Experimental and FE Modeling Investigation of Spot Welded Thin Steel Sheets

The spot welded thin steel sheets specimens are experimentally and numerically examined in this paper. The two specimens are joined using Resistance Spot Welding (RSW) method. The spot-welded joints consist of three zones with different material properties. Change of material properties during the welding process is caused by mechanical and thermal loading. The mechanical properties of thin steel sheets are determined by several tension tests. The specimens are cut in three different directions regarding a rolling direction of the basic material plate. Shear resistance of the spot welded joints is experimentally examined on the universal testing machine by displacement-controlled tensile loading tests. The numerical analysis is performed by large-strain plasticity theory implemented into a Finite Element Method based software. Comparison of the Finite Element (FE) modeling and experimental results verifies the proposed stress integration algorithm and modeling technique as powerful tools for prediction of the spot-welded joint behavior

The Influence of Wagon Structure Part Shape Optimization on Ultimate Fatigue Strength

This study investigates how shape optimisation affects the ultimate fatigue strength of a mechanical part. The mechanical part chosen for this investigation is an axle guard of running gear elements of the Hccrrs 2x2 axle car-carrying wagon. The static and fatigue strength analysis procedure according to the UIC 517 standard and numerical methods have been applied. Material properties were determined experimentally and the necessary numerical calculations were performed by using the finite element method. The observed axle guard is exposed to low cycle fatigue. ε-N curves and material properties of the S355J2+N steel grade are obtained by combining theoretical formulae and a mathematical function. According to the obtained experimental and numerical results the number of cycles until failure for both shapes of axle guards is obtained

Načelo jednake vrijednosti u priznavanju neformalnog i informalnog učenja: Koncept koji različito percipiraju ključni dionici u sustavu visokog obrazovanja

The recommendation of the Council of European Union of December 2012 introduced the concept of equal value of standards used to obtain qualifications through validation of non-formal and informal learning and standards used in formal education, with recommended implementation of such validation systems in all EU member states by 2018. This triggered policy development in a number of EU member states including Croatia in order to propose new legislation, quality assurance recommendations and support to such provision. This article presents the results of three quantitative research studies in higher education which involved a total of 2027 participants from different stakeholder groups relevant for the recognition of prior learning in higher education. The results reveal general support to the concept with lack of understanding of its full implications and significant differences in approaches and attitudes of higher education institutions and other stakeholders, especially users of validation, towards assessment standards, assessment methods and use of learning outcomes. This implies that changes in assessment concepts and more use of summative methods based on standards linked to national qualifications framework might be slower and harder to implement in Croatia than EU level policy makers might expect.Preporuka Vijeća Europske unije iz prosinca 2012. uvela je koncept jednake vrijednosti standarda koji se koriste za stjecanje kvalifikacije putem vrednovanja neformalnog i informalnog učenja i standarda koji se koriste u formalnom obrazovanju, s preporukom da se takvi sustavi vrednovanja implementiraju u svim zemljama članicama EU do 2018. To je potaknulo razvoj politika u više zemalja članica EU, uključujući i Hrvatsku, s ciljem donošenja prijedloga novih zakona, preporuka za osiguravanje kvalitete i pružanja potpore takvim odredbama. Ovaj članak predstavlja rezultate triju kvantitativnih istraživanja u visokom obrazovanju koja su uključivala ukupno 2027 sudionika iz različitih interesnih skupina relevantnih u području priznavanja prethodnog učenja. Rezultati otkrivaju općenito podupiranje koncepta, s nedostatkom razumijevanja njegovih cjelovitih implikacija, kao i značajne različitosti u pristupima i stavovima visokoobrazovnih institucija i drugih dionika, posebno korisnika vrednovanja, prema standardima i metodama provjere znanja i upotrebi ishoda učenja. Sve to implicira da će se promjene vezane uz koncepte provjere znanja i veću upotrebu sumativnih metoda utemeljenih na standardima vezanim uz nacionalni kvalifikacijski okvir potencijalno sporije i teže implementirati u Hrvatskoj nego što to kreatori politika na razini EU očekuju

The analysis of choice influence in fatigue failure criteria on integrity assessment of wagon structure

U radu je predstavljen S-N pristup analize otkaza zavarenih spojeva uslijed zamora povezan s metodom konačnih elemenata. Pri analizi otkaza uslijed zamora kriteriji rabljeni za analizu su Goodmanov kriterij i kriterij utemeljen na opsegu efektivnog naprezanja. Goodmanov kriterij i kriterij utemeljen na opsegu efektivnog naprezanja, za određivanje stupnja sigurnosti do otkaza uslijed zamora, implementirani su u softverski paket PAK. Numeričkim proračunima određen je stupanj sigurnosti do otkaza u cilju procjene integriteta dijelova vagonske konstrukcije u skladu s najčešće rabljenim standardima za proračun i analizu vagonskih konstrukcija. Na osnovu izračunatih stupnjeva sigurnosti do otkaza dobivenih Goodmanovim kriterija i kriterija utemeljenih na opsegu efektivnog naprezanja pokazano je da obje metode daju dobre rezultate. Oba kriterija identificiraju prave uzroke pojave pukotina na donjem postolju vagona za prijevoz kontejnera. Dobiveni rezultati i njihovo međusobno dobro poklapanje oba kriterija za određivanje otkaza uslijed zamora nam daju za pravo da se oba kriterija mogu ravnopravno koristiti za procjenu integriteta vagonskih konstrukcija.This paper presents the S-N approach to fatigue failure analysis of welded joints that integrates well with finite element modelling. Goodman\u27s criterion and fatigue criterion based on the equivalent stress range were used for the analysis of the fatigue failure. Goodman\u27s criterion and fatigue criterion based on the equivalent stress range, for determining fatigue safety factor are implemented in the software package for finite element analysis PAK. Numerical calculation of fatigue safety factor was determined to assess the integrity of wagon structure parts according to the most commonly used European standards for wagon analysis. According to failure safety factors obtained by Goodman\u27s criterion and fatigue criterion based on the equivalent stress range it should be noticed that both methods give good results. Both criteria give us adequate identification causes of cracking on the underframe of wagon for containers transportation. The obtained results and their well matching prove reliability of both fatigue failure criteria and that they can be used for integrity assessment of wagon structure parts

ANALYSIS OF ROUGHNESS PARAMETERS OF LATERAL BACK SURFACES OF MODEL HOB MILLING TOOLS DURING CYLINDRICAL GEAR CUTTING

The problem of generating is analyzed in science and practice in various ways by identifying it once as an element of the machine, and the second time as a part of production, that is, a final product. The nature of the materials of the machine elements, the loads in the contact zone, the relative velocities, the topography of the contact surfaces, and the temperature in the contact zone influence on the tribological characteristics of the elements, and hence on the characteristics of the tribo-mechanical systems. The surfaces of the tribo-mechanical elements of the machines through which mutual contact is realized are essentially thin layers of materials whose composition and properties differ significantly from the properties of the basic mass element material. There are a significant number of tribo-mechanical systems in the energy sector. Gear cutting is the most important operation in the production of gears. The quality of the gear cutting is one of the conditions for achieving the required quality of the work-piece. The gear is an element of a large number of tribo-mechanical systems. The geometrical parameters of the hob milling, the accuracy of the profiling and the accuracy of manufacture significantly affect the productivity and machining costs. In this paper, the topography and roughness parameters of lateral back surfaces of the model hob milling tools are analyzed before and after cylindrical gear cutting

Differential contribution of the m7G-cap to the 5′ end-dependent translation initiation of mammalian mRNAs

Many mammalian mRNAs possess long 5′ UTRs with numerous stem-loop structures. For some of them, the presence of Internal Ribosome Entry Sites (IRESes) was suggested to explain their significant activity, especially when cap-dependent translation is compromised. To test this hypothesis, we have compared the translation initiation efficiencies of some cellular 5′ UTRs reported to have IRES-activity with those lacking IRES-elements in RNA-transfected cells and cell-free systems. Unlike viral IRESes, the tested 5′ UTRs with so-called ‘cellular IRESes’ demonstrate only background activities when placed in the intercistronic position of dicistronic RNAs. In contrast, they are very active in the monocistronic context and the cap is indispensable for their activities. Surprisingly, in cultured cells or cytoplasmic extracts both the level of stimulation with the cap and the overall translation activity do not correlate with the cumulative energy of the secondary structure of the tested 5′ UTRs. The cap positive effect is still observed under profound inhibition of translation with eIF4E-BP1 but its magnitude varies for individual 5′ UTRs irrespective of the cumulative energy of their secondary structures. Thus, it is not mandatory to invoke the IRES hypothesis, at least for some mRNAs, to explain their preferential translation when eIF4E is partially inactivated

Cloning whole bacterial genomes in yeast

Most microbes have not been cultured, and many of those that are cultivatable are difficult, dangerous or expensive to propagate or are genetically intractable. Routine cloning of large genome fractions or whole genomes from these organisms would significantly enhance their discovery and genetic and functional characterization. Here we report the cloning of whole bacterial genomes in the yeast Saccharomyces cerevisiae as single-DNA molecules. We cloned the genomes of Mycoplasma genitalium (0.6 Mb), M. pneumoniae (0.8 Mb) and M. mycoides subspecies capri (1.1 Mb) as yeast circular centromeric plasmids. These genomes appear to be stably maintained in a host that has efficient, well-established methods for DNA manipulation

European Atlas of Natural Radiation

Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earth’s atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earth’s crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose. This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources. It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations. This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to: • familiarize itself with natural radioactivity; • be informed about the levels of natural radioactivity caused by different sources; • have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor; • and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.JRC.G.10-Knowledge for Nuclear Security and Safet

European Atlas of Natural Radiation

Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earth’s atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earth’s crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose.This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources. It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations.This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to: • familiarize itself with natural radioactivity;• be informed about the levels of natural radioactivity caused by different sources;• have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor;• and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.Additional information at: https://remon.jrc.ec.europa.eu/About/Atlas-of-Natural-Radiatio

The analysis of choice influence in fatigue failure criteria on integrity assessment of wagon structure

© 2016, Strojarski Facultet. All rights reserved. This paper presents the S-N approach to fatigue failure analysis of welded joints that integrates well with finite element modelling. Goodman’s criterion and fatigue criterion based on the equivalent stress range were used for the analysis of the fatigue failure. Goodman’s criterion and fatigue criterion based on the equivalent stress range, for determining fatigue safety factor are implemented in the software package for finite element analysis PAK. Numerical calculation of fatigue safety factor was determined to assess the integrity of wagon structure parts according to the most commonly used European standards for wagon analysis. According to failure safety factors obtained by Goodman’s criterion and fatigue criterion based on the equivalent stress range it should be noticed that both methods give good results. Both criteria give us adequate identification causes of cracking on the underframe of wagon for containers transportation. The obtained results and their well matching prove reliability of both fatigue failure criteria and that they can be used for integrity assessment of wagon structure parts