The article provides an analysis of the results of an experimental study of oscillatory processes occurring in mobile lifts with working platforms (MLWP) during the working operations. According to the developed research methodology, the results of measurements of acceleration along the horizontal and vertical axes of the machine at the point of articulation of the boom and at the point of attachment of the working platform to the boom were obtained and analysed. The analysis of the obtained oscillograms indicates that the greatest oscillations occur at the point of attachment of the working platform to the boom along the vertical axis. Accordingly, a detailed analysis of the influence of the operating parameters of the mobile lift on the oscillatory processes occurring during the operation of the machine at the point of attachment of the working platform to the boom along the vertical axis was carried out.

When manufacturing machine parts using additive 3D technologies, we are faced with the task of choosing a specific manufacturing technology, material, and settings for the 3D printing process. These factors affect the manufacturing time, cost, accuracy, strength and other criteria for the performance of machine parts. Based on this, the purpose of the study is to develop recommendations for optimizing models of machine parts for 3D printing. The study describes the main approaches to optimizing three-dimensional models of machine parts at the design stage. This optimization avoids a number of problems that arise when using various 3D technologies: FDM (fused deposition modeling), SLA (laser stereolithography), etc. Depending on the type of the designed part and the applied additive 3D technology, additional requirements and restrictions are imposed on the models. The issues of optimizing models in terms of 3D printing time, manufacturing cost, geometry (accuracy) of the resulting model are considered, and the issues of the strength of the entire part or its individual elements are also partially investigated. Specific design solutions and recommendations for the manufacture of rotation parts, in particular, shafts and gears, are given. The issues of occurrence of some defects associated with overheating, uneven cooling and plastic shrinkage are considered. The simplest models for studying critical parts for strength are described. Recommendations have been developed for determining the properties of machine parts manufactured using additive 3D technologies for their design. This study will be of interest primarily to developers of 3D models and is designed to eliminate some of the problems that arise during 3D printing at the product design stage.

The problem of identifying the load acting on the elements of structures belongs to the class of inverse problems of the mechanics of a deformable solid, which are often incorrect. Solving such problems is associated with the instability of the calculation results, which requires the development of special methods for their research. This predetermines the relevance of this study. The object of the study is a single-pass cylindrical shell consisting of two rigidly fastened butt-fastened sections made of different materials. Each of the shells is assumed to be elastic isotropic, having a cross-section of medium thickness. The equations of axisymmetric deformation of shells are used within the framework of Timoshenko hypotheses. An approach to solving direct and inverse problems for such discretely heterogeneous objects is proposed, which implies the conditional separation of a discretely heterogeneous cylindrical shell along the length, followed by the addition of functions of fictitious loads. The main analytical relationships for building a system of integral Volterra equations are given, for which an analytic-numerical solution is derived. The final ratios have been obtained, which make it possible to calculate the kinematic and force parameters of the study object in the process of non-stationary deformation. The inverse problem of identifying arbitrary loads acting on a shell that is heterogeneous in length is solved in a general form. An algorithm for the restoration of pulse loads has been developed, which is robust to errors in the initial data (about 5 %). The material related to solving direct and inverse problems for shells that are discretely heterogeneous in length can significantly advance the methodology for identifying pulse loads acting on structural elements

Non-stationary loading of a mechanical system consisting of a hinged beam and additional support installed in the beam span was studied using a model of the beam deformation based on the Timoshenko hypothesis with considering rotatory inertia and shear. The system of partial differential equations describing the beam deformation was solved by expanding the unknown functions in the Fourier series with subsequent application of the integral Laplace transform. The additional support was assumed to be realistic rather than rigid. Thus it has linearly elastic, viscous, and inertial components. This means that the effect of a part of the support vibrating with the beam was considered such that their displacements coincide. The beam and additional support reaction were replaced by an unknown concentrated external force applied to the beam. This unknown reaction was assumed to be time-dependent. The time law was determined by solving the first kind of Volterra integral equation. The methodology of deriving the integral equation for the unknown reaction was explained. Analytic formulae and results of computations for specific numerical parameters were given. The impact of the mass value on the additional viscoelastic support reaction and the beam deflection at arbitrary points were determined. The research results of this paper can be helpful for engineers in designing multi-span bridges.