## General Mechanical

#### Repeating dynamic drop test on geometry while preserving internal stresses

• NAVID SALAM
Subscriber

Dear peteroznewman

I am conducting a dynamic drop test on a given geometry made of Molded Pulp Packaging as shown in the picture below. It involves a drop plate falling on an element at a certain speed. The results obtained are the deceleration of the drop plate and the internal stresses of the element. I would like to conduct a second dynamic simulation of the drop plate dropping on the element while preserving its internal stresses due to strain hardening. However, I have not found a tool to carry this out except for importing the pure deformed geometry without its internal stress. I also looked into cyclic load but I am not sure if its an option for a double drop test.

• Erik Kostson
Ansys Employee

Hi

Perhaps try and estimate the load from the impact (run a drop test and calculate the reactions), and apply it as a a load that repeats it self (so like one would have it falling down over and over again).

That could be one way (to do what you want is not straightforward using dynamic explicit analysis for drop test).
All the best

Erik

• peteroznewman
Subscriber

One idea is to have two drop plates in the simulation, use Transient Structural and have two contact sets: Contact #1 for Drop Plate #1 contacting the Pulp and Contact #2 for Drop Plate #2 contacting the Pulp. Configure the Drop Plates so they are almost touching the Pulp and use an initial velocity to avoid spending time computing the free fall.

Use a series of steps and control which drop plate contact is active.

These are not the literal steps since it can take two steps to establish an initial velocity for example.

Step 1.  Drop Plate #1 has an initial velocity, Drop Plate #2 is supported and solve transient for 100 ms.

Step 2. Time Integration Off, support Drop Plate #1, turn off Contact #1.

Step 3. Drop Plate #2 has an initial velocity and solve transient for another 100 ms.

At the end you will have made two impacts on the same Molded Pulp Package.

• NAVID SALAM
Subscriber

Dear Petro thank you for the reply.

May I ask how do you create two time steps and thee simultaneous contact points for the 2 different plates. I am not able to control the factors as you mentioned effectively.