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The combined effect of high temperature and high loading rate on the fracture resistance of a grade S355J0 steel section

Anthony Horn Corus Research, Development & Technology

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Introduction

• Structural integrity assessment techniques

require definition of:

– Resistance (e.g. strength, toughness) – Demand (e.g. stress, crack driving force)

• When Demand>Resistance, failure predicted
• For extreme loading conditions, resistance is a

function of demand, e.g.

– strength and toughness are both functions of applied strain rate and temperature

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Objective

• To characterise how material toughness of a

Corus section changes over:

– a range of temperatures from ambient to +550°C – a range of loading rates from quasi-static to impact – a combination of the two

• Benefit:

– to enable fracture mechanics assessments to be made under conditions of high temperature, high strain rate,

• r a combination of both

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Methodology

• Fracture resistance characterised

using J-Resistance curves

• Quasi-static loading rates:

– compact tension (CT) specimens tested and analysed in accordance with ASTM E1820-09

• Intermediate and high loading rates:

– pre-cracked Charpy (PCV) specimens tested in accordance with ISO14556 – test results analysed using ISO/FDIS 26843 to obtain J-R curves

Ductile crack extension Δa

J

J0.2

0.2mm

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Material investigated

• Grade S355 J0 structural steel

– manufactured by Corus

• 457 x 191x 89 UB section
• Flange thickness 17.7mm
• Yield stress 396MPa, UTS 520MPa

W

1/6 W 1/6 W

All specimens machined with crack tip at 1/6th flange width (1/6FW) position

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Test Matrix

Specimen Rate Room T +200°C +400°C +550°C Compact Tension Quasi-static 2 4 4 2 Pre-cracked Charpy specimens 25° drop angle 3 3 3 3 45° drop angle 3 3 3 3 150° drop angle* 3 3 3 3

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Test Matrix

Specimen Rate Room T +200°C +400°C +550°C Compact Tension Quasi-static 2 4 4 2 Pre-cracked Charpy specimens 25° drop angle 3 3 3 3 45° drop angle 3 3 3 3 150° drop angle* 3 3 3 3

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50 100 150 200 250 300 350 400 0.0 0.5 1.0 1.5 2.0 Δa (mm) J (kJ/m²)

+200°C Room temperature (dotted lines) +550°C (dashed lines) +400°C (solid lines)

Measured J-R curves: Quasi-static loading rate

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Measured J0.2 values: Quasi-static loading rate

• Dip in values observed in tests at +200°C

20 40 60 80 100 120 100 200 300 400 500 600 Temperature (°C) J 0.2 (kJ/m²)

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Test Matrix

Specimen Rate Room T +200°C +400°C +550°C Compact Tension Quasi-static 2 4 4 2 Pre- cracked Charpy specimens 25° drop angle 3 3 3 3 45° drop angle 3 3 3 3 150° drop angle* 3 3 3 3

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Measured J-R curves: High loading rate

• Measured using pre-cracked Charpy specimens

at 150° drop angle

100 200 300 400 500 600 700 0.0 0.5 1.0 1.5 2.0 Δa (mm) J (kJ/m²) Room temperature +200°C +400°C +550°C +200°C

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Measured J0.2 values: All loading rates

• Dip in J0.2 values only evident at quasi-static

loading rates

J0.2

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Conclusions

• 1. At all temperatures studied, tearing resistance

increases with increasing loading rate

J0.2

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Conclusions

• 2. At intermediate loading rates, tearing resistance

decreases linearly with increasing temperature

J0.2

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Conclusions

• 3. At high loading rates, tearing resistance is

approximately independent of temperature up to +400°C before dropping sharply

J0.2

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Conclusions

• 4. At quasi-static loading rates, there is a dip in

tearing resistance at +200°C due to dynamic strain ageing

J0.2

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Conclusions

• 5. There is a trade-off between the ‘beneficial’

effect of high strain rate and ‘detrimental’ effect

• f high temperature

J0.2

J≈100 kJ/m² J≈100 kJ/m²

Thank you for your attention

Any questions?