acm (shell gap)

Creates a hexa element with RBE3 (Nastran/OptiStruct) or DCOUP3D (Abaqus) elements projecting and connecting to the surrounding shell elements. This realization does not use the shell thickness to calculate the hexa offset, therefore the hexa will project and be touching the shell elements.

For Nastran and OptiStruct, this realization uses the prop_nastran_acm.tcl property script. For Abaqus, it uses prop_abaqus_acm.tcl.

Figure 1.

ACM Realization Options

Option	Action
thickness	Select a thickness option used for dimensioning and positioning hexas. shell gap Project the hexa spot to touch the shell elements. The position is independent from any thickness. equival. (T1+T2)/2 Create hexa elements with RBE3 elements projecting and connecting to the surrounding shell elements. This realization uses the shell thickness to calculate the hexa offset from the shell elements. In the case where the model is a 3T connection, the acm (equivalenced-(T1+T2)/2) realization will join the hexa elements. Figure 2. detached (T1+T2)/2 Create hexa elements with RBE3 elements projecting and connecting to the surrounding shellstr elements. This realization uses the shell thickness to calculate the hexa offset from the shell elements. In the case where the model is a 3T connection, the acm (detached-(T1+T2)/2) realization will not join the hexa elements. Figure 3. mid thickness Calculate the hexa spot size (thickness) as the air gap between the two connected parts. If there is no gap, or even a penetration, the hexa spot size will always be modeled with 1.0. const thickness Specify the hexa spot size (thickness). maintain gaps Calculate the hexa spot size (thickness) as the gap distance reduced by two times the specified value for maintain gaps. The position is independent from any thickness.
num hexas	Create a hexa cluster with 1, 4, 8, 12, 16 or 32 hexas, which are arranged in a predefined pattern. Figure 4. Note: Available for all ACM realization types.
coats	Define the number of hexa elements required along the thickness. Multiple solid coats are supported.
orthogonal faces	Force the creation of perfectly orthogonally-shaped hexas. Figure 5. . The two leftmost realizations were performed with the orthogonal faces option enabled. Note: Available for any kind of ACM weld, if num hexas is set to 1.