I am modeling an indentation problem in which a rigid indentor contacts a pipe outer surface and indent the pipe with the specified indentation depth. Then, while the rigid indenter is held (simulating a rock which remains in contact with the pipe), the pipe is internally pressured under a constant amplitude internal pressure. The problem I have is that I do this problem for a very shallow (about 2 mm) up to a very deep (up to 60 mm) depth. However, for shallow dents the Mises stress at the critical location drops over indentation depth and at some depth it starts increasing with indentatin depth. What I was expecting is that I have a monotonically increasing mises stress with increasing denth depth.
Is this a FE problem? or is this physically possible because of snap through happening? I have tried different options in ABAQUS and I am not sure if this is a physical thing or if this something like a contact or other numerical inaccuracy.
Thanks in advance for all of the comments.