Wallner Lines
Definition
Rib-shaped features on a glass fracture surface produced by the interaction of the propagating crack front with reflected elastic stress waves; their curvature maps the crack-front shape and their convergence point locates the crack origin.
- Material
- Glass fracture surfaces
- Appearance
- Rib-shaped surface features
- Cause
- Crack front interacting with reflected elastic stress waves
- Forensic use
- Curvature and convergence point locate the crack origin
Common questions
How do examiners use Wallner lines to find where a glass fracture started?+
The lines curve away from the direction the crack was traveling, so tracing several Wallner lines back to the point where their curvature converges pinpoints the origin of that particular fracture, which helps reconstruct impact sequence when a pane has multiple fractures.
Can Wallner lines alone tell an examiner which side of the glass the force came from?+
Not by themselves. Direction of force typically relies on the radial and concentric fracture pattern together with rib marks and conchoidal features on the edge, with Wallner lines contributing origin location rather than force-side determination on their own.
Related terms
- 3R Rule
- The fracture-analysis mnemonic: Radial cracks form at Right angles to the Reverse (far, non-impact) side of the glass. Applied to the fracture...
- Bayesian Likelihood Ratio (LR)
- The statistical framework that evaluates glass-fragment evidence by comparing the probability of the observed fragment population assuming contact with the source glass...
- Concentric Cracks
- Approximately circular cracks centred on the impact point; they form second, on the near (impact) face, and terminate when they encounter pre-existing...
- Cone Fracture
- A conical crack produced by concentrated contact loading (Hertzian contact), opening on the far (exit) face of the glass; the cone geometry...
- Entrance Bevelling
- The widening of a bullet-penetration hole toward the exit side, analogous to bevelling in bone wounds; the narrower opening is on the...
- Fracture Termination Rule
- The principle that a propagating crack terminates when it encounters a free surface created by a pre-existing crack; at any T-junction, the...
- Hackle Marks
- Ridges on the fracture surface oriented perpendicular to the crack propagation direction; they appear in the mist and hackle zones at higher...
- Mirror Region
- The smooth, flat area of a fracture surface nearest the crack origin, where the crack was propagating slowly and stably before accelerating...
- Mist Region
- The transitional fracture surface zone between the smooth mirror region and the rough hackle region, where the crack begins to bifurcate at...
- Radial Cracks
- Cracks extending outward from an impact point in approximately straight lines, like spokes on a wheel; they form first, on the rear...
- Secondary Transfer
- The movement of a glass fragment from a primary surface (which contacted the broken glass) to a secondary surface (which contacted the...