EMSHIP Erasmus Mundus Master Course in Integrated Advanced Ship Design

Transcription

1 EMSHIP Erasmus Mundus Master Course in Integrated Advanced Ship Design Global and Local Strength Analysis in Equivalent Quasistatic Head Waves, for a Tanker Ship Structure, Based on Full Length and 2-3 Cargo Holds 3D-FEM Models Supervisor: Prof. Leonard Domnisoru, "Dunarea de Jos" University of Galati Reviewer: Prof. André Hage, University of Liege Master student: Cioarec Dan Sebastian Galati, February /14/2013 1

2 Chemical Tanker 4000 t Ship Hull Structure Input Data, granted by Ship Design Group, Galati 3D-CAD/FEM full extended model on the ship length, using coarse mesh - development of the 3D-CAD model and 3D-FEM model - boundary conditions - equivalent quasi-static loads and shipwave vertical inplane equilibrium 1D - equivalent beam model - ship hull equilibrium parameters under head quasi-static wave -bending moments and shear forces 3D-FEM two cargo holds model, using coarse mesh - model used to validate the boundary conditions 3D-FEM two cargo holds model, using fine mesh Results: - deformation and stress - hot-spot stress evaluation 3/14/2013 2

3 Ship Hull Structure Input Data Chemical Tanker 4000 Tones prototype ship (granted by Ship Design Group 2007) The 2D - Offset Lines (granted by Ship Design Group Galati, 2007) Main dimensions: Length Over All : m Length Between Perpendiculars: m Breadth moulded: m Design draught: 5.45 m Depth at side (moulded): 8.60 m 3/14/2013 3

4 3D-CAD/FEM Full Extended Model on the Ship Length Dividing the ship to blocks (Ship Design Group 2007) In order to develop the 3D-CAD model, the entire length of the ship was divided into 7 main blocks. Project design data 3D CAD Model 3/14/2013 4

5 3D-CAD/FEM Full Extended Model on the Ship Length Full sized 3D - CAD model without shell plating Full sized 3D - CAD model 3/14/2013 5

6 3D-CAD/FEM Full Extended Model on the Ship Length Aft block of the 3D - CAD model Aft block of the 3D - FEM model Fore block of the 3D - CAD model Fore block of the 3D - FEM model 3/14/2013 6

7 3D-CAD/FEM Full Extended Model on the Ship Length Amidships block of the 3D - CAD model Amidships block of the 3D - FEM model The 3D-FEM full extended model is obtained in the Solid Works Cosmos/M 2007 program, by assembling all the GFM files corresponding to the block model FEM objects presented above. 3/14/2013 7

8 The Global Ship Strength Analysis Based on 1D-Equivalent Beam Model The 1D equivalent beam model for the ship hull is selected for an evaluation of the global strength at the initial design stage, without the possibility to include the local hot-spots stress domains. In order to obtain the equilibrium conditions of the ship hull girder under equivalent head waves, it is used a nonlinear iterative procedure for the free floating and trim condition, making possible to take into account the ship hull shape geometrical nonlinearities. The 1D equivalent beam model numerical analysis is performed by P_ACASV program, developed at the Galati Naval Architecture Department. The input data for the 1D analysis contains the mass distribution diagram along the ship's length and the equivalent beam transversal sections strength characteristics. The height of the equivalent quasi-static head wave is considered to be in the range hw = m, with the step increment Δhw = 1 m. 3/14/2013 8

9 The Global Ship Strength Analysis Based on 1D-Equivalent Beam Model Results Hogging 2.50E+05 M [KNm] 1D-Beam Model Hogging / Quasi-static Wave / CTK Full Load 8.00E+03 T [KN] 1D-Beam Model Hogging / Quasi-static Wave / CTK Full Load 2.00E E E E E E E E E E E E E E hw=0m hw=1m hw=2m hw=3m hw=4m x [m] hw=5m hw=6m hw=7m hw=8m hw=8.123m Bending moment M [knm] for 1D computation Sagging hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m hw=6m hw=7m hw=8m hw=8.123m Shear force T [kn] for 1D computation x [m] 5.00E+04 M [KNm] 1D-Beam Model Sagging / Quasi-static Wave / CTK Full Load 1.00E+04 T [KN] 1D-Beam Model Sagging / Quasi-static Wave / CTK Full Load 0.00E E E E E E E E E E E E E E E E E hw=0m hw=1m hw=2m hw=3m hw=4m x [m] hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m hw=6m hw=7m hw=8m hw=8.123m Bending moment M [knm] for 1D computation hw=5m hw=6m hw=7m hw=8m hw=8.123m Shear force T [kn] for 1D computation 3/14/ x [m]

10 The Global Ship Strength Analysis Based on 1D-Equivalent Beam Model Results Maximum hogging stresses based on 1D-equivalent beam model, h w =8.123 m Panel stress Stress max 1D Stress adm_gs max/adm_gs Maximum σ x deck Maximum σ x bottom Maximum τ xz side Maximum sagging stresses based on 1D-equivalent beam model, h w =8.123 m Panel stress Stress max 1D Stress adm_gs max/adm_gs Maximum σ x deck Maximum σ x bottom Maximum τ xz side The maximum stresses are smaller than the admissible values, the highest ratio being recorded for the bottom, max/adm GS =0.41 in hogging and 0.50 in sagging conditions. The 1D model results will be used for further comparison with the 3D FEM models 3/14/

11 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Boundary conditions Nodes Constraints Type ND_AFT U X U Z Neutral Forced, for equilibrium objective function definition ND_FORE U Z Forced, for equilibrium objective function definition CENTRE PLANE U Y ; R X Symmetry, natural 3/14/

12 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Loading conditions Onboard mass components Chapter Mass [t] Pressure P (kn/m 2 ) Steel Cargo tanks Miscellaneous Outfitting Machinery Accommodation Systems Electrical TOTAL Independent filled up structural cargo tanks Position Mass (t) Pressure P (kn/m 2 ) CARGO Tank CARGO Tank CARGO Tank CARGO Tank CARGO Tank CARGO Tank CARGO Tank /14/

13 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Mass distribution Mass distribution in Light Ship case (hull steel only) Mass distribution in the Full cargo loading case Mass per unit length (t/m) Mass per unit legth (t/m) Lightship mass distribution x (m) Mass distribution in full cargo loading case x (m) Pressure distribution 3/14/

14 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Results wave sagging conditions (hw = 8.123m) Vertical deflection on Z direction (m) Hydrostatic pressure from the external equivalent quasi-static wave Equivalent vonmises stress distribution detail [kn/m 2 ] Equivalent vonmises stress distribution [kn/m 2 ] 3/14/

15 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Results wave sagging conditions (hw = 8.123m) SIGx [N/mm2] DECK 1D-beam Model Sagging / Quasi-static Wave / CTK Full Load SIGVON [N/mm2] DECK max(max) 3D-FEM Model Sagging / Quasi-static Wave / CTK Full Load Deck stress hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x [m] hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x [m] hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH SIGx [N/mm2] BOTTOM 1D-beam Model Sagging / Quasi-static Wave / CTK Full Load SIGVON [N/mm2] BOTTOM max(max) 3D-FEM Model Sagging / Quasi-static Wave / CTK Full Load Bottom stress hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x [m] hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x [m] hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH σ X, 1D model σ von [Mpa] 3D-FEM full extended model TAUxz [N/mm2] N-N 1D-beam Model Sagging / Quasi-static Wave / CTK Full Load TAUxz [N/mm2] N-N max(max) 3D-FEM Model Sagging / Quasi-static Wave / CTK Full Load hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x [m] hw=6m hw=7m hw=8m hw=8.123m adm_gs adm(-) Tangential side stress hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m x[m] hw=6m hw=7m hw=8m hw=8.123m adm_gs adm(-) τ xz [Mpa] 1D model τ xz 3D-FEM full extended model 3/14/

16 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Results wave sagging conditions (hw = 8.123m) Maximum sagging stresses based on 3D-FEM full extended model Panel stress Maximum σ x deck Maximum σ vonm deck Maximum σ x bottom Maximum σ vonm bottom Panel stress Maximum τ xz side Stress 3D ReH Cs=ReH/Stress_3D Stress 1D 3D/1D D adm 3D / adm 1D 3D/1D The maximum stresses results in the deck panel, with significant hot spots around the liquid cargo tank hatch. More accurate hotspots stress factors will be computed based on finer mesh model. 3/14/

17 The Numerical Analysis of Global-Local Ship Hull Strength, Based on the 3D-FEM Full Extended Model Results wave hogging conditions (hw = 8.123m) Hydrostatic pressure from the external equivalent quasistatic wave Equivalent vonmises stress distribution [kn/m 2 ] SIGx [N/mm2] DECK 1D-beam Model Hogging / Quasi-static Wave / CTK Full Load SIGVON [N/mm2] DECK max(max) 3D-FEM Model Hogging / Quasi-static Wave / CTK Full Load Deck stress hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH σ X, 1D model x [m] hw=0m hw=1m hw=2m hw=3m hw=4m hw=5m hw=6m hw=7m hw=8m hw=8.123m adm_gs ReH σ von, 3D-FEM full extended model x [m] Panel stress Stress 3D ReH Cs=ReH/Stress_ 3D Stress 1D 3D/1 D 3/14/2013 Maximum σ x deck Maximum σ vonm deck Maximum σ x bottom Maximum σ vonm bottom Panel stress Maximum τ xz side D adm 3D / adm 1D 3D/1 D Maximum hogging stresses based on 3D-FEM full extended model 17

18 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Coarse Mesh Model Extended on Two Cargo Holds The two cargo holds compartments of the ship ( Ship Design Group 2007) The longitudinal coordinates along X axis of the two cargo holds model are from m to m, including the bulkhead at the end of the second cargo hold. The 3D- FEM of the two cargo holds model 3/14/

19 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Coarse Mesh Model Extended on Two Cargo Holds Boundary Conditions Nodes Constraints Type UX Neutral ND_AFT UY; RX Symmetry, Natural RZ Neutral ND_FORE RZ Neutral UY; RX Symmetry, Natural CENTRE LINE PLANE UY; RX Symmetry, Natural Displacements and rotations Elements rigid-bar for the boundary conditions of the two cargo holds 3D-FEM model Conditions Still water Hogging Sagging Node location Coordinate [m] Displacement w [m] Rotation Ɵ[rad] Node AFT Node FORE Node AFT Node FORE Node AFT Node FORE /14/

20 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Coarse Mesh Model Extended on Two Cargo Holds Results wave hogging conditions (hw = 8.123m) Hydrostatic Pressure from the external equivalent quasi-static wave Vertical deflection on Z direction (m) SIGVON [N/mm2] DECK max(max) 3D-FEM Model Hogging / Quasi-static Wave/CTK Full /2COMP(N) Equivalent vonmises stress distribution [kn/m 2 ] hw=0m hw=8.123m adm_gs ReH_AH40 Equivalent vonmises Deck Stress,σ von [Mpa] 3/14/ x [m]

21 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Coarse Mesh Model Extended on Two Cargo Holds Results Deck elements: hw = m Max. σ x Stress 3D Full Max. σ x Stress 3D 2 Comp σ x 3D Full / σ x 3D 2 Comp Maxi. σ vonm Stress 3D Full Max. σ vonm Stress 3D 2 Comp σ vonm 3D Full / σ vonm 3D 2 Comp Hogging Sagging Bottom elements: hw = m Maximum σ x Stress 3D Full Max. σ x Stress 3D 2 Comp σ x 3D Full / σ x 3D 2 Comp Max.σ vonm Stress 3D Full Max. σ vonm Stress 3D 2 Comp 3/14/ σ vonm 3D Full / σ vonm 3D 2 Comp Hogging Sagging Side elements: hw = m Max.τ xz Stress 3D Full Max. τ xz Stress 3D 2 Comp τ xz 3D Full / τ xz 3D 2 Comp Hogging Sagging ±3% differences

22 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Fine Mesh Model Extended on Two Cargo Holds A finer mesh mode was developed between the longitudinal coordinates of x= m to m. The model was realised by using triangle shell elements, having a total number of elements of and a total number of nodes of Fine Mesh Mesh size comparison between a) coarse mesh size in 3D FEM full extended model and b) fine mesh size two cargo holds compartments 3D FEM model 3/14/

23 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Fine Mesh Model Extended on Two Cargo Holds Results wave hogging conditions (hw = 8.123m) Hydrostatic Pressure from the external equivalent quasi-static wave Vertical deflection on Z direction (m) SIGVON[N/mm2] DECK max(max) 3D-FEM Model Hogging/Quasi-static Wave/CTK Full/2COMP(F- HS) Equivalent VonMises stress distribution [kn/m 2 ] x [m] hw=0m hw=8.123m adm_gs ReH_AH40 Equivalent vonmises Deck Stress, σ von [Mpa], with Hotspot correction 3/14/

24 The Global-Local Ship Hull Strength Analysis, Based on 3D-FEM Fine Mesh Model Extended on Two Cargo Holds Results wave hogging conditions (hw = 8.123m) Deck elements Bottom elements hw = 8.123m Max σ x Stress 3D Full Max σ x Stress 3D 2 Comp Fine mesh σ x Fine 2C/3D Full Max σ vonm Stress 3D Full Max σ vonm Stress 3D 2 Comp Fine mesh σ vonm Fine 2C/3D Full Hogging Sagging hw = 8.123m Max σ x Stress 3D Full Max σ x Stress 3D 2 Comp Fine mesh σ x Fine 2C/3D Full Max σ vonm Stress 3D Full Max σ vonm Stress 3D 2 Comp Fine mesh σ vonm Fine 2C/3D Full Hogging Sagging Side elements hw = 8.123m Maximum τ xz Stress 3D Full Maximum τ xz Stress 3D 2 Comp Fine Mesh τ xz Fine 2C/3D Full Hogging Sagging The safety coefficient with reference to the yield stress limit has the minimum value for the deck stress in hogging and in sagging max 35% differences

25 Comparative Results and Conclusions Stress comparison on all components for each numerical model analysed In conclusion, by using the user subroutines developed with Solid Works Cosmos/M 2007 FEM software, the numerical FEM analysis provides reliable data for the ship strength assessment (under equivalent quasi-static head waves), having a good concordance between the structural models developed in this study. For further studies, as fatigue analysis, should combine the advantages of the four structural models analysed in this work, taking into account the sensitivity of the ship hull structure models, for higher risk panels identification 3/14/

26 CIOAREC DAN SEBASTIAN THANK YOU FOR YOUR ATTENTION! 3/14/