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Corrosion evolution and axial mechanical performance degradation of corroded M24 high-strength bolts
Abstract To investigate the axial static performance degradation of high-strength bolts subjected to long-term atmospheric corrosion in coastal environments, a neutral salt spray accelerated corrosion test was performed on M24 high-strength bolts over a period ranging from 0 to 330 days. Microscopic morphology observations and axial tensile tests were conducted after corrosion. A linear relationship between mass loss rate and corrosion period was established, and the evolution of pit depth and aspect ratio was proposed. Based on the tensile test, the failure modes of corroded high-strength bolts were categorized as bolt breakage and thread shear-out. The critical mass loss rate for the transition between these two modes was found to be 7.05% (corrosion period of 180 days). Equations characterizing the degradation of residual ultimate strength and relative stiffness as a function of mass loss rate were derived. Furthermore, based on average thickness loss and pit loss, a theoretical analysis on ultimate strength degradation was conducted, and its results were compared to the refined numerical simulations. Both methods were found to provide acceptable outcomes, and numerical results demonstrated more precise and conservative. With numerical method, parametric analysis was conducted, involving 5 groups and 222 models, leading to the formulation of a general ultimate bearing capacity assessment equation concerning bolt diameter and thread pitch.
Highlights The evolution of depth and aspect ratio of corrosion pits was clarified. Two failure modes of corroded high-strength bolts, bolt breakage and thread shear-out, and their mechanical deterioration mechanism were revealed. Based on average thickness loss and corrosion pit loss, theoretical degradation formulas for the tensile strength were established. A general evaluation formula for ultimate bearing capacity of corroded high-strength bolt was proposed.
Corrosion evolution and axial mechanical performance degradation of corroded M24 high-strength bolts
Abstract To investigate the axial static performance degradation of high-strength bolts subjected to long-term atmospheric corrosion in coastal environments, a neutral salt spray accelerated corrosion test was performed on M24 high-strength bolts over a period ranging from 0 to 330 days. Microscopic morphology observations and axial tensile tests were conducted after corrosion. A linear relationship between mass loss rate and corrosion period was established, and the evolution of pit depth and aspect ratio was proposed. Based on the tensile test, the failure modes of corroded high-strength bolts were categorized as bolt breakage and thread shear-out. The critical mass loss rate for the transition between these two modes was found to be 7.05% (corrosion period of 180 days). Equations characterizing the degradation of residual ultimate strength and relative stiffness as a function of mass loss rate were derived. Furthermore, based on average thickness loss and pit loss, a theoretical analysis on ultimate strength degradation was conducted, and its results were compared to the refined numerical simulations. Both methods were found to provide acceptable outcomes, and numerical results demonstrated more precise and conservative. With numerical method, parametric analysis was conducted, involving 5 groups and 222 models, leading to the formulation of a general ultimate bearing capacity assessment equation concerning bolt diameter and thread pitch.
Highlights The evolution of depth and aspect ratio of corrosion pits was clarified. Two failure modes of corroded high-strength bolts, bolt breakage and thread shear-out, and their mechanical deterioration mechanism were revealed. Based on average thickness loss and corrosion pit loss, theoretical degradation formulas for the tensile strength were established. A general evaluation formula for ultimate bearing capacity of corroded high-strength bolt was proposed.
Corrosion evolution and axial mechanical performance degradation of corroded M24 high-strength bolts
Guo, Qi (Autor:in) / Zhao, Zizhong (Autor:in) / Lu, Yan (Autor:in) / Xing, Ying (Autor:in) / Zhang, Fengxian (Autor:in) / Yang, Chenqing (Autor:in)
10.12.2023
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch