The effect of bolt length in the fatigue strength of M24×3 bolt studs

• We evaluated the effect of M24×3 class 8.8 bolt length on the fatigue behavior of bolt studs.
• Two different bolt lengths were evaluated. A slim spread sleeve was used for the longer bolts.
• The fatigue strength increases with increasing bolt stud length.

In this study we evaluated the effect of bolt length on the fatigue behavior of joints with bolt studs used in the flange/housing assembly of a gas compressor for polyethylene polymerization. The bolt stud used is the M24×3 class 8.8. Two different bolt lengths were evaluated. A slim spread sleeve was used in the case of the longer bolts. The torque control was used to achieve the tightening preload. However, the preload and cyclic strains were monitored. The fatigue strength increases with increasing bolt stud length, even with the use of the slim spread sleeve. The study showed a difference between the theoretical and the experimental load factor for the case of short joints.