W pracy przedstawiono wyniki badań rozwoju pęknięć zmęczeniowych przy wahadłowym zginaniu w próbkach jednostronnie utwierdzonych wykonanych ze stali 18G2A. Do badań użyto próbek płaskich z koncentratorem naprężeń w postaci jednostronnego karbu. Badania prowadzone były na maszynie zmęczeniowej MZGS-100 przy częstotliwości zmian obciążenia 28,8 Hz. Badania wykazały, że karb w próbce ma istotny wpływ na prędkość rozwoju szczeliny zmęczeniowej, a w szczególności ma znaczny wpływ na wartość przenoszonego obciążenia. Im łagodniejszy był karb w próbce badanej tym prędkość pękania zwiększała się wraz ze wzrostem obciążenia. Dla przykładu, przy maksymalnym obciążeniu prędkość pękania próbek z karbem łagodnym była około dziesięciokrotnie większa. Również nośność próbek z karbem łagodnym (U) była większa w stosunku do próbek z karbem ostrym (V).

EN

The work presents the results of investigating development of fatigue cracking under pendular bending in unilaterally restrained samples made of the 18G2A steel. For the purpose of the research plane samples were used with concentration of stress in the form of unilateral notch. The research was carried out on the fatigue machine MZGS-100 at the loading change frequency of 28,8 Hz. The investigations showed that the notch in the sample has a substantial influence on the rate of development of fatigue slit and especially it has a significant effect on the value of the exerted loading. The softer the notch in the investigated sample the bigger rate of cracking accompanied by the increased loading. For example, at maximum loading the rate of cracking in the samples with a soft notch was about ten times bigger. The bearing strength of samples with a soft notch (U) was also bigger in comparison to the samples with a sharp notch (V).