The fatigue failure occurs because even though the overall applied stress may remain below the yield strength, at a local length scale, the stress intensity exceeds the tensile strength of the titanium. Finally, a sudden fracture of the titanium material occurs when the remaining cross-section of the material is too small to surport the applied load. Next, the crack gradually propagates as the load continues to cycle. Surface defects such as pits or scratches may accelerate the nucleation. The microcracks are normally located at or near the surface, where the stress is at a maximum. First, a tiny crack initiates or nucleates often at a time well after cyclic loading begins. The fatigue failure of titanium and its alloys typically occur in three stages. The Mechanism of Titanium’s Fatigue FailureĪ longitudinal fatigue crack on the internal surface of a titanium grade 2 welded pipe It initiates tiny cracks which propagate and may cause catastrophic rupture finally.

A fatigue loading is the fluctuating or repetitive stresses and strains which may cause localized permanent structural change at some point or points. During these applications, titanium structures are often exposed to fatigue loading. Thus, titanium and its alloys find extensive use in chemical and petrochemical industry, power engineering, biomedical implants, and aviation & aerospace industry, etc. Titanium materials can be used for structural applications due to outstanding corrosion resistance to various chlorides and oxidizing media, exceptional biocompatibility, and its high strength-to-weight ratio which improves the structural efficiency greatly. The titanium material refers to commercially pure (unalloyed) titanium or titanium alloys used for structural purpose. The fatigue of titanium refers to the lowering of strength or failure of a titanium material due to repetitive/ cyclic stress which may be above or below the yield strength.

How to find fatigue strength