The paper presents a new way to conduct passive elimination of vibrations consisting of covering elements of structures with low dynamic stiffness with polylactide (PLA). The PLA cover was created in 3D printing technology. The PLA cover was connected with the structure by means of a press connection. Appropriate arrangement of the PLA cover allows us to significantly increase the dissipation properties of the structure. The paper presents parametric analyses of the influence of the thickness of the cover and its distribution on the increase of the dissipation properties of the structure. Both analyses were carried out using finite element models (FEM). The effectiveness of the proposed method of increasing damping and the accuracy of the developed FEM models was verified by experimental studies. As a result, it has been proven that the developed FEM model of a free-free steel beam covered with polylactide enables the mapping of resonance frequencies at a level not exceeding 0.6% of relative error. Therefore, on its basis, it is possible to determine the parameters of the PLA cover. Comparing a free-free steel beam without cover with its PLA-covered counterpart, a reduction in the amplitude levels of the receptance function was achieved by up to 90%. The solution was validated for a steel frame for which a 37% decrease in the amplitude of the receptance function was obtained.

This paper presents the effects of modeling the stress in the burnished layer of a complex spatial surface that was previously milled. A spatial kinematic-geometric model of the surface structure after milling is used. This paper presents the results of a numerical experiment on the synergic influence of the technological milling and burnishing parameters responsible for the final state of the geometric structure of a surface on the post-machining stress in the surface layer. The stress in the surface layer plays an important role because it is frequently responsible for the development of cracks, corrosion, and cavitation (in the surface area of injection aluminum molds, press tools, and core cutters). A proper understanding of the mechanisms responsible for the origin and development of residual stress will be conducive to the improvement of functional properties and longer tool life.

The article presents the results of experimental dynamic investigations of three steel-concrete composite beams. The beams differed in the stiffness of their shear connection. Steel stud connectors were used in B1 and B2 beams, whereas in B3 beam a perforated steel slat was used. The main goal of the study was to determine basic dynamic characteristics of the beams. Impulse excitation was used in the investigations. The obtained results made it possible to validate two numerical models: (i) a continuous one which was developed using the Timoshenko beam theory; (ii) a discrete one which was developed according to the rigid finite element (RFE) method. After validation of the parameters of both models it turned out that both models provide results consistent with experimental results.

This paper presents a method for modeling the dynamic properties of steel–polymer concrete beams, the basic structural components of machine tools, assembly lines, vibratory machines, and other structures subjected to time-varying loads during operation. The presented method of modeling steel–polymer concrete beams was developed using the finite element method. Three models of beams differing in cross-sectional dimensions showed high agreement with experimental data: relative error in the case of natural frequencies did not exceed 5% (2.2% on average), the models were characterized by the full agreement of mode shapes and high agreement of frequency response functions with the results of experimental tests. Additionally, the developed beam models supported the reliable description of complex structures, as demonstrated on a spatial frame, obtaining a relative error for natural frequencies of less than 3% (on average 1.7%). Full agreement with the mode shapes and high agreement with the frequency response functions were achieved in the analyzed frequency range.

Miniaturization is a dominant trend in machine building which requires the use of advanced techniques of manufacturing and control. Apart from dimensional and shape precision of miniaturized components, surface geometry, particularly roughness and so-called microroughness that results from the use of advanced treatment techniques, plays an important role in correct assembly, reliable operation and durability of the whole machine. The selection of filtration method in surface geometry of micro-objects can be a substantial problem. The authors of the paper propose to use wavelet filtration in digital processing of a point cloud to remove measurement noise and not to change the surface character of the measured object. Also, the authors propose, in this paper, some criteria for selecting the number of wavelet filtration levels based on minimalization of the RMS value. It is supposed to improve the efficiency of low-pass filtration of small areas of the surface, particularly compared to traditional λs Gaussian filtration.

This study presents spatial vibration modelling of steel–concrete composite beams. Structures of this type are commonly used as elements of composite floors and primary carrying girders in bridge structures. Two-dimensional models used to date did not enable analysis of all eigenmodes, specifically torsional, flexural horizontal, and distortional. A discrete computational model was developed in the convention of the rigid finite element method, the so-called RFEM model. It was assumed that the concrete slab and the steel I-section would be modelled separately. This approach realistically reflects the actual performance of the connection, comprising studs connecting the concrete slab and the steel section. The model was used to analyse two steel–concrete composite beams with different connector spacings. The paper presents the results of experiments conducted on the two composite beams. Their dynamic characteristics, including frequency and vibration modes, were determined with impulse response methods. Based on experimental research, identification of connection parameters with substitute longitudinal moduli of elasticity of reinforced concrete was conducted. A comparison of experimental results with those calculated with the model confirmed their good agreement.