gcrc 2018 presentation (04)이제명

GCRC-SOP 8th Year International Workshop

Project 2-4

1Project 2-4 : Performance Evaluation and Application Technology in Extreme Environment

Global LNG demand will grow to 450 million tons by 2030, from 284 million tons in 2017, with

Asia driving the growth (Bloomberg New Energy Finance, 2018)

Demand for LNG carriers has been on a steady increase due to a rise in LNG demand in line

with eco-friendly policies in China and the proactive push for energy exports by the United

States

Introduction

2

Purpose: Performance evaluation and application technology of the material and structure

in extreme environment (cryogenics, impact, and thermal stress)

Contents: Topic 1 : Assessment of dynamic behavior of insulation materials at cryogenics

(Extreme Environment: Cryogenics, Impact)

Topic 2 : Assessment of thermal stress on steel structure caused by cryogenic leakage (Extreme Environment: Cryogenics, Thermal stress)

Method: Experiments

Project 2-4 : Performance Evaluation and Application Technology in Extreme Environment

Results of Topic 1


Research background

• Sloshing impact loads can lead to defect on the insulation system

• Defected insulation system arise heat penetration into inner cargo hold

4

Sloshing & hydrostatic pressure

Cryogenics (-163°C)

Primary Barrier

Plywood

(R)PUF

Triplex

(R)PUF

PlywoodMastic

LNG Carrier

Cargo Containment System

Extreme Environment

• PUF has a closed cell structure with a high compressive strength,

leakage resistance, a low density, and low thermal conductivity

• Mechanical strength and thermal conductivity of the PUF are

significantly affected by its own density state


Introduction

• Investigation of density dependent mechanical and thermal

characteristics of PUF under impact loading condition

• Investigation of optimum density condition of PUF

Research Goal

• Material : Polyurethane Foam (PUF) (blowing agent: HFC-245fa)

• Density : 90, 113, 134, 150, and 180 kg/m3

• Test temp. : 20 and -163°C

• Impact energy : 110 J

Conditions

• Fabrication of density-dependent PUF using polyol system,

Isocyanate, and blowing agent

• Polyol system : Isocyanate : blowing agent = 100 : 116 : x


Manufacturing process of PUF in lab scale

HEAT ~~~~~~~

RISINGMIXING

AB A : POLYOL SYSTEM

B : ISOYANATE + HFC‐245fa

POLYURETHAE FOAM4500RPM

Material Preparation


Drop Tower Impact Apparatus

• Impact load testing was done using the free drop impact test

• CEAST 9340 Drop Tower Impact Apparatus

- Energy range: 0.3 ~ 405 J

- Impact velocity: 0.77 ~ 4.65 m/s

- Drop height: 0.03 ~ 1.10 m

- Weight range: 1.00 ~ 37.5 kg

• Test condition : Impact energy 110 J guide rail

loadcell

specimen

lifter

impactor

anti-rebound system

supporter


Density dependent SS Curve(110J_-163℃)

Mechanical Results

• Yield strength, the end of initial elastic response, increases with increase in strain rate

• Up to the onset of densification dynamically deformed PUF is capable of high energy

absorption

• In cryogenic temperature, peak force and stress fluctuation increased as the cells get

stiffer than room temperature

Comparison static load with dynamic load


Microstructural Results

• Generally cells that consist of PUF are smaller and dense in high-density PUF, resulting in

small deformation and high peak force in elastic region

• As the density of PUF increase, size of cell decrease resulting in high thermal conductivity

90kg/m3 113kg/m3 134kg/m3 151kg/m3 180kg/m3

Density(kg/m3)

Thermal conductivity(W/mK)

90 0.02471

113 0.02588

134 0.02709

151 0.03012

180 0.03421

• Glass fiber reinforced polyurethane foam (RPUF) is produced by

adding glass fiber to improve the mechanical performance of PUF

• Necessity of investigation of mechanical response of insulation

material by low energy repetitive impact load


Introduction

• Effects of repetitive impact loads on mechanical characteristics of

reinforced polyurethane foam (RPUF)

• Performance degradation of RPUF owing to repeated impact loads

Research Goal

• Material : glass fiber-reinforced polyurethane foam (RPUF)

• Density : 120 kg/m3 (15 wt% fiber-glass)

• Test temp. : 20°C

• Impact energy : 2.39, 3.07, and 3.75 J

Conditions


Velocity-time history in accordance with the impact energy and the repetitive

3.75 J

Mechanical Results

• Impact velocity-time history was investigated according to the impact condition

• Initial velocity, rebound velocity, and acceleration increased with the increase of

impact energy

• With the repetitive impact, rebound velocity and acceleration decreased

2.39 J3.07 J3.75 J


2.39 J 3.07 J 3.75 J

Force time history of RPUF specimen under various impact condition

Mechanical Results

• Force time history in accordance with the impact energy and the number of repetitions

• Under the repetitive impact of 2.39 J, almost no change in force time history

• Maximum force decreased and duration increased under the repetitive impact of 3.75 J


Displacement/force/deformation under repetitive impact

Mechanical Results

• Quantitative evaluation of impact performance degradation by impact energy and the

number of repetitions

• Under 3.75 J, Maximum force 13.4% decreased, displacement 40.2% increased

• Plastic deformation was observed only at 80th impact of 3.75 J (Approx. 2%)

2.39 J3.07 J3.75 J

2.39 J3.07 J3.75 J

2.39 J3.07 J3.75 J

• Composites used in LNG cargo containment system consist of PUF,

plywood, and epoxy resin as an adhesive between PUF and plywood

• Additional enhancement through absorption energy is necessary for

impact loading against LNG sloshing


Introduction

• Dynamic response of specimens fabricated from PUF, plywood, and

epoxy resin with varying weight fractions of embedded glassbubble

• Investigation of glassbubble wt% dependent mechanical and

thermal characteristics of PUF-plywood under impact load.

Research Goal

• Material : PUF-plywood (resin : epoxy with glassbubble)

• Glassbubble (wt%) : 0, 10, and 20

• Test temp. : 20 and -163°C

• Impact energy : 30 J

Conditions

Polyurethane foam

Epoxy resin

Plywood- Size = 50 × 50 mm2

- Thickness = 7.19 mm- Density = kg/m3

- Lamina = 5 layers


Material Preparation

• Polyurethane foam is made of POLYOL + ISOCYANATE + Agent Blowing in accordance

with weight fraction of 1000:1160:50

• Epoxy resin with hollow glassbubble is physically mixed about 30min and the

ultrasonic dispersion of 20kHz use about 30min


Experimental Scenarios & Verification of repeatability

• To evaluate the dynamic response of the specimens with epoxy resin, impact tests

were conducted at an impact energy of 30 J.

• All tests were conducted at 78.2 s-1, which corresponds to an impact height of

361mm and an impactor mass of 8.475 kg

• For verification, each of the scenarios was repeated five times under the same test

environment.

• Deviations : < 5% (AT tests) and <10% (CT tests)


Microstructural Results

• SEM images at 300 and 100 μm were examined

• 0wt% : display the excellent dispersion from the manufactured composites without pores

• The microstructures of epoxy resin/HGM with 20 wt.% appeared the agglomeration

O wt% 1O wt%

O wt% 1O wt%

2O wt%

2O wt%


Mechanical Results

• The fluctuation in force-deformation is clearly reduced with further content of HGM.

• Dynamic relationship at cryogenic temperature shows strain hardening.

• In contrary, the relationship at ambient temperature shows strain softening.

Results of Topic 2


IEA Energy Outlook, 2017

Research background

Increase of demand on LNG carrier, LNG bunkering, FSRU, etc.

• 29 FSRUs currently in operation worldwide and additional 14 FSRUs until 2022

(Westwood Global Energy, 2017)

Cryogenic spill can be significant problem to personnel and assets

• Cryogenic burns, asphyxiation, steel embrittlement, NG cloud, etc. (Lloyd’s Register, 2015)

• LNG vessel and LNG fueled ship have the same problem

Representative accident of LNG leakage


Research background

Methods to prevent undesirable accident from LNG spill

• Cryogenic spill protection(CSP) coating application

• CFD-based estimation of cryogenic fluid spill hazard area

• Cryogenic spill experiment and structural numerical analysis

Securing structural integrity from understanding cryogenic behavior of hull steel → Top Priority

Database for damage assessment for cryogenic fluid leakage on hull structure

21

Cryogenic Spill Protection coating Deck Spill simulation LNG internal spill simulation


Experimental setup of the liquefied nitrogen spill

Test method

Investigation of the effect of cryogenic spill of steel plate with initial defect

Polyurethane cooling trough installed to divide the spill area

Cryogenic fluid : Liquid nitrogen(LN2)

• LN2(-196°C) was selected considering lower temperature and safety than LNG(-163°C).

Experimental equipment

• The strain gauge measures the thermal stress of the steel plate where deformation occurs

• DAQ(Data aquisition) records strain on steel plate in real time

Experimental equipment; (a) strain gauge (b) thermocouple(c) Cyanoacrylate (CN) adhesive (d) data aquisition

(a) (b)

(c) (d)


Pre-notched defect

intermittent welding defect

Test method

Frist scenario: Pre-notched plate (SS400)

• Plate thickness: 8T / Initial crack length: 40mm

Second scenario: intermittent welded plate (SS400)

• Plate thickness: 10T / Defect welding length: 20mm

cooling trough and gauge attachment location


Test result of Pre-notched and intermittent welded plate

Pre-notchedplate Strain 1

Strain 2

Strain 3

Strain 2Strain 1

Strain 3

Strain 1

Strain 3

Strain 2

Strain 1

Strain 3

Strain 2

Intermittentwelded plate


Plate type - AH36

Thickness – 6mm

Welding – Flux Cored Arc Welding(FCAW) method

• Automatic welding to improve the penetration defect (Over 90% use in shipbuilding industry)

Specimen Type Selection

Initial defect condition on the plate is excluded.

Welding condition is considered.

• Focusing on the center part of the weld directly affected by the cryogenic temperature

Modification of Test Condition

Crack propagation of intermittent welded plate

Steel type: AH36 Length: 500mm Width: 500mm


Test specimen and equipment

Specimen Preparation

1

2

3

4

5

6

78 Welding method: FCAW Welding passes: 3 Root gap: 60o (4mm) Root face: 60o (2mm) Welding rod: E71T-1C (1.4mm) Ceramic backing: U type (6mm)

Upper jigLower jig

Automatic welding machine

: Strain gage point

Minimize weld start and end defects Ensure safety by preventing welding crack

Insulation type: Polyurethane foam Boundary range : Partial


Constraint of AH36 Steel and welding (FCAW)

• Cooling at ambient temperature during 1 day to eliminate the effect of time after welding

Selection of spill area and measurement site and installation

• Liquid nitrogen spill for 20 minutes

Test process for cryogenic spill

Methodology

LN2 Spill (20min) Boiling Complete vaporization


Thermal strain at each point located on the steel plate (AH36)

1

2

3

4

Y

X

Analysis of thermal strain (inside boundary)

• Compressive strain mainly occurs at internal part of the boundary

• At both end points(location 2, 3), strain is higher than at the center

• Strain difference due to distance from weld line is not evident

• Initial over-cooling causes abrupt tensile thermal stress

-------- x-axis ------- y-axis

Leakage Test Results

2 3 41


5

6

78

Y

X

Analysis of thermal strain (outside boundary)

• The exterior part of the boundary is clearly different from the internal

point and the trend of the measurement results

• Completely different strain trend depending on the axial direction

• Near the welding part, more thermal deformation occurs

• In location 7, 8, no permanent deformation occurs

Leakage Test Results

Thermal strain at each point located on the steel plate (AH36)

-------- x-axis ------- y-axis

6 7 85


Residual stress measurement (hole drilling/strain gauge)

Investigation on the effect of residual stress, thickness and spill boundary on thermal behavior

Additional Experiment

Steel typeThickness

(mm)Welding

Insulation area

AH36

5O

None

10 Partial

X15 Full

Numerical analysis for cryogenic spill assessment

Transient thermal analysis for welding process and cryogenic spill environment

• Residual stress prediction (Welding condition)

• Simulation of thermal deformation (Cryogenic spill)

Numerical Analysis

31

Publications International Journal (SCI)

• 9 papers Domestic Journal (non-SCI)

• 6 papers Conference Presentation

• 50 papers (domestic) & 4 papers (international)

Education MS Graduate

• 3 people Ph. D. Graduate

• 1 people

Intellectual Properties Pending

• 3 domestic patent Registered

• 2 domestic patent

Enter Project No: Project Title in Slide Master


Optimum Density Selection

Peak stress variation depending on density

20℃ -163℃

Optimal

range

Optimal

range

• Optimum density can be determined by plotting the max. stress when the same amount

of impact energy is absorbed (energy-absorption diagram)

• Optimum density is obtained at 113kg/m3 in cryogenic temp whereas at 150kg/m3 in

room temperature


Part 1

PUF with density of 90, 113, 134, 151, 180 kg/m3 revealed that high-density represent

small deformation and high peak force in elastic region

Optimum density is 113kg/m3 in cryogenic temp whereas 150kg/m3 in room temp.

Part 2

RPUF with specific impact energy of 956, 1228, 1500 J/m2 revealed that Maximum force

decreased 13.4% and displacement increased 40.2% under 1500 J/m2

Plastic deformation is observed only at 80th under 1500 J/m2

Part 3

Reinforced insulation materials with the contents of 0, 10, 20 wt.% revealed that high-wt.%

is best performance of cryogenic absorbing energy

However, the agglomeration at 20 wt.% is observed


Preliminary Test

The notch was not sharp enough to show sufficient stress concentration → No crack

Structure with the welding defect are extremely vulnerable to crack propagation

under cryogenic spill

Experimental Investigation on Cryogenic Spill

Outside the boundary, the deformation were different in accordance with axial direction.

Regardless of liquid nitrogen contact, large strain was measured near the welding part.

Near welding part + outside boundary → a large amount of permanent deformation occurs.

gcrc 2018 presentation (04)이제명

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