Utjecaj sastava zaštitnog plina pri MIG postupku zavarivanja na mehanička svojstva niskougljičnih čelika

The present study is focused on the mechanical properties of the deposited material which was extracted from welded region. This study explains the effect of the shielding gas composition on tensile behavior, R = - 1 fatigue response and various tempe-rature impact test results of MIG welded low carbon steels. In tensile tests, the stre-ngth values are increased with increase of CO2 content, whereas the ductility is decreased. In the fatigue tests, the fatigue strength and the number of cycles to failure enhanced as the content of CO2 increased. However, the impact toughness of the filler material is seriously influenced by the content of the shielding gas. An increase in CO2 content caused significant decrease in toughness values at all temperatures.Ovaj rad se usredotočio na mehanička svojstva dodatnog materijala uzetog iz zavarenog područja. Rad objašnjava utjecaj sastava zaštitnog plina na vlačnost, R = -1 zamor i rezultate ispitivanja žilavosti na raznim temperaturama niskougljičnih čelika zavarenih metodom MIG. U testovima za ispitivanje vlačne čvrstoće vrijednosti čvrstoće su povećane kao rezultat povećanog sadržaja CO2, a plastičnost je smanjena. U testovima za ispitivanje zamora povećala se dinamička čvrstoća kao i broj ciklusa prije pucanja zajedno s povećanom količinom CO2. Međutim, žilavost materijala za dodavanje jako ovisi o zaštitnom plinu. Povećanje količine CO2 značajno smanjuje žilavost na svim temperaturama

Corrosion and mechanical-microstructural aspects of dissimilar joints of Ti-6Al-4V and Al plates

In this study, Ti-6Al-4V and Al plates were joined by explosive welding at various explosive loads. Tensile-shear, bending, hardness, microstructure and corrosion behaviours of the explosively joined samples were investigated. At the end of the tensile-shear tests carried out according to ASTM D 3165-95 standard, no seperation was observed in the interfaces of the joined samples. The results of the bending tests also showed no sign of any distinctive seperation, crack and tear in the interfaces. The highest hardness values were measured in regions next to interfaces. The optical microscope and SEM examinations revealed that an increment in wavelength and amplitude was observed with increasing explosive load. It is seen from the corrosion test results that materials loss was high at the beginning of the corossion tests but the rate of material loss decreased later on. Furthermore, increasing deformation with increasing explosive load increased the materials loss in corrosion tests. © 2006 Elsevier Ltd. All rights reserved.07/2002-07We would like to thank to M.K.E Barutsan Company, Turkey for their kindly supplying the materials, equipment and staff. This work was financially supported under Gazi University Project (07/2002-07)

The effect of cold and hot reformation process to mechanical properties of deformed automobile chassis material

Vehicles are damaged as a result of traffic accidents. Chassis and body parts of damaged vehicles are reformed by using cold and hot deformation methods. High-strength low alloy (HSLA) steel material coated (galvanised) with S320GD+Z quality (DIN EN 10326) zinc, which is used in chassis production, was used in this study. Steel sheet materials were damaged. Damaged automotive chassis material was reformed with cold and hot reformation processes. Tensile, notch impact, bending and hardness tests were applied to the reference material which were not deformed and materials to which reformation process was applied. In the light of obtained results, the effect of reformation process on mechanical properties of automotive sheet was determined

Longitudinal patterns of white matter fibre density and morphology in children are associated with age and pubertal stage

Purpose: The pubertal period involves dynamic white matter development. This period also corresponds with rapid gains in higher cognitive functions including attention, as well as increased risk of developing mental health difficulties. We performed a longitudinal investigation of the relationship between white matter fibre properties and pubertal stage, attentional difficulties, and internalising problems Methods: This study reports on a community-based sample of children aged 9-13 years (n=130, 47 female). Diffusion magnetic resonance imaging (dMRI) data were acquired on a 3.0T Siemens Tim Trio (b=2800 s/mm2, 60 directions) at two time-points approximately 16 months apart: time-point 1 (age: M = 10.4, SD = .44 years old), time-point 2 (age: M = 11.7, SD = .51 years old). We leverage the fixel-based analysis (FBA) framework, to derive measures of: fibre density (FD), fibre cross-section (FC), and fibre density and cross-section (FDC), in 17 manually delineated white matter tracts. We apply a longitudinal mixed-effects modelling analysis: to understand how specific fibre properties vary with age, sex, and pubertal stage; and as a function of the development of internalising behaviours and attentional difficulties. Results: We observed significant increases in FD, FC, and FDC across a large number of white matter pathways, with protracted development of frontal pathways such as the inferior fronto-occipital fasciculus (IFOF) and uncinate fasciculus (UF). We observed a linear relationship between FBA metrics and pubertal stage, in the right superior longitudinal fasciculus (SLF). Increases in FD were associated with greater attentional dysfunction, particularly in older males. Lastly, we found evidence for an association between lower FD and greater internalising problems in the right UF, a region known to be implicated in psychiatric disorders. Discussion: These longitudinal results shed light on regional fibre developmental profiles in early puberty. The development of fibre density and morphology across ages 9-13 years involved the expansion of key white matter tracts, excluding regions known to have protracted development over adolescence. The associations between mental health and attentional problems with fibre density in the UF suggests that this region may be sensitive to adopting a different neurodevelopmental course in the presence of such symptoms. Overall, our findings highlight the interrelated nature of fibre development with puberty, mental health problems, and attentional difficulties

ADHD at age 7 and functional impairments at age 10

This is the author accepted manuscript. The final version is available from the American Academy of Pediatrics via the DOI in this recordBackground and Objectives Attention-Deficit/Hyperactivity Disorder (ADHD) cohort studies have typically involved clinical samples, and have usually recruited children across wide age ranges, limiting generalizability across complexity and developmental stage. We compared academic, emotional-behavioral and social functioning at age 10, and predictors of outcomes, in a nonreferred cohort of children recruited at age 7, between full syndrome (FS) ADHD, subthreshold (ST) ADHD and non-ADHD controls. Methods This was a prospective, cohort study with a 3 year follow-up period. Children were recruited from 43 socio-economically diverse schools in Melbourne, Australia. Multi-informant outcomes at age 10 were academic functioning (Wide Range Achievement Test-4; Social Skills Improvement System), emotional-behavioral functioning (Strengths and Difficulties Questionnaire (SDQ) Total)) and social functioning (SDQ Peer Problems). Outcomes were compared across the groups using adjusted random effects linear regression analyses. Results 477 children (62% male) were recruited at mean (SD) age 7.3 years (0.4). There were 179 FS participants, 86 ST and 212 controls. Sample retention was 78.2% at 3-year follow-up. Both the FS and ST groups were functioning worse than controls on almost all outcome measures. The best predictors of outcome for children with ADHD were working memory (academic outcome, p<0.001), ADHD symptom severity (emotional-behavioral outcome, parent: p <0.001, teacher: p<0.01), and autism spectrum disorder symptoms (emotional-behavioral outcome, parent p=0.003; social outcome, parent p=0.001). Conclusions Children with FS and ST ADHD at age 7 experience persisting functional impairments across domains at age 10. The predictors identified at age 7 present potential targets for intervention to ameliorate impairments