التفاصيل البيبلوغرافية
| العنوان: |
Towards Understanding the Effects of Current Input on Fatigue Mechanisms in Resistance Spot Welding of Advanced High Strength Steels |
| المؤلفون: |
Cleek, Conner |
| المساهمون: |
Jordon, Brian, Allison, Paul, Bewer, Luke |
| بيانات النشر: |
University of Alabama Libraries |
| سنة النشر: |
2020 |
| مصطلحات موضوعية: |
Fatigue, Liquid Metal Embrittlement, Resistance Spot Welding |
| الوصف: |
Electronic Thesis or Dissertation ; In this study, the relationship of welding parameters to fatigue mechanisms is examined in spot welding of advanced high strength steels. Lightweighting efforts in the automotive industry are part of a push for greater fuel economy and improved consumer safety. TBF-1180 is an advanced high strength steel being developed for use in structurally critical components, however its fatigue behavior is not well understood. Electro galvanized TBF-1180 possesses corrosion resistant properties, however the additional zinc layer allows for the possibility of zinc-penetrative liquid metal embrittlement (LME) to occur during resistance spot welding (RSW). Additionally, variations in weld input and correspondingly heat input can affect the performance of welds due to microstructural changes that occur. In this study, the effect of LME and changes in microstructure were assessed in separate experiments for their fatigue impact in TBF-1180. Welds were fabricated in a traditional lap shear geometry in order to investigate the effects of LME, while an hourglass shaped cap geometry was used for welds with microstructural variation. Fatigue testing revealed that for lap-shear coupons containing LME cracks, no deleterious effect was observed. Cap geometry specimens were assessed for performance in a control and a high-current low-time condition, and a significant fatigue knockdown factor was found. Post-mortem fractography on both specimen geometries revealed that fatigue cracks initiated at the inner faying surface, regardless of the presence of LME. Finite element analysis confirmed that the LME cracks in the lap shear weld experience compressive stresses during loading, contributing to the lack of fatigue impact. Experimental conditions used for the cap geometry had lower heat input, which can result in less retained metastable austenite after welding, leading to reduced crack growth resistance. To tests the hypothesis that less retained metastable austenite after welding can cause a reduction ... |
| نوع الوثيقة: |
thesis |
| اللغة: |
English |
| Relation: |
The University of Alabama Electronic Theses and Dissertations; The University of Alabama Libraries Digital Collections; https://ir.ua.edu/handle/123456789/8401 |
| الاتاحة: |
https://ir.ua.edu/handle/123456789/8401 |
| Rights: |
All rights reserved by the author unless otherwise indicated. |
| رقم الانضمام: |
edsbas.1C955798 |
| قاعدة البيانات: |
BASE |