Why we use v-notch in charpy impact test ?

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SUMMARY

The Charpy impact test utilizes a v-notch to assess the ductility and toughness of materials, particularly heat-treated metals. This notch serves as the initiation point for failure, allowing for predictable and repeatable fracture patterns when subjected to stress. The test is superior to simple hardness tests, which do not accurately reflect structural integrity as they only evaluate surface properties. The v-notch ensures that the hammer impacts the sample at its weakest point, providing reliable results for material evaluation.

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  • Understanding of Charpy impact testing methodology
  • Familiarity with material ductility and toughness concepts
  • Knowledge of stress crack propagation mechanics
  • Experience with heat treatment processes in metallurgy
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  • Research the ASTM E23 standard for Charpy impact testing
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Materials scientists, metallurgists, and engineers involved in quality control and material selection for structural applications will benefit from this discussion.

phydis
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Why we use v-notch in charpy impact test ?
 
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It's a ductility [or toughness] test. A simple hardness test is not representative of structural integrity as it only tests the surface. For heat treated metals, a v-notch test is more representative.
 
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He asked "Why"..
 
The notch is the start of the failure. Stress crack propagation results from the notch being cut into the sample, and the hammer hitting the sample right at the notch.
 
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Predictable, repeatable fractures happen at the consistently weakest point on the bar.
 
For a good demonstration see:
 
russ_watters said:
Predictable, repeatable fractures happen at the consistently weakest point on the bar.

That too, good point Russ.
 

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