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PREVLEKA ZA VAKUUMSKO OBLAČENJE AVTOMOBILSKIH VZGLAVNIKOV
Darja Lešnik, 2009, undergraduate thesis

Abstract: V diplomskem delu so proučene deformacije prevlek za vakuumsko oblačenje avtomobilskih sedežnih vzglavnikov. V podjetju prihaja do pogoste menjave prevlek za vakuumsko oblačenje avtomobilskih vzglavnikov, katere so posledica toplotnih deformacij tkanine, zdrsa niti v področju šiva in zračne prepustnosti prevleke v področju šiva. Zaradi navedenih težav, s katerimi se srečujejo v podjetju, je namen diplomskega dela proučiti zahteve tkanin za izdelavo prevlek in določiti ustrezne parametre za zagotavljanje potrebne kakovosti prevleke za vakuumsko oblačenje avtomobilskih vzglavnikov. V ta namen so bile izvedene analize mehanskih lastnosti izbranih tkanin in raziskave uporabe varilne tehnike kot alternativne tehnike spajanja prevleke za vakuumsko oblačenje avtomobilskih vzglavnikov. Na podlagi rezultatov raziskave je ugotovljeno, da med izbranimi tkaninami za izdelavo prevlek za vakuumsko oblačenje avtomobilskih zglavnikov izkazuje obstoječa tkanina večji del pričakovanih parametrov. Raziskava alternativne tehnike spajanja, ki bi preprečila deformacije prevlek v področju šiva je pokazala, da izbrana tehnika kot tehnika spajanja ne zagotavlja v primeru uporabljenih materialov ustrezne kakovosti in elastičnosti šiva.
Keywords: avtomobilski vzglavnik, prevleka za vakuumsko oblačenje, tekstilni material, trdnost spoja, deformacije
Published: 08.12.2009; Views: 1678; Downloads: 108
.pdf Full text (2,41 MB)

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The effect of a material's heterogeneity on the stress and strain distribution in the vicinity of a crack front
Dražan Kozak, Nenad Gubeljak, Jelena Vojvodič-Tuma, 2007, original scientific article

Abstract: In this investigation a high-strength low-alloyed (HSLA) steel of the 700-MPa strength class was used as a base material. A butt-welded joint with X grooves was produced with an overmatched weld metal that had a yield strength 23 % greater than that of the base material. Three-point bending B x 2B test specimens (thickness B = 36 mm) were extracted from the welded joints. The straight crack front (a0 = 35,571 mm) crosses different microstructures through the thickness of the specimen. Both fracture-mechanics tests and a 3D finite-element analysis were performed. The CTOD parameter of the fracture toughness was measured and calculated numerically. The loading level at which stable crack growth occurred was also determined. The comparison of the experimental and numerical values of the CTOD (bs) displacements showed good agreement. The principal stress, ▫$/delta_{y}$▫, the Mises equivalent stress, ▫$/delta_{eq}$▫. and the plastic equivalent strain, ▫$/epsilon_{pl, eq}$▫, at the moment of crack initiation were studied for six equidistant layers from the surface to the mid-thickness of the specimen. The dependence of the crack-opening stress (denoted as ax in this paper) on the local fracture-toughness value was considered as the parameter which determines the direction of the crack-front propagation. The results show that the lower strength of the base metal contributes to the crack-path deviation in the mid-thickness of the specimen. Both the crack-path deviation and the higher toughness of the base metal increase the critical fracture toughness value of the welded joint.
Keywords: trdnost spoja z večjo trdnostjo vara, razpoka, porazdelitev napetosti, porazdelitev deformacij, analiza končnih elementov
Published: 10.07.2015; Views: 557; Downloads: 36
.pdf Full text (575,99 KB)
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