Residual Stress in Crimped Shell and its Adverse Effect on Performance
|Date Published||January 1, 2006|
When a metal shell is crimped in a hose assembly, it is induced with residual stresses. Especially, the tensile stress in the circumferential direction is of particular interest in this paper. The residual stress is often unheeded or underestimated when the shell is designed based on the loading condition in service. However, high residual stress can cause a premature failure of hose assembly by plastically deforming the shell with applied pressure inside the hose. The hose assembly discussed in this paper is consisted of nylon reinforced composite hose, restrictor and deep drawn shell of two different materials, 1008 cold rolled steel and 5052 aluminum. Static and impulse pressure tests were conducted with the hose assembly. The first is to measure strains on the crimped shell under static pressure and the latter to simulate the loading condition in service. Explicit finite element analysis was carried out on the crimping process and then on the static pressure test. In the analysis, the residual stresses, which had been introduced from the crimping analysis, were incorporated in the subsequent pressure test. The overall stress and strain history of the shell is plotted to assess the possibility of material yielding during the impulse pressure test. It is shown that the residual stress has significantly lowered the allowable stress amplitude in the shell. In order to improve the performance of hose assembly, suggestions are made to reduce the tensile residual stress.