Why we use v-notch in charpy impact test ?

In summary, the v-notch is used in Charpy impact tests because it is a more accurate representation of ductility and toughness compared to simple hardness tests. The notch acts as the starting point of failure and allows for predictable and repeatable fractures to occur at the consistently weakest point on the bar.
  • #1
phydis
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Why we use v-notch in charpy impact test ?
 
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  • #2
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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  • #3
He asked "Why"..
 
  • #4
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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  • #5
Predictable, repeatable fractures happen at the consistently weakest point on the bar.
 
  • #6
For a good demonstration see:
 
  • #7
russ_watters said:
Predictable, repeatable fractures happen at the consistently weakest point on the bar.

That too, good point Russ.
 

FAQ: Why we use v-notch in charpy impact test ?

1. Why is the v-notch used in the Charpy impact test?

The v-notch is used in the Charpy impact test because it creates a localized stress concentration in the material being tested. This allows for a more precise measurement of the material's impact toughness.

2. What is the purpose of the v-notch angle in the Charpy impact test?

The v-notch angle is carefully chosen to ensure that the material being tested fails within the notch during the impact test. This ensures that the impact energy is fully absorbed by the material at the point of failure.

3. How does the v-notch affect the results of the Charpy impact test?

The v-notch has a significant impact on the results of the Charpy impact test. It determines the stress concentration and the location of failure in the material, which ultimately affects the measured impact energy.

4. Is the v-notch necessary for all materials in the Charpy impact test?

No, the v-notch is not necessary for all materials in the Charpy impact test. It is typically only used for brittle materials, such as metals, which are prone to sudden and catastrophic failure. For more ductile materials, a different type of notch or no notch at all may be used.

5. Can the v-notch angle be changed in the Charpy impact test?

Yes, the v-notch angle can be changed in the Charpy impact test. However, it is important to maintain consistency in the angle used for testing in order to accurately compare results between different materials. Any changes in the v-notch angle should be carefully documented and taken into consideration when analyzing the impact test results.

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