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Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis

Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt...

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Autores principales: Feng, Derong, Dong, Chenxi, Hu, Yunpeng, Wang, Yamei, Ma, Jianhua, Huang, Zhangdong, Wan, Qiang
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9229667/
https://www.ncbi.nlm.nih.gov/pubmed/35744109
http://dx.doi.org/10.3390/ma15124049
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author Feng, Derong
Dong, Chenxi
Hu, Yunpeng
Wang, Yamei
Ma, Jianhua
Huang, Zhangdong
Wan, Qiang
author_facet Feng, Derong
Dong, Chenxi
Hu, Yunpeng
Wang, Yamei
Ma, Jianhua
Huang, Zhangdong
Wan, Qiang
author_sort Feng, Derong
collection PubMed
description Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt was investigated using a tensile test and finite element analysis (FEA). The microstructure of the as-received bolt consisted of a high proportion of α phase, some β phase, and a small amount of α′ phase formed via martensite phase transformation during the rammer process. The experimental force–displacement curves revealed an average yield load of 55.9 kN and a breaking load of 67.65 kN. The corresponding yield strength was calculated to be 0.9 GPa, which was smaller than the standard value of TC4. This was attributed to the preload-induced stress concentration on the thread surface, leading to obvious strain hardening, which can lead to crack initiation. The effect of preload was further confirmed by the fractographies in which the initial crack was observed on the thread surface. The fractographies suggested that hybrid fracture occurred on the tensile loaded bolt. The initial failure was brittle fracture on the thread surface, transforming into ductile fracture in the screw. The results can contribute to understanding the effect of preload on the load carry capacity of high-lock bolts and provide a strategy to design its assembly specification.
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spelling pubmed-92296672022-06-25 Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis Feng, Derong Dong, Chenxi Hu, Yunpeng Wang, Yamei Ma, Jianhua Huang, Zhangdong Wan, Qiang Materials (Basel) Article Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt was investigated using a tensile test and finite element analysis (FEA). The microstructure of the as-received bolt consisted of a high proportion of α phase, some β phase, and a small amount of α′ phase formed via martensite phase transformation during the rammer process. The experimental force–displacement curves revealed an average yield load of 55.9 kN and a breaking load of 67.65 kN. The corresponding yield strength was calculated to be 0.9 GPa, which was smaller than the standard value of TC4. This was attributed to the preload-induced stress concentration on the thread surface, leading to obvious strain hardening, which can lead to crack initiation. The effect of preload was further confirmed by the fractographies in which the initial crack was observed on the thread surface. The fractographies suggested that hybrid fracture occurred on the tensile loaded bolt. The initial failure was brittle fracture on the thread surface, transforming into ductile fracture in the screw. The results can contribute to understanding the effect of preload on the load carry capacity of high-lock bolts and provide a strategy to design its assembly specification. MDPI 2022-06-07 /pmc/articles/PMC9229667/ /pubmed/35744109 http://dx.doi.org/10.3390/ma15124049 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Feng, Derong
Dong, Chenxi
Hu, Yunpeng
Wang, Yamei
Ma, Jianhua
Huang, Zhangdong
Wan, Qiang
Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title_full Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title_fullStr Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title_full_unstemmed Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title_short Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis
title_sort fracture mode transition during assembly of tc4 high-lock bolt under tensile load: a combined experimental study and finite element analysis
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9229667/
https://www.ncbi.nlm.nih.gov/pubmed/35744109
http://dx.doi.org/10.3390/ma15124049
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