Tensile test simulation force-displacement inaccuracies
Ruark Potgieter
Hello!
I am trying to simulate a tensile test of woven polypropylene in ls dyna. However, I am running into problems with the force and displacement the simulation returns.
I conducted tensile tests on a material, and I want to recreate my results from the tensile tests. The force-displacement I received from my testing was used to create an engineering stress-strain graph. This graph was entered into MAT_FABRIC after choosing my formulation as 24. This graph was entered using Def_curve and setting DATTYP=-2, which represents an engineering stress-strain curve. The testing is performed at 10 mm/min and that is what in the prescribed_motion boundary at the top nodes, where the grip face would be. The bottom nodes are fixed, as they would be inside the grip face during the physical test. The units used are mm-ms-kg-N.
The results of the 31 states in my implicit analysis are
that the force is almost 2x what it should be, based on my experiments, and the
maximum force is reached earlier than it should. From my force-displacement
graph I gathered from my experiments, the maximum force is reached at 28mm,
while in the simulation the max force is reached at 20 mm. The max force
determined through the experiments is 1100N, while the simulation has a maximum
force of 1900 N. The stress-strain curve I entered does not seem like it is
being followed at all. Another piece of information which is essential is the
fact that the internal energy was correct in the 31 states run, it amounted to
about 25J, which made sense if calculated from the stress-strain input graph I
gave.
I would like to know what I should change to ensure that the material reacts as expected, without any added stiffness. Please let me know if anyone has an idea on what can be done to increase the accuracy. I will attach my keyword file, a comparative graph between experiment and simulation and the d3hsp file.
