Longitudinal crack of drill pipe boxjoint is brittle fracture at low stress.
钻杆接头的各种纵向开裂属于低应力脆性断裂。
2
Although it is hard to avoid the sources of fracture, the longitudinal fracture failure on the boxjoint can be prevented if proper measures are taken to prevent further extension of the fracture.
虽然裂纹源很难避免，但如果能够阻止裂纹的扩展，也能够防止钻杆内螺纹接头纵向开裂失效。
3
The connection of the two bodies is built around a sequence of full and empty, with a courtyard and an elevator handled as transparent box, as the centerpiece of the joint.