Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve

Bolts are subject to complex loads and prone to loosening failure in transverse random service environments. To establish a loosening life evaluation method applicable to different types of bolts, numerous bolt clamping-force recession curves were obtained by bolt-loosening tests, and the relationsh...

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Main Authors: Guangwu Yang, Han Zhao, Long Yang, Wenyang Shao, Shoune Xiao, Tao Zhu, Yuqing Yuan
Format: Article
Language:English
Published: Nature Portfolio 2025-07-01
Series:Scientific Reports
Subjects:
Online Access:https://doi.org/10.1038/s41598-025-02936-6
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author Guangwu Yang
Han Zhao
Long Yang
Wenyang Shao
Shoune Xiao
Tao Zhu
Yuqing Yuan
author_facet Guangwu Yang
Han Zhao
Long Yang
Wenyang Shao
Shoune Xiao
Tao Zhu
Yuqing Yuan
author_sort Guangwu Yang
collection DOAJ
description Bolts are subject to complex loads and prone to loosening failure in transverse random service environments. To establish a loosening life evaluation method applicable to different types of bolts, numerous bolt clamping-force recession curves were obtained by bolt-loosening tests, and the relationship between the transverse displacement external load and loosening life (D–N curve) was established. Subsequently, an equivalent model of the bolt external load and screw load was established based on Castigliano’s theorem, and an equivalent model of the screw load and screw-tooth root stress was established based on the deformation coordination equation of elastic mechanics. Based on the above bolt-load equivalent models, the screw-tooth root stresses were equivalently characterized by the transverse displacement of the bolted connection, and then the screw-tooth root equivalent stress–loosening life curve (S u –N curve) was established to normalize the D–N curves with different bolt diameters. Finally, a bolt-loosening bench test of an antenna bracket under transverse random vibration was performed, and the loosening life of the bolts was evaluated using the S u –N curve. The maximum relative error between the test and theoretically predicted lives was only 6.26%, which verified the accuracy of the bolt-loosening life evaluation method based on the bolt-load equivalence and provided a certain reference for the bolt-loosening life evaluation and anti-loosening design in a random vibration environment.
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spelling doaj-art-0bab0c7c07fd4615b07f3acc5acb55f72025-08-20T03:03:36ZengNature PortfolioScientific Reports2045-23222025-07-0115111410.1038/s41598-025-02936-6Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curveGuangwu Yang0Han Zhao1Long Yang2Wenyang Shao3Shoune Xiao4Tao Zhu5Yuqing Yuan6State Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong UniversityState Key Laboratory of High-speed Maglev Transportation Technology, CRRC Qingdao Sifang Co., Ltd.Bolts are subject to complex loads and prone to loosening failure in transverse random service environments. To establish a loosening life evaluation method applicable to different types of bolts, numerous bolt clamping-force recession curves were obtained by bolt-loosening tests, and the relationship between the transverse displacement external load and loosening life (D–N curve) was established. Subsequently, an equivalent model of the bolt external load and screw load was established based on Castigliano’s theorem, and an equivalent model of the screw load and screw-tooth root stress was established based on the deformation coordination equation of elastic mechanics. Based on the above bolt-load equivalent models, the screw-tooth root stresses were equivalently characterized by the transverse displacement of the bolted connection, and then the screw-tooth root equivalent stress–loosening life curve (S u –N curve) was established to normalize the D–N curves with different bolt diameters. Finally, a bolt-loosening bench test of an antenna bracket under transverse random vibration was performed, and the loosening life of the bolts was evaluated using the S u –N curve. The maximum relative error between the test and theoretically predicted lives was only 6.26%, which verified the accuracy of the bolt-loosening life evaluation method based on the bolt-load equivalence and provided a certain reference for the bolt-loosening life evaluation and anti-loosening design in a random vibration environment.https://doi.org/10.1038/s41598-025-02936-6Bolt-loosening lifeEquivalent stress–loosening life curveTransverse random vibrationLoosening life evaluationBolt-load equivalence
spellingShingle Guangwu Yang
Han Zhao
Long Yang
Wenyang Shao
Shoune Xiao
Tao Zhu
Yuqing Yuan
Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
Scientific Reports
Bolt-loosening life
Equivalent stress–loosening life curve
Transverse random vibration
Loosening life evaluation
Bolt-load equivalence
title Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
title_full Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
title_fullStr Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
title_full_unstemmed Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
title_short Bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
title_sort bolt loosening evaluation method based on normalized screw root equivalent stress and loosening life curve
topic Bolt-loosening life
Equivalent stress–loosening life curve
Transverse random vibration
Loosening life evaluation
Bolt-load equivalence
url https://doi.org/10.1038/s41598-025-02936-6
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