04 Dec Drop and Impact
A drop test simulation in FEA is modelled as a non-linear transient dynamic analysis (https://fea-solutions.co.uk/non-linear-transient-dynamic-analysis/), as it is a dynamic (https://fea-solutions.co.uk/static-vs-dynamic-analysis/) time dependent (https://fea-solutions.co.uk/transient-analysis/) problem that includes non-linear behaviour (https://fea-solutions.co.uk/non-linear-behaviour/).
To model the drop, a ground plane is created to simulate the impact surface, and the object under scrutiny is given an initial position very close to the ground plane. Its initial velocity is adjusted to represent the drop height.
The drop is simulated at discrete times steps, with very small increments between these steps, typically one thousandth of a millisecond. That is why the computing time for a drop test analysis can be very long, taking days rather than hours.
Usually only the first impact of the drop is analysed. After that the simulation is aborted. The bounce-back and secondary impact would further increase the computing time and is usually not required as the first impact is with the highest velocity, causing the highest stresses and strains within the structure.
Drop and Impact analyses are usually performed using explicit solvers (https://fea-solutions.co.uk/implicit-vs-explicit/).
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