I'm trying to use VUSDFLD in abaqus to change fracture energy according to strain rate. The model consists of two cubes, which are bonded with cohesive elements. The left cube rotates 35° in 200 seconds. And of course the cohesive elements in the middle would have different strain rates. So I use VUSDFLD to link different strain rates with different levels in Field 1.

First, I intentionally set the fracture energy very high for all 5 levels in Field 1 as follows.

Fracture energy Field 1

1 300 1

2 300 2

3 300 3

4 300 4

5 300 5

In picture 1, it shows that FV1 ranges from 1 to 5, and the sample doesn't break in the middle, just as expected.

Second, I changed the fracture energy of the third level to be low as follows, expecting that the sample would break at the third level, but not the rest.

Fracture energy Field 1

1 300 1

2 300 2

3 3 3

4 300 4

5 300 5

However, as shown in picture 2, the sample breaks in the middle. Could anyone tell me what went wrong, please?