Dynamic Stability of Cylindrical Shells under Moving Loads by Applying Advanced Controlling Techniques Part I—Using Periodic Stiffeners

Abstract

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%.

Dynamic Stability of Cylindrical Shells under Moving Loads by Applying Advanced Controlling Techniques—Part II: Using Piezo‐Stack Control

“…The expected deforming vibration due to these pressures ranges between 7.2 and 25 kHz, Part 1 [16], that is, far enough from the first mode frequency of the piezoelectric stack (64 kHz), as shown in Figure 2. …”

“…The measurements are carried out at two operating helium pressures, 1600 and 2000 psi, and the controller (piezo-stack) is installed very close to location number 2 on the gun tube, as indicated in part 1 [16]. The expected deforming vibration due to these pressures ranges between 7.2 and 25 kHz, Part 1 [16], that is, far enough from the first mode frequency of the piezoelectric stack (64 kHz), as shown in Figure 2. …”

“…Using periodic stiffeners distributed on the shell tube surface is tried theoretically by Ruzzene and baz [9,10], Aldareihem and Baz [11,12], and others [13][14][15], and studied experimentally in part 1, Eldalil and Baz [16].…”

“…As indicated in part 1 [16], the stiffeners are composed of three parts, two half rings (2, 3), in Figure 5, and one outer ring, surrounding the shell tube (1); consequently, in active control, the outer ring is removed and the stacks (4, 7) are rested on the upper and lower half rings. A stainless steel clamp strip (6) is used to hold the components fixed in position, and the screw (5) is used to create initial tension in the clamp strip and consequently generates compression force distributed around the shell tube substituting the removed outer ring of the stiffener.…”