The purpose of the article is analyzing the impact of taxation on the effective income tax rates paid by Polish companies. The authors present the results of a study made on the biggest firms, listed on the Warsaw Stock Exchange and included in the WIG20 index. In the research they bring closer the concept of tax aggressiveness – by looking at the effective tax rates (ETRs) achieved by WIG20 companies in years 2010-2014. The study is structured into 5 groups, according to the industry in which the analyzed companies operate. The results prove the sectoral differences in the level of ETRs. While the financial enterprises pay relatively high taxes in relation to the achieved gross profit, the energy sector has a negligible rate of effective taxation. At the same time companies operating in fuel and raw materials industry achieve highly unstable effective tax rates.

The use of thermoplastic elastomers (TPE) in 3D printing technology enables the use of this technology to produce prototype seals with an unusual shape or design solution. Tribological tests were carried out on a pin-on-disc test stand. The influence of contact pressure and sliding velocity on the friction coefficient of the TPE-steel friction pair under mixed lubrication conditions was analyzed. Based on the obtained tribological test results, it was found that the coefficient of friction of the thermoplastic TPE elastomer on steel in the presence of hydraulic oil (mixed lubrication) at a sliding velocity below 1 m/s does not exceed μ = 0.25. The obtained friction coefficient values are comparable to the results for other elastomeric materials used for technical seals. It was found that the influence of contact pressure on the value of the friction coefficient in the tested friction pairs is varied and depends, for example, on the sliding velocity. It was recommended to carry out research on the assessment of durability (wear intensity) and structure (porosity) of the material in elements manufactured using 3D printing to obtain full knowledge of the possibility of using these materials in the area of technical aircraft seals.

The article presents a new design solution for hydraulic gerotor machines. The main focus has been placed on the strain analysis of the behavior of a cycloidal gear set made of plastic. The gears comprise the main work unit of hydraulic gerotor machines, which are powered by driving the gear set. In state of the art, the rotational motion of the gear set was effected by driving the inner gear. This article proposes a modified method of power transmission in which the outer gear is the driving gear. Such a solution also results in modifications to the design of the hydraulic machine. The design and its analysis were performed with the use of Finite Element Method (FEM). The FEM technique has been used in several ways. It has enabled a modified design solution, as well as strain analysis of the modified cycloidal gear set, with the use of Finite Element Method (FEM). FEM technique has also been here combined with experimental research. This combination allowed stating maximum working parameters for the cycloidal gear set made of plastic. The above activities have led to a concept of a new hydraulic gerotor machine, which differs from the traditional designs. The device according to the new design is capable of carrying substantially higher working loads than devices according to previous designs.

Article shows the analysis of stresses and displacements which occur in the cycloidal gears during working of their in gerotor machine. Authors considered a possibility of using of a plastic (polyoxymethylene POM) as a material of design for the gears. Analysis has been conducted with using of the finite element method for several working position of cycloidal gear. The author also noted the influence of the type of tooth profile on the strength of the gear set. The stating of the highest value of pressure which can use in gerotor machine which plastic gears is the result of analysis. Analysis shows that gear sets made of Polyoxymethylene can work to the value of pressure p=6-8 MPa.