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2 2024

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Key challenges and threats for operators of the 112 emergency number during the COVID-19 pandemic on the example of the Mazowieckie Voivodeship

Nepelski Mariusz, Gwadera Izabela, Łożyńska Martyna, Stankiewicz Karolina, Fronczak Natalia, Żyszkiewicz Łukasz

Zeszyty Naukowe SGSP / Szkoła Główna Służby Pożarniczej

2024

Nr 90 (tom 2)

57--66

The article attempts to analyze emergency calls to the 112 number and demonstrate the challenges and threats faced by the 112 operators in the Mazowieckie Voivodeship during the COVID-19 pandemic, a disease caused by the SARS-CoV-2 coronavirus. The research focuses on changes in the type of calls, an increase in the number of calls and other difficulties that operators have had to face. The analysis is based on data from the period of 2017 to 2022, particularly highlighting the new challenges caused by the pandemic, such as handling requests connected with COVID-19. The authors draw attention to the important role of operators in public health protection and their exposure to stress in difficult working conditions. The study aims to understand the burden on the emergency notification system in the context of the pandemic and to highlight the role of operators in this process.

FEM Analysis of Residual Stresses in Welded Aluminum and Polyamide 6

Praski Marcin, Kowalczyk Piotr, Szumowski Radosław, Stankiewicz Karolina, Leski Andrzej

Fatigue of Aircraft Structures

2024

Iss.16

57--74

Thermoplastic composites enable weldable, recyclable aircraft structures, but thermal mismatch between metals and polymers can introduce detrimental residual stresses. This study develops a finite element method (FEM) framework to predict residual stress fields in resistance-welded joints between aluminum 7075 and carbon-fiber-reinforced polyamide 6 (PA6). Transient thermal analyses with multilinear, temperature-dependent properties were coupled to mechanical analyses; contact conditions transitioned from frictional to bonded at PA6 melting. Three thermal cycles (20°C→220°C→20°C, 20°C→240°C→20°C, 20°C→260°C→20°C) were examined to assess peak-temperature effects. The simulations show stress contours that decay with distance from the bond and reveal pronounced peaks in both normal and shear components at weld edges, consistent with shear-lag theory. Within the bonded interior, average stresses are relatively low, whereas edge concentrations identify likely sites for debonding or delamination initiation. The magnitude of residual stresses increases with thermal gradient, underscoring the need for parameter control during welding. The FEM outputs will be validated against uniaxial tension and three-point bending tests on welded specimens, with future work quantifying fatigue-life reduction under combined thermal and mechanical cycling. The results highlight mitigation priorities for bonded repairs and hybrid aerospace structures, including process-curve tuning (current/pressure/cooling) and edge-region design measures.