Design for an Internal Circular Compression Band Restraint Device (Marman Clamp, V-Band)

An application requirement is addressed that does not allow a conventional external vband to be used . An internal v-band design was done which satisfies the performance requirements . This report describes that design and the results of the analysis. The desired result of this analysis is to verify that the v-band will not fail under the applied load, the v-band is not self-locking and therefore fail to release when desired, the required expansion force is not greater than a specified limit, and that the natural vibration modes and frequencies do not present any anticipated problems (such as resonance and/or mode coupling) in the application . A successful design is illustrated using the output from a Finite Element Analysis . A sensitivity analysis indicates the importance and interrelationships between several key design parameters, a result that tends to agree with many years of v-band design experience at Sandia National Laboratories. Introduction A requirement for a cylindrical mechanical coupling device can easily be fulfilled with a conventional circular compression band restraint, typically termed a `v-band' . The v-band coupling technique is well understood for coaxial cylinders butted end-to-end . In the past this has typically been accomplished by providing a pair of matched engagement flanges on the outer surface of the cylinders l ' 2 and coupling the cylinders together using the engagement flanges and a circular compression band installed as shown in Figure 1 . Note the flanges and the v-band incorporate angled contact faces that translate a portion of the radial compression force into an axial force to effectively preload the butt joint . Figure 1 . A typical external v-band installation An application requirement for a v-band design was presented that did not allow conventional external v-band use, for a variety of reasons . An alternative internal v-band design was proposed which would satisfy the performance requirements . This report describes that design and the results of the analysis . The v-band is intended to be inserted inside a pair of cylindrical mating parts butted together end-to-end to provide a robust, decoupling mechanical joint, as shown in Figure 2. Figure 2 . A generic internal v-band installation