Abstract
This report describes a finite element analysis of the breech closure for the 155 mm Cannon M199, which is normally mounted on the Towed Howitzer M198. In this configuration it has has an excellent record for reliability in the field and is easy to service. However when the breech is used in an ammunition test environment, some maintenance problems exist. The analysis is for a 9 body problem with 13 contact surfaces and was solved for both static and dynamic load cases. The two dynamic loads were of similar shape with different loading times. The 9 bodies in the model include, a facility mount, four major structural components, the obturator seal and 3 minor components. The results show that the major components are normally subjected to quasi-static loading but under fast `pressure spike' loadings, the dynamic effect can be important. This is particularly true for the contact between minor components which can show extreme behavior with the fast loading rates.