## LS Dyna

#### Arrow Simulation

• Ndumiso
Subscriber

I'm simulating an arrow release from a bow. An arrow is made of four basic parts as shown in the picture attached. The contacts of all these parts are bonded in my simulation. I imposed a velocity as an initial condition on the nock of the arrow. After setting the end time as 0.0007, the arrow moves a very short distance and there's no deflection which is something that should be there.

I'm suspecting that the arrow is a rigid body and I'm not sure why it moves a short distance. Can someone please assist with fixing these problems?

• peteroznewman
Subscriber
nWhat velocity did you apply as an initial condition?nHow far does a rigid body traveling at that velocity go in 0.0007 seconds?nHow many frames of output did you request?nDid the simulation complete calculating to the end time you input?n
• peteroznewman
Subscriber
@Ndumiso, nYou have a second discussion on the same topic.n

HelloI am working on my final year research project where i am required to evaluate the dynamic spine (deflection of the arrow shaft in flight) using explicit dynamics. I ran an experiment in which i used a chronograph to measure the velocity of the arrow. This velocity is used as an initial condition in explicit dynamics. I also draw an arrow with its components and a simplified archery bow. The bow is also equipped with a plunger button (spring with a disk head) which is depressed by the arrow upon release. To represent a plunger button i also draw a disk making contact with an arrow in Autodesk Inventor and then a added a spring in workbench.To achieve the dynamic spine of the arrow i am required to simulate an archer releasing an arrow from the bow. I imposed a fixed support on the bow and a velocity on an arrow nock (rear end of the arrow). The problem i am having is the arrow not moving at all after running for so long and the simulation runs almost the whole day.Please see the attached geometry pictures to get the idea of what i am talking about.https://us.v-cdn.net/6032193/uploads/W1NYFKBMIM5G/archery-png.pnghttps://us.v-cdn.net/6032193/uploads/7Y4JX0AOYNV9/archery1-png.pngCould you please assist with this?Your help is highly appreciated.Kind regards,Ndumiso Mdlulihttps://forum.ansys.com/discussion/21310/arrow-release-simulation

It might be cleaner if all the discussion was held on that thread and none on this one.n
• Ndumiso
Subscriber
nThank for your assistance on my other discussion, very helpful. I hope continuing with the discussion here won't be a problem.nThe velocity is applied as an initial condition.nThe distance it travels is very short. Less than half the length of your thumb. nI requested100 frames.nYes, the simulation did complete calculating.n
• Ndumiso
Subscriber
n
• peteroznewman
Subscriber
nWhat bending moments are applied to the arrow to cause it to bend?nMaybe what you modeled will not cause bending along the arrow length. You need a lateral force or a moment on the arrow to cause bending. Where is that coming from?.
• Ndumiso
Subscriber
So the arrow was pre-stressed on static structural by applying a displacement on the tip (front end) to constrain it from moving sideways and up but free to move forward. And a displacement was only applied on the nock (rear end) with a displacement of 40 mm. Please the attached picture (this represents the arrow before going into explicit dynamics). This is to mimic a real life situation. The results were then exported to explicit dynamics where the velocity is imposed on the nock. nIt is bending a bit now but I get see enough movement due to the short distance the arrow travels. And also since I can't input the end time of the pre-stress (due to the initialization error I'm receiving)nn