Charpy Impact/Chevron Notch 1

[subhas123]

Can someone provide Battle Hypothesis/Formula for acceptance criteria for Charpy Impact.

How is Chevron Notch Made?

 

[Maui]

I don't know what you mean by a Battle Hypothesis, but I can tell you how the V-notch is typically made in a Charpy impact specimen. The notch is usually produced by a broaching operation. It's a simple technique that works quite well, and it takes at most a minute to finish the notch in a tool steel or high speed steel specimen. I've done it myself - there's nothing to it. All you need is the tool set-up, and a specimen that's been ground to size, and you're good to go.

The acceptance criteria for the test depends upon the specification that you're working to. What's the spec?


Maui

 

[kenvlach]

Not sure what you mean by acceptance criteria. Perhaps a minimum energy absorption requirement at a specified testing temperature, e.g., 15 ft-lbs at -20^oC.

The geometry of Charpy test specimens is given in
ASTM E23-02a Standard Test Methods for Notched Bar Impact Testing of Metallic Materials

http://www.astm.org/DATABASE.CART/REDLINE_PAGES/E23.htm

 

[sayee1]

E1304-97(2002) Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials.

1.1 This test method covers the determination of plane-strain (chevron-notch) fracture toughnesses, Iv or IvM, of metallic materials. Fracture toughness by this method is relative to a slowly advancing steady state crack initiated at a chevron-shaped notch, and propagating in a chevron-shaped ligament (Fig. 1). Some metallic materials, when tested by this method, exhibit a sporadic crack growth in which the crack front remains nearly stationary until a critical load is reached. The crack then becomes unstable and suddenly advances at high speed to the next arrest point. For these materials, this test method covers the determination of the plane-strain fracture toughness, Ivj or IvM, relative to the crack at the points of instability.

Note 1-One difference between this test method and Test Method E399 (which measures Ic) is that Test Method E399 centers attention on the start of crack extension from a fatigue precrack. This test method makes use of either a steady state slowly propagating crack, or a crack at the initiation of a crack jump. Although both methods are based on the principles of linear elastic fracture mechanics, this difference, plus other differences in test procedure, may cause the values from this test method to be larger than Ic values in some materials. Therefore, toughness values determined by this test method cannot be used interchangeably with Ic.
1.2 This test method uses either chevron-notched rod specimens of circular cross section, or chevron-notched bar specimens of square or rectangular cross section (Figs. 1-3). The terms "short rod" and "short bar" are used commonly for these types of chevron-notched specimens.

1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Maui/Kenvlach
Is chevron notch same as Charpy V Notch, I am not sure but I think it is not!! Please clarify!

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
The whole of science is nothing more than a refinement of everyday thinking!!!

 

[kenvlach]

The E1304 test method is obviously different than the Charpy test of E23: slow force vs. fast (impact) application, respectively.

I don't have the E1304 spec., but would deduce that the E1304 specimen geometry also differs, even chevron-notched bar specimens of square cross-section, simply because this spec. doesn't reference E23. In comparison, E812-91(1997) Standard Test Method for Crack Strength of Slow-Bend Precracked Charpy Specimens of High-Strength Metallic Materials references E23.