Appropriate selection of polymeric materials enables their wide application not only in machine construction elements, suspension and interior equipment of vehicles. Simultaneously with the development of new polymer materials, the processes of their processing developed. This also applies to incremental technologies. Rapid prototyping methods using 3D printers are largely based on various types of polymer materials. Currently, 3D printing is a well-known technique for producing functional elements, especially the Melt Extrusion Polymers (MEP) method, which is the oldest of the known techniques of spatial production. The main reason of the technology is designing and then manufacturing parts for many fields, including engineering, medicine, as well as the automotive and aviation industries. The article is a review of the literature on the use of composites based on thermoplastic polymers to develop new polymer materials used for 3D printing by MEP.

Polymer fiber composites are increasingly being used in many industries, including the defense industry. However, for protective applications, in addition to high specific strength and stiffness, polymer composites are also required to have a high energy absorption capacity. To improve the performance of fiber-reinforced composites, many researchers have modified them using multiple methods, such as the introduction of nanofillers into the polymer matrix, the modification of fibers with nanofillers, the impregnation of fabrics using a shear thickening fluid (STF) or a shear thickening gel (STG), or a combination of these techniques. In addition, the physical structures of composites have been modified through reinforcement hybridization; the appropriate design of roving, weave, and cross-orientation of fabric layers; and the development of 3D structures. This review focuses on the effects of modifying composites on their impact energy absorption capacity and other mechanical properties. It highlights the technologies used and their effectiveness for the three main fiber types: glass, carbon, and aramid. In addition, basic design considerations related to fabric selection and orientation are indicated. Evaluation of the literature data showed that the highest energy absorption capacities are obtained by using an STF or STG and an appropriate fiber reinforcement structure, while modifications using nanomaterials allow other strength parameters to be improved, such as flexural strength, tensile strength, or shear strength.

The problem of damping torsional vibrations of the crankshaft of a multi-cylinder engine is very important from the point of view of the durability and operational reliability of the drive unit. Over the years, attempts have been made to eliminate these vibrations and the phenomena accompanying them using various methods. One of the methods that effectively increases the durability and reliability of the drive unit is the use of a torsional vibration damper. The torsional vibration damper is designed and selected individually for a given drive system. A well-selected damper reduces the amplitude of the torsional vibrations of the shaft in the entire operating speed range of the engine. This paper proposes a thermo-hydrodynamic model of a viscous torsional vibration damper that enables the determination of the correct operating temperature range of the damper. The input parameters for the model, in particular the angular velocities of the damper elements as well as the geometric and mass dimensions of the damper were determined on a test stand equipped with a six-cylinder diesel engine equipped with a factory torsional vibration damper. The damper surface operating temperatures used in model verification were measured with a laser pyrometer. The presented comparative analysis of the results obtained numerically (theoretically) and the results obtained experimentally allow us to conclude that the proposed damper model gives an appropriate approximation to reality and can be used in the process of selecting a damper for the drive unit.

Two types of hydrodynamically lubricated plain journal bearings were subject to examination differing in the method used to feed them with oil. The first type was fed from a lubrication pocket and the second from the bearing face side. Mathematical models were developed with two-way oil flow allowing to determine the oil film bearing capacity, the maximum pressure, the maximum temperature, and the film oil minimum height for given position of journal relative to solid bush. Static characteristics were developed used in the further course of the study to compare operating parameters of the considered types of bearings. Another issue considered in the paper is the effect of oil VG grade on bearing performance with conditions of oil feeding taken into account and results of the research presented.

Among the essential issues facing designers of strain wave gears, the provision for correct lubrication should be of paramount importance. The present paper presents the results of research on elasto-hydrodynamic oil film in meshing of a harmonic drive with an involute tooth profile. The research was carried out based on theoretical models developed by Dowson and Higginson. For the discussed structural problem, results of the study are presented graphically in the form of static characteristics of the oil film. Correct operation regimes were determined for two different oils. The paper also provides a review of information concerning the design and principle of operation of strain wave transmission.