Potential energy term in fracture

[jangheej]

Hi
I have a simple question about thin-film peeling physics.
A lot of papers say that the potential energy term in peeling off a tape is F(1-cos@)del c in the picture attached. It says that the potential energy term arises due to the movement of the applied force, which i don't really understand.

(1)How is the movement of the force related to the potential energy increase of thin film peeling?


Also, I did an experiment with varying @ and checked that the equation R(adhesive energy) = F(1-cos@)del c is reasonable.
But another question is, when I pull the tape in another direction (the direction in which we would usually peel off the tape), following the same logic, the equation then becomes R=F(1+cos@)del c. So I also drew a graph of F and 1/(1+cos@), but in this case, it didnt show a linear relationship as it should but showed an inverse relationship.

(2)In the second case of peeling, is the equation that I derived wrong or right?

thnx! :D

 

[LightHero]

The equation F(1-cos@)del c is correct, as it describes the potential energy increase that occurs when you peel off a tape. In order to understand the relationship between the force and potential energy, you need to consider the elastic energy stored in the adhesive bond between the tape and the substrate. The elastic energy of the adhesive bond is dependent on the angle between the force vector and the normal vector of the substrate. When the force vector is aligned along the normal vector, the elastic energy is minimized. As the force vector is moved away from the normal vector, the elastic energy increases due to the strain in the adhesive bond. This increasing strain corresponds to the increase in potential energy, which is described by F(1-cos@)del c. In the second case, the equation you derived is correct, as it describes the potential energy increase that occurs when you pull the tape in the other direction. However, the graph you plotted does not show a linear relationship because the equation is not linear. Instead, it is an inverse relationship, as the potential energy decreases as the angle between the force vector and the normal vector increases.