Hello Prepromax users,
I am a new user of Prepromax/Calculix and starting to experiment with the plastic analysis capability of the software. I am setting up a simple perfectly plastic material model and have defined 10 load (pressure) increments to analyze a pressure vessel dished head and cylinder. I have set the yield strenght to 50MPa, just for testing, and run an analysis for which i know it should converge (reach stress redistribution). Plotting the last load increment I noticed the Von Mises stresses are as high as 67MPa on larger areas of the model (the knuckle area of the head). I don’t understand this since the material should flow at 50MPa and not strain harden. Can anyone tell me what is happening? I have set the plastic material as 50MPa yield @ 0 [-] plastic strain. Aside of this does anyone know what flow stress is used to define yield (Von Mises, Tresca, etc) in a plastic analysis and how to set this?
Thanks a lot for the help!