This article presents the results of research into the causes of the wear of the piston pin mounted in piston bosses by means of a hinge joint and in the connecting rod small end by means of the thermocompression bond. Changes in geometry and in the pin-top surface structure, which are caused by the mutual influence of the mating surfaces in variable lubrication conditions, are presented. The progress of scuffing as a result of insufficient lubrication of the mating elements or oil film breaking is demonstrated. The state of destruction was confirmed by the results of surface roughness measurements showing the formation of build-ups. The loss of the thermocompression bond surface, caused by the penetration of sintered engine oil fractions containing biofuel additive components and spent engine oil improver packages, was noted. The progressing forms of wear are the cause of engine failures due to the pin movement towards the cylinder wall, and due to boss breakage in the piston.

Increasing the use of renewable biofuels in internal-combustion-engine (ICE) vehicles is a key strategy for reducing greenhouse gas emissions and conserving fossil fuels. Hybrid vehicles used in urban environments significantly reduce fuel consumption compared to conventional internal-combustion-engine cars. In hybrid vehicles integrating electric propulsion with biofuels offers even more significant potential to lower fuel consumption. One would like to think they should also be less polluted in all cases, but some results show that the opposite is true. This study’s aim was to evaluate a hybrid vehicle’s energy and environmental performance using different gasoline–bioethanol blends. A Worldwide Harmonized Light Vehicles Test Cycle (WLTC) study was conducted on a Toyota Prius II hybrid vehicle to assess changes in energy and environmental performance. During the WLTC test, data were collected from the chassis dynamometer, exhaust gas analyser, fuel consumption meter, and engine control unit (ECU). The collected data were synchronised, and calculations were performed to determine the ICE cycle work, brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), pollutant emissions (CO, HC, and NO_x), CO₂ mass emissions per cycle, and brake specific pollutant emissions per kilometre. The study shows that the performance of the hybrid vehicle’s ICE is strongly influenced by the utilisation of electrical energy stored in the battery, especially at low and medium speeds. As the bioethanol concentration increases, the engine’s ECU advances the ignition timing based on the knock sensor signal. A comprehensive evaluation using the WLTC indicates that increasing the bioethanol concentration up to 70% improves the energy efficiency of the hybrid vehicle’s internal combustion engine and reduces pollutant and CO₂ emissions.

The purpose of the investigations was to assess the influence of repeated sleeve assembly on the wear of forced-in joint elements. The test methodology assumed operating a forced-in joint in rotational bending conditions, dismantling the joint after every thousand fatigue cycles, and then joint reassembling. The total number of fatigue cycles was 106, or as many as needed for fatigue cracking. The macroscopic observations of the shaft surface demonstrated the traces of fretting wear in the form of randomly spaced grey and dark brown stains at the axle seat circumference close to the joint edge. The size and number of the wear traces would increase with the number of fatigue cycles. The top layer wear also depended on the number of sleeve/shaft assembly processes. The microscopic observations confirmed fretting wear, which developed on the shaft surface. Numerous instances of surface microabrasion as well as micropullouts and surface scratches were observed. Material build-ups were also observed, which would crack and migrate. The chemical analysis of the composition of wear products demonstrated the presence of iron and oxygen atoms, which confirms the oxidation of wear products. The measurement of the maximum force needed to remove the sleeve from the shaft after the next fatigue cycle showed the need to use a greater force each time; however, a smaller force was needed to press the sleeve onto the shaft. As a result of the development of fretting wear, shafts would become fatigue-worn after 3.6 × 10⁶ fatigue cycles.

The article shows the results of measuring the mechanical losses of a piston engine in two new ways and explains the necessary engine modification for these measurements. At the same time, it compares the results of measuring mechanical losses in the internal combustion engine (ICE) in the current (hitherto exploited) way and in new ways. The first method is not replacing the cylinder charge and regulating the cylinder pressure by feeding compressed air through self-acting valves into the cylinders of the motoring engine. The second method is a closed working cycle by means of an exhaust–intake connection, in which the load pressure in the cylinder is adjusted and maintained by a controlled-intake air supply. With the current method of measuring mechanical losses of a reciprocating internal combustion engine (ICE) by motoring, there are less than half the pressures in the cylinder compared to the pressures during real engine operation (i.e., in the combustion mode). Lower pressures in the cylinder reduce the force load on the piston group and the crank mechanism, and the detected mechanical losses in the engine are thus significantly reduced compared to the reality. In the laboratories of the propulsion units of the Faculty of Mechanical Engineering of the Technical University in Liberec, research is underway on a new method of measuring mechanical losses of a reciprocating internal combustion engine by motoring with charge pressure profiles in engine cylinders comparable to cylinder pressures during standard engine operation. The paper shows the results of measuring the mechanical losses of a piston engine in two new ways and explains the necessary adjustment of the engine for these measurements. At the same time, it compares the results of measuring mechanical losses in a reciprocating engine in the current (hitherto used) way and new ways. The first method is not changing the cylinder charge and regulating the pressure in the cylinder by inserting compressed air through automatic valves into the cylinders of the motoring engine. The second method is a closed working circuit involving connecting the exhaust to the intake, in which the charge pressure in the cylinder is set and maintained by a controlled supply of compressed air to the intake manifold. The first method proved to be a more suitable way to investigate mechanical losses in ICE and determine the dependence of these losses on the pressure conditions in the engine cylinder.

This paper deals with the design of a calibration device for measuring the residual torque of the vehicle brake. It informs about the problems and purpose of the brakes, requirements placed on the brake system, and the design of vehicle brake systems. The practical part of the research contains the design of four versions of the calibration device and the 3D model of the proposed calibration device. There is also a new calibration methodology and calculation of the theoretical fault of the calibration device. An analysis and comparison of the original and new torque sensor calibration methods are presented at the end of this paper. By comparing the original and new calibration methods, it was revealed that the deviations from the required torque value compared to the original calibration version decreased from an average value of 0.154 Nm to 0.0047 Nm, and the variance of the measured values decreased on average from 0.00276 Nm to 2.07 × 10⁻⁶ Nm. The proposed new torque sensor calibration method has shown a positive contribution to the accuracy of torque sensor calibration, which as a result will significantly increase the reliability and accuracy of measuring the residual torque of automobile brakes and shorten the measurement time.

Fretting wear is a phenomenon occurring in many engineering objects, including push fit connections. In view of a large number of factors conducive to wear development, it is difficult to describe the mechanism of wear initiation and development. Therefore, various methods are sought to limit wear development. The use of a lubricant may be one of those ways. The aim of this article is to present the results of testing the influence of a lubricant medium on the development of fretting wear in interference fit connections. As a lubricant medium, MoS₂ and Whitmore greases were used. For that purpose, wear tests were first conducted on the shaft/sleeve tribological kinematic pair, and then observations and laboratory measurements were performed. The observations demonstrated the presence of fretting wear traces on all tested samples, irrespective of the tribological kinematic pair being tested. The main kind of damage consisted of material build-ups which, during operation, become oxidised and, while moving along the connection, caused local abrasion and micropits. The best results in restricting the development of fretting wear were achieved with Whitmore grease.