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Joanna Rymarz, Andrzej Niewczas and Daniel Pieniak

Abstract

The purpose of this paper was to present a reliability comparison of city transport buses on the example of Solaris Urbino 12 and Mercedes- Benz 628 Conecto LF at Municipal Transport Company in Lublin. A reliability index for the most failure parts and complex systems for the period of time up to first damage was determined. It has been demonstrated, that during the operation significant reliability differences occur between the buses produced nowadays.

Open access

Agata Walczak, Daniel Pieniak, Andrzej Niewczas, Agata M. Niewczas and Paweł Kordos

Abstract

In this paper the reliability assessment of structural reliability of the selected light-cured dental composites based on the biaxial flexural strength test results has been presented. A two-parameter Weibull distribution was applied as a reliability model in order to estimate probability of strength maintenance in the analysed population. Weibull distribution parameters were interpreted as a characteristic material strength (scale parameter) and structural reliability parameter in terms of ability to maintain strength by each of specimen from the general population (shape parameter). 20 composite specimens underwent strength tests, including 2 “flow” type composites and 2 standard composites (with typical filler content). “Flow” type composites were characterized with lower characteristic strength and higher structural reliability comparing to other studied composites.

Open access

Daniel Pieniak, Agata Walczak and Agata M. Niewczas

Abstract

The aim of the study was to compare microhardness and wear resistance of ceramic-polymer composites with micro and nano-hybrid structure. For the studies commercial composites were used, containing filler particles of the same type but different sizes, nano-sized (Filtek Ultimate) and micro-sized (Filtek Z250) composites. Tribological testing was conducted using ball-on-disc micro-tribometer. Vickers testing method was applied for microhardness studies with the use of Futertech FM 700 device. It has been demonstrated that the wear of Filtek Ultimate is almost twice lower in comparison to wear of Filtek Z250 composite. It has been concluded that the use of filler nanoparticles significantly increased wear resistance of the material. Additionally, lack of correlation between material microhardness and wear resistance has been demonstrated.

Open access

Agata Walczak, Daniel Pieniak, Andrzej Niewczas, Wiktor Gawroński, Piotr Wiśniowski and Leszek Gil

Abstract

The paper presents analysis of the availability of medium firefighting and rescue vehicles chassis used by State Fire Brigade in Warsaw. For analysis of availability of vehicles chassis the technical availability factor has been used. Additionally, in the paper time to restore of the vehicles chassis regarding causes of unavailability has been presented. In the tests the data obtained from the Decision Support System (DSS) of Warsaw State Fire Brigade were applied. The research included the period from January 2012 to May 2015. Based on the results, it can be statement that the operating mileage is the crucial factor of operating degradation of firefighting vehicles chassis.