Hello all, I am having some difficulty applying pre-tension to a bolt modelled with beam elements (type B31). The bolt is formed by a wire, partitioned into 3 sections and meshed. It is assigned a circular section appropriate for an M64 bolt. I apply a 'Bolt load' to the ​​​​​​​central section of the wire and apply the pre-tension force (+1.5e6N). The bolt always seems to deform or buckle causing the connecting parts to displace significantly. I have tried both positive and negative bolt loads. With a +ve force the parts receive a clamping force, the nodes appear to move together to create the tensile force in the bolt but the elements between the nodes do not seem to shorten in length and instead the nodes displace sideways to accommodate the change in length. Large moments appear to get introduced into the beam. Has anyone experienced this please?​​​​​​​ Regards Ed

Abaqus ​​​​​​​