Automatic identification and definition of bolted contacts
Performing simulations on complex assemblies is an arduous task as the connection between each part interface must be defined. Certain simulation packages can identify part interfaces and automatically create a bonded contact definition at each of these interface locations. Bonded contact areas are treated as if part interfaces are welded or glued together. However, this is insufficient for bolted connections as bolts are neither glued nor welded to achieve the intended connection.
Bolted connections are typically treated as bonded contacts at the clamping interface of the bolt head, clamping interface of the nut and the bolt shank/nut interface. Bolt pretension clamps components between the bolt head and the nut. The interfaces touching the clamped material are modelled as being bonded to the interfacing material. Nuts are typically modelled as being bonded to the bolt shank. This models the interaction between the screw threads of both the bolt and the nut.
Components that are bolted do not interface with the bolt shank directly. Sliding contacts are used to model this interaction. Therefore, to correctly approximate the physics of a bolted assembly, analysts require at least 4 connections (3 bonded, 1 sliding). For a small number of bolted connections this procedure can be performed manually. However, for large bolted assemblies with hundreds of bolts and nuts, this manual process is not feasible.
Altair SimSolid™ automatically identifies parts with a hexagonal shape as either a bolt head or a nut. If the hexagonal shape is connected to a cylinder, then it is automatically characterised as a bolt. The remaining hexagonal part is characterised as the nut. When users activate the automatic connection tool and provide both a gap and penetration tolerance, for connection interfaces, then SimSolid intelligently identifies each part of the assembly and creates a bonded contact at applicable part interfaces. Bolted connections, however, are handled separately by automatically defining both bonded and sliding contacts at the required locations for achieving the correct physics during a simulation as depicted in Fig 1.