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Pros and Cons of element deletion in Abaqus
Mon, 2010-07-19 11:04 - priyadd84
Hi all ... i have been doing element deletion extensively in my analysis but was wondering ... wat are the Pros and Cons of using this method. To my knowledge was wondering how the deleted mass and energy are conserved through out the analysis. Thank you all.
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Explicit FEM code, element deletion, conservation of energy
Good question, I can answer your question base on my experience using explicit FEM code (LSDYNA) for crash analysis. because of the highly elements distortion in the crash front time step decreases and technically simulation does not proceed so we need to delete distorted elements on crash front, we may delete elements for another reason like failure but in the first case(crash front) those elements still can take load (stress) and removing them means remove some energy from system that is why most crash analysis are under predicted. Using meshless methods you may improve your simulation. But deleting distorted elements is the price we pay to precede our simulation.
Hope this helps
Azadeh
In context to failure
Thank you Azadeh for your reply. I use element deletion for failure (crack propagation in specific). You mentioned that the deleted elements can still take loads, i dont understand this statement. You mean element deletion means just masking the failed elements? but still the mass is sitting there? Azadeh and others please throw some light on this. Thank you.
Hello Mike, I recently
Hello Mike,
I recently saw your blog, and I wanted to share some thoghts.
Element deletion is crucial if you simulate parts that can fly away (e.g. during a crash), or penetration occurs, but there are some issues.
Deleting the element removes mass and energy of the system. The mass and energy of the system is shared on the nodes, and the ones which become free after the element deletion, simply fly away. So if you have substantial element removal it will affect your simulation accuracy. However, in many cases highly distorted elements need to be removed from the calculation. In penetration problems failed elements (e.g. due to high plastic strains) can still take compressive forces, so an early element removal increases the penetration depth. You should care, that your element deletion, or failure is a function of stress triaxiality (ABAQUS has built-in features). Deleting an element in contact situation means that formerly interior faces (behind the deleted element) become exterior faces. So the contact algorithm has to calculate new contact surfaces, and new cvontact forces, and sometimes it can cause numerical instabilities (it happened to me at least). Without element deletion, the contact calculation is much easier. Last but not least, even in simple tensile tests the deletion based on plastic strain should be verified with experiments (and not simply taking the A5 or A10 of a steel data sheet).
As I said there are some issues to think about, and the accurcy is clearly depending on the complexity of the problem. But I think there is nothing agains element deletion.
Regards, Andras
BRITTLE FRACTURE and Element Removal in ABAQUS
Hello Andras,
I am new to ABAQUS for Dynamic Explicit Analysis and I had a quick question for you for which I needed your experience and advise please:
I need to know "How do we do Element Deletion / Remeshing for the Explicit Loading?" I mean how I can remove elements in each time-step to model my progressive failure and at the same time maintain the continuity of my explicit dynamic analysis.
I have a glass panel (brittle material) that is subjected to a linear triangular load in the shock tube, I want to know (at each time step) which elements reach to their max failure stress so I can remove them from the geometry and proceed to the next time step. My ultimate goal is to identify and trace the crack patterns on the glass panel.
I have heard that there is *BRITTLE FRACTURE built-in feature in ABAQUS that automatically takes care of the Element Removal and the Re-meshing but I absolutely do not know how I need to move forward using this.
I appreciate your expert opinion or any hints of yours on this problem of mine
Thanks in advance,
Hossein
strain based element deletion
Dear All,
I am trying to model plasticity damaged model form machining. In this model I need to remove highly distorted element on strain basis. Hence, I need to edit inp file. Can any one help me to remove strain based element removal?
Thanks
Vivek
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