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Characterization of Ultra-High Fracture Toughness Steel: Fracture Toughness and Fatigue Propagation Testing
Thaman, Nathaniel Douglas
Thaman, Nathaniel Douglas
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Abstract
The structural integrity of highway bridges heavily relies on material selection, with steel being preferred for its strength-to-weight ratio. However, steel is susceptible to fatigue cracks caused by cyclic loading, which can potentially lead to catastrophic failure by fracture. Federal regulations mandate stringent biennial inspections, particularly for non-redundant steel tension members (NSTM), aiming to detect fatigue cracks early due to historical concerns about steel's fracture susceptibility. Current material-focused practices initially intended to alleviate inspection burdens incur significant costs without substantial inspection reduction. In this study, three distinct Ultra-High Toughness (UHT) steels were identified for evaluation. The research began with evaluating the effect of interpass temperature on weld metal behavior, followed by initial material characterization. Charpy V-Notch (CVN) impact tests were conducted on the base metal, weld metal, and heat-affected zone of each steel to assess impact toughness. The focus of this study, one selected UHT steel underwent full material characterization, including fracture toughness, KJc, testing for reference temperature, To, characterization, and fatigue crack growth rate testing. This investigation aims to determine if UHT may be used to reduce inspection intervals and/or level of rigor for components currently classified as NSTM.
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Date
2024-05-31
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University of Kansas
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Keywords
Civil engineering, Fatigue, Fracture