mechdrive1
Mechanical
Hello,
I ran an Explicit (dynamic, coupled temp-disp) model for friction stir spot welding like process in which the tool penetrates the first layer of the workpiece (two layers, one above the other). The first layer of workpiece is Eulerian whereas the tool is Lagrangian which makes the model a CEL model. I requested 'All energies total' for the entire model for the given step. I haven't used mass scaling or element deletion. I have observed negative values for ALLWK, ALLHF, ALLPW. The values of ALLHF and ALLPW turned positive within some time but the variable ALLWK has negative values for much longer time. Another thing which I observed is that value of ALLIHE (internal heat energy) is quite high (slightly varying around 4675 J) when compared to all other energies whose values vary roughly from negative to zero to 45 J. I am unable to understand why ALLWK is negative at the starting and why ALLIHE is so large compared to other energies.
FYI, I have specified inelastic heat fraction=0.9, amt. of friction energy dissipated to heat=1.0 and 64.5% of this heat goes into the first layer of workpiece while rest goes to tool. Friction co-eff.=0.4. Also, the mesh is finer in the interaction region where tool penetrates the first layer of the workpiece.
I am attaching the graphs for different energies for reference purpose.
Another observation is that the value calculated by ABAQUS for the variable ETOTAL and the value I calculated for the same variable using the below energy balance are different which can be seen in the graph 'ETOTAL, Ecalc. vs. time' where Ecalc has been computed by according to the below balance.
ETOTAL= ALLKE + ALLSE+ ALLPD + ALLCD + ALLDMD + ALLDC + ALLFC + ALLIE + ALLVD + ALLFD + ALLIHE –ALLWK – ALLPW – ALLCW - ALLMW – ALLHF
The values of ALLCD, ALLDMD, ALLMW have been calculated as zero by ABAQUS but there was no output for variables ALLDC, ALLFC, and ALLCW. I have assumed the latter three variables (ALLDC, ALLFC, ALLCW) zero as there is no distortion control for Eulerian material although it's there for Lagrangian tool. I have no idea about the fluid cavity energy ALLFC. I am also trying to find why there was no output for constraint penalties ALLCW.
Can please someone explain why can there be negative ALLWK, ALLHF, and ALLPW? Any suggestions/corrections in my calcuations or assumptions are welcome!
Thanks.
I ran an Explicit (dynamic, coupled temp-disp) model for friction stir spot welding like process in which the tool penetrates the first layer of the workpiece (two layers, one above the other). The first layer of workpiece is Eulerian whereas the tool is Lagrangian which makes the model a CEL model. I requested 'All energies total' for the entire model for the given step. I haven't used mass scaling or element deletion. I have observed negative values for ALLWK, ALLHF, ALLPW. The values of ALLHF and ALLPW turned positive within some time but the variable ALLWK has negative values for much longer time. Another thing which I observed is that value of ALLIHE (internal heat energy) is quite high (slightly varying around 4675 J) when compared to all other energies whose values vary roughly from negative to zero to 45 J. I am unable to understand why ALLWK is negative at the starting and why ALLIHE is so large compared to other energies.
FYI, I have specified inelastic heat fraction=0.9, amt. of friction energy dissipated to heat=1.0 and 64.5% of this heat goes into the first layer of workpiece while rest goes to tool. Friction co-eff.=0.4. Also, the mesh is finer in the interaction region where tool penetrates the first layer of the workpiece.
I am attaching the graphs for different energies for reference purpose.
Another observation is that the value calculated by ABAQUS for the variable ETOTAL and the value I calculated for the same variable using the below energy balance are different which can be seen in the graph 'ETOTAL, Ecalc. vs. time' where Ecalc has been computed by according to the below balance.
ETOTAL= ALLKE + ALLSE+ ALLPD + ALLCD + ALLDMD + ALLDC + ALLFC + ALLIE + ALLVD + ALLFD + ALLIHE –ALLWK – ALLPW – ALLCW - ALLMW – ALLHF
The values of ALLCD, ALLDMD, ALLMW have been calculated as zero by ABAQUS but there was no output for variables ALLDC, ALLFC, and ALLCW. I have assumed the latter three variables (ALLDC, ALLFC, ALLCW) zero as there is no distortion control for Eulerian material although it's there for Lagrangian tool. I have no idea about the fluid cavity energy ALLFC. I am also trying to find why there was no output for constraint penalties ALLCW.
Can please someone explain why can there be negative ALLWK, ALLHF, and ALLPW? Any suggestions/corrections in my calcuations or assumptions are welcome!
Thanks.
