You need to add, in addition to the assembly constraints, some analysis connections (like bolt tightening or pressure fitting) that will modelize the connection between the meshparts.
Meshparts in CATIA V5 are not compatible, that means that there is no commun nodes between the mesh part, that is why you need to connect those meshparts.

thanks for ure help visitor10215

are u familiar with FEA analysis then? ive got a slightly more complicated problem if u can help

Ive tried modelling a simple hollow cylinder that is clamped at the base just so that i can grasp the FEA concept for fluid representation before i apply the concept to my larger fuel tank problem

in the generative structural anaylsis ive setup parameters to use in a formula for the pressure i.e. density - gravity and height in the tank.

but i think i have two problems:
first, i dont think im correctly setting the height parameter that i need to drive the equation - i created a height parameter using a length parameter with multiple values for different heights i need to analysis

secondly and most importantly - the results im getting show the max pressure at the top of the model rather than at the bottom - obviously with a fluid in the tank max pressure should be at h=base of the tank. ive tried so many ways to get the software to recognise that max pressure is at the base but ive had no luck

if u have any idea mate id be so chuffed - ive spent ages trying to get it to work

cheers