Bimetallic shallow shells are thermal sensors. The paper presents relevant technical information on bimetallic shallow shells and describes some interesting physical experiments. It is shown how, through simple measurementsand calculations, it is possible to determine the initial speed (~3.5 m/s), the acceleration (~30000 m/s2) and the lower and upper snap temperature (~22 °C; ~32 °C) of the bimetal. The results from calculations are comparable to those obtained by a high speed camera. The videos give an even deeper insight into the phenomenon of the snap-through.
COBISS.SI-ID: 36937989
The paper discuses a method for obtaining the equilibrium configurations of a Reissner shear-deformable cantilever beam subject to a tip follower force. Along with the classical follower force, where the angle between the force and normal to the beam cross-section remains constant, the tip rotational load is also discussed. In the latter case there are multiple possible equilibrium configurations of the beam for a given force. The theory is enhanced with numerous numerical examples and examples of deformed beams presented in graphic form.
COBISS.SI-ID: 2429795
The paper deals with the geometry optimization of a slender cantilever beam subjected to a concentrated force acting at the free end. The two-parametric mathematical model of lateral torsional buckling is based on the BernoulliEuler beam theory and is given in dimensionless form. The optimization procedure is performed using the optimal control theory and the relation between state and adjoint variables is presented. The boundary value problem derived from the optimization procedure is solved numerically and compared to solutions obtained via an alternative optimization approach called sequential approximate optimization.
COBISS.SI-ID: 12854043
When dealing with small and light structures, difficulties occur when measuring the modal parameters. The resonant frequencies are usually relatively high and therefore a wide frequency range is needed for the measurement. Furthermore, the mass that is added to the structure by the sensors causes structural modifications. To overcome these difficulties, an improved method using an operational modal analysis instead of an experimental modal analysis is proposed in this study. It is derived from the sensitivity-based operational mode-shape normalisation with a consideration of the mode-shape variation. The measurement of the excitation force is not needed, because the operational modal analysis is used and only two simultaneous response measurements at an unknown excitation are required. The proposed method includes the cancellation of the added mass, resulting in mode shapes and resonant frequencies of the unmodified structure. The numerical and experimental results on small and light structures are compared with the results of the experimental modal analysis. The comparison shows that the proposed approach allows measurements over a wide frequency range and increases the accuracy of the results compared to the sensitivity-based operational mode-shape normalisation and also compared to the particular experimental modal analysis method that was used in this study. The advantages of the proposed method can be seen whenever the mass that is added to the structure by the accelerometer is not negligible and therefore a variation of the mode shapes occurs.
COBISS.SI-ID: 13110043
The main benefit in using optimally shaped blanks in sheet metal forming is in maximizing the efficiency of the forming process and, since there is no need for additional cutting operations after the finished forming operation, in substantial reduction of the overall production cost. The paper presents a numerical method for optimal blank shape determination which is suitable in various sheet metal forming applications. The optimal blank shape is determined in iterative way so that the edge geometry of the formed product fits its reference geometry as close as possible. The iterative process starts at blank shape from which the product is produced with its edge fitting its reference geometry just approximately. In subsequent iterations the blank shape is continuously improved in accordance with the developed optimisation method. In order to determine the product edge geometry resulting from the current blank shape, a computer simulation of the forming process and the springback is performed in each iteration. Since its effectiveness highly depends on the quality and physical objectivity of the computer simulation, the developed numerical blank shape optimisation procedure has been validated also experimentally by considering forming of a product with rather complex edge geometry as the case study.
COBISS.SI-ID: 12737819