In this paper the optimization of the spool and housing geometry in a small hydraulic seat valve to enable the reduction of the axial flow forces to a minimum value is described. Non-optimized hydraulic valve geometry is usually the main cause for many problems related to response time, actuation force and energy consumption. To overcome these limitations and problems we have done a thorough numerical and experimental analysis of a seat valve. The main influential geometry parameters of the seat valve are defined for numerical analyses. In the next step the basic theory of the numerical simulation, including the 3D modelling, meshing and parameterization, is explained. The reduction of the flow forces in a small hydraulic seat valve is treated in detail by using a commercial simulation tool, Ansys CFX. The validation of the numerical fluid model of the valve is done by comparing simulation and experimental results obtained with the test rig for axial flow force measurement. With the validated numerical fluid model of the valve new fluid models are built taking into account all influential geometry parameters of the valve for the purpose of the final optimization of the valve geometry. The results of the simulation analyses show that the axial component of the flow forces can be reduced significantly just by modifying the geometry of the valve spool and housing. Thus the valve dynamic characteristics, such as response time, are significantly improved while the necessary actuation force and power consumption are reduced.
COBISS.SI-ID: 13766683
This paper demonstrates a new methodology for designing a virtual factory model and model executi on on the bas is of a real schedule plan. The main characteristic of the developed method is that the inputs are regarded as one of the main parameters of the production process, and the main objective is to create a low-cost production process model. The methodology is adjusted for use in SMEs (Small and Medium-Sized Enterprises) with individual or unique type of production. For such companies, the method represents an ability to optimize existing production processes through detecting and eliminating possible errors and disturbances before the real production process is executed at an acceptable cost. The applicability and suitability of the developed m et hod for virtual production performance has been proven with the verification process, where the input data for the simulation was obtained from a real company. The simulation results have shown that the presented methodology is a useful tool for the optimization of the production process.
COBISS.SI-ID: 13367835
In this paper, we present and propose the interactive pushpull lean game with a specific approach for training/testing of production processes. With our approach of combining the psychologically effective physical lean game and the simulation lean game for deeper analyses of the production process, we can successfully overcome the communication and motivation problems of production and management workers when new production strategies are being introduced into the company to raise the competitiveness. The game only takes two hours and it has been proven to be effective with leadership teams and shop floor workers alike in more than 50 realcase production environments. The game is played in two parts where each part is in sharp contrast to the other with respect to results. Once the participants of the game see the effects of both production strategies, they become extremely engaged and motivated, and it becomes much easier to manage organizational improvements. In the third chapter of the paper, we present the Virtual factory computer models of the game dynamic, showing the same results as obtained with groups. The two simulation models serve to test and verify the interactive game. The paper ends with the discussion and conclusions.
COBISS.SI-ID: 13828379
The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.
COBISS.SI-ID: 1206698
In order to obtain input data for numerical simulations of tube forming, the material properties of tubes need to be determined. A tube tensile test can only be used to measure yield stress and ultimate tensile stress. For tubes with a large diameter/thickness ratio (D/t), tensile specimens are cut out and processed in a similar way as with sheet metal. However, for thin tubes with a diameter/thickness ratio below 10, the tensile specimens could not be cut out. The flow curve of the analyzed tube with a small diameter and D/t ratio of 7 was determined with a ring-shaped specimen. The experimental force-travel diagram was acquired. A reverse-engineering method was used to determine flow curves by numerical simulations. Using an L25 orthogonal array of the Taguchi method different flow curve parameters and friction coefficient combinations were selected. Tube upsetting with determined parameter combinations was performed with the finite element method. With analysis of variance influential equations among selected input parameters were determined for the force levels at six upsetting states. With the evaluation of known friction coefficients and flow curve parameters, K, n, and [epsilon sub]0 according to the Swift approximation were determined and proved by the final shape of the workpiece.
COBISS.SI-ID: 15008283