What Does Crack Tip Mean?
Crack tip, as the name implies, is the singular point at which the crack propagates depending on its material. If the material is brittle, the crack tip is sharp and is more susceptible to crack propagation than a ductile material whose crack tip is blunt making it better resistant to crack propagation. Sewer and water pipelines that are buried under the earth are susceptible to various loads and soil conditions that can sometimes lead to corrosion and fracture or cracks in pipes.
These pipes should be rehabilitated in order to prevent crack propagation and eventual failure of the pipe. Cured-in-place pipe (CIPP), sliplining and mechanical spot repair are some of the trenchless methods that can be used to rehabilitate these pipes.
Trenchlesspedia Explains Crack Tip
In ductile pipe materials, the maximum stress lies a little further from the tip of the crack. The crack tip stresses cause plastic deformation leading to energy consumption at the crack tip. This results in blunting of the crack, which means lesser energy is available for crack propagation and therefore increased fracture resistance.
On the other hand, in brittle materials the maximum crack opening stress is present at the crack tip that breaks bonds at the crack tip leading to crack propagation. At the region of highest stress, there is a nucleation of voids and the region between the crack tip and the void behaves like a specimen under tension.
As a result micro-voids are formed in this region that coalesce and extend the crack.