This error might result from an initial check, abaqus is performing. In this initial check, prior to all of your steps, abaqus checks if your material behaves elastic. That's at least my experience with this error. Maybe abaqus changed something regarding this initial check. A workaround is to implement an if...else statement and assign your material in this initial check an elastic behaviour.

Hi,

I got the same issue before and solved it by using Abaqus 2016. However, this problem commonly happened once using lower versions. (P.S. since Abaqus 2016, this problem has been sorted out as for as I known.) I guess there were some bugs or unreasonable settings for the initial check when using VUMAT in Abaqus. Basically, it will automatically choose a time increment to initialise the explicit programme (i.e. obtaining initial conditions for forward integration algorithm). If a non-linear material behaviour has been defined in the VUMAT and the tangential stiffness at 0-strain is too small (approx. 0) or the stiffness curve varies unrealistically, this problem may occur. However, these commercial FE codes are not open sources, we cannot get adequate information to confirm exactly what kind problem it is. Anyway, it seems Abaqus has already fixed it right now.

I hope this helps.

Regards,

Shuai

Thanks Johannes and Shuai, looks like I have to "get around" the pre check of Abaqus.