Papers by Keyword: Experiment

Abstract: The paper deals with a comparison of the punching shear capacities of the experimental flat slabs without shear reinforcement weakened by openings adjacent columns with the results obtained by the prEC2 model for prediction punching capacity that is introduced in the second generation of Eurocode 2. Within the experiments, 4 slabs with dimensions of 2.5 m x 2.5 m and with a thickness of 200 mm and 8 slabs with a thickness of 250 mm were tested and evaluated. Specimens with a thickness of 200 mm were supported by an elongated column with dimensions of the column’s cross-section 950 x 150 mm and the second set of specimens with a square column with a dimension of 200 mm. The position of openings around the perimeter of the column as well as the distance from a column face were changing. Assessed punching shear capacities and their comparison with laboratory tests show that the prEC2 model significantly underestimates punching capacity when the opening is located at the face of support or near the shorter side of the elongated column if the reduction of the control perimeter length is steering by a radial projection of the opening.

Abstract: UHPC (ultra-high performance concrete) is an excellent material applicable also for strengthening of existing structures. Recently published papers were focused mainly on the behaviour of strengthened slabs subjected to bending, in this paper, experiments on punching and on strengthening of columns are mentioned. Strengthening of bridge decks requires a special composition of UHPC with high fibre contents and with the ability of casting in the slope. The appropriate mix for UHPC was developed within the research project. The experience gained from the extensive experimental program resulted in development of rules for strengthening of existing structures using UHPC, which follow the European codes and Czech recommendations for design of structures made of UHPC.

Abstract: For the purpose of determining the optimal value for the technological parameters from the experimental results when evaluating the forming ability through the processing time during the processing of SUS 304 sheet material by SPIF technology. The article has conducted experiments to collect parameters and experimental planning to establish a mathematical model; at the same time, determine the optimal value for the parameters of the machining process such as tool diameter, tool feed and tool running speed which directly affect the machining time. The optimal technological parameters have practical applicability to improve the efficiency and productivity of the processing process for SUS 304 sheet metal in particular and other sheet metal materials in general.

Abstract: Experimental research on the process of cold tubes drawing was performed in order to obtain important information about the behaviour of the tube material in the drawing tool during the drawing to the required outer diameter of Ø12 mm. The DEFORM-3D simulation software was an important tool for verifying the plastic flow of material in the drawing tool (i.e. drawing die), as well as for optimizing the technological parameters of cold tubes drawing. In the finite element (FE) analysis, emphasis was placed on determining the influence of tool geometry, strain degree, drawing speed and friction on the size of the drawing force and the quality of production of drawn tubes. The paper points out the importance of simulation software for common comparison of results obtained from laboratory experiment and FE analysis of the process of tubes drawing. By comparing the results, the reliability of the used simulation software was proved, as the results were identical for all monitored technological parameters. Computer simulation brings valuable knowledge that is important for the correct design of the drawing tool as well as for the technology of production of tubes with precise dimensions.

Abstract: The article considers an advanced method of ceramic mold and rod forming from liquid mixtures on non-organic bonding materials. Their application allows significantly improving the environmental situation and, at the same time, making molds and rods better in terms of their mechanical properties. In its turn, it results in a more precise geometry of the molds obtained. The developed composition allows applying only Russian materials, lowering the net cost comparing with a conventional business of ceramic mold casting (Shaw process) while providing high technological properties of forms and rods.The authors conducted the analysis of the phase composition of technological materials and provided a rationale for possible import substitution.The experimental part of the research work contains two series of experiments; the first one included the selection of the ceramic mix composition by the amount of gelatinization agent. The second series of experiments studied the impact of vacuum processing on the properties of rods after their curing. The authors present experimental precise molds for the oil and gas complex of the Russian Federation.

Abstract: On the basis of theoretical and experimental studies, the prerequisites and the method of calculation of bent and compressed-curved reinforced concrete structures with zone reinforcement made of steel fiber, working under static and short-term dynamic loads, are formulated. In the developed method for calculating the strength of normal and inclined sections, a nonlinear deformation model is implemented, which is based on the actual deformation diagrams of materials. The developed calculation method is brought to the program of calculation of reinforced concrete structures with zone reinforcement of steel fiber under short-term dynamic loading, taking into account the inelastic properties of materials. The numerical studies made it possible to determine the influence of various parameters of steel-fiber reinforcement on the strength of reinforced concrete elements. To confirm the main results of the developed calculation method, experimental studies of reinforced concrete beam structures reinforced with conventional reinforcement and a zone steel-fiber layer are planned and carried out. Experimental studies were carried out under static and short-term dynamic loads. As a result of the conducted experiments, data were obtained that characterize the process of destruction, deformation and cracking of steel-reinforced concrete elements under such types of loading. The dependences of changes in the energy intensity of reinforced concrete structures with zone reinforcement made of steel fiber in the compressed and stretched cross-section zones under dynamic loading are obtained. The effectiveness of the use of fiber reinforcement of normal and inclined sections of bent and compressed-curved elements to improve the strength and deformative.

Abstract: This paper deals with the hydro-forming of a flat thin metallic disc to achieve a forward domed disc which will be subsequently adopted to manufacture a rupture disc. The plastic deformation induced by the hydraulic energy is numerically simulated through an isotropic hardening plasticity model using a non-linear explicit finite element analysis (FEA). The variation in disc’s central deformation, thickness, equivalent plastic stress and equivalent plastic strain with respect to the applied hydraulic pressure are determined from FEA simulations. The hydro-forming setup is then designed and manufactured, and the metallic disc is experimented under hydro-forming process. The reduction in thickness due to stretching of the thin disc is evaluated from experiment and simulation and a close agreement is found. This research attempt helped in finalizing the hydro-forming fluid pressure, the feasibility and the accuracy of practically achieving the desired geometry of the metallic disc. The near-fixidity effects on abrupt variation in sheet thickness and plastic strain are well captured through simulations which are very difficult to be studied through hydro-forming experiments.

Abstract: Currently, the most promising high-tech and productive process is friction stir welding. An important element of this technology is the determination of the material temperature in the stir zone, which can be determined by calculation based on the amount of heat input introduced into the welding zone. To determine this value, experimental of the dependence of heat input on the tool rotation speed and welding speed were carried out. For this, a scheme of experiments has been selected in which the material to be welded (aluminum alloy AMg5) is modeled as an experimental tube with a diameter of 20 mm, and the tool (made of tool steel R6M5) is modeled as a working plate. On the designed and manufactured stand, studies of the dependence of the heat-liberation value for the speeds of rotation of the experimental tube 42-105 rad/s were carried out. In this case, due to the pressing force of the experimental tube and the working plate, a constant temperature of the place of friction was maintained. The obtained experimental data were used to calculate the heat-liberation value and heat power on each concentric ring 2 mm wide at the end of the working tool with a diameter of 20 mm, as well as the total heat power for different speeds of rotation and welding.When carrying out experiments on the bench, heat losses were determined by thermal conductivity along the rod on which the experimental tube is fixed, as well as from the working plate made of tool steel through the gasket onto the working table and by convection from the surface of the rotating experimental tube into the environment. The calculation results showed that each of these losses does not exceed 3-10%. These losses are taken into account in the heat supply calculations.

Abstract: Numerical methods used to calculate strength are based on energy approaches and minimization of functionals of one type or another. Yet the model of a material is limited to stable processes of deformation. As a result, a considerable number of deformation properties related to realization of the softening stage in materials of structural elements remains unaccounted for. To describe fracture as a new phenomenon in the behavior of structures, one needs to apply newer experimental and calculational approaches. The article cites results of modelling and experimental notions on the stage of softening in materials and its role in determining their durability. It is proposed to define the durability of a structurally inhomogeneous material as its capacity of equilibrium deformation beyond its ultimate strength under specified loading conditions. That reflects nonlocality of criteria for the failure of the material, their dependence both on its own properties and the geometry of a structural element. Complete stress-strain diagrams for structural materials of various classes and examples on how the softening stage is realized in structural materials are given.

Abstract: The article presents the results of experimental studies to determine the relationship between the electrolysis modes and the properties of electroplating coatings for mathematical modeling of the dynamics of the electrolytic process (MDEP), described by a system of ordinary differential equations due to the complex relationship of the kinetics of chemical reactions, hydrodynamics and mass transfer in the electrolyte flow, the kinematics of electrode plates, and the influence of the electric field of the "anode-cathode" pair on all these processes. At the same time, the experimental base was a series of full-scale experiments to restore the seats of the root supports of cylinder blocks with electroplated coatings. The final result of the research is the procedure for constructing an optimal resource-saving mode of electroplating, which is a zinc-iron alloy.