ASTM E 399 – 90

Properties and Testing of Materials

خواص واختبار المواد

بسم اهلل الرحمن الرحيم

Determination of Fracture Toughness“Plane-Strain Fracture Toughness of Metallic Materials”

متانة االنهيارتعيين

Toughness

• Toughness measurement by calculating the area under the stress-strain curve from static tests

• Material fractures occur by progressive cracking

Stress Concentration at crack tip by Photo-elasticity

Notch Toughness

Defined as “the ability of a material to absorbenergy”, (usually when loaded dynamically) in thepresence of a flaw

Laboratory measurement of impact energy by

Charpy test (V-notch impact specimen)

Izod test

Dynamic tear test …

The general purpose of the various kinds of notch-toughness tests is to model the behavior of actual structures so that the laboratory test results can be used to predict service performance.

Impact Energy

Introduction

Hardness Strength

Impact Energy Toughness

Laboratory measurement of impact energy

Charpy test

Izod test

…

Charpy test

Impact Energy

Stress concentrating notch

Charpy Impact Test

Sensitivity of Impact Test Data

• Test conditions

• Notch sharpness

• Nature of stress concentration at notch tip

• Test temperature

• Internal atomic structure of the material

Sensitivity of Impact Test Data

Ductile to brittle transition temperature

Most structural steels can fail in either a ductile or brittle manner depending on

several conditions such as temperature, loading rate, and constraint.

Ductile fractures are generally preceded by large amounts of plastic

deformation and usually occur at 45° to the direction of the applied stress.

Brittle or cleavage fractures generally occur with little plastic deformation and

are usually normal to the direction of the principal stress.

Ductile to brittle transition temperature

Why is it of great practical importance???

•Alloy Loses toughness and it is susceptible

to catastrophic failure below this transition

temperature

•It is a design criterion of great importance.

Several disastrous failures of ships occurred because of this phenomenon.

Plane stress & Plane strain

)(1 s

yy

ss

xxs

s

xxE

)(1 s

xx

ss

yys

s

yyE

ss E1 x

0s

ZZ

Microscopic Fracture Surface

Fracture Toughness

Fracture Toughness the most widely used

material property “single parameter” from

fracture mechanics”.

It is represented by the symbol KIC, defined as

“The critical value of the stress intensity factor

at crack tip necessary to produce catastrophic

failure under simple uni-axial loading.

Fracture Toughness

The value of Fracture Toughness is given by:

(1)

Y is a dimensionless geometry factor

f is the overall applied stress at failure

a is the length of the surface crack or one half of an internal crack

KIc have the units of MPam ( for plane strain conditions in which the

specimen thickness is comparatively large ).

Fracture Toughness

KIc (plane strain conditions).

Kc (plane stress conditions).

ASTM E 399

Failure Modes by cracking

Types of relative movements of two crack surfaces

Failure Modes by cracking

The opening mode,

Mode I

The sliding or shear mode, Mode II

The stress field at the crack tip can be treated as one or a combination of

the three basic types of stress fields

The tearing mode,

Mode III

Typical Fracture Toughness values

KIc represents the inherent ability of a

material to withstand a given stress-field

intensity at the tip of a crack and to resist

progressive tensile crack extension

under plane-strain conditions.

KIc represents the fracture toughness of

the material and has units of (MN/m3/2).

KIc Fracture toughness

Is the material-toughness property depends on the particular material,

loading rate, and constraint as follows:

Kc = critical stress-intensity factor for static loading and plane-stress

conditions of variable constraint. Thus, this value depends on specimen

thickness and geometry& crack size.

KIc = critical-stress-intensity factor for static loading and plane-strain

conditions of maximum constraint. Thus, this value is a minimum value

for thick plates.

KId = critical-stress-intensity factor for dynamic (impact) loading and plane-

strain conditions of maximum constraint.


Kc, KIc, or KId = C a ,

C = constant, function of specimen and

crack geometry,

= nominal stress, ksi (MN/m2),

a = flaw size, in. (mm).


Experimental determination of KIc

KIC test procedure

1 – Determine critical specimen size dimensions

2 – Select a test specimen and prepare shop drawing3 – Fatigue crack the test specimen (by cyclic loading)

4- Obtain test fixtures and displacement gauges

5- Alignment, positioning of loads, loading rate, friction, eccentricity, …

6- Test record of the load displacement.

7- Measurements of specimen dimensions and fractures to calculate KQ

(B, S, W, a).

8- Analysis of P- records.

9- Calculation of conditional KIc (KQ).

KIC test procedure

1 – Determine critical specimen size dimensions

2

2

2

0.5

5.2

5.2

ys

Ic

ys

Ic

ys

Ic

KdepthSpecimenW

KthicknessSpecimenB

Kdepthcracka

CTS, Slow bend Specimens

KIC test procedure

2 – Select a test specimen and prepare shop drawing

Specimen Design

KIC test procedure

3 – Fatigue crack the test specimen (by cyclic loading)

KIC test procedure

4- Obtain test fixtures and displacement gauges

5- Alignment, positioning of loads, loading rate, friction, eccentricity, …

Gauges for CTS

Gauges for Slow bend test specimen

Testing Machine

Tensile cracking experimental setup

Instron Screw Machine

PC

AESystem

Pin grips

MTSExtensometer

AEsensor

Fracture Toughness Specimens

KIC test procedure

6- Test record of the load displacement.

7- Measurements of specimen dimensions and fractures to calculate KQ (B, S, W, a).

8- Analysis of P- records.

9- Calculation of conditional KIc (KQ).

Load –Displacement Curve

P- test record 5% offset line

Determination of PQ

KIC test procedure

• Calculation of conditional KIC (KQ) for SBTS

2

9

2

7

2

5

2

3

2

1

23

7.386.378.216.49.2W

a

W

a

W

a

W

a

W

a

WB

SPK

Q

Q

• PQ = Load as determined

• B = Thickness of specimen

• S = Span length

• W = Depth of specimen

• a = Crack length as determined

KIC test procedure

• Calculation of conditional KIC (KQ) for CTS

2

9

2

7

2

5

2

3

2

1

21

9.6380.10177.6555.1856.29W

a

W

a

W

a

W

a

W

a

WB

PK

Q

Q

• PQ = Load as determined

• B = Thickness of specimen

• W = Width of specimen

• a = Crack length as determined

ASTM E 399 – 90Plane-Strain Fracture Toughness of Metallic Materials

1- This test method covers the determination of the plane strain fracture toughness (KIc) of metallic materials by tests using a variety of fatigue-cracked specimens having a thickness of 0.063 in. (1.6 mm) or greater.2- This test method also covers the determination of the specimen strength ratio Rsx where x refers to the specific specimen configuration being tested. This strength ratio is a function of the maximum load the specimen can sustain, its initial dimensions and the yield strength of the material.3- This test method is divided into two main parts. The first part gives general information concerning the recommendations and requirements for KIc testing. The second part is composed of annexes that give the displacement gage design, fatigue cracking procedures, and special requirements for the various specimen configurations covered by this method. In addition, an annex is provided for the specific procedures to be followed in rapid-load plane-strain fracture toughness tests.

ASTM C1018

Flexural Toughness and First Crack Strength of Fiber Reinforced Concrete (Using Beam With

Third Point Loading)

RILEM 50-FMC

Determination of the Fracture Energy of Mortar and Concrete by Means of Three-Point Bend

Tests on Notched Beams

2

.

00 )(

m

J

m

N

A

mgWG

lig

f

W0 = area under the load – deflection curve (N/m)

m = m1 + m2

δ = deformation at the final failure of the beam (m)

Alig. = area of the ligament at mid span (m2)

Alig.

Thanks

ASTM E 399 – 90

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