Reply To: Stress fluctuates in Explicit solver

[Chris Quan]

Both Explicit Dynamics and LS-DYNA systems are doing dynamic simulations. When a loading is applied to a geometry, the loading is a dynamic load. The stress incurred is dynamic in nature and thus subject to oscillations due to stress wave propagation and interactions.

In your model, 5000 N is applied at the time = 0. This means that an impact force directly hits the structure at the initial time. A stress wave is thus created at the impact end and propagates towards the other end, then is reflected from the other end, travels back towards the impact end, and finally interacts with the new stress wave from the impact  end due to the increasing external force.

You didn't mention what boundary condition on the other end is in your post. If it is the stress-free boundary condition, the reflection wave is rarefaction wave and thus the resulting stress is decreased while the rarefaction wave travels through the model. Furthermore, the new stress wave from the impact end due to the increasing external force will increase the magnitude of the stress.