hello, i am running an explicit analysis in abaqus for an impact test. i want the impactor to hit my plate several times (repeated impact). i want the second impact to start from the end of the first impact directly and so on? how can i do this? is it by defining many steps or restart analysis or how? do i have to define many jobs? please help me if you can... thank you
Hi Mohammed,
Using a multi step analysis is the best way. Another way is to define a load history of the multiple impact.
Dr. Sirous Yasseri, i did a multi step as you suggested. i used two steps. each step has the same duration. it completes the first step and gives me the contact force and displacement between the impactor and target as i requested. however, at some point the impactor will leave the target and the contact force will be zero but the displacement wont be zero. until here everything is ok... now i want the second step to hit the target from the same displacement that was obtained at the end of the first step and with a new contact force. after i run the second step , the displacement will change but the contact force will remain zero till the end of the second step and this is does not benefit me.. how to overcome this problem? thank you
What you are getting doesn’t sound to be in error to me. Contact pressure is not cumulative. If there is a problem it is the way you are applying the repeated impact.
I would have thought if you remove the impactor the contact pressure should recover (almost zero), but the residual stresses/strains and displacements are not zero. The elastic part recover but the plastic part is permeant. I am assuming that you have defined the target as elastic-plastic material. I am also assuming that you are doing a twostep analysis when performing repeated impact. If time between two impacts is large enough, the elastic part will recover. There won’t be any contact and hence contact pressure is zero. Also be sure that the second analysis is the connotation of the first, since otherwise Abaqus removes the old load history.
I am curious how you have modelled multi-impact. I thing you have modelled the impactor as a rigid body and applied an initial velocity in Abaqus explicit. One way (see papers below) would be to have several impactors at different distances from the target. How you get the previous impactor out of the way of the incoming one. Look carefully how you are directing impactors towards the target.
If you are applying the impact force as an impulse load, then you can check your results by apply a time history of multi pulse loading instead.
http://www.simulia.com/forms/world/pdf2002/wilhelmy2.pdf
https://hal.archives-ouvertes.fr/hal-01101649/document
https://apm.iitm.ac.in/smlab/mss/download/54.pdf
http://www.shotpeener.com/library/pdf/1999033.pdf
https://femci.gsfc.nasa.gov/workshop/2004/presentations/08_Indermuehle/Indermuehle_Impact.pdf
Yes Dr. Sirous Yasseri, I modelled the impactor as a rigid body and applied an initial velocity in Abaqus explicit and i run the job. now i want to do a second impact but i dont know how .. should i define new step and new job or how?.... i tried the way you suggested by using several impactors at different distances from the target. however, i could not get the previous impactor out of the way of the incoming one...
Dear Mohammed,
I don't know answer to your question. I am too busy to do it myself in order to find a way out.
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