Accession Number : ADA317116

Title :   Fatigue Life Assessment of Steel Pressure Vessels with Varying Stress Concentration, Residual Stress, and Initial Cracks.

Descriptive Note : Final rept.,

Corporate Author : ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS

Personal Author(s) : Underwood, J. H. ; Parker, A. P.

PDF Url : ADA317116

Report Date : JUL 1996

Pagination or Media Count : 23

Abstract : A single-parameter representation of local stress range, initial crack size, and material yield strength is proposed for describing the intensity of the fatigue loading of a structural component. A logarithmic plot of single-parameter fatigue life results provides a single straight-line description of fatigue life behavior over a broad range of material, configuration, and loading conditions. Expressions for calculating the local stress range at the failure site are outlined, including effects of vessel and stress concentrator configuration, applied and overstrain residual stresses, and pressure applied to hole and crack surfaces. The single-parameter approach was used in a comparison of fatigue life results from 41 full-size hydraulic pressure cycle tests of cannon pressure vessels with 12 combinations of material strength, failure location, and applied and residual stresses. A log plot of mean results of the 12 data groups is well represented by a single straight line with a negative slope reasonably close to that predicted by fracture mechanics analysis. A significant outlier from the straight-line trend of the data is a useful indicator of cracking due to other than conventional mechanical fatigue. Two examples of an outlier from the trend of cannon pressure vessel data were confirmed by metallography to be caused by environmental cracking. A third outlier was related to preexisting initial cracks due to rapid machining. The effect of material yield strength on fatigue behavior can be simply and well represented using the single-parameter approach. The R2 correlation coefficient of a logarithmic straight-line fit to the 12 sets of cannon pressure vessel results increased from 0.81 to 0.86 upon inclusion of the effect of material strength.

Descriptors :   *FATIGUE LIFE, *STEEL, *STRESS CONCENTRATION, STRESS STRAIN RELATIONS, STRESS ANALYSIS, CRACKING(FRACTURING), HIGH STRENGTH ALLOYS, FRACTURE(MECHANICS), CRACK PROPAGATION, RESIDUAL STRESS, PRESSURE VESSELS, YIELD STRENGTH, FAILURE(MECHANICS), CYCLIC LOADS, HYDRAULIC PRESSURE.

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE