Note: This post uses a development version of the 3DExperience Calibration App to show a new capability that will be released with R2026 FD01 (early in 2026). I have done this work in July, 2025.
PA 12 (also known as Nylon 12) is a good general-use plastic with broad additive applications and is known for its toughness, tensile strength, impact strength and ability to flex without fracture. PA 12 has long been used by injection molders due to these mechanical properties.
Several years ago a test lab shared some test data on PA12. The test data consists of :
- Three monotonic pull tests at rates of 5, 50, and 500 mm/min (crosshead velocities).
- One cyclic test to see hysteresis loops.
- Three stress relaxation tests performed below the yield stress.
All test data is from uniaxial deformations. Earlier attempts (prior to 2025) at using the Abaqus PRF to model these tests were not successful because the available creep laws for the viscous networks could not mimic the saturation of stress that occurs in the monotonic pull tests near ultimate. In Abaqus, the TLVP (Two Layer Visco-Plastic) model is similar to the PRF model in that it is a network model. Like the PRF model it has an elastic-plastic network and a viscoelastic network. The Anand and Darveaux creep laws are available in the TLVP model. While we call them "creep laws" these are really visco-plastic in nature, and can represent the saturation of stress that one sees in the monotonic pull tests.
Here is a post from 2023 that shows the use of the TLVP model for this PA12 test data:
Nylon 12 (PA 12, Polyamide 12) ; TLVP model
The Darveaux model and a Modified Darveaux model were added to the PRF model in the 2024 FD03 release of the Abaqus solvers.
I revisited this nylon 12 material and have taken the TLVP material model from 2023 and morphed it into a PRF model.
Here is the TLVP material model from 2023:
**Units
** Length - Millimeter
** Mass - Tonne
** Time - Second
** Temperature - Kelvin degree
**
*MATERIAL, NAME = TLVP
*ELASTIC, TYPE = ISOTROPIC
2154.0765, 0.4
*PLASTIC, HARDENING = JOHNSON COOK
26.931895, 36.724585, 0.32377983, 0, 1773, 1273
*VISCOUS, LAW = DARVEAUX
** Css QR_Ratio alpha n eT B f
0.01, 1000, 0.092222, 4.5448, 0.00088295, 11999.701, 0.44018
Here is the new PRF version :
*MATERIAL, NAME = PRF
*HYPERELASTIC, HENCKY, MODULI=INSTANTANEOUS
** E nu
2154.0765, 0.4
*PLASTIC, HARDENING = JOHNSON COOK
26.931895, 36.724585, 0.32377983, 0, 1773, 1273
*VISCOELASTIC, NONLINEAR, LAW = DARVEAUX, NETWORKID=1, SRATIO=0.44018321
** data line for TLVP model
** C Q/R alpha n eT B f
**0.01, 1000, 0.092222216, 4.5448432, 0.00088295167, 11999.701, 0.44018321
** data line for PRF model
** C alpha n eT B
0.000330, 0.092222216, 4.5448432, 0.00088295167, 11999.701
Here is the PRF model in the Calibration App:
Some notes on the Darveaux model parameters for TLVP:
Some notes on the Darveaux model parameters for PRF:
The parameter α enters the hyperbolic sine function, sinh. Negative values of α are not possible because it will cause a negative value of the sinh function. If α=0, then sinh = 0 and the creep strain rate will be zero (no creep). Therefore it makes sense that α should be positive.
The parameter ϵT controls the primary creep. We expect the creep rate to be greater during primary creep, so ϵT≥0 (note also that B>0 so that primary creep effects decay exponentially). When t=0 the creep strain rate is (1+ϵTB) times greater than at steady state. Setting ϵT=0 would simply mean that primary creep is ignored and not included in the simulation.
The zip file attached here contains the calibration app's 3dxml file, a material model snippet and a .png image from the calibration app.
Back to: Sharing Material Test Data
Back to: Material Modeling and Calibration - An Overview and Curriculum
