Three-Dimensional Surface Crack Growth of Maraging Steel Spherical Pressure Shell

Yongmei Zhu,Jiahao Yang,Rujun Li

doi:10.3390/jmse9111280

Abstract

This study focused on the three-dimensional surface crack growth of a spherical pressure shell. Eight maraging steel 18Ni (250) samples were fabricated and tested, and the fatigue crack growth rate curves were obtained. Considering the influence of plastic closure effect and sample thickness on crack growth, the fitting formula of fatigue crack growth only related to materials was obtained. Based on the three-dimensional crack closure theory and the strip yield model, a three-dimensional surface crack growth model of spherical pressure shell was established. By using a self-written program and FRANC3D, the three-dimensional surface crack growth simulations of the spherical shell were completed. The influence of the initial shape ratio and initial depth of the crack on the crack growth and the fatigue life of the spherical shell was analyzed.

Highlights

Deep-sea manned submersibles are high-end marine equipment used for deep-sea exploration and scientific research, as well as the development of ocean mineral resources
Existing large-depth manned submersibles adopt spherical pressure shells, which have the advantages of simple structure, uniform force, good bulk density, and bearing capacity, and which play a role in ensuring the normal operation of internal equipment and personnel safety during the dive [1,2]
Under the combined action of the alternating external pressure of seawater and the welding residual stress, the surface welding toe is prone to cracks and growth, resulting in structural fatigue damage and even failure

Summary

Introduction

Deep-sea manned submersibles are high-end marine equipment used for deep-sea exploration and scientific research, as well as the development of ocean mineral resources. Luo et al [3] analyzed the fatigue crack growth of 7050 aluminum alloy flat plates They found that the crack growth under the standard test strongly depends on the test conditions, and the material parameters obtained were only applicable to the straight-through crack growth under a specific thickness and loading mode. The research on fatigue crack growth behavior and theory has been relatively mature, there are few studies on the surface crack growth of the spherical pressure shell of deep submersibles. The 3D stress state of the crack tip is different from the standard test, so the fatigue performance parameters measured by the 18Ni (250) sample under the standard test were directly used to analyze the growth of the 3D cracks on the surface of the spherical shell and predict the life. To ensure the accuracy of the test results, the 8 samples were grouped in pairs, and t1e#s,te2d-2t#NwS, au3imcm-e1pb#luee,rn3d-2e#r,e4a-cS1ht#re,gsrasonRudapti4oo-2f #s.trTeFhsreseqLruotaeeatndsicotiny.sg(TcHhhzee)m8esaimsMspahxleoimswuwnmLeiornaedTn(uKabmNlM)ebei1nr.iemFduir1ms-t1,#a, 1-2#, 22-mmlength pr11e---12c##rack was pref0a.b1 ricated on the5sample, th5e fatigue crack 0g.r5owth rate test wraatisocsaRrrwi22e--ed12r##eou0t.1b,y0.s3i,n0u.5so, 0iad.n3adl wave loading at a 0.7, respectiv5ely

Material Properties

Simulation of Three-Dimensional Surface Crack Growth of Spherical Shell

The Effect of Crack Initial Shape Ratio on Crack Growth