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Automated Fatigue Evaluation of Seam Welds.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
2015 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesisAlternative title
Automatiserad utmattningsbedömning av sömsvetsar. (Swedish)
Abstract [en]

In this thesis the ability to predict fatigue in welded designs has been investigated for a set of postprocessors. Results from previously performed testing of twelve test coupons (four geometries, each consisting of three sheet thicknesses) has been compared to results achieved from computation using handbook methods, as well as the results from the investigated post-processors. In addition to the test coupons a rear axle housing has analyzed in order to investigate the post-processors ability to predict fatigue in welds on a real life component.

CAD models of the test coupons and the rear axle housing has been imported into the pre-processor Hypermesh where they have been converted into mid surface models and meshed. For some of the post-processors the welds were defined in the pre-processor as well. The models generated in Hypermesh were then imported to Abaqus where loads and boundary conditions corresponding to the previously performed tests were applied before the model was solved. The Abaqus results file containing stresses which was imported into the post-processors FEMFAT, Verity and DesignLife, where fatigue computation on the welds of the analyzed components were performed. Audis in house developed post-processor SuperWeld has also been evaluated. For this postprocessor, results provided by Audi has been implemented in the study. Besides accuracy in the results, user friendliness has also been an important factor when giving a recommendation regarding what method to use for fatigue prediction of welded designs in the future. Verity in fe-safe was the post-processor that gave the best accuracy in the results for the test coupons and FEMFAT for the rear axle housing. Regarding user friendliness FEMFAT obtained the highest grade. The recommendation made was to use FEMFAT to predict fatigue in welded designs in the future. This due to the fact that FEMFAT already is implemented at Scania, has a high level of user friendliness and is considered to predict fatigue with a good enough accuracy.

In this thesis the ability to predict fatigue in welded designs has been investigated for a set of postprocessors.

Results from previously performed testing of twelve test coupons (four geometries, each

consisting of three sheet thicknesses) has been compared to results achieved from computation using

handbook methods, as well as the results from the investigated post-processors. In addition to the test

coupons a rear axle housing has analyzed in order to investigate the post-processors ability to predict

fatigue in welds on a real life component.

CAD models of the test coupons and the rear axle housing has been imported into the pre-processor

Hypermesh where they have been converted into mid surface models and meshed. For some of the

post-processors the welds were defined in the pre-processor as well. The models generated in

Hypermesh were then imported to Abaqus where loads and boundary conditions corresponding to the

previously performed tests were applied before the model was solved. The Abaqus results file

containing stresses which was imported into the post-processors FEMFAT, Verity and DesignLife,

where fatigue computation on the welds of the analyzed components were performed. Audis in house

developed post-processor SuperWeld has also been evaluated. For this postprocessor, results provided

by Audi has been implemented in the study. Besides accuracy in the results, user friendliness has also

been an important factor when giving a recommendation regarding what method to use for fatigue

prediction of welded designs in the future.

Verity in fe-safe was the post-processor that gave the best accuracy in the results for the test coupons

and FEMFAT for the rear axle housing. Regarding user friendliness FEMFAT obtained the highest

grade. The recommendation made was to use FEMFAT to predict fatigue in welded designs in the

future. This due to the fact that FEMFAT already is implemented at Scania, has a high level of user

friendliness and is considered to predict fatigue with a good enough accuracy.

Abstract [sv]

I detta arbete har förmågan att prediktera utmattning i svetsade konstruktioner hos ett antal postprocessorer utvärderats. Resultat från tidigare utförd provning på tolv provkuponger (fyra geometrier bestående av vardera tre plåttjocklekar) har jämförts med dels resultat erhållna vid beräkning med dagens handboksmetoder, men också de resultat som erhållits genom analyser i de utvärderade postprocessorerna. Utöver provkupongerna har även en bakaxelbrygga analyserats i syfte att undersöka postprocessorernas förmåga att analysera utmattning av svetsar i en verklig komponent.

Arbetet har gått till så att CAD-modeller av de analyserade geometrierna har importerats i preprocessorn Hypermesh där de har konverterats till skalmodeller och meshats. För de postprocessorer som erfordrar att svetsar definieras redan i preprocessorn har så skett. De i Hypermesh genererade modellerna har sedermera lösts i Abaqus där krafter och randvillkor överensstämmande med de tidigare utförda utmattnings proven har applicerats. Lösningsfilen från Abaqus, innehållandes spänningar, har importerats i postprocessorerna FEMFAT, Verity och DesignLife där utmattningsberäkning på komponenternas svetsar har utförts. Utöver dessa postprocessorer har även resultat från Audis egenutvecklade postprocessor SuperWeld inkluderats i utvärderingen. Vid utvärderingen av SuperWeld har analysresultat från Audi erhållits. Utöver noggrannhet i resultat har också användarvänlighet varit en avgörande faktor för vilken metod som skulle komma att rekommenderas för framtida bruk.

Vad beträffar noggrannhet i resultat är Verity den postprocessor som bäst överensstämmer med utförd provning av provkuponger och FEMFAT vad beträffar akaxelbryggan. Gällande användarvänlighet fanns FEMFAT vara den postprocessor som fick högst betyg. Den slutgiltiga rekommendationen blev att i framtiden använda FEMFAT för att utmattningsutvärdera svetsade konstruktioner. Detta då FEMFAT redan finns implementerat på företaget, visar på god användarvänlighet, samt förutser utmattning med vad som bedöms vara tillräcklig noggrannhet.

Place, publisher, year, edition, pages
2015.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-177807OAI: oai:DiVA.org:kth-177807DiVA: diva2:874332
Subject / course
Solid Mechanics
Supervisors
Examiners
Available from: 2015-11-27 Created: 2015-11-26 Last updated: 2015-11-27Bibliographically approved

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