No abstract

Actions aimed at improving the energy performance of buildings increase the share of heat loss through thermal bridges and windows in a building's energy balance. This is especially true of buildings currently under construction. In addition, it is known that the correct installation of windows is one of the biggest obstacles that must be overcome in order to achieve higher energy efficiency and reduce the impact of linear thermal bridges. Therefore, the study analysed, numerically and experimentally, the energy properties of PVC window frames with improved metal stiffening profiles, which were introduced to reduce the risk of window frame deformation and reduce leakage caused by faulty installation. The value of the frame thermal transmittance coefficient and the linear heat transfer coefficients were determined numerically. The simulation results showed that filling large air spaces with insulation material allowed for the reduction of the U f frame's thermal transmittance coefficient by over 10%. Moreover, where the window connects with the wall, there was a reduction in the linear thermal bridges' influence on heat losses. The reduction in the linear thermal transmittance coefficient Ψ was 9.6%, 1.0%, and 3.5% for the window sill, jamb, and lintel, respectively, compared to a frame without insulation. Moreover, experimental studies were conducted on the influence of the insulation of the PVC window frame with metal closed stiffening profiles on the linear thermal bridge located at the joint with the glass. It was found that the incidence factor I tb decreased by more than 6%. Thus, there is also a positive effect on the linear thermal bridge at the joint of the glass pane with the window frame.

The free transverse vibrations of shafts with complex geometry are studied using analytical methods and numerical simulations. A methodology is proposed for evaluating the results of a natural transverse vibration analysis as generated by finite element (FE) models of a shaft with compound geometry. The effectiveness of the suggested approach is tested using an arbitrarily chosen model of the injection pump shaft. The required analytical models of the transverse vibrations of stepped shafts are derived based on the Timoshenko thick beam theory. The separation of variables method is used to find the needed solutions to the free vibrations. The eigenvalue problem is formulated and solved by using the FE representation for the shaft and for each shaft-simplified model. The results for these models are discussed and compared. Additionally, the usefulness of the Myklestad–Prohl (MP) method in the field of preliminary analysis of transverse vibration of complex shaft systems is indicated. It is important to note that the solutions proposed in this paper could be useful for engineers dealing with the dynamics of various types of machine shafts with low values of operating speeds.

The geometric structure of mating surfaces has a crucial influence on the friction and resulting wear processes. This is particularly important in the case of injection pumps, where ensuring appropriate surface quality and tightness in a long-term operation process is extremely important in order to maintain nominal operating parameters. It is extremely important during variable pump operation conditions, start-up and shutdown, when there is a significant deterioration of cooperative conditions resulting from insufficient lubrication of the mating surfaces. The contact pressures on the mating surfaces are increasing and they are in contact with each, causing significant wear and high movement resistance. The technology of the application of special coatings is used in industrial scenarios for the deposition of thin layers to modify the surface layer in order to improve tribological properties, increase abrasive wear resistance, and improve the visual quality of the surface. The authors compared the current possibilities of the technique (ceramic coatings) with the commonly known methods for strengthening the cooperative surface (phosphating). As part of the work, several potentially applicable types of protective coatings were tested.

The use of HSM technology in the technological processes of milling and machining elements of aircraft structures made from (among other materials) aluminum alloys makes possible the production of elements with complex shapes, appropriate levels of precision workmanship, as well as surface roughness and waviness. The efficiency of the machining process is also a crucial factor, allowing it to compete with other manufacturing technologies. The achievement of these effects consists of many factors related to the machining process: machine tools and their rigidity, machining parameters, type of processed materials, as well as machining tools. The requirements for the tools used are related to the workpiece material and its specific properties, as well as the extreme machining conditions used (especially cutting speed vc and efficiency of the cutting process).