Safety evaluation method for preventing delayed fracture of high strength bolt below M100mm

Abstract

The invention relates to a safety evaluation method for preventing delayed fracture of a high strength bolt below M100mm, which comprises the steps of: finding out a relationship between the root arc radius r of threads of the high strength bolt and the thread depth t of the high strength bolt by a finite element simulation design; determining a stress concentration factor Kt of the high strength bolt by establishing the relationship; introducing Kt into a formula to obtain a stress strength factor of the high strength bolt; and finally obtaining K1c or K1scc>=nK1 and K1c or K1scc<nK1 according to decision principle of linear elastic fracture mechanics K1c or K1scc>=K1. The safety evaluation method is theoretic. Because the finite element simulation design is adopted, the method has the characteristics of scientificity, systematicness, simplicity and practicality, and is more economical than test of mechanical performances, such as strength and toughness of the high strength bolt.

Description

technical field The invention belongs to the technical field of bolt safety assessment, in particular to a safety assessment method for preventing delayed fracture of high-strength bolts below M100mm for bolts of grade 12.9 or above used in atmosphere, marine atmosphere and seawater environment. Background technique For bolts of grade 12.9 and above used in the atmosphere, marine atmosphere and seawater environment, due to the deterioration of the use environment, the problem of delayed fracture of the bolts is very prominent. Delayed fracture refers to a phenomenon in which a bolt under static stress suddenly undergoes brittle failure of its material structure after a certain period of use. This phenomenon is a kind of environmental embrittlement caused by material-environment-stress interaction, and it is a form of hydrogen-induced material deterioration (or hydrogen damage or hydrogen embrittlement). When the tensile strength of the bolt is greater than 1200MPa, its sens...

AI Technical Summary

Problems solved by technology

① Most of them adopt strength check, and design high-strength bolts by increasing the strength safety factor. However, due to the problem of delayed fracture, it is not suitable for high-strength bolts of grade 12.9 and above;

However for K I value, K I The value is difficult to determine, so far no theoretical solution has been found

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