Page 97 - Quick Guide to Welding and Weld Inspection by S.E. Hughes, Clifford Matthews

Non-destructive and Destructive Testing

Figure 6.10 A typical Charpy curve

Fig. 6.10) and determine the ductile-to-brittle transition
temperature. The ductile-to-brittle transition temperature is
the temperature at which the test specimen will start to
become more brittle than ductile. You would therefore not
want to use the material at design temperatures below this as
it would have an increased risk of failing in a brittle manner.
Remember that this is not an accurate test reflecting the
material behaviour under actual service conditions, so the
results should therefore be used with caution.
A more accurate test to check a material’s likelihood of
failing in a brittle manner is the crack tip open displacement
(CTOD) test, sometimes referred to as a K IC test.
Hardness testing
The most common hardness tests are Vickers, Rockwell and
Brinell. Hardness is defined as the ability of a material to
resist indentation on its surface. Hardness tests consist of
impressing a ball (Brinell or Rockwell) or diamond shape
(Vickers or Rockwell) into the material under a specified
loading and measuring the width of the indentation to give a
relative hardness reading (Fig. 6.11). The smaller the width of

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Woodhead Publishing Ltd – A Quick Guide to Welding and Weld Inspection
Data Standards Ltd, Frome, Somerset – 17/9/200906QG Welding chap6.3d Page 81 of 87