摘要：The load acting on a cylindrical shell, with added periodic stiffeners,
under a transient pressure pulse propelling a pullet (gun case) has been experimentally
studied. This study is based on two modes of velocities, the first is subcritical mode and
the second is supercritical mode. The stiffeners are added to the gun tube of an
experimental gun facility, of 14 mm bore diameter. The radial strains are measured by
using high-frequency strain gage system in phase with a laser beam detection system.
Time-resolved strain measurement of the wall response is obtained and both precursor
and transverse hoop strains have been resolved. The time domain analysis has been done
using “wavelet transform package” in order to determine the frequency domain
modes of vibrations and detect the critical frequency mode. A complete comparison
of the dynamic behavior of the shell tube before and after adding periodic stiffeners has
been done, which indicated that a significant damping effect reaches values between 61.5
and 38% for subcritical and critical modes. The critical frequency of the stiffened shell
is increased, so the supercritical mode is changed to subcritical mode. The amplification
and dispersion factors are determined and constructed; there is a reduction in the
corresponding speed frequencies by about 10%. Also the radial-bending vibrations and
tube muzzle motions are detected at muzzle velocity ratio of 0.99%, the results indicated
that there is a significant improvement in increasing the number of rounds per second by
about 36% and increasing the pointing precision by about 47%.
