Fracture Analysis on Pin Thread Joint of Central Tube of RTTS Packer

The fracture reasons for the pin thread joint of central tube of RTTS packer were analyzed through macroscopic examination, chemical composition analysis, mechanical property testing, metallographic examination, fracture analysis and finite element calculation. The results showed that failure form was overload breakage in the root of the first complete buckle of pin thread. It becaused the stress value in the root of pin thread had already at or near the material yield strength when the high-pressure perforating operation had on (and at the moment of low pressure after the explosion of the bullet gun), which resulted in plastic yield damage.