United States Department of Transportation
i
Cold Dwell Fatigue of Titanium Alloys: History, Current State, and Aviation Industry Perspective [Supporting Software]
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2024-11-13
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[ZIP-480.02 MB]
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Abstract:This report summarizes the current state of understanding related to cold dwell fatigue (CDF) of titanium alloys, which is a failure mechanism that can lead to uncontained failure of rotating components. Jet engine manufacturers have brought forward their collective field and spin rig experience related to CDF and coupled it with a thorough literature review to offer an aviation industry perspective on this critical safety issue. Numerous factors are known to influence susceptibility to CDF including intrinsic factors like alloy composition, microstructure, and residual stress as well as extrinsic factors like applied stress, dwell time, and temperature. Of particular importance is the presence of microtextured regions (MTRs) present in the material. Definitions and best practices for characterizing this microstructural feature are proposed. The mechanisms of damage accumulation, early crack nucleation, and rapid crack propagation through MTRs during CDF are reviewed along with additional effects of microtexture on material properties including conventional fatigue, sustained load cracking, and stress corrosion cracking. The microstructural condition of finished components depends on the details of billet processing, component forging, and heat treatment practice. The mechanisms of microstructure evolution at each step of the process are summarized and directional guidance is given relative to important factors controlling MTR and alpha colony formation. Laboratory coupon testing, accelerated tests for dwell sensitivity, and aspects of specimen versus component behavior are discussed. Multiple pathways that lead to CDF failure are summarized and strategies to mitigate the risk of CDF are highlighted including aspects of alloy composition, processing/microstructure relationships, design, and nondestructive inspection. This report concludes with identification of directions for further research. Several appendices are provided which summarize major research programs related to CDF and additional methods to characterize MTRs using destructive and nondestructive evaluations methods.
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Content Notes:The software in the zip file supports relates to the report "Cold Dwell Fatigue of Titanium Alloys: History, Current State, and Aviation Industry Perspective,” available at https://doi.org/10.21949/rfzv-6285
Software Description: One version of the application is available for download in a zip format. Once downloaded, the file can be unzipped and placed anywhere on a system that is Python capable, or it can be copied onto a flash drive or other media that can be used on a system that is Python capable. One file for the application installation is available for download: 1. PW24-Ti-Microtexture-Workflow-v2.0.1-Pubicly-Released
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