On the other hand, with brittle fracture, cracks spread very rapidly with little or no plastic deformation. The cracks that propagate in a brittle material will continue to grow once initiated. Crack propagation is also categorized by the crack characteristics at the microscopic level. A crack that passes through the grains within the material is undergoing transgranular fracture. A crack that propagates along the grain boundaries is termed an intergranular fracture. Typically, the bonds between material grains are stronger at room temperature than the material itself, so transgranular fracture is more likely to occur. When temperatures increase enough to weaken the grain bonds, intergranular fracture is the more common fracture mode. Testing
Fracture in materials is studied and quantified in multiple ways.
This is done by taking the test piece with its fabricated notch of length 
  
    
      
        
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   and sharpening this notch to better emulate a crack tip found in real-world materials. Cyclical prestressing the sample can then induce a fatigue crack which extends the crack from the fabricated notch length of 
  
    
      
        
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    to 
  
    
      
        
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  .