A method of measurement and determination on fracture toughness of structural materials at high temperature

Patent metadata

Field	Value
Publication number	US-2016299046-A1
Application number	US-201414915659-A
Country	US
Kind code	A1
Filing date	Sep 25, 2014
Priority date	Sep 25, 2014
Publication date	Oct 13, 2016
Grant date	—

Abstract

Disclosed is a method of measurement and determination on fracture toughness of structural materials at high temperature, comprising: preliminary assessing the ductility of a material based on a high-temperature uniaxial tensile test and the fracture characteristic; designing and manufacturing a CT specimen; conducting a monotonic loading fracture test on the CT specimen at high temperature; modifying a load-displacement curve output by a testing machine; determining a passivation coefficient M for the crack of the structural material; reversely recursing instant load-displacement data pairs corresponding to the instant crack length; calculating a J_R crack extension resistance curve of the tensile test; examining the validity of the J_R crack extension resistance curve and the fracture toughness J IC ; calculating the fracture toughness per equivalent of the structural material K IC . The present invention overcomes the difficulty of placing an extensometer inside a high-temperature furnace.

First claim

1 . A method of measurement and determination on fracture toughness of structural materials at high temperature, comprising:
Step 1. conducting a high-temperature tensile test on a standard tensile specimen of a structural material to obtain high-temperature tensile mechanical properties of the material, and determining that the material exhibits a ductile fracture behavior; Step 2. preliminarily estimating the fracture toughness K IC of the structural material at high temperature to obtain the width (W) and thickness (B) of the CT specimen, wherein,

J
IC

=

K
IC
2



(

1
-

v
2

)

E

,



W
=

a
0

+

b
0

≥

2
×
10




J
IC



/



σ
Y

,



σ
Y

=

(

σ
ys

+

σ
uts

)

2

,



2
≤

W


/


B

≤
4

E, ν stand for elastic modulus and Poisson ratio of the material respectively, the unit of E is MPa; a 0 , b 0 stand for initial average crack length and initial average ligament size of the CT specimen respectively, the unit is mm, σ ys , σ uts stand for yield strength and tensile strength of the structural material respectively, the unit is MPa;
Step 3. inducing a fatigue crack with a length of 1.0˜2.0 mm on the CT specimen through a high frequency fatigue testing machine, then grooving a side slot with a depth of 10% B at both sides of the specimen with a crack surface along the thickness direction;
Step 4. measuring the thickness (B) and width (W) of the CT specimen, and placing the specimen into a heating equipment with a furnace, and heating;
Step 5. turning on an INSTRON or MTS testing machine, monotonic loading the specimen, and obtaining a load-displacement curve of the specimen by a load displacement transmission device on the testing machine;
Step 6. cooling the CT specimen to room temperature, opening furnace's cavity, tensing the specimen till fracture through a testing machine, then measuring an initial crack length α 0 i and a final average crack length α f i at nine spots on the crack surface by an optical microscopy or a camera to obtain an initial average crack length α 0 and a final crack length α f of the crack, wherein,

a
0

=

1
8



[

1
2



(

a
0
1

+

a
0
9

)

+

∑

i
=
2

8





a
0
i

]

,



a
f

=

1
8



[

1
2



(

a
f
1

+

a
f
9

)

+

∑

i

Assignees

• Univ East China Science & Tech
• Shanghai Electric Power Equipment Co Ltd Shanghai Steam Turbine Factory
• Shanghai Electric Power Equipment Co Ltd Shangh Ai Steam Turbine Factory

Inventors

• Xuan Fuzhen
• Wang Haitao
• Wang Qiongqi
• Mei Linbo
• Liu Xia
• Huang Yuhui

Classifications

• G01N3/18 Primary

  Performing tests at high or low temperatures · CPC title

• G01N3/00

  Investigating strength properties of solid materials by application of mechanical stress · CPC title

• G01N3/08

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N2203/0017

  Tensile · CPC title

• G01N2203/0069

  Fatigue, creep, strain-stress relations or elastic constants · CPC title