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

Khaled M Saadeldin Eldalil,Amr M S Baz

doi:10.1155/2009/317202

Khaled M Saadeldin Eldalil, Amr M S Baz

Open Access

https://doi.org/10.1155/2009/317202

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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%.

Highlights

The analysis of moving loads on elastic structures has drawn the attention of many researchers over the last century
The extent of the efforts dedicated to studying this problem is justified by the wide variety of structures which are subjected to moving loads, such as bridges, gun barrels, rails, work pieces during machining operations, as well as fluid-conveying pipes
The load acting on a cylindrical shell, with added periodic stiffeners, under a transient pressure pulse propelling a pullet has been experimentally studied

Summary

Introduction

The analysis of moving loads on elastic structures has drawn the attention of many researchers over the last century. The extent of the efforts dedicated to studying this problem is justified by the wide variety of structures which are subjected to moving loads, such as bridges, gun barrels, rails, work pieces during machining operations, as well as fluid-conveying pipes. In all these structures, the emphasis is placed on studying two basic phenomena. The second considered phenomenon is associated with the dynamic instabilities that can be generated when the velocity of the moving loads exceeds certain critical values. Vibration of gun barrels is one of the most affected because it leads to dispersion of shot patterns. Longer barrels are more susceptible to these vibrations, Fryba [1]

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