Predicting the Ultimate Axial Load Capacity of Joints formed using V-Band Retainers

V-band retainers are widely used in the automotive, aircraft and aerospace industries to connect a pair of circular flanges to provide a joint with good axial strength and torsional rigidity. V-band retainers are manufactured using a cold roll forming process. Despite their wide application, once assembled to a pair of flanges little is known about the interaction between flange and band. Moreover the failure mode of V-band retainers when applying an axial load is not fully understood.

In this thesis the ultimate axial load capacity of V-band retainers is predicted using finite element and theoretical models and validated using experimental testing. It was shown that the ultimate axial load capacity was strongly dependent on the joint diameter, increasing between 114mm and 235mm, and decreasing beyond that. Moreover, the peak in ultimate axial load capacity was dependent on parameters such as the axial clamping load and coefficient of friction, and its position lay between 235mm and 450mm, as predicted by the finite element models. Other geometrical parameters such as flange and band thickness showed large impacts on the ultimate axial load capacity as well.

A theoretical model was developed that allowed the ultimate axial load capacity to be calculated from a single formula for larger bands and using a simple algorithm for smaller bands. This model supported the findings that, depending on the band diameter, the ultimate axial load capacity had a peak, but predicted its position at approximately 181mm. This position at 181mm was validated by the experimental data. However, when compared to the tests, the finite element and theoretical models both over-predicted the ultimate axial load capacity. Both the finite element models and practical tests showed that for small V-bands axial failure is due to a combination of section deformation and ring expansion, whereas large V-bands fail due to ring expansion only. These two distinct types of behaviour were incorporated into the theoretical model.

The hardness development throughout the cold roll forming process was predicted using finite element models. This was validated by hardness measurements, for which a new technique was generated, that directly linked plastic strain and hardness values.