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Designing the gear body structure to control vibration behaviour
Riad Ramadani, 2018, doktorska disertacija

Opis: This research presents a new approach aiming to reduce gear vibration as well as its weight by modifying the gear body structure. The primary objective was to reduce vibration and noise emission of spur gears. For this purpose, a solid gear body was replaced by a cellular lattice structure, which was expected to raise the torsional elasticity of the gear body. The cellular lattice structure was designed and optimized by FE-based topology optimization software CAESS ProTOp, which is based on strain energy control. For experimental purposes, the optimized gear was produced from Titanium alloy Ti-6Al-4V ELI by using Selective Laser Melting technique. A polymer matrix was added to increase the damping of the structure. In order to test the gears, a new test rig with closed loop was conceived, designed and produced. The test rig is equipped with two gear pairs: with the tested one and with the driving one. The gears have been run and tested at different speeds and torque. The acceleration, strain and sound pressure of a running gear pair was measured. The final processing of the signal was done by a specially developed software based on LabView. By employing the fast Fourier transformation the time signal of acceleration, strain and sound pressure has been converted to the frequency spectrum and time frequency spectrogram. The results obtained by testing the solid and cellular lattice gear body were compared. It was experimentally confirmed that the cellular lattice structure of a gear body and addition of a polymer matrix may significantly reduce the vibration.
Ključne besede: Gear vibration, cellular lattice structure, topology optimization, test rig
Objavljeno v DKUM: 27.02.2018; Ogledov: 2402; Prenosov: 229
.pdf Celotno besedilo (13,76 MB)

The multilevel MINLP optimization approach to structural synthesis: the simultaneous topology, material, standard and rounded dimension optimization
Stojan Kravanja, Simon Šilih, Zdravko Kravanja, 2005, izvirni znanstveni članek

Opis: The paper describes the simultaneous topology, material, standard and rounded dimension optimization of mechanical structures, performed by the Mixed-Integer Non-linear Programming (MINLP) approach. Beside the generation of an MINLP mechanical superstructure, the development of a general multilevel MINLP formulation for a mechanical superstructure is presented. The consideration of the discrete materials as well as standard and particularly rounded dimensions in structural synthesis significantly increases the combinatorics of the discrete optimization, which as a result may become too difficult to solve. A Linked Multilevel Hierarchical Strategy (LMHS) has been introduced for the solving of such large combinatorial problems. In order to decrease the effect of non-convexities, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been applied. Four numerical examples of different complexities are presented to illustrate the proposed multilevel MINLP optimization approach: the optimization of two steel trusses, a composite I beam and a hydraulic steel roller gate Intake gate, erected in Aswan II, Egypt.
Ključne besede: structural optimization, structural synthesis, MINLP, topology opitmization, material optimization, discrete variable optimization, multilevel MINLP strategy, truss, composite beam, roller gate
Objavljeno v DKUM: 01.06.2012; Ogledov: 2710; Prenosov: 106
URL Povezava na celotno besedilo

MINLP optimization of a single-storey industrial steel building
Tomaž Žula, Zdravko Kravanja, Stojan Kravanja, 2008, izvirni znanstveni članek

Opis: The paper presents the topology and standard sizes optimization of a single-storey industrial steel building, made from standard hot rolled I sections. The structure consists of main portal frames, connected with purlins. The structural optimization is performed by the Mixed-Integer Non-linear programming approach (MINLP). The MINLP performs a discrete topology and standard dimension optimization simultaneously with continuous parameters. Since the discrete/continuous optimization problem of the industrial building is non-convex and highly non-linear, the Modified Outer- Approximation/Equality-Relaxation (OA/ER) algorithm has been used for the optimization. Alongside the optimum structure mass, the optimum topology with the optimum number of portal frames and purlins as well as all standard cross-section sizes have been obtained. The paper includes the theoretical basis and a practical example with the results of the optimization.
Ključne besede: civil engineering, topology optimization, sizing optimization, nonlinear programming, MINLP
Objavljeno v DKUM: 31.05.2012; Ogledov: 2462; Prenosov: 66
URL Povezava na celotno besedilo

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