Analysis of Causes of Fracture of Titanium Alloy Screw Bolt

Titanium alloy has a high specific strength, a wide working temperature range and excellent corrosion resistance. It is widely used in the aerospace field to make compressor blades, discs, casings and fastening parts; however, it is different from structural steel and stainless steel. Compared with superalloys, it has greater sensitivity to surface damage and defects.

Any negligence in the processing, assembling and use of titanium alloy parts will cause unexpected adverse consequences for the use performance of titanium alloy parts, and even serious fracture accidents may occur.

There have been many fracture accidents in the use of titanium alloy screws, most of which are related to fatigue; therefore, fatigue resistance is one of the most important indicators to measure the reliability of titanium alloy parts. The fatigue resistance of titanium alloys is particularly sensitive to the surface integrity of parts. Many surface factors, such as pollution, scratches, inclusions, corrosion, etc., can induce the initiation and propagation of fatigue cracks, leading to parts fracture.

1. The cracking property of right-angle joints is fatigue cracking, and the reason for cracking is related to the large stress that the joint bears and the thick oxygen-rich α layer in the source area;

2. In view of the large force on the joint, it is recommended to appropriately increase the design margin under the premise of completely removing the oxygen-rich α layer.

3. In order to avoid fatigue fractures caused by wear and tear and destroy the surface integrity of the titanium alloy, the titanium screw manufacturer recommends that the single lug is in vertical contact with the bolt during the assembly process; at the same time, in order to better ensure the surface integrity of the titanium alloy bolt, it is recommended Increase the chamfer at the edge of the single ear hole, and increase the bushing structure at the bolt connection position.
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