Early Stage Researcher
Lloyd’s Register EMEA (United Kingdom)

Project 5: Integrity management of ship structures

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Research Interests:

Marine and subsea engineering; Finite element analysis; Physical model testing; Probabilistic modelling and reliability assessment; Health monitoring; Fatigue and fracture; Shell buckling; Composite mechanics; Fluid-structure interaction; Ice load and modelling; Structural design and construction

Biography:

He obtained his BSc in Naval Architecture and Marine Engineering from Wuhan University of Technology, and MSc in Mechanics of Ship and Marine Structures from China Ship Research & Development Academy. His MSc project applied toroidal shells in subsea pressure structures. He developed a simplified mechanics model for stiffened toroidals, and defended his MSc thesis with distinction.

He worked as a research engineer at China Ship Scientific Research Centre for 3.5 years. Further to his MSc project, he investigated stiffened toroidals analytically and experimentally in a NSFC-funded project, in which he was deputy project manager. He also engaged in other national projects about development of underwater vehicles and stations, where he developed his capabilities in numerical simulation, scaled-model testing, engineering design, field measurements and testing.

He joined Lloyd’s Register EMEA in Dec 2015 as research fellow for European TRUSS project, where he is developing probabilistic models for reliability of passenger ships.

Research Outputs:

  • Du Q.H., Zou G., Zhang B. W., Wan Z. Q. (2015), “Simplified theoretical solution of circular toroidal shell with ribs under uniform external pressure”, Thin-Walled Structures, 96 (11):49-55. DOI: http://dx.doi.org/10.1016/j.tws.2015.07.019
  • Zou G., Du Q.H., Zhang B.W. (2014), “Characteristic analysis of pressure toroidal structures on strength”, Ship Science and Technology, 36 (2):14-19.
  • Du Q.H., Bian R. G., Zou G. (2013), “Assembled toroidal structures”, Patent No. 102182207A.
  • Zou G., Peng X.N, Du Q.H. (2012), “Theoretical solution and essential research on stiffened toroidal shells”, Journal of Ship Mechanics, 16 (1):83-92.
Publications in TRUSS

Crack initiation and propagation threatens structural integrity of welded joints and normally inspections are assigned based on crack propagation models. However, the approach based on crack propagation models may not be applicable for some high-quality welded joints, because the initial flaws in them may be so small that it may take long time for the flaws to develop into a detectable size. This raises a concern regarding the inspection planning of high-quality welded joins, as there is no generally acceptable approach for modeling the whole fatigue process that includes the crack initiation period. In order to address the issue, this paper reviews treatment methods for crack initiation period and initial crack size in crack propagation models applied to inspection planning. Generally, there are four approaches, by: 1) Neglecting the crack initiation period and fitting a probabilistic distribution for initial crack size based on statistical data; 2) Extrapolating the crack propagation stage to a very small fictitious initial crack size, so that the whole fatigue process can be modeled by crack propagation models; 3) Assuming a fixed detectable initial crack size and fitting a probabilistic distribution for crack initiation time based on specimen tests; and, 4) Modeling the crack initiation and propagation stage separately using small crack growth theories and Paris law or similar models. The conclusion is that in view of trade-off between accuracy and computation efforts, calibration of a small fictitious initial crack size to S-N curves is the most efficient approach.

Crack initiation and propagation threatens structural integrity of welded joints and normally inspections are assigned based on crack propagation models. However, the approach based on crack propagation models may not be applicable for some high-quality welded joints, because the initial flaws in them may be so small that it may take long time for the flaws to develop into a detectable size. This raises a concern regarding the inspection planning of high-quality welded joins, as there is no generally acceptable approach for modeling the whole fatigue process that includes the crack initiation period. In order to address the issue, this paper reviews treatment methods for crack initiation period and initial crack size in crack propagation models applied to inspection planning. Generally, there are four approaches, by: 1) Neglecting the crack initiation period and fitting a probabilistic distribution for initial crack size based on statistical data; 2) Extrapolating the crack propagation stage to a very small fictitious initial crack size, so that the whole fatigue process can be modeled by crack propagation models; 3) Assuming a fixed detectable initial crack size and fitting a probabilistic distribution for crack initiation time based on specimen tests; and, 4) Modeling the crack initiation and propagation stage separately using small crack growth theories and Paris law or similar models. The conclusion is that in view of trade-off between accuracy and computation efforts, calibration of a small fictitious initial crack size to S-N curves is the most efficient approach.