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Low Cycle Fatigue Assessment of Nodular Cast Iron GJS-500-7
KTH, School of Engineering Sciences (SCI).
2026 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Utvärdering av egenskaperna i lågcykelutmattning hos segjärn GJS-500-7 (Swedish)
Abstract [en]

Nodular cast iron is widely used at Scania in a variety of components. This thesis aims to assessthe low cycle fatigue properties of the nodular cast iron GJS-500-7, a widely used cast iron gradeat Scania. A total of 40 uni-axial test specimen were cut out of 5 serially produced Scania parts.Monotonic uni-axial tests were performed to verify the casting process and enabled the implemen-tation of a new material curve in Abaqus. A large number of uni-axial low cycle fatigue tests wereperformed for a variety of strain ratios. A combined Basquin and Coffin-Manson axial fatiguemodel was fitted and three separate kinematic hardening models were fitted by experimental dataand implemented into Abaqus. Low cycle fatigue testing in force-control was performed simulta-neously for verification of cyclic models. The performance of the three models were evaluated inthe ability to recreate the strain in force testing. All three kinematic models, linear, multi-linearand Chaboche, failed to recreate the mean strain from the ratcheting effect which occurred in theforce-controlled testing, but were sufficient in their ability to capture the amplitude in the strain-time signals. The multi-linear model was not stable for this analysis. The linear model performedthe best and is recommended for use in cyclic analysis. An acceptance criterion for total strainamplitude in GJS-500-7 can not be fully recommended, however recommendation is made forthe use of strain-controlled alternating points which have been used historically for dimensioningagainst low cycle fatigue.

Abstract [sv]

Segjärnets användning på Scania är mycket utbrett och denna uppsats har som mål att karaktärisera segjärnet GJS-500-7 och dess egenskaper i lågcykelutmattning. 40 stycken cirkulära provstavar tillverkades för axiell provning ur 5 stycken serieproducerade basfästen. Dragprov genomfördes för att säkerställa gjutprocessen och tillät implementeringen av en ny materialmodell i Abaqus. Därefter genomfördes ett stort antal töjningsstyrda lågcykelutmattningsprov med varierande töjningsamplitud. En axiell utmattningsmodell togs fram av typen Basquin, Coffin-Manson och tre separata kinematiska hårdningsmodeller togs fram från provningsdatan. Parallellt genomfördes kraftstyrda utmattningsprov för att tillåta verifiering av hårdningsmodellerna. De kinematiska modellerna utvärderades i deras förmåga att återskapa töjning i ett kraftstyrt prov varav alla misslyckades med att fånga mitt-töjningen synlig i de kraftstyrda proven. Alla tre modeller var bättre i deras förmåga att fånga töjningsamplitud men den multi-linjära modellen var numeriskt instabil. Den olinjära Chaboche modellen rekommenderas för beräkning av cyklisk belastning. Ett acceptanskriterie för töjningsamplitud kunde ej fastställas, dock rekommenderas användningen av alternerande utmattningsdata för vidare utvärdering av lågcykelutmattning i GJS-500-7 då det används på Scania historiskt.

Place, publisher, year, edition, pages
2026.
Series
TRITA-SCI-GRU ; 2026:025
Keywords [en]
Cast Iron, Fatigue, Low Cycle Fatigue, FEA
Keywords [sv]
Segjärn, Utmattning, Lågcykelutmattning, FEA
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-377511OAI: oai:DiVA.org:kth-377511DiVA, id: diva2:2042635
External cooperation
Scania CV AB
Supervisors
Examiners
Available from: 2026-03-02 Created: 2026-03-02 Last updated: 2026-03-02Bibliographically approved

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