Birdstrike Analysis, Load on attachment Fasteners

[juancervi]

Greetings!

Currently I'm analyzing birdstrike in external installations added to a FAR 25 aircraft. The approach is ABAQUS Explicit, SPH for the BIRD (EoS, bird ressults validated against AFFDL reports, etc.), elastoplastic behavior of the aircraft structure (Johnson Cook Plasticity, Johnson cook Damage). The thing is that I have taken the Mesh used for the static analysis, which uses bar elements to represent the fasteners and the loads in the attachment elements are really high, so is there any special reccomendation modelling joints for this dynamic analises? shall I connect the mesh drectly (plates with plates, no bar elements for the fasteners). Is there any recommended strategy using ABAQUS conectors? The goal of my analysis is to show that the added structure will take some localized damage and deformation, but it won't detach from the structure.

 

[FEA way]

Abaqus offers many options to model connections between parts. In such analysis you can use beam type MPC constraints, mesh-independent fasteners as well as connectors. There are some differences between all of them but usually they can be used interchangeably. When making your choice keep in mind that it would be very good to include failure of these connections so that they are removed when load is too high.

 

[juancervi]

I have some data on fasteners failing under combined conditions, were can i find some info about how to implement this connector damage in ABAQUS? the DS help doesn`t say to much

 

[FEA way]

Connector failure behavior lets you define failure criteria of maximum displacement or force/moment in specific directions (when the criterion is reached connector is released). You can also use conector damage behavior that allows you to define more complex criteria of damage initiation and evolution. Unfortunately deletion of connectors that reached maximum damage is not available in Explicit.

You can find more information in the chapters „Connector failure behavior” and „Connector damage behavior” of Elements Guide.