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Strength analysis of welded joints in support structures of heavy machinery subjected to changeable loading conditions

Smolnicki Tadeusz, Sokolski Piotr

Eksploatacja i Niezawodność

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2024

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Vol. 26, no. 1

art. no. 175889

EN

The durability of bearing units of large machines depends mainly on the condition of their welded joints. With this in mind, we developed numerical models of the analyzed bearing units, for which we performed FEM simulations of the stresses in welded joints inseveral basic load cases. In each of the respective variants the technical condition of the bearing nodes was different and it corresponded to the severity of the degradation processes. Different positions of the superstructure in relation to the undercarriage were also taken into account. The simulations used the hot-spot method dedicated to FEM analyses of complex welded structures. We discovered that the loads have a significant influence on the values and distribution of von Mises principal stresses and their axial components. Based on the carried out analyses, we identified the most unfavorable load cases that generate the highest stresses in the welded joints of the assessed nodes. We also demonstrated that the applied method effectively assesses the stresses of welded joints subjected to variable working loads.

2

Analysis of the Influence of Wear Crack of Chain Drive on Stress in Its Elements

Sokolski Piotr

Tribologia

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2023

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nr 2

65--72

EN

Pin joints of chain transmissions are areas of stress concentration, which can lead to the formation of cracks in the links. This process often contributes to a critical weakening of the cross-section in the lugs of these links, which results in its damage and may lead to the failure of the entire drive. The article analyses the influence of exemplary wear damages of chain transmission elements on the magnitude of stress concentration. The impact of the load, crack size, and its location on the level of stress increase was assessed. The location of cracks in the lugs of chain plates transmission links which lead to the most significant increase in stress level was identified.

PL

Połączenia sworzniowe przekładni łańcuchowych są miejscem koncentracji naprężeń, które mogą prowadzić do powstawania pęknięć w ogniwach. Proces ten często przyczynia się do krytycznego osłabienia przekroju w uchach tych ogniw, co skutkuje jego zniszczeniem i może prowadzić do niesprawności całego napędu. W artykule przeanalizowano wpływ przykładowych uszkodzeń zużyciowych elementów przekładni łańcuchowych na wielkość spiętrzenia naprężeń. Dokonano oceny wpływu wielkości obciążenia, wielkości pęknięcia oraz jego lokalizacji na poziom przyrostu naprężeń. Zidentyfikowano położenie pęknięć uch płytek gąsienicowych przekładni łańcuchowych, które prowadzą do największego spiętrzenia wytężenia.

3

Assessment of the acoustic microclimate and rating of noise hazards in the inner transport system of a bucket wheel excavator: a case study

Sokolski Piotr, Sokolska Justyna

Transport Problems

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2022

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T. 17, z. 1

187--200

EN

Noise and acoustic microclimate have an important influence on working conditions in industry. However, there are many sources of noise in machinery that create occupational hazards. In particular, these problems occur in belt conveyors, which are components of integrated continuous material handling systems. In large heavy-duty machines used for surface mining (bucket wheel, bucket chain excavators, and stackers), the most acoustically active areas are located in the zones of conveyor lines. For this reason, the present article presents the results of comprehensive research of noise in a transport system in a bucket wheel excavator operated in a surface mine. The most significant sources of noise were tested. Two analysis approaches (deterministic and probabilistic) were applied. Lower values of permissible exposure time were obtained using the latter method. This approach should be selected, as it takes into account the real conditions of operation of the tested object. The research and analysis showed that in real operating conditions of large working machines (multi-bucket wheeled excavators), the noise level cannot be treated in deterministic categories. This is due (among other factors) to the fact that the working loads are randomly variable in various operating conditions, which also causes the nature of noise in the area of these machines and their surroundings to change randomly. For this reason, the acoustic climate and the assessment of the level of noise hazards in such machines should be analyzed by taking into account the random nature of noise.

4

Assessment of the influence of the coefficient of friction on the temperature distribution of a disc brake during the braking process

Sokolski Piotr, Sokolska Justyna

Tribologia

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2019

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nr 6

95--99

EN

Brake assemblies are key mechanisms in the aspect of safe and reliable operation of devices and machines. Due to intense thermal processes that occur during braking, the brakes are exposed to an accelerated wear. The article assesses the impact of tribological cooperation conditions between the caliper and the disc of a disc brake on the temperature of a disc. The variable value in the simulations was the coefficient of friction between the cooperating surfaces. A direct effect of the increase of the analysed parameter on the enhancement of brake elements’ temperature was found. At the same time, a similar nature of thermal processes was observed for all values of the friction coefficient taken into account.

PL

Zespoły hamulców są kluczowymi mechanizmami w aspekcie bezpiecznej i niezawodnej pracy urządzeń oraz maszyn. Z uwagi na intensywne procesy cieplne zachodzące podczas hamowania hamulce narażone są na przyspieszone zużywanie. W artykule dokonano oceny wpływu warunków współpracy tribologicznej pomiędzy zaciskiem a tarczą hamulca tarczowego na rozkład temperatury tarczy. Wielkością zmienną w symulacjach była wartość współczynnika tarcia pomiędzy współpracującymi powierzchniami. Stwierdzono bezpośredni wpływ wzrostu analizowanego parametru na zwiększenie temperatury elementów hamulca. Jednocześnie zaobserwowano zbliżony charakter przebiegu procesów cieplnych dla wszystkich wartości współczynnika tarcia uwzględnionych w symulacjach.