A bolted joint is used to hold two or more parts together to form an assembly of a mechanical structure. In order to achieve expected physical behaviors of a bolted joint structure, a detailed three-dimensional bolt model, which fully includes the bolt pretension effect and the frictional behavior at contact interfaces, is desirable. However, for a large, complex structure, detailed modeling of bolted joints is difficult because of problem size restrictions and computational costs associated with analyzing the entire structure.

The bolt thread modeling technique available for 2D and 3D contact elements offers simplified modeling with accuracy close to that of a true threaded bolt model. Bolt threads can be simulated by assigning a bolt section (defined by the SECTYPE command) to contact elements that are overlaid on a smooth cylindrical bolt surface. To approximate the behavior of the bolt, calculations are performed internally based on the user-specified thread geometry data and the end points of the bolt axis (input via the SECDATA command).

The bolt thread modeling technique is useful for system level modeling where the primary bolt function is to transfer a load. The absence of geometric details and refined mesh discretization in the thread region also makes it a computationally inexpensive method. This technique can be applied to 3D models and 2D axisymmetric models