Main Question or Discussion Point
Is the only difference between these two impact tests how the specimen is held in position for the test? Charpy holds it like a simply supported beam, and Izod does it as if it was a cantilever?
This statement would indicate more resistance to fracture using the Izod test.HOWEVER, the numbers from those two test methods are not comparable. There is no accepted method of comparing CVN and IZOD numbers, but it is commonly known that the IZOD test produces higher numbers than a CVN test on an identical material sample, ie, CVN is more conservative.
Yeah, 1st it's the C(T)s or SEN(B)s for lower bound values (or if only have indirect data correlations), nowadays quite often followed by a constraint analysis (the number of these has increased quite rapidly during the last few years), analysis of biaxiality & membrane/bending effects, coupling to what fracture type really to expect (changes in "fracture appearance"), residual stresses ..... the list is often pretty long really. Especially if want to / need to aim for 'best estimates'...........
The issue we've had with tests of fracture toughness is how close the stress field in the test matches the stress field for in-service loading.