Based on a non-linear mathematical model of lateral buckling of a slender beam with a narrow rectangular cross section, the variational formulation of the two-parametric optimization problem is given in the dimensionless form. An optimal shape is obtained by solving the variational problem using the Rayleigh-Ritz method with the orthogonal system of trigonometric functions. By a partial solution of the Euler-Lagrange differential equation of the variational problem, a proof is given that in the case of the optimal shape, a maximal reference stress according to the total strain energy theory is constant along the beam. An example of extrapolation of the two-parametric optimization problem solution is represented.
COBISS.SI-ID: 12294171
Constrained recovery of a compressively prestrained shape memory alloy (SMA) is experimentally and theoretically investigated. Thermomechanical properties of the SMA during the process of constrained recovery are experimentally obtained. Optimization of geometry in buckling of an ideally straight, simply supported column with a nonconstant cross section due to constrained recovery is theoretically investigated. Using the experimentally obtained thermomechanical properties, the critical buckling force and temperature of the optimized column are calculated. Various experiments were conducted in order to verify the calculated results. The calculated critical load and predicted buckling temperatures show good agreement with buckling experiments reported in this article.
COBISS.SI-ID: 12172059
The ac magnetostriction in electrical steel is commonly characterized in the time domain (e.g., the peak-to-peak, zero-to-peak amplitude) and also in the frequency domain (e.g., a harmonic analysis). However, due to the dynamical coupling of the test sample with the experimental set-up, the characterization of the magnetostriction (especially the one in the frequency domain) can give the wrong result. This research focuses on an experimental frequency characterization of magnetostriction and gives the theoretical background of the test sample’s dynamical coupling with the experimental set-up. The discussed natural dynamics of the test sample from the point of view of the different boundary conditions that can be used at the experiment gives a clear picture of the dynamical coupling. Besides the theoretical background, a detailed experimental approach is presented. This research theoretically and experimentally showed that the dynamical coupling of the sample can result in incorrect characterization of the magnetostriction. However, with the theoretical guidelines presented, the dynamical coupling can be completely avoided, which results in an accurate characterization of the magnetostriction.
COBISS.SI-ID: 12403227
In the article, the exact solution of a sinusoidal loaded simply supported rectangular plate is given for the case of an isotropic plate and for the case of a transversally inextensible plate. Asymptotic and numerical comportment with Reissner, Mindlin and Reddy plate models is present.
COBISS.SI-ID: 2174563
A mechanical system's modal parameters change when fatigue loading is applied to the system. In order to perform a vibration-based fatigue test these changes must be taken into account in order to maintain constant-stress loading. This paper presents an improved fatigue-testing methodology based on the dynamic response of the test specimen to the harmonic excitation in the near-resonant area with simultaneous monitoring of the modal parameters. The measurements of the phase angle and the stress amplitude in the fatigue zone are used for the real-time adjustment of the excitation signal according to the changes in the specimen's modal parameters. The presented methodology ensures a constant load level throughout the fatigue process until the final failure occurs. With the proposed testing methodology it is possible to obtain a S-N point of the Woehler curve relatively quickly and to simultaneously monitor the changes of the specimen's natural frequency and damping. The presented methodology with real-time control is verified on an aluminium Y-shaped specimen (106 load cycles are achieved in 21 minutes) and is applicable to a specimen with arbitrary geometry.
COBISS.SI-ID: 12402971