Charpy Impact Test Conversion

• As per ASME BPVC VIII-1, when you use a reduced thickness specimen, with a certain condition and dimensions of (10 mm x 6.7 mm) specimens may be used in lieu of full size standard specimens (10 mm x 10 mm). However, when this option is used, the acceptance value shall be 75 ft/b_f (100 J) min.

• But if you used a specimen with thickness 5 mm, I haven't a reply except my recommendation to read carefully the full Para. UG-84 of ASME PVBC, Section VIII, Division 1. The following is some important notes indicates where and when you can use a reduced thickness of specimen for impact test:

UG-84(c) Test Specimens

UG-84(c)(1) Each set of impact test specimens shall consist of three specimens.

UG-84(c)(2) The impact test specimens shall be of the Charpy V-notch type and shall conform in all respects to Fig. UG-84. The standard (10 mm x 10 mm) specimens, when obtainable, shall be used for nominal thicknesses of 7⁄16 in. (11 mm) or greater, except as otherwise permitted in (c)(2)(a) below.

(a) For materials that normally have absorbed energy in excess of 180 ft-lbf (240 J) when tested using full size (10 mm x 10 mm) specimens at the specified testing temperature, subsize (10 mm x 6.7 mm) specimens may be used in lieu of full size specimens. However, when this option is used, the acceptance value shall be 75 ft/b_f(100 J) minimum for each specimen and the lateral expansion in mils (mm) shall be reported.

UG-84(c)(3) For material from which full size (10 mm x 10 mm) specimens cannot be obtained, either due to the material shape or thickness, the specimens shall be either the largest possible standard subsize specimens obtainable or specimens of full material nominal thickness which may be machined to remove surface irregularities. [The test temperature criteria of (c)(5)(b) below shall apply for Table UCS-23 materials having a specified minimum tensile strength less than 95,000 psi (655 MPa) when the width along the notch is less than 80% of the material nominal thickness.] Alternatively, such material may be reduced in thickness to produce the largest possible Charpy subsize specimen. Toughness tests are not required where the maximum obtainable Charpy specimen has a width along the notch less than 0.099 in. (2.5 mm).

.........................................

For a conversion table, see an article by H.Mc Nicol (?) in the 1960 "Welding Journal". He did the tests on mild steel for 1/4 and 1/2 thickness of the standard Charpy samples.

Thanks for the advice. I try to use it.