Glass Fracture What causes glass to break Force
Glass Fracture
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
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
Radial and Concentric Fractures Force exerted from this side. You can see that the glass is compressed on the side of the force. This is the side opposite of the force. You can see how the glass is stretched. This stretching causes the concentric fractures.
Formation of Fractures Radial fractures occur first on side OPPOSITE the force. Concentric fractures occur second on SAME side as force.
• Look at the diagram on your notes page. Answer the question. Describe what happens to the glass when it breaks.
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 Perpendicular to the edge Parallel to the edge
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
Difference between ridge lines on radial and concentric fractures Ridge lines 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
The 4 R’s • Ridge lines on Radial fractures are at Right angles to the Rear!
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