I have carried out fracture test of Zr-2.5Nb pressure tube material in axial (crack growth along axial direction of the tube) and transverse direction of the pressure tube using CT specimen. The CT specimens are cut after cold flattening of the pressure tube. The transverse CT specimens got buckled during fracture test whereas there was no buckling in axial CT specimens. The strength in transverse direction is about 20 % higher than that in axial direction. I want to if there is any relation between buckling load and strength for CT specimen for a given geometry.
With regards
AKBIND
In general, there is a relation between YS and plastic collapse (limit) load. It is
P = 1.455Xbsy for plane strain
P = 1.071Xbsy for plane stress
where X = [(2a/b2) +4a/b) + 2]^1/2- 2a/b-1
a= crack length; b=remaining ligament (W-a), sy= yield stress
Above limit loads are per unit thickness.
As such Zr alloy will have a strong texture and hence aniostropic properties (20% high in strength as you have pointed out in one direction). On the top of that you have flattened the tube, there by severely work hardening the material. The YS of the flattened material is liable to be different. If you can perform a tensile test on the flattened material, it would give some idea on strength increment due to flattening process. I suggest you use "this" YS to calculate the limit load.
Can't you work on curved CT geometry? You may have to do a bit of FEM to get the correct SIF expression (I am sure this would be available in literature). Somehow, I am not comfortable with the flattening business. After all, you are altering the material property (by flattening) and trying to evaluate the fracture resistance, not a good idea.
Dear Sivaprasad,
After cold flattening, the flattened tube was annealed at 400 oC for 24 hrs. This is common practice after cold flattening. After annealing , tensile strength is 20 % higher in transverse direction.
The second one, I want to calculate the buckling load not limit load. The buckling occur in thinner CT specimen and specimen has lateral movement in thickness direction.
with regards
AKBIND
OK...got it. You are talking about out of plane bending, as in thin cross-section. How about designing an anti-bucking device?
Dear Sivaprasad,
I want to know why there is buckling in transverse CT specimen but no buckling in longitudinal specimen.
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