I am doing analysis of RC structure under high velocity impact loading. I always face with the error "Negative volume". Could you explain in detail about this error? and how to fix the error?
Thanks
negative volume is detected when, in a solid element, one node crosses one of the face of the same element. Often it depends on the solid element shapes and it happens with soft materials or with high velocity impact forces. Let's find the option for control the compression ratio and let's check the element aspect-ratio before to run the calculation.
Negative volume error usually happens when a large deformation occurs and two opposite faces of one or some elements pass through each other. Using meshh free methods such as SPH(which is available in ls Dyna) would probably resolve the problem. But if you want to use Lagrangian meshes, try the following instructions:
Stiffen up the material behavior at high strains by editing the stress strain curve.
Use element formulation with less integration points.
Increasre the damping factor.
Use a layer of null shell element on opposite faces of your geometry.
Good luck.
I may be late to answer but here are some additional tips that may help resolving such problems:
1. try hourglass control
2. reduce the timestep scale factor in Control Timestep to 0.67
3. Try using ERODE
Their are many reasons might cause negative error (before you discard your model, make sure you checked every parameters)
personally, i think you can change the control timestep TSSAC at first, the velocity you applied( if the velocity is applied on your model ) also matters. if error still occurs, may be you need you change the contact. I met some negative problems last summer, i thought the way i build model is wrong from the beginning, in fact it turned out to be the material problem. I just change from plastic to elastic, it was solved.
You can try to change ELFORM for instance, specially for solid lag. SEC.
The option of contact constraint might cause the error "negative volume" as well. In my impact simulations I found that the best and most stable option was to use the option SOFT = 2 (pinball segment based contact).
Hello, Rodolfo M N Fleury Ammar Babiker Shabnam Rahimnezhad
Xiaoguang Xiao Duc-Kien Thai Hamed Bakhtiari Alessandro NaddeoI have an acute problem. I am trying to model a reinforced concrete beam and I am having mass less nodes problem for the reinforcement (which are beam elements).
What exactly are massless nodes ? Till have not found some good literature.
Any inputs would be highly appreciated.
Abhirup Bhattacharjee , sometime it occurs when you're having nodes not assigned to any elements (mistakenly happens for rebars modelling), recheck your model again for those nodes and check if deleting them will solve your issue. Otherwise, simply add any trivial mass for those nodes using *ELEMENT_MASS.
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