Common causes of failures in the industrial bolt and nut connections

Bolt and nut connections are widely used in various industries such as automotive, aircraft, and construction, etc. as a reliable method of connecting parts. In fact, this method has advantages such as ease of installation, ability to separate, and reuse compared to other connection methods like welding, gluing, or riveting. Industrial bolts and nuts are made using different technologies, including hot forging, cold forging, and machining, each of which has its own advantages and limitations and should be selected according to the connection application and working conditions. In addition, manufacturing processes directly affect the mechanical properties and performance of joints, making it essential to understand their implications for potential weaknesses and failure modes. Because the quality and performance of these connections significantly affect the strength, stability, and lifespan of the main structure, and this issue becomes more important as the system gets bigger. The main purpose of this article is to investigate common failures in bolt and nut connections, identify their causes, and provide practical solutions. For this purpose, the importance of the strength of this type of connection was discussed in real failures, which, in addition to causing financial and human losses, have also been recorded in human memories. Next, the most important causes of failures related to the installation of the connection, including the value of preload, improper torque application, and lack of a locking system were investigated. The mentioned parameters were introduced as controllable factors and a suitable solution was presented for their optimal settings with the aim of the best connection efficiency. Finally, two failure mechanisms, i.e., corrosion and fatigue, in bolt and nut connections were discussed. The aforementioned mechanisms were named as autonomous factors. Therefore, the methods provided in the industry are meant to postpone such failures and not to completely prevent them. © 2025 Elsevier B.V., All rights reserved.