Split Mandrel Process
The WCI patented split-mandrel process, as introduced in 1983, does not use a disposable sleeve. Instead, it uses an automatically lubricated, longitudinally split mandrel, allowing it to partially collapse to facilitate insertion into the hole. After insertion, a small pilot is pushed through the inner diameter of the mandrel, retaining the splits of the mandrel in a solid position as it is withdrawn back through the hole.
As the mandrel passes through the hole with either the split sleeve or split mandrel process:
- The material preceeding the major diameter of the mandrel is compressed into the surrounding area (applied expansion).
- As the major diameter passes through the hole, the material behind the major diameter partially resumes its original configuration (retained expansion).
This combination creates residual compressive stresses radially around the hole. Generally speaking, the fatigue life extension of the coldworked structure is extended several times, with life extension being reduced as the applied stress approaches the tensile strength of the material.
For a further description of this process, please call our technical sales department, or downloadand Engineering Handout WCI-EH-9202.