Search

This report aims to have an overview to development actions of a knowledge-based know-how cluster of metal additive manufacturing (AM) in Finland's South Karelia region. This report aims also to investigate the needs of regional industries to become more aware and open towards using AM in their production lines. At first, a brief history of additive manufacturing introducing the preliminary concepts of metal AM, its generic principles and available processes are discussed. Next, the status of AM activities in Finland and other Nordic countries is discussed. Finally, it shares the results of a case study to get the reader more familiar with metal AM. The case study of this report shows that 3D printed metals such as stainless steel 316L have a strong potential to compete with their traditionally manufactured counterparts, even excel them regarding many specific material properties and applications. Tämän raportin tarkoituksena on läpikäydä Etelä-Karjalan metallien lisäävän valmistuksen (engl. additive manufacturing, AM) osaamiskeskittymän perustamiseen liittyviä näkökohtia. Tässä katsastettu alueellisen teollisuuden tarpeita, jotta lisäävän valmistuksen käyttöönottoa voitaisiin laajentaa paremman tietopohjan kautta. Aluksi tässä raportissa käsitellään lyhyesti metallien lisäävän valmistuksen historiaa, ja esitellään tekniikan keskeisimmät käsitteet, sen yleiset periaatteet ja käytettävissä olevat prosessit. AM-toiminnan tilasta Suomessa ja muissa Pohjoismaissa esitellään myös yhteenveto. Lopuksi raportissa käydään case studien tuloksia läpi, jotta metallien lisäävän valmistuksen käytännön sovelluksia ja niiden mahdollisuuksia voidaan ymmärtää paremmin. Nämä esimerkit osoittavat selkeästi sen, että metallien (kuten 316L) 3D-tulostuksella, on suuri mahdollisuus olla teollisesti varteenotettava valmistustekniikka. Useimmat tulostettujen kappaleiden ominaisuudet ovat samat kuin perinteisestikin valmisteluilla, ja joissain tapaukissa jopa paremmat. Publishers version

With the increasing demands of the applications of environmentally friendly materials in different engineering fields, especially steel industry, which is one of the highly consumed energy sectors, high and ultra-high strength steels (HSS/UHSS) are potentially capable to meet eco-friendly requirements of the 21st century. With their superior properties, high strength and low weight, it makes it possible to build efficient structures. However, due to their microstructure sensitivity to heat input from welding, these materials may lose a part of their desirable characteristics such as static capacity and fatigue life. Hence it is vital to find possible strengthening solutions for welded UHSS. Carbon fiber reinforced polymers (CFRP) have already proven their superior capability in strengthening metallic structures. There are numerous successful applications of CFRP to enhance fatigue life of different structural details such as: I-beams, biaxial load carrying connections, hollow sections, and plates. However, the strengthened base material in nearly all of them were mild steel, with exceptions of limited work in high strength steels (HSS) up to 700 MPa. This thesis aims to fill the knowledge gap in strengthening of HSS/UHSS welded plates and tubes under quasi-static and fatigue loading using CFRP laminates. Experimental testing, finite element analysis (FEA) were adopted. Microstructure evaluation of welded UHSS using scanning electron microscopy (SEM) as well as electron backscattered diffraction (EBSD) were implemented. Issues such as debonding of CFRP and UHSS were also studied.

With the increasing applications of high and ultra-high strength steel (HSS/UHSS) in engineering structures, there is a need to address rehabilitation and strengthening of such steel grades using carbon fibre reinforced polymer (CFRP). The bond between HSS/UHSS and CFRP is vital to ensure the efficiency of the strengthening. The existing bond study was focused on mild steel as substrate, with very limited work on HSS up to the grade of S690. Since HSS/UHSSs are designed to undergo much higher loading in service, much higher shear stress is expected in the adhesive layer, leading to a higher chance of premature debonding. In this paper, the bond between HSS/UHSS plates and ultra-high modulus (UHM) CFRP laminates under static tensile loading is studied experimentally, numerically and theoretically. Both single-sided and double-sided schemes were adopted. The numerical simulation using LS-DYNA software package was implemented and a reasonable agreement with the experimental results is found. A theoretical bond model was developed to relate the bond strength to the imposed strain in the steel member outside the bonded region. Post-print / Final draft