Mechanics and Control
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ISSN 2083-6759
e-ISSN: 2300-7079
Issue Date
2015
Volume
Vol. 34
Number
No. 1
Description
Journal Volume
Mechanics and Control
Vol. 34 (2015)
Projects
Pages
Articles
The use of self-excited vibrations for dynamic strain measurements carried out by vibrating wire tensometers
(2015) Cieplok, Grzegorz; Bednarski, Łukasz; Sieńko, Rafał
This study examines a set of vibrating wire extensometers in which a van der Pol generator has been used to maintain the natural vibrations of the wire. Excited in this way, self-exited vibrations allow for uninterrupted strain measurements over time, including fast-changing strains as well as chaotic nature strains. For the two typical vibrating wire gauges used in the industry, the impact of the wire extension speed on its metrological characteristics and applicability has been analyzed.
Rotor dynamics and stator vibrations of a novel IPM synchronous motor
(2015) Goraj, Robert; Spagnolo, Aristide
This paper presents the rotor-dynamical computations of a technology demonstrator of an interior permanent magnet (IPM) synchronous motor designed at the Research and Technology Center of Siemens AG within the framework of the European-funded project called MotorBrain. The computations were split into parts consisting of modal and harmonic analyses performed numerically using FEM algorithms and the post-processing estimation of the amplitudes of rotor displacement and velocity within the whole range of a motor’s rotation speed. The authors determined modal damping ratios and found resonance frequencies. In a further step, forces were applied to the rotor in order to determine the oscillation amplitudes of points placed along the rotor's geometrical axis (in the cases of both mechanically- and electromagnetically-excited rotors). The computations were performed for the excitation of the first and second flexural vibration mode. Except for rotor-dynamical computations, the authors performed vibration analyses of the stator along with the motor housing. The stator resonance frequencies and their modal deformation shapes were determined. In a further step, electromagnetic forces acting on the stator teeth were numerically found. These forces were then applied to each stator tooth in order to perform harmonic vibration analyses in an attempt to determine the spatial average velocity of the motor housing circumference area.
The use of digital image correlation in the study of Achilles tendon strain field
(2015) Holak, Krzysztof; Kohut, Piotr; Młyniec, Andrzej; Tomaszewski, Krzysztof; Uhl, Tadeusz; Ekiert, Martyna
This paper presents an application of a vision-based measurement method in the experimental mechanics of biological materials. The displacement and strain fields of a human Achilles tendon specimen under a tensile test were computed using the digital image correlation method. Different software applications, both commercial and open source, were compared. The performance of algorithms was tested based on a referential measurement carried out by commercial software with the affine model of deformation implemented. The root mean square error of the difference between strain obtained using the reference measurement and each of the analyzed programs was computed. Additionally, an example of a full-field computation of displacement and strain field was presented.