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Meaningful finite element discretization scheme: a case for circular disk subjected to four radial loads
Get PDFIn finite element (FE) modelling, apart from proper element selection, selection of an appropriate discretization scheme is crucial in correctly evaluating the intended variables. Photoelasticity plays an effective role in selecting an appropriate discretization scheme for modelling problems in stress analysis. A meaningful FE discretization is very important in evaluating the desired parameters in FE analysis. The adaptive mesh refinement emphasizes the need for a meaningful discretization of domain. This paper presents a discretization strategy for meaningful discretization of the circular disk subjected to four equal radial loads. The work evolved the generation of software for the disk subjected to four radial loads perpendicular to each other. Due to symmetry of the problem only quarter of the disk is discretized
The influence of friction on the dynamic model for a 6-DOF parallel robot with triangular platform
Get PDFThe dynamic analysis is an important element of the mechanical design and control of parallel mechanisms. This paper presents a method for the dynamical modeling of the guided in three points parallel robots with six degrees of freedom having triangular platform, including the friction. The evaluation of the full generalized forces is performed in two stages. In the first stage, the drive generalized forces are established, based on the dynamical equations without friction. Using the Newton-Euler equations, the reactions from each joint are computed. In the second stage the additional drive generalized forces due to the frictions from the active and passive joints are computed by means of two approaches. The first approach considers the whole mechanism. The generalized additional forces which include the friction effect from the corresponding drive joints and the friction effect from all passive joints are calculated using principle of virtual power and the mechanism Jacobi matrices. The second approach treats the kinematic chains as independent. The generalized additional forces are evaluated using the virtual work principle. In both approaches the passive joints are approximated with compliant joints whose momentum are equal to the friction torques of these joint
Researches of temperature influence on parameters of rotor rotation of rotary system
Get PDFRotary systems with bearings of sliding friction are analyzing in this paper. It is researching influence of temperature change on characteristics of work of searching system. It had done experimental researches trying to ascertain how temperatures change is doing influence on parameters of work of rotary systems with bearings of sliding. Experimental measurements are doing by methodology that is making specially, using different transducers of measurement. It is describing and giving principal system of measurement and analysis, its photo, scheme of measurement and methodology of experiments performance. It is getting primary signals of measurement of rotor vibrations, temperature changes and results of analysis are giving in graphs. It is doing analysis of getting results and it is establishing interdependences of searching parameters, their consistent patterns of changes and influence on quality of work of searching syste
Calculation of vibrations of an incompressible elastic structure
Get PDFRubber and photo-elastic materials at elevated temperatures exhibit incompressible behavior. The vibrations of a structure by taking the incompressibility constraint into account by the penalty method are analyzed. Reduced order numerical integration of the penalty term is performed. Graphical representation of volumetric strains at the points of reduced integration is proposed for validation of the calculated eigenmodes
Validation of vibration analysis using photo-elastic coatings
Get PDFThe analysis of vibrations is performed using a plate bending element assuming that a coating has no effect to the motion of the plate. The stresses in the coating are calculated by using the procedure of conjugate approximation. Then the relative error norms for the finite elements are determined. They are represented graphically and serve for validation of the results of calculations in hybrid experimental - numerical procedures
Design considerations of a microelectrostatic motor
Get PDFThis work analyses influences of geometry of the micromotor on its performance. Using finite element modeling (FEM) a detailed study of electrostatic force fields between two interacting poles and developed moment of rotation is done. The results received are expanded to the whole motor design where its control and torque characteristics are evaluated. Finally, optimal motor construction conclusions are drawn and new motor is produced by UV lithograph
Usage of the powder metallurgy method for fabrication of titanium implant alloy
Get PDFIn the paper research of the new implant titanium alloy obtained by powder metallurgy method were presented. The Ti15Mo2,8Nb alloy was fabricated from pure alloying component powders. The structure was observed by scanning electron microscope and analyzed by X-ray diffraction. The effect of grinding time of mixtures as well as the size of titanium powder grain on compatibility, compression strength and yield point of sintered alloys was analysed. It was found that grain size has a significant effect on strength properties of the alloy. However, the prolonging of grinding time caused deterioration of compatibility as well as mechanical properties of sinter
Directional conjugate smoothing for analysis of axi-symmetric fluid vibrations
Get PDFNumerical implementation of the Abel transform for the construction of digital fluid holographic images is analyzed in this paper. Volumetric strains are obtained from the numerical calculations using the displacement formulation by the method of finite elements. Then the field of volumetric strain is obtained by using the procedure of conjugate approximation with smoothing. Numerical procedure is developed for the calculation of the Abel transform on the basis of the right rectangle numerical integration rule and thus the digital holographic image is constructed. The obtained digital holographic images are used in the hybrid experimental – numerical procedure for the determination of the correlation with the experimental holographic image
The research of characteristics of electric arc on weld pool formation
Get PDFStability and controllability of a welding arc have a large influence on both the weld quality and welding productivity in the process of welding. Metal fusing and weld forming depend on the forces affecting the arc. Welding current creates electromagnetic forces, which basically define the influence of arc forces on molten metal. While estimating the magnitude of the influence of electromagnetic forces, it is necessary to investigate the radial distribution of arc pressure on the surface of a weld pool and take into account the dependence of distribution of electromagnetic forces on the non-consumable electrode tip geometry
Damage quantification using modal parameters
Get PDFNatural frequencies and mode shapes of a structure change whenever a structure has any kind of damage. However, detection of location and magnitude of damage has always been difficult. This paper presents a technique to locate and quantify the damage when the natural frequencies and mode shapes of undamaged and damaged structure are known. First, the structure is modeled using finite element formulation. Each element is assigned a damage index that is initially zero for undamaged condition. Modal analyses of undamaged and damaged structures are performed. The damage indices are computed using non-negative least squares method. Results based on aluminum beams are presented to establish the effectiveness of this method