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1.
Behaviour of cellular materials under impact loading
Matej Vesenjak, Zoran Ren, Andreas Öchsner, 2008, original scientific article

Abstract: The paper describes experimental and computational testing of regular open-cell cellular structures behaviour under impact loading. Open-cell cellular specimens made of aluminium alloy and polymer were experimentally tested under quasi-static and dynamic compressive loading in order to evaluate the failure conditions and the strain rate sensitivity. Additionally, specimens with viscous fillers have been tested to determine the increase of the energy absorption due to filler effects. The tests have shown that brittle behaviour of the cellular structure due to sudden rupture of intercellular walls observed in quasi-static and dynamic tests is reduced by introduction of viscous filler, while at the same time the energy absorption is increased. The influence of fluid filler on open-cell cellular material behaviour under impact loading was further investigated with parametric computational simulations, where fully coupled interaction between the base material and the pore filler was considered. The explicit nonlinear finite element code LS-DYNA was used for this purpose. Different failure criteria were evaluated to simulate the collapsing of intercellular walls and the failure mechanism of cellular structures in general. The new computational models and presented procedures enable determination of the optimal geometric and material parameters of cellular materials with viscous fillers for individual application demands. For example, the cellular structure stiffness and impact energy absorption through controlled deformation can be easily adapted to improve the efficiency of crash absorbers.
Keywords: mechanics, porous materials, cellular materials, impact loading, mechanical testing, fluid-structure interaction, failure mechanism
Published: 31.05.2012; Views: 1032; Downloads: 49
URL Link to full text

2.
An efficient k'-means clustering algorithm
Krista Rizman Žalik, 2008, original scientific article

Abstract: This paper introduces k'-means algorithm that performs correct clustering without pre-assigning the exact number of clusters. This is achieved by minimizing a suggested cost-function. The cost-function extends the mean-square-error cost-function of k-means. The algorithm consists of two separate steps. The first is a pre-processing procedure that performs initial clustering and assigns at least one seed point to each cluster. During the second step, the seed-points are adjusted to minimize the cost-function. The algorithm automatically penalizes any possible winning chances for all rival seed-points in subsequent iterations. When the cost-function reaches a global minimum, the correct number of clusters is determined and the remaining seed points are located near the centres of actual clusters. The simulated experiments described in this paper confirm good performance of the proposed algorithm.
Keywords: algorithms, clustering analysis, k-means, cost-function, rival penalized mechanism, datasets
Published: 31.05.2012; Views: 1288; Downloads: 81
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UV polymerization of poly (N-isopropylacrylamide) hydrogel
Manja Kurečič, Majda Sfiligoj-Smole, Karin Stana-Kleinschek, 2012, original scientific article

Abstract: This contribution is focused on the determination of polymerization and crosslinking mechanism of poly (N-isopropyl- acralymide) hydrogel and its swelling properties. Hydrogels were synthesized by environmental friendly UV polymerization method, from monomer N-isopropylacrylamide (NIPAM) and crosslinker N,N´-methylenebisacrylamide (BIS) of different concentrations. UV polymerization was performed in an UV chamber using UVA light with the wave length 350 nm. Surface morphology and pore structure analysis was carried out using SEM microscopy. The polymerization and crosslinking mechanism was determined by Fourier Transform Infrared spectroscopy (FT-IR). It was confirmed that crosslinker concentration influences the hydrogel structure and swelling properties. By increasing the crosllinker concentration the hydrogel structure changes from homogen to heterogen and the equilibrium degree of swelling decreases.
Keywords: poly (N-isopropylacrylamide) hydrogel, UV polymerization, FTIR, polymerization mechanism, swelling properties, SEM
Published: 01.06.2012; Views: 1103; Downloads: 56
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5.
Optimal kinematic design of a link-drive mechanism with prescribed velocity characteristics
Bojan Vohar, Karl Gotlih, Jože Flašker, 2003, short scientific article

Abstract: The paper presents an example of a link-drive mechanism for a deep drawing mechanical press. Because of its characteristics such a drive is much more appropriate than conventional crankshaft or eccentric drive. The existing design of the drive has proved unsatisfactory and does not meet all the demands and constraints, which are ideal for deep drawing process. Optimization of the drive is therefore necessary. The intention is to achieve the required velocity characteristics in a defined area of movement. Firstly, the drive is analyzed and a mathematical model is made and prepared for optimization procedure. The process is time-dependent, so it cannot be used directly in the optimization algorithm. Mathematical model is transformed intoa form suitable for the standard non-linear optimization procedure and then optimization is carried out. The method used is sequential quadratic programming. The final objective of the optimization process is to find such dimensions of link-drive members that the given requirements are satisfied in the best possible manner.
Keywords: mechanics, dynamics of mechanical systems, closed kinematic chains, mathematical modelling, non-linear optimization, drive optimization, drive dimensioning, kinematic analysis, link-drive mechanism, deep drawing press
Published: 01.06.2012; Views: 1414; Downloads: 79
URL Link to full text

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CAD mechanism simulations via web environments
Gorazd Hren, Ivan Žagar, 2012, original scientific article

Keywords: CAD, web services, mechanism simulation, VRML
Published: 10.07.2015; Views: 519; Downloads: 16
URL Link to full text

9.
Design of independent suspension mechanism for a terrain vehicle with four wheels drive and four wheels steeering
Shpetim Lajqi, Stanislav Pehan, Naser Lajqi, Afrim Gjelaj, Jože Pšeničnik, Sašo Emin, 2013, original scientific article

Abstract: In this paper a terrain vehicle with four wheels drive and four wheels steer intended to use for recreational purpose is presented. The main purpose is to design the suspension mechanism that fulfills requirements about stability, safety and maneuverability. Nowadays, as well as in the past, the development of the suspension systems of the vehicle has shown greater interest by designers and manufacturers of the vehicles. Research is focused to do a comprehensive study of different available independent suspension system (MacPherson, double wishbone, multi-link) and hence forth develop a methodology to design the suspension system for a terrain vehicle. Few chosen suspension systems are analyzed into the very details in order to find out the optimal design of it. During development process of the suspension system should be considered design constraints and requirements provided in the checklist. Afterwards the simulation results for kinematics analyses of suspension mechanism are performed in Working Model 2D and MATLAB environments. Achieved results are discussed in detail in order to find the best solution that will fulfill pretentious requirement from developed suspension system. All these investigations and reviews related to the suspension system will be exploited in order to obtain the optimal suspension geometry to equip a terrain vehicle, with such system.
Keywords: terrain vehicle, design, suspension mechanism, suspension geometry
Published: 10.07.2015; Views: 679; Downloads: 40
URL Link to full text

10.
Manipulability of a haptic mechanism within the cylindrical space of an MR scanner
Matej Rajh, Srečko Glodež, Jože Flašker, Karl Gotlih, 2012, original scientific article

Abstract: The aim of this paper is to present developed 3 DOF haptic mechanism and 3D visualization method for analysis of mechanism manipulability problems within limited space. Improvement in mechanism manipulability within cylindrical space is crucial for devices, which operate in MR tunnel. This solution enables the plotting of quantitative 3D representation for each point in the mechanism's workspace, using selected resolution which can be determined in advance. The cross-section between the limited space and the whole arbitrary workspace shows the ability for movement execution.
Keywords: gibljivost, Jacobijeva matrika, delovni prostor, haptični mehanizem, MR-združljivost, omejen prostor, manipulability, Jacobian matrix, workspace, haptic mechanism, MR compatibility, limited workspace
Published: 10.07.2015; Views: 524; Downloads: 59
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