The implementation of low-energy construction includes aspects related to technological and material research regarding thermal insulation. New solutions are sought, firstly, to reduce heat losses and, secondly, to improve the environment conditions in isolated rooms. The effective heat resistance of insulating materials is inversely proportional to temperature and humidity. Cement composites filled with lightweight artificial aggregates may be a suitable material. Selecting a proper method for measuring the thermal conductivity of concrete is important to achieve accurate values for calculating the energy consumption of buildings. The steady state and transient methods are considered the two main thermal conductivity measurement approaches. Steady state is a constant heat transfer, whereby the temperature or heat flow is time independent. In the transient method, temperature changes over time. Most researchers have measured the conductivity of cement-based materials based on transient methods. The availability and cost of equipment, time for experimental measurements and measurement ability for moist specimens may be some of the reasons for using this method. However, considering the accuracy of the measurements, the steady state methods are more reliable, especially for testing dry materials. Four types of composites were investigated that differed in filler: natural aggregate, sintered fly ash filler, sintered clay and granular foam glass aggregate. The method of preparing the samples for testing is especially important for the obtained results. The samples, with a specific surface roughness, will show a lower coefficient of thermal conductivity by 20–30%; therefore, the selection of the type of contact layer between the plate of the measuring device and the sample is of particular importance.

The degradation process of 316L stainless steel caused by cavitation was investigated by means of finite element analysis. The damage characteristics of metal specimens subjected to the cavitation bubble collapse process were recreated by simulation with a micro-jet water hammer. The simulation results were compared with the cavitation pits created in the experimental tests. In the experiment, different inlet and outlet pressures in a test chamber with a system of barricade exciters differentiated the erosion process results. Hydrodynamic cavitation caused uneven distribution of the erosion over the specimens’ surface, which has been validated by roughness measurements, enabling localisation and identification of the shape and topography of the impact pits. The erosion rate of the steel specimens was high at the beginning of the test and decreased over time, indicating the phase transformation and/or the strain-hardening of the surface layer. A numerical simulation showed that the impact of the water micro-jet with a velocity of 100 m/s exceeds the tensile strength of 316L steel, and produces an impact pit. The subsequent micro-jet impact on the same zone deepens the pit depth only to a certain extent due to elastoplastic surface hardening. The correlation between post-impact pit geometry and impact velocity was investigated.

Active foil bearings are a kind of gas foil bearing. They contain actuators which allow for modification of the bearing sleeve size and the shape of the lubrication gap. Rotor vibrations can be actively controlled by these changes. It is possible, among other things, to reduce the starting torque, control the vibration amplitude at different speeds and improve operational safety. Prototypes of active foil bearings are being developed based on different mechanical concepts. This paper provides an analysis of the linear mechanisms that are the base, and they are crucial for such developments. In the literature, there is a lack of characteristics of these actuators tested under real operating conditions of an active foil bearing. This article aims to fill this gap. New test rigs have been developed and used to precisely investigate the possibility of using actuators in active foil bearings. Since their geometry and control methods differ, the measurement systems have been adapted accordingly. The actuators studied were piezoelectrics, shape-memory alloys (SMAs) and stepper motors. Each of them was characterized by different operating characteristics. The results obtained allow for a comparison of the actuators. This approach is especially useful for the design and analysis of active foil bearings.

The erosion process of a 4 μm monolayer CrN coating deposited on 316L stainless steel due to cavitation was investigated using finite element analysis (FEA). To estimate load parameters from cavitation pit geometry resulting from high impact velocity and high strain rate, the explicit dynamic solver was employed. Water microjet impacts at velocities of 100, 200 and 500 m/s were simulated to recreate different cavitation erosion intensities observed in the experiment. The resulting damage characteristics were compared to previous studies on uncoated 316L steel. The relationship between impact velocity and postimpact geometry was examined. Simulations revealed that only impact at 500 m/s can exceed the maximum yield stress of the substrate without penetrating the coating. Subsequent impacts on the same zone deepen the impact pit and penetrate the coating, leading to direct substrate degradation. The influence of impact velocity on the coating degradation process is discussed.