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Modelling and simulation of local mechanical properties of high silicon solution-strengthened ferritic CGI materials
Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.ORCID-id: 0000-0003-2698-5445
Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.ORCID-id: 0000-0003-2671-9825
Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.ORCID-id: 0000-0002-0101-0062
Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:hj:diva-32050OAI: oai:DiVA.org:hj-32050DiVA, id: diva2:1040015
Tillgänglig från: 2016-10-26 Skapad: 2016-10-26 Senast uppdaterad: 2017-08-14
Ingår i avhandling
1. The influence of microstructure on mechanical and tribological properties of lamellar and compacted irons in engine applications
Öppna denna publikation i ny flik eller fönster >>The influence of microstructure on mechanical and tribological properties of lamellar and compacted irons in engine applications
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Lamellar graphite iron (LGI) is commonly used in diesel engine applications such as piston rings–cylinder liner where an excellent combination of physical and tribological properties is essential to avoid scuffing and bore polishing issues. The excellent tribological behaviour of LGI alloys is related to the graphite lamellas, which act as solid lubricant agents by feeding onto the tribosurfaces under sliding conditions. However, increasingly tighter emissions and fuel economy legislations and the higher demands on enhanced power and durability have encouraged both engine designers and manufacturers to introduce pearlitic compacted graphite irons (CGI) as an alternative material replacing LGI, although the poor machinability of pearlitic CGI alloys compared to the LGI remains a challenge.

The focus of this study is placed on investigating how the microstructure of LGI and CGI alloys affects their mechanical and tribological properties. This was initially undertaken by investigating representative, worn lamellar cast iron piston rings taken from a two-stroke large-bore heavy-duty diesel engine. As known that it is tribologically essential to keep the graphite open under sliding conditions, in particular under starved lubrication regimes or unlubricated conditions to avoid scuffing issues; however, this study revealed the closure of a majority of graphite lamellas; profoundly for those lamellas that were parallel to sliding direction; due to the severe matrix deformation caused by abrasion. Both microindentation and microscratch testing, which were used to crudely simulate the abrasion under starved lubricated condition in combustion chamber, suggested a novel mechanism of activating the graphite lamellas to serve as lubricating agents in which the matrix deformation adjacent to the graphite initially resulted in fracturing and then extrusion of the graphite lamellas.

Additionally, in order to investigate the relation between matrix constituents, mechanical properties and machinability of cast iron materials, solution-strengthened CGI alloys were produced with different levels of silicon and section thicknesses. The results showed significant improvements in mechanical properties and machinability while deteriorating the ductility. Moreover, multiple regression analysis, based on chemical composition and microstructural characteristics was used to model the local mechanical properties of high Si ferritic CGI alloys, followed by implementing the derived models into a casting process simulation which enables the local mechanical properties of castings with complex geometries. Very good agreement was observed between the measured and predicted microstructure and mechanical properties.

Ort, förlag, år, upplaga, sidor
Jönköping: Jönköping University, School of Engineering, 2016. s. 80
Serie
JTH Dissertation Series ; 17
Nyckelord
Cast iron, Si solution-strengthened CGI, microstructure, mechanical properties, modelling and simulation, tribology, abrasive wear, scratch testing
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:hj:diva-32052 (URN)978-91-87289-18-7 (ISBN)
Disputation
2016-11-25, E1405, Jönköping University, School of Engineering, Jönköping, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2016-10-26 Skapad: 2016-10-26 Senast uppdaterad: 2016-10-26Bibliografiskt granskad

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Ghasemi, RohollahOlofsson, JakobJarfors, Anders E. W.Svensson, Ingvar L.

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Ghasemi, RohollahOlofsson, JakobJarfors, Anders E. W.Svensson, Ingvar L.
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JTH, Material och tillverkningJTH. Forskningsmiljö Material och tillverkning – Gjutning
Metallurgi och metalliska material

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