Seam weld solution for shell-shell connection modeling

Industrial FE models, such as an automotive BIW finite element mesh, are almost always general purpose finite element meshes. This means that one mesh of the structure such that this mesh then can be used for NVH or acoustic analysis or even used in a flexible multibody simulation. For this kind of application it is sufficient to model welded sheet structures using a simple shell element representation for the connecting sheets while still obtaining an accurate load flow through the welded structure. For durability calculations however, a detailed model of the seam weld becomes important to calculate a correct fatigue life estimate.

The seam weld solution that Specialist Durability offers makes optimal use of all the advantages of today's general purpose finite element meshes (one mesh suffices, simple representation, fast calculations) and couples the results from the general purpose FE mesh to an extensive library of detail seam weld models to accurately calculate the local stresses in the seam weld.

For seam welds modeled by connecting multiple sheets with a shell representation, the shell representation is sufficient to accurately model the load flow through the structure. This means that during the durability calculation first the complete (global) shell mesh will be solved. This can happen fast and has the results are compatible with the approaches used and adapted by other companies. [1] The connection with the weld detail models happens only after the global finite element analysis has been performed. At this point the nodal results (forces and moments) from the connecting nodes are transferred as input for the detail models. The connecting node can be nodes from "direct" (element to element) connections or nodes from "indirect" (element to RBE/MPC to element) connections. Possible connections are shown in the following figure. [1]

Shell-Shell Connection, Both Direct (Shell-Shell) and Indirect (RBE/MPC)

Using the forces directly delivered from the FE analysis, rather than weakly defined structural stresses that undergo all kinds of derivation procedures, has proven to be critical for the success of this approach. The approach has also been proven to be less dependent of the mesh quality than structural stress-based methods. [1]

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The development of a weld detail library

The detail model

The load cases

Defining the local stress components

The coarse model

The transition matrix

Seam weld solution for solid-solid connection modeling

Seam weld solution for shell-solid connection modeling

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Seam weld solution for shell-shell connection modeling, Simcenter 3D 2021.1 Series

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