Fracture Analysis on High Strength Bolts Under Tension

Static eccentric tensile tests at 0°, 5° and 10° inclined angles have been carried out on M24 high strength bolt made from 20Mn2TiB, 16CrMnB and 40Cr steels of 10.9 and 12.9 strength classes. Tensile strength 6_BN as well as the reduction of area ψ_KN of the bolt has been measured. Crack initiation and propagation processes have been observed and fracture morphology has been examined as well. In the light of these experimental results we discuss the required hardenability of a bolt and suggest that the hardenability standard for bolts as specified in IS0898/1-1978 may be left open for further discussion. The bolts made of low carbon martensitic high strength steels have many advantages.