Abstract
Ship hatch corner is a common structure in a ship and its fatigue problem has always been one of the focuses in ship engineering due to the long–term high–stress concentration state during the ship’s life. For investigating the fatigue life improvement of the ship hatch corner under different shot peening (SP) treatments, a series of fatigue tests, residual stress and surface topography measurements were conducted for SP specimens. Furthermore, the distributions of the surface residual stress are measured with varying numbers of cyclic loads, investigating the residual stress relaxation during cyclic loading. The results show that no matter which SP process parameters are used, the fatigue lives of the shot–peened ship hatch corner specimens are longer than those at unpeened specimens. The relaxation rate of the residual stress mainly depends on the maximum compressive residual stress (σRSmax) and the depth of the maximum compressive residual stress (δmax). The larger the values of σRSmax and δmax, the slower the relaxation rates of the residual stress field. The results imply that the effect of residual stress field and surface roughness should be considered comprehensively to improve the fatigue life of the ship hatch corner with SP treatment. The increase in peening intensity (PI) within a certain range can increase the depth of the compressive residual stress field (CRSF), so the fatigue performance of the ship hatch corner is improved. Once the PI exceeds a certain value, the surface damage caused by the increase in surface roughness will not be offset by the CRSF and the fatigue life cannot be improved optimally. This research provides an approach of fatigue performance enhancement for ship hatch corners in engineering application.
Highlights
As a large–scale structure integrating safety, economy and practicability, the ship’s fatigue problem is the focus of attention
The model is composed of two parts: one is the foundation support of the T section, an opening made at the web to prevent the web bulking during the fatigue tests, and the other is the ship hatch corner specimen which is welded to the panel and welded with the U–shaped chuck symmetrically on both sides of the upper end
Treatment in the ship engineering field, this paper illustrates the relationship between the stress relaxation and fatigue life of the actual ship hatch corner structure in the shot
Summary
As a large–scale structure integrating safety, economy and practicability, the ship’s fatigue problem is the focus of attention. Society (IACS) Regulations for Bulk Carriers [1] and China Classification Society (CCS)’s “Guidelines for Fatigue Strength Assessment of Hull Structures” [2] both provide relevant regulations for ship hull structures that are prone to fatigue problems. Guoqing et al [3] proposed to use the equivalent wave method to evaluate the fatigue life of hatch corners. The results of the equivalent wave method agree well with those from the spectral fatigue analysis. Selle et al [4] used the finite element method with a fatigue assessment technique developed by Germanischer
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