The discussion centers around identifying an appropriate constitutive law for modeling crack propagation in high-density polyethylene (HDPE) using Ansys. It explores the behavior of HDPE under large deformations, particularly in the context of tensile testing and potential crystallization during crack formation.
Participants express differing views on the appropriate constitutive law for HDPE, with some advocating for elastic-viscoplastic models and others for elastic-plastic models. The discussion remains unresolved regarding which model is most suitable.
Participants highlight the challenges in determining material parameters for viscoplastic models and the potential discrepancies between laboratory measurements and field conditions, which may affect model accuracy.
There are lots of constitutive equations out there that describe viscoelastic materials qualitatively, in terms of a set of material parameters. However, I know of none that are capable of describing the behavior of a real material like HDPE quantitatively for an arbitrary deformation. So, even though you can make laboratory measurements to determine a set of material constants, unless the kinematics of the deformation experienced in the field is very close to the laboratory kinematics, the model will not make accurate predictions for the actual field kinematics.zerrouki said:there are some authors who state that the constitutive law is elastc-viscoplastic. but the difficulty is how to determine the parameters of the viscoplastic part ?? take in account that these parameters need experimental data that require special machine to do the tests. Furthermore, there are others that declared the constitutive law as elastic-plastic, but, is this law appropriate for HDPE ??
I'm not familiar with that model. Sorry.zerrouki said:i thought to use perzyna option to model the viscoplastic behaviour of the HDPE, have you some informations about this model ? ( if it can work with large deformation or with just small ones ?).