Wallner Lines and Hackle Marks
Definition
Wavy curved lines (Wallner) and step-like ridges (hackle) on a fracture surface that record the direction the crack front was moving. Used to trace cracks back to the origin.
- Wallner lines
- Wavy curved lines from stress-wave interaction
- Hackle marks
- Step-like ridges on the fracture surface
- Shared function
- Record direction of crack propagation
- Application
- Trace fractures back to their origin
Common questions
What is the practical difference between Wallner lines and hackle marks on a broken surface?+
Wallner lines are smooth curved arcs left by stress waves crossing the advancing crack, while hackle marks are small ridge-like steps formed as the crack front twists through the material, and both are read together because they can confirm each other's indicated direction.
Are these markings unique to glass?+
No. Similar fractographic features appear on other brittle materials such as plastics and ceramics, so the same reading principles used for window glass fracture analysis extend to other brittle evidence when a crack's direction of travel needs to be reconstructed.
Related terms
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