Fatigue of Compound Cylinders
Abstract
Compound cylinders have historically been designed such that the maximum shear stress is equal in each cylinder sector. This is the optimum condition for yielding in the cylinder since all sectors yield at the same pressure. If compound cylinders are subject to fatigue, this is not the case. A better design criterion is to equate the maximum tensile normal stress in each sector, since the maximum tensile stress controls fatigue crack propagation. This assumes that most of the life is spent in crack propagation. The derivation of the geometric conditions resulting in equal tensile stresses in each sector is presented in this report. The geometric optimization of the general cylinder with n sectors is very complex and is a function of the internal and external pressures and the allowable stress, unlike the optimization that assumes that the maximum shear stress dominates. There is one case for which the two methods can be explicitly compared, i.e., a cylinder with only two sectors and no external pressure. This case is studied in detail. The liners of these cylinders are much thinner when the maximum shear stress is assumed than when the maximum shear stress is equalized. To demonstrate that the maximum normal stress is a superior technique, several cylinders were designed to have a constant fatigue life by using both this method and the maximum shear stress method.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1990
- Accession Number
- ADA227323
Entities
People
- J. A. Kapp
- P. S. Crofton
Organizations
- United States Army Armament Research, Development and Engineering Center