Bolt hole crack - Rail defects

Bolt hole crack - Rail defects

Figure 1: Bolt hole crack originating in lower quadrant with significant progression.

Defect name: Bolt hole crack
Record No.: 2689
Type of defect (Internal/Surface): Surface
Defect classification: Rail defects
Steel name: Steel
Steel composition in weight %: No data.
Note: Miscellaneous defects
Description – Bolt hole crack means a crack across the web, originating from a bolt hole, and progressing on a path either inclined upward toward the rail head or inclined downward toward the base. Fully developed bolt hole cracks may continue horizontally along the head/web or base/web fillet, or they may progress into and through the head or base to separate a piece of the rail end from the rail. Multiple cracks occurring in one rail end are considered to be a single defect. However, bolt hole cracks occurring in adjacent rail ends within the same joint must be reported as separate defects.

A bolt hole crack is normally the result of stresses associated with pumping or swinging joints, improper drilling, excessively worn joint bars, or abnormal rail end impacts from rolling stock. Unchamferred holes that result a drilling burr on the edge of the hole left by the drilling operation can result in defect development. Growth is normally erratic and the rail can frequently rupture from a very small defect when the rail end is subjected to unusual stresses.
Reference: Not shown in this demonstration version.