1. Glass Fracture

2. What causes glass to break?
Force – such as a bullet, vehicle or rock
Depending on the type of glass, you will see a point of impact and cracks in the glass radiating from the point of impact; ridge lines will help determine the side of impact
Heat
Varies because the fractures are wave-shaped and irregular; no ridge lines

3. Glass definitions to know
Side of compression – Compression means squeezed; this is the side the force is exerted on
Side of tension – tension is where something is stretched; this is the side of glass opposite the force
Radial fractures – lines that radiate from the point of impact
Concentric fractures – broken circles formed around the point of impact

4. Radial and Concentric Fractures
This is the side opposite of the force. You can see how the glass is stretched. This stretching causes the concentric fractures.
Force exerted from this side. You can see that the glass is compressed on the side of the force.

5. Formation of Fractures
Radial fractures occur first on side OPPOSITE the force.
Concentric fractures occur second on SAME side as force.

6. Look at the diagram on your notes page. Answer the question
Look at the diagram on your notes page. Answer the question. Describe what happens to the glass when it breaks.

7. What are ridge lines?
On the edges of broken glass, curved lines can be seen. These are called ridge lines.
On one side the ridge lines are perpendicular; on the other side, the ridge lines are parallel to the edge
Parallel to the edge
Perpendicular to the edge

8. Ridge lines and point of impact
Ridge lines can help determine the point of impact
Different depending on if you are looking at glass broken on a radial fracture or a glass fracture
Ridge lines can predict point of impact reliably when using glass broken at a radial fracture versus concentric fracture

9. Difference between ridge lines on radial and concentric fractures
In radial fractures, you’ll see the perpendicular lines on the side opposite the force or point of impact
In concentric fractures, you’ll see the perpendicular lines on the same side of the force or point of impact
Ridge lines

10. The 4R’s
Ridge lines on Radial fractures are at Right angles to the Rear!