Razvoj metod za ovrednotenje strižnih parametrov izven ravnine pločevine kriterija tečenja Barlat Yld2004-18p

Vilhar, Vid (author), Pepelnjak, Tomaž (mentor), Starman, Bojan (comentor)

Numerične simulacije so dandanes nepogrešljiv del načrtovanja procesov preoblikovanja pločevine. Pri tem je ključnega pomena pravilen popis mehanskega odziva obravnavanega materiala. Izkušnje so pokazale, da mehansko obnašanje v smeri debeline pločevine ni zanemarljivo. Za upoštevanje tega vpliva je potreben popis strižnih lastnosti materiala pravokotno na ravnino pločevine. Trenutno pristopi k popisu takšnega materialnega odziva temeljijo na kristalografskih preiskavah, ki so zahtevne in dolgotrajne. Pričujoča raziskava bazira na predhodnih analizah strižnega obnašanja pločevine po njeni debelini opredeljenega s pomočjo vtiskovanja kroglice. Razvili smo novo obliko vzorca za strižne preizkuse in izvedli uvodne simulacije za določitev geometrije strižnih preizkušancev z namenom, da so razlike v poteku preoblikovalnih sil glede na usmerjenost pločevine čim bolj očitne. Nato smo zasnovali in izdelali orodje za izvedbo strižnega preizkusa ter izvedli eksperimente na vzorcih aluminijeve zlitine AW 5754. Dodatno smo za namen validacije popisa pločevine po debelini izvedli tudi globoki in stanjševalni vlek rondele. Pri tem smo opazovali pojavljanje ušes na robu lončka. Pokazali smo, da je s strižnimi parametri, pridobljenimi z metodo vtiskovanja kroglice v površino pločevine in uporabo kriterija tečenja Barlat Yld2004-18p mogoče zanesljivo napovedati pojav šestih ušes, ki so značilna za nekatere aluminijeve zlitine.

• Language: Slovenian
• Keywords: funkcija tečenja, anizotropija, preoblikovanje pločevine, aluminijeve zlitine, globoki vlek, strig, valjanje
• Work type: Master's thesis/paper
• Organization: FS - Faculty of Mechanical Engineering
• Year: 2024
• Publication date in RUL: 24.11.2024

Secondary language

• Language: English
• Title: Development of methods to evaluate out of plane shear parameters of Barlat Yld2004-18 yield function

Abstract

Nowadays, numerical simulations are an indispensable part of any sheet metal forming process. It's important to characterize the mechanical response of the material correctly. According to researches, the influence of mechanical behaviour in through-thickness direction should not be neglected. To take it into account, out-of-plane shear material characterization is required. Currently, approaches to describe such a material response are based on crystallographic investigations, which are demanding and time-consuming. This study is based on preliminary analysis of through thickness shear behaviour of sheet metal defined using ball indentation test. We have developed a new shear test specimen and performed simulations to define it’s geometry in order to show the differences in forming forces, depending on material orientation. We designed and manufactured a tool, that enabled performing of shear tests on AW 5754 aluminium sheet specimens. In order to validate through thickness shear characterization, deep drawing and ironing tests had also been performed to observe an earing phenomenon. Using out-of-plane shear parameters, obtained via ball indentation test, and Barlat Yld2004-18p yield criterion, we predicted occurence of six ears during deep drawing process, which are typical for some aluminium alloys.

• Keywords: yield function, anisotropy, sheet metal forming, aluminium alloys, deep drawing, shear, rolling