What is the appropriate constitutive law for HDPE?

[zerrouki]

hello all
i want to model crack propagation in HDPE using Ansys, first i need to define the behaviour of this material,
so, what is the adequate constitutive law for HDPE.
thanks all

 

[Chestermiller]

Are the strains small? Is there going to be any crystallization during the crack formation?

 

[zerrouki]

hello
the HDPE have a large strain that can reach 600% in tensile test, about the of crack propagation, the process carried out in room temperature.
thanks for interest.

 

[Chestermiller]

Developing a general constitutive equation that describes actual HDPE behavior at large deformations is quite a challenge. I don't think that one exists. Is there any way of providing a simplified approximate quantification of the kinematics for this specific deformation?

 

[zerrouki]

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 ??

 

[Chestermiller]

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 ??

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]

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 ?).

 

[Chestermiller]

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 ?).

I'm not familiar with that model. Sorry.