Determination of Fracture Toughness 1

[GregPerry]

Dear all,

1. Can fracture toughness be determined from Charpy Impact Values? If so what is the formula recommmended.

2. Does anyone have fracture toughness values for the following shaft materials:
EN24 'T'
EN26 'T'

Thanks

Greg

 

[CoryPad]

For high strength steels in the upper shelf region, the equation is:

(K/sigma)^2 = 0.64 ((CVN/sigma)-0.01)

where

K = plane strain fracture toughness in MPa m^0.5
sigma = yield strength in MPa
CVN = Charpy V notch value in J

 

[AJohnson]

Greg,

Yes there are correlations, but there is not one simple one. There are different correlations for the upper shelf, the transition region, and the lower bound. I could list a few equations, but I feel they would be of no help without you reading all the background text that goes with them. Most of these correlations are investigated in depth in Chapter 5 of "Fracture and Fatigue Control in Structures: Applications in Fracture Mechanics" by John M. Barsom and Stanley T. Rolfe. Andy

 

[TVP]

Greg,

Do you have information on the mechanical properties-- yield strength, tensile strength, impact, hardness, etc.? I can give you some estimates for SAE 4340, which is similar to EN24 (817M40). EN26 (826M40) should be tougher for a given strength/hardness level, due to its higher Ni content: 2.30-2.80 vs. 1.30-1.70.

 

[TVP]

I forgot to inquire about processing-- quenched and tempered? What is the tempering temperature? As-rolled? Anything subsequent like shot peening, etc.?