A catastrophic loss of relative motion between contacting components caused by the formation of strong adhesive bonds, local welding, or extreme plastic deformation at the contact interface such that applied driving torque cannot produce sliding without causing severe damage.

Principle

Seizure occurs when contact conditions produce bonds or geometry changes whose shear or breakaway strength exceeds the available driving or reversing torque; once established, motion either requires destructive forces to resume or remains permanently impeded until the interface is altered.

Demonstration

Illustrative scenario: A plain journal bearing operating into lubricant starvation allows asperity welding between shaft and bearing. As load and temperature rise, welded regions grow until the shaft cannot rotate; attempts to restart impose high stresses that fracture bearing material and score the shaft, producing a seized assembly.

Misapplication

Calling any sudden jam a seizure: a mechanical jam from trapped debris or a broken key is operationally similar but different in mechanism and repair—seizure implies tribological adhesion or plastic welding at the contact interface rather than foreign‑object interference.

Consequence

Immediate stoppage of motion, potential catastrophic component damage (scoring, fracture, spalling), loss of system capability, and need for disassembly and repair or replacement; in some systems seizure can cascade to secondary failures (overloads, overheating).

Reversal

If the adhesive bonds are microscopic and contact temperatures fall before significant plastic deformation, partial reversion or relubrication can restore motion; conversely, at elevated temperatures other metallurgical changes (diffusion bonding) may produce irreversible junctions distinct from room‑temperature seizure.

Boundary

Clearly within: shaft‑bearing welding producing immobility despite driving torque. Boundary case: a temporarily stalled motor that restarts once a transient load clears (not true seizure). Clearly outside: failure due to mechanical interference (jammed foreign object) or electrical lock where motion is prevented by control system or power loss rather than surface adhesion.

Semantic Tension

Systems require friction to transmit torque but excessive friction or adhesion causes seizure; designers must balance frictional interfaces for function against the risk that inadequate lubrication or high contact stress will produce irreversible locking.

Synthesis

Seizure is the terminal tribological failure where adhesion or extreme plastic change transforms a sliding interface into a solid junction; preventing it requires keeping contacts within film‑lubricated, thermally managed, and material‑compatible regimes or designing sacrificial elements that fail before seizure occurs.