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Transportation infrastructure consists mainly of critical elements. They are subjected to a large set of requirements for strength, rigidity, reliability. The article considered deformation behavior of spherical bridge bearing at different introduction depth parameters of sliding layer. The influence of contact surface treatment on the character of contact parameters distribution is studied. Earlier the polymers and composites behavior was viewed as an elastic-plastic material. However, for predicting their life-cycle it is necessary to consider them as viscoelastic. The article compared the parameters obtained by modeling elastic-plastic and viscoelastic materials behavior. The influence of sliding layer thickness on the deformation structure behavior was also discussed. It is revealed that sliding layer modeling as an elastic-plastic body is sufficient for numerical calculations on determination of strength characteristics. However, it is necessary to consider the sliding layer as a viscoelastic/viscous-elasticplastic material to design the life cycle of the structure taking into account rheology, thermomechanics and cyclic loads in different directions.

This article considers the deformation behavior of Panda optical fiber using different models of material behavior for the tasks of predicting residual stresses after drawing when cooling from 2000 °C to room temperature (23 °C) and indenting the fiber into an aluminum half-space at different parameters. These studies were conducted for single- and double-layer protective coatings (PCs), at different values of external load and thickness of single-layer PC. This paper determined the fields of residual stresses in the fiber formed during the drawing process. They are taken into account in modeling the fiber performance in the further process of this research. This article investigated two variants of PC behavior. The influence of behavior models and the number of covering layers on the deformation of the "fiber-half-space" system was analyzed. This paper establishes qualitative and quantitative regularities of the influence of the external load magnitude and relaxation properties of PCs on the deformation and optical characteristics of Panda optical fiber. [ABSTRACT FROM AUTHOR]

Polymers have gained a foothold in the international market and are actively utilized at a large scale in various industries. They are used as sliding layers in various types of friction units. However, there is a lack of research on their deformation behavior under different design conditions. This work is focused on studying the influence of the geometrical design of lubrication recesses in a polymer sliding layer operating under conditions of frictional contact interaction. The article investigated an element of bridge-bearing steel plate with recesses for lubrication. Two geometrical configurations of recesses are studied: the annular groove and spherical well in the engineering software package ANSYS Mechanical APDL. Polytetrafluoroethylene (PTFE) is considered an elastic-plastic sliding layer. A comparative analysis of two models with different geometrical configurations of cutouts for lubrication, with/without taking into account its volume in the recess, has been conducted. The article establishes that in the absence of lubrication in the recesses, large deformations of the polymer sliding layer occur. This effect negatively affects the structure as a whole. Changing the geometry of the recess for lubrication has the greatest effect on the intensity of plastic deformations. Its maximum level is lowered by almost ~60% when spherical notches are used for lubrication instead of grooves. The friction coefficient of the polymer has a great influence on the contact tangential stress. At the experimental coefficient of friction, it is lowered on average by ~85%. The friction coefficient of the lubricant has almost no effect on the deformation of the cell (<1%). [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a highly precise technology that not only facilitates the machining of components into desired shapes but also enables the alteration of the physical and chemical properties of workpieces. The complexity of the process is due to a number of regulating factors such as the material of the workpiece and tools, dielectric medium, and other process parameters. Based on the material type, electrode shape, and process configuration, various shapes and degrees of accuracy can be generated. The study of erosion is based on research into processing techniques, which are the primary tools for using EDM. Empirical knowledge with subsequent optimization of technological parameters is one of the ways to obtain the required surface quality of the workpiece with defect minimization, as well as mathematical and numerical modeling of the EDM process. This article critically examines all key aspects of EDM, reflecting both the early foundations of electrical erosion and the current state of the industry, noting the current trends towards the transition of EDM to the 5.0 industry zone in terms of safety and minimizing the impact of the process on the environment. [ABSTRACT FROM AUTHOR]

The study of the rheological properties of a lubricant allows for the assessment of the structure's durability in which they are used. Computer engineering enables the prediction of the structure performance using refined mathematical models of its materials. This paper presents an experimental investigation of the rheological behavior of a lubricant that is actively used in bridge structures. The paper proposed a methodology for determining the rheological characteristics of the lubricant using a rotational viscometer. Additionally, the article performed the task of identifying the mathematical model of the lubricant behavior based on the Maxwell body, using two approaches: the Anand model and the Prony series. The proposed models allow for numerical modeling of the structure's performance throughout their lifecycle within the scope of computer engineering. [ABSTRACT FROM AUTHOR]

Since the advent of mass media, ‘going public’ has been a key tool in the strategic inventory of presidents seeking to promote their policies to politicians and the public. Over the last decade, social media has offered presidents and their office with a new platform to address the nation directly without relying on traditional media gatekeepers. Nevertheless, both ‘going public’ strategies and presidents’ use of social media have almost exclusively been researched in the context of the presidential systems. The aim of this article is to extend research and offer the first systematic study of presidential Twitter use in European semi-presidential systems. We conceptualise presidential Twitter use as a form of presidential activism that is complementary to the use of formal powers or informal attempts to influence policy. Whereas the latter are driven by institutional or partisan conflict, going public strategies and presidential Twitter use primarily address societal concerns and, hence, are motivated by contextual factors outside the core realm of party politics. Instead, we should expect social conflict and societal grievances to determine demand and supply of presidential Twitter use. We test our propositions using a new dataset of tweets by presidents in European semi-presidential systems 2010–2020. [ABSTRACT FROM AUTHOR]