Finding broken studs or bolts is one of the most unwanted scenarios we can imagine, especially when working on automobiles and other mechanical equipment. There are many people who have tried to develop different methods to remove any broken bolt from their properties ranging from the cylindrical protector of the carburetor of your motorcycle to the metal plates of your garage doors. Methods like drilling and welding are now available on the internet in response to the increasing cases of broken bolts.
The real question is: “What causes a broken bolt?“
1. Overexertion
The word “overexertion” is already enough to understand this cause; however, there is more than that. There are 3 types of load experienced by the bolt: preload, service load, and tensile load. Preload refers to the internal stress that keeps the two joint materials intact, while service load refers to the external factors that cause the joint materials to exert separate stresses. Tensile load, on the other hand, refers to a static stress that pulls both ends of the bolt separately. Regular tightening and turning of the nut will increase the tensile load on the bolt. If the tensile load exceeds the tensile strength, then the bolt will sustain permanent damage, causing it to break. It is necessary to determine the appropriate amount of torque applicable to specific types of bolts to avoid overstressing.
2. Fatigue
About 85% of all broken bolt boxes are due to fatigue. All bolts, especially security bolts, were designed to fail in due time. In other words, its efficiency is not for life. This can be explained by going back to preload and service load. Each bolt or stud undergoes a cycle of preload and service load. Fatigue is then determined by how many load cycles a bolt can withstand. This is why most equipment manuals suggest replacing bolts after one to two years, especially when the bolt is frequently exposed to stress factors such as those from forming equipment and stamping machines.
3. Corrosion
Corrosion, by contrast, refers to effects caused by external elements, such as chemicals excreted from nearby parts or exposure to incompatible metal components. For example, bolts near the vehicle’s engine can acquire oil leaks and other engine fluids. These chemicals will cause the bolt to deteriorate over time; that is chemical corrosion.
Another type of corrosion is when the bolt was used to join incompatible metal components. Due to the incompatibility, the bolt deteriorates and can also break. This is what we call galvanic corrosion. Although corrosion is one of the main causes of broken bolts, it is still a rare case and can only be found in advanced metallurgical industries such as mechanical engineering, mining, and construction.
Among these three, including fatigue, most cases of broken bolts followed by overstressing. Corrosion varies with situations and rarely happens. Keeping these factors in mind will help you maintain the efficiency of your equipment by preventing bolt breakage.