Predicting the collision damage of steel ring-stiffened cylinders and their residual strength under hydrostatic pressure

Do, Quang Thang,Muttaqie, Teguh,Park, Sang-Hyun,Shin, Hyun Kyoung,Cho, Sang-Rai Elsevier 2018 Ocean engineering Vol.169 No.-

<P><B>Abstract</B></P> <P>This study focusses on deriving a formulation to predict the permanent damage of steel ring-stiffened cylinders subjected to dynamic lateral mass impact and their ultimate strength in both intact and damaged conditions under hydrostatic pressure. The damage scenario considered in this study can represent the collision accidents of offshore ring-stiffened cylinder structures with supply vessels or floating objects. To validate the numerical modelling and analytical techniques, six small-scale ring-stiffened cylinder models were fabricated. Drop tests with a knife-edge indenter were performed to generate the damage on four cylinder models. Then, all the models were subjected to hydrostatic pressure tests for assessing their ultimate strength in damaged and intact conditions. Next, rigorous parametric studies on the actual design of full-scale ring-stiffened cylinder examples were performed by changing the design variables. Simple design equations were derived for predicting the extent of local denting damage and the residual strength of the damaged ring-stiffened cylinders. The accuracy of the derived formulation has been established by comparison with the results of tests and finite element analyses, showing a good agreement for all the loading cases. This formulation can be useful for the purposes of design of ring-stiffened cylinders under the risk conditions of marine structures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Residual strength formulations of damaged ring-stiffened cylinders have been derived and proposed. </LI> <LI> A simple design equation to predict the extent of the maximum permanent dent depth of ring-stiffened cylinders under dynamic mass impact were also proposed. </LI> <LI> Nonlinear numerical methods for ring-stiffened cylinders are provided with reasonable accuracy and reliability. </LI> </UL> </P>

Dynamic lateral mass impact on steel stringer-stiffened cylinders

Do, Quang Thang,Muttaqie, Teguh,Shin, Hyun Kyoung,Cho, Sang-Rai Elsevier 2018 International journal of impact engineering Vol.116 No.-

<P><B>Abstract</B></P> <P>This paper focuses on the impact responses of large-diameter, thin-walled steel stringer-stiffened cylinders subjected to low-velocity mass impact. The impact scenarios employed in this study represent load actions as a result of supply vessel collisions with the main legs of floating offshore platforms and wind turbine structures. Two steel stringer-stiffened cylinders were fabricated and drop tests were performed at mid-span, using a rigid knife-edged indenter. The details of the experimental setup, test procedure and test results are reported in this paper. The experimental data appear to be useful for future benchmark studies. Numerical predictions of the impact response of the test models were simulated by means of the explicit solver of the finite element software package ABAQUS. The numerical predictions show a good agreement with the test results. The effect of the strain-rate hardening definition on the results is highlighted. Furthermore, parametric studies were conducted on stringer-stiffened cylinder models in order to clarify the progressive impact responses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dynamic mass impact tests have been performed to investigate the response of stringer-stiffened cylinders. </LI> <LI> Numerical simulations of the impact response of the stringer-stiffened cylinders are conducted. </LI> <LI> The effects of the strain-rate hardening definition on the numerical results are highlighted. </LI> <LI> Parametric studies were conducted on stringer-stiffened cylinder models to clarify the effect of boundary conditions, impact velocities, impact locations, stringer-stiffeners as well as striker header shapes. </LI> </UL> </P>

Hepatic Artery Thrombosis Associated with Fungal Infection: Report of Two Cases

( Dang Do Hai ),( Nghia Nguyen Quang ),( Thang Le Quang ),( Khai Ninh Viet ),( Tuan Tran Minh ),( Phuong Tran Ha ),( Tuan Hoang ),( Dung Tran Dinh ) 대한간학회 2023 춘·추계 학술대회 (The Liver Week) Vol.2023 No.1

Numerical studies of the failure modes of ring-stiffened cylinders under hydrostatic pressure

Teguh Muttaqie,Do Quang Thang,PRABOWOADITYARIO,조상래,손정민 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.4

The present paper illustrates a numerical investigation on the failure behaviour of ring-stiffened cylinder subjected to external hydrostatic pressure. The published test data of steel welded ring-stiffened cylinder are surveyed and collected. Eight test models are chosen for the verification of the modelling and FE analyses procedures. The imperfection as the consequences of the fabrication processes, such as initial geometric deformation and residual stresses due to welding and cold forming, which reduced the ultimate strength, are simulated. The results show that the collapse pressure and failure mode predicted by the nonlinear FE analyses agree acceptably with the experimental results. In addition, the failure mode parameter obtained from the characteristic pressure such as interframe buckling pressure known as local buckling pressure, overall buckling pressure, and yield pressure are also examined through the collected data and shows a good correlation. A parametric study is then conducted to confirm the failure progression as the basic parameters such as the shell radius, thickness, overall length of the compartment, and stiffener spacing are varied.

Implicit-based computer-aided design for additively manufactured functionally graded cellular structures

Nguyen Cong Hong Phong,Kim Youngdoo,Do Quang Thang,Choi Young 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.3

Additive manufacturing has enabled the fabrication of complex structures such as cellular structures. Although numerous design frameworks have been proposed for cellular structures, their effectiveness was limited owing to the use of B-rep-based representation. To address the limitations in previous research, this study proposes an implicit-based computer-aided design framework customized for additively manufactured functionally graded cellular structures (AM-FGCSs). The proposed design framework effectively aids in both single- and multiscale structural optimization for designing FGCSs. Moreover, implicit-based modeling afforded a reliable geometric representation that could efficiently assist computation tasks such as visualization, validation, and process planning for fabrication. In addition, two case studies were conducted to demonstrate the effectiveness of the proposed framework for designing FGCSs. The first case study on a three-point bending beam design problem proved the practicality of implicit-based representation in multiscale structural design. Meanwhile, the second case study validated the proficiency of the proposed framework in process planning for fabrication and engineering analysis, the two most vital computation tasks in designing cellular structures.

Experimental investigations on the failure modes of ring-stiffened cylinders under external hydrostatic pressure

Sang-Rai Cho,Teguh Muttaqie,Quang Thang Do,Sinho Kim,Seung Min Kim,Doo-Hwan Han 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.6

This paper reports on the experimental investigations on the failure modes of ring-stiffened cylinder models subjected to external hydrostatic pressure. Nine models were welded from general structural steel. The shells were initially formed by cold-rolling, and flat-bar ring frames were welded to the shell. The hydrostatic pressure tests were conducted by using water as the medium in pressure chambers. The details of the preparation and main test were briefly explained. The investigation identified the consequence of the structural failure modes, including: shell yielding, local shell buckling between ring stiffeners, overall buckling of the shell together with the stiffeners, and interactive buckling mode combining local and overall buckling. In addition, the ultimate strengths were predicted by using existing design codes. Non-linear numerical computations were also conducted by employing the actual imperfection coordinates. Finally, accuracy and reliability of the predictions of design formulae and numerical were substantiated with the test results.

Experimental investigations on the failure modes of ring-stiffened cylinders under external hydrostatic pressure

Cho, Sang-Rai,Muttaqie, Teguh,Do, Quang Thang,Kim, Sinho,Kim, Seung Min,Han, Doo-Hwan The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.6

This paper reports on the experimental investigations on the failure modes of ring-stiffened cylinder models subjected to external hydrostatic pressure. Nine models were welded from general structural steel. The shells were initially formed by cold-rolling, and flat-bar ring frames were welded to the shell. The hydrostatic pressure tests were conducted by using water as the medium in pressure chambers. The details of the preparation and main test were briefly explained. The investigation identified the consequence of the structural failure modes, including: shell yielding, local shell buckling between ring stiffeners, overall buckling of the shell together with the stiffeners, and interactive buckling mode combining local and overall buckling. In addition, the ultimate strengths were predicted by using existing design codes. Non-linear numerical computations were also conducted by employing the actual imperfection coordinates. Finally, accuracy and reliability of the predictions of design formulae and numerical were substantiated with the test results.