Dear all,
Recently, I have been working on the simulation of a pile-soil interaction with CEL method in Abaqus/Explicit. I simulate the sand with the Sand Hypoplasticity Model provided by Prof. Masin. And I use the VUMAT_UMAT Interface from Prof. Bienen.
However, When I call the Vumat.for file, two errors always appears:
Error 1: The option *user material,type=mechanical completely defines the material behavior. It can not be used with an option that defines part of a material`s behavior
Error 2: A material property that is not allowed with a user material has been specified
PS: The picture shows the error message and the sand constitutive model parameters setting.
I did not find a solution to these two errors on the Internet, so I ask for help. Any suggestion or comment will be appreciated.
Hi Kunpeng, can you explain why you define also elastic material behaviour? All the material behaviour should be governed by vumat.
Hi Prof. Masin, if I delete elastic material behaviour, another error will be generated：
ERROR in job messaging system: Error in connection to analysis
There is also a warning message：
A material defined in user subroutine VUMAT must be defined as purely elastic (using the initial elastic modulus) at the beginning of the analysis (stepTime=0). This is an informative message. It does not necessarily indicate that user subroutine VUMAT is incorrectly defined.
This is similar to the problem Panpan Guo encountered: https://soilmodels.com/general-questions-on-implementation-of-sand-hypoplasticity-model-with-abaqus-umat/
1. as Prof. Mašín said，all the material behaviour should be governed by vumat. So, we can’t define elastic material when using hp model through vumat.
2. ’A material defined in user subroutine VUMAT must be defined as purely elastic’, which is just a warning message, not a mistake. So, it will not affect the the operation of user subroutines.
3. When an error message “zero or negative initial dilatational modulus caused by bad material data” appears, we should Uncheck this option“ material editor: General-User Material: VUMAT defines effective modulus”. About it’s mechanism, ples refer to USER ASSISTANCE of ABAQUS. Searching for key words“VUMAT defines effective modulus”
Hi Kunpeng, did you notice and activate this line in umat?
c For use in ABAQUS EXPLICIT, activate the following line
c if(kstep.eq.1 .AND. kinc.eq.1) testing=3
testing==3 means that elasticity is activated for the initialisation step
Hi Prof. Masin,
Yes, of course. This line is activated. But the problem still exists.
I see. This seems as a general problem of VUMAT usage, hope that someone using Abaqus explicit will be able to help.
Hi Prof.Masin,
Thank you for sharing the hypoplasty model.
I would like to know that if the model (clay Hypoplasty) includes the large deformations and plastic strains, and can you guide me on how to define and declare values to parameters of the model inside the Abaques application.
Appreciatively.
Hi, please study “Mašín, D. (2015) Part 4: Determination of material parameters, PhD course “Hypoplasticity for Practical Applications” handouts [Presentation]”, it is awailable for download in SoilModels publication database. Regards David
Thank you
Hi,
when using a umat or vumat, the following information needs to be included in the .inp file:
*Material, name=Material-xyz
*Depvar
integer_number,
*User Material, constants=integer_number
constants_definition
The information you included above reads *User material, type=mechanical. Please also check that the number of material constants defined here match that in the umat/vumat.
Hi,
I used VUMAT_UMAT interface from Dr. Bienen to transfer the Sanisand UMAT to VUMAT. I used the dynamic explicit step to do the analysis. I got the warning message like
“A material defined in user subroutine VUMAT must be defined as purely elastic (using the initial elastic modulus) at the beginning of the analysis (stepTime=0). This is an informative message. It does not necessarily indicate that user subroutine VUMAT is incorrectly defined.”
In Sanisand UMAT there has no these lines
c For use in ABAQUS EXPLICIT, activate the following line
c if(kstep.eq.1 .AND. kinc.eq.1) testing=3
testing==3 means that elasticity is activated for the initialisation step
The problem is not fixed by activating the following line:
c For use in PLAXIS, activate the following line
if(kstep.eq.1 .AND. kinc.eq.1) testing=1
c For use in ABAQUS, the line above should be inactive
Could you give me any suggestion?
Many thanks,
Shile
How i transfer the umat to vumat for the hypoplastic model, so i could used the Explicit solver?