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On the local variation of the crack driving force in a double mismatched weld
Jožef Predan, Nenad Gubeljak, Otmar Kolednik, 2007, izvirni znanstveni članek

Opis: A material inhomogeneity in the direction of crack extension causes a difference between the near-tip crack driving force, Jtip, and the nominally applied far-field crack driving force, Jfar. This difference can be quantified by a material inhomogeneity term, Cinh, which is evaluated by a post-processing procedure to a conventional finite element stress analysis. The magnitude of the material inhomogeneity term is evaluated for cracks in an inhomogeneous welded joint made of a high-strength low-alloy steel. Both a crack proceeding from the under-matched (UM) to the over-matched (OM) and from the OM to the UM weld metal are treated. The effects of the inhomogeneity of the different material parameters (modulus of elasticity, yield strength, and strain hardening exponent) on Cinh and Jtip are systematically studied. The results demonstrate that the material inhomogeneity term is primarily influenced by the inhomogeneity of the yield strength. A crack growing towards an OM/UM interface experiences an accelerated crack growth rate or a pop-in, an UM/OM interface leads to a reduced crack growth rate or a crack arrest. The application of global assessment methods of the mismatch effect which are included in the Engineering Treatment Model (ETM) or in the Structural Integrity Assessment Procedures for European Industry (SINTAP) is discussed.
Ključne besede: crack driving force, material inhomogeneity, mismatched weld, interface, J-integral, finite element modeling
Objavljeno: 31.05.2012; Ogledov: 848; Prenosov: 25
URL Povezava na celotno besedilo

4.
Intelligent interface in a flexible production environment
Igor Drstvenšek, Ivo Pahole, Miha Kovačič, Jože Balič, 2005, izvirni znanstveni članek

Opis: The paper describes a universal postprocessor initially intended to translate NC code for non-standard NC controllers. By adding arithmetic modules and connecting it to the technological database (TDB) it's functionality is broaden to a wider range of production planning problems, such as quick calculations of costs, evaluation of production possibilities and disposability of tools, etc. Thus, an automation tool is gained that enables its user to participate in a virtual manufacturing market and quickly and effectively evaluate jobs offered.
Ključne besede: production technology, virutal manufacturing, postprocessing, NC interface, CAM
Objavljeno: 01.06.2012; Ogledov: 819; Prenosov: 24
URL Povezava na celotno besedilo

5.
On fracture behaviour of inhomogeneous materials - a case study for elastically inhomogeneous bimaterials
Otmar Kolednik, Jožef Predan, G.X. Shan, N.K. Simha, Franz Dieter Fischer, 2005, izvirni znanstveni članek

Opis: This paper presents a case study, examining the influence of a sharp bimaterial interface on the effective crack driving force in a fracture mechanics specimen. The inhomogeneity of the elastic modulus in linear elasticand non-hardening and hardening elastic-plastic bimaterials is considered. The interface is perpendicular to the crack plane. The material properties and the distance between the crack tip and the interface are systematically varied. The effect of the material inhomogeneity is captured in form of a quantity called "material inhomogeneity term",▫$C_inh$▫. This term can be evaluated either by a simple post-processing procedure, following a conventional finite element stress analysis, or by computing the J-integral along a contour around the interface, ▫$J_int$▫. The effective crack driving force,▫$J_tip$▫, can be determined as the sum of ▫$C_inh$▫ and the nominally applied far-field crack driving force, ▫$J_far$▫. The results show that ▫$C_inh$▫ can be accurately determined by both methods even in cases where ▫$J_tip$▫-values are inaccurate. When a crack approaches a stiff/compliant interface,▫$C_inh$▫ is positive and ▫$J_tip$▫ becomes larger than ▫$J-far$▫. A compliant/stiff transition leads to a negative ▫$C_inh$▫, and ▫J_tip$▫ becomes smaller than ▫$J_far$▫. The material inhomogeneity term, ▫$C_inh$▫, can have the same order of magnitude as ▫$J_far$▫. Based on the numerical results, the dependencies of ▫$C_inh$▫ on the material parameters and the geometry are derived. Simple expressions are obtained to estimate ▫$C_inh$▫.
Ključne besede: mechanics of structures, fracture toughness, inhomogeneous materials, J-integral, crack driving force, interface, material force
Objavljeno: 01.06.2012; Ogledov: 741; Prenosov: 7
URL Povezava na celotno besedilo

6.
Experimental investigation of the stability of particulate dispersoid suspensions in aluminium and magnesium melts
Varužan Kevorkijan, 2000, izvirni znanstveni članek

Opis: The rejection of Si3N4,Mg3N2, AlN and Si particles from different slurries consisting of molten aluminum and magnesium alloy with 10% of silicon or pure molten metals was experimentally investigated by measuring changes in the electrical resistance of the slurries before and after rejection occurred. In stirring experiments, only individual powder fractions which passed through a 45 µm sieve screen and remained on a 30 µm screenwere applied. The experiments showed that the rejection of Si3N4 particles from Al-10%Si and Mg-10%Si melts occurs when more than 17-18 vol.% of the ceramic phase is dispersed into the melt, while in pure Al and Mg molten metals spontaneous rejection occurs at 7-8 vol.% of the introduced ceramic phase. A similar tendency of rejection (at 16-18 vol.% of particulate in slurry) was also observed during the introduction of silicon particles into Al-10%Si and Mg-10%Si melts.
Ključne besede: metal matrix composites, particle reinforcement, interface, chemically activated wetting
Objavljeno: 01.06.2012; Ogledov: 872; Prenosov: 22
.pdf Celotno besedilo (215,84 KB)
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7.
EFFECT OF GELATINE SCAFFOLDS FABRICATION AS POLYPROPYLENE MESH COAT ON IMPLANT BIOCOMPATIBILITY
Selestina Gorgieva, 2014, doktorska disertacija

Opis: This work presents the methodological study, processing and optimization of novel, technologically acceptable procedure for in situ coating of polypropylene (PP) mesh (used for hernia treatment) with physico-chemically, mechanically and micro-structurally different gelatin (GEL) scaffolds to assess implant composite biocompatibility impact. In order to systematically follow the experimental work progress and respective achievements, whole research path is subdivided into three main sections. In the first section, the procedure for fabrication of gradiently micro-porous GELscaffolds on the cryo-unit’s cooling plate surface, using spatiotemporal and temperature- controlled gelation and freezing, followed by lyophylizaton was studied. Subsequently, cross-linking procedure using different molarities of reagents (EDC and NHS) and reaction media (100% PBS or 20/80% PBS/EtOH mixture) was performed for variable time extensions (1-24 h), rendering scaffolds physico-chemical properties. In this way, scaffolds with micro-structures having porosity gradient from 100 µm to 1000 µm and pores with rounded to ellipsoid morphology were formed, which, in combination with ethanol (EtOH) addition in cross-linking media modulates the swelling capacity towards twice lower percentages (~600%) comparing with scaffolds cross-linked in 100% PBS. Whilst the presence of EtOH reduce the cross-linking kinetic by retaining the scaffolds’ micro-structure formed during freezing, the 100% PBS and higher EDC molarity resulted in 40% cross-linking degree, being expressed as a thermal resistance up to 73 °C. The presented integral fabrication procedure was shown to allow tuning of both, the physical and micro-structural properties of scaffold, utilized in preparation of materials for specific biomedical applications. In the second part, the complex relation between surface and interface-related physico-chemical properties and gradient micro-structuring of 3D GELscaffolds, being fabricated by simultaneous temperature- controlled freeze-thawing cycles and in situ cross-linking using variable conditions (pH and molarity of carbodiimide reagent) and fibroblast cells viability (by tracking of their spreading and morphology) was established. Rarely- populated cells with rounded morphology and small elongations were observed on scaffolds with apparently negatively- charged surface with a lower cross-linking degree (CD) and consequently higher molecular mobility and availability of cell-recognition sequences, in comparison with the prominently- elongated and densely- populated cells on a scaffold’s with positively- charged surface, higher CD and lower mobility. Surface micro-structure effect was demonstrated by cell’s vacuolization and their pure inter-communication being present on scaffold’s bottom side with smaller pores (25±19 µm) and thinner pore walls (9±5 µm), over the air- exposed side with twice bigger pores (56±38 µm) and slightly thicker pore walls (12±6 µm). Strong correlation of preparation conditions (pH and reagents molarity) with CD (r2=0.96) and moderate correlation with local molecular mobility (r2 =-0.44), as well as micro-structure features being related to temperature gradient, imply on possibility to modulate scaffold’s properties in a direction to guide cell’s viability and most likely its genotype development. The third part presents an innovative strategy for the fabrication of bio-active PPmesh-GELscaffold composites with a potential for abdominal hernia treatment, where mesothelial cells in-growth have to be stimulated together with fibroblasts on-site proliferation, while formation of fibrin-developing, viscera-to-abdominal wall adhesions should be reduced, together with bacteria- related infections. In this respect, the plasma pre-activated PPmesh was coated with micro-structured GELscaffold, with pore size in 50 µm to 100 µm range at the upper-side and loosely- porous network at the composite bottom side, being modulated by sample thickness and freezing end- temperature applied. Simultaneously, the
Ključne besede: gelatin, targeted cross-linking, controlled freezing, gradiental micro-porosity, scaffold, surface and interface chemistry, physico-mechanical properties, polypropylene mesh, composite, biocompatibility.
Objavljeno: 07.05.2014; Ogledov: 971; Prenosov: 75
.pdf Celotno besedilo (4,98 MB)

8.
Vpliv uporabnika na spletno marketinško platformo
Slavica Šuman, 2017, magistrsko delo

Opis: As a part of the Master thesis, we wanted to improve user experience, user interface and usability of Forsikringsportalen platform. Based on literature review and case studies conducted from the same or similar area of research, we redesigned certain elements of the platform. The performance of the redesigned elements was measured with Preference and Question tests as well as gathering of statistical data. With gathered results, we formed a conclusion that will help the company to engage users more. With the implemented improvements and increased percentage of first-time logins, the company can focus on the engagement after the login.
Ključne besede: Forsikringsportalen, usability, user experience, user interface, online platform
Objavljeno: 06.10.2017; Ogledov: 257; Prenosov: 0

9.
Materials design for language m-learning
Dejan Pukšič, Melita Zemljak, Marjan Krašna, 2015, izvirni znanstveni članek

Opis: Today's smart phones are versatile multimedia devices. Their processing power is incredible compared to decades-old personal computers (PCs), and the time is right to use them in education. The touch screen has provided a haptic user interface that cannot be considered as merely another mouse. The design of m-learning materials therefore needs to follow a special set of rules to maximize the efficiency of constraints posed by the devices and the user interface. In the article the design considerations are presented in the context of a practical application for using mobile devices in language learning with the application BlaBla$^{TM}$.
Ključne besede: m-learning, design, mobile assisted language learning, haptic user interface
Objavljeno: 21.09.2017; Ogledov: 163; Prenosov: 43
.pdf Celotno besedilo (729,26 KB)
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10.
The Bosnian-Croatian-Serbian adnominal possessive dative at the syntax-pragmatics interface
James Joshua Pennington, 2012, izvirni znanstveni članek

Opis: In Bosnian, Croatian, and Serbian, the adnominal possessive dative (APD) construction is used alongside the nominal adjectival construction to express possession. APD usage is double-edged – i.e., there are both issues of sociolinguistics/perceptual dialectology involved as well as more formal syntactic- pragmatic ones. My respondents consistently labeled APD usage as “archaic,” “old-fashioned,” “characteristic of the uneducated,” or “country-talk”. However, judging by very similar acceptance levels of APDs in particular contexts in all dialects, it appears that semantic role of the possessor and the level of contextual effects and processing load involved in interpreting possessive constructions weigh heavily on their acceptance. Therefore, I offer a model that attempts to capture APD usage in terms of a set of hierarchical relationships between the “possessor” and the “possessed”.
Ključne besede: sociolinguistics, adnominal possessive dative, perceptual dialectology, dialect geography, syntax-pragmatic interface
Objavljeno: 13.02.2018; Ogledov: 117; Prenosov: 124
.pdf Celotno besedilo (805,16 KB)
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