Fracture toughness testing machine and fracture toughness test method

Patent metadata

Field	Value
Publication number	US-12345686-B2
Application number	US-202017774728-A
Country	US
Kind code	B2
Filing date	Nov 13, 2020
Priority date	Nov 14, 2019
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

A fracture toughness testing machine evaluates fracture toughness of a specimen in pure mode. The testing machine includes: a testing-load applying device for applying a predetermined testing load to the specimen, in which the stresses are present; and a cancelling-load applying device for applying a cancelling load to the specimen to cancel the stresses therein. The cancelling-load applying device includes: a pressing-force applying portion that applies a pressing force to the specimen as the canceling load; and a pressing-force determining portion that determines magnitude of the force. The pressing-force determining portion calculates the magnitude of the force using pre-stored equations so that an energy release rate related to in-plane shear mode crack deformation becomes zero.

First claim

The invention claimed is:

1. A testing machine for evaluating fracture toughness at a bonded interface of a specimen by applying a predetermined testing load to the specimen, the specimen being obtained by bonding a first member and a second member, which are made of dissimilar materials, in a state where a thermal residual stress is present therein, and having a crack formed at part of the interface between the members, the fracture toughness testing machine comprising:
a base;
specimen supporting portions fixed to the base;
a testing-load applying device that is a tensile force applying portion configured to apply a tensile force as the predetermined testing load to the specimen so as to open the crack; and
a cancelling-load applying device for applying a cancelling load to the specimen, including: a pressing-force applying portion that is configured to operate so as to apply a pressing force with a constant magnitude to the specimen as the cancelling load; and a pressing-force determining portion that is configured to determine the constant magnitude of the pressing force by calculating the constant magnitude of the pressing force with the use of pre-stored equations so that an energy release rate related to in-plane shear mode crack deformation becomes zero, corresponding to G II =0, whereby the cancelling-load applying device is configured to apply the cancelling load to the specimen so as to cancel the thermal residual stress,
wherein the specimen supporting portions are configured to support two end portions of the specimen, one of the specimen supporting portions is disposed at one of the two end portions of the specimen where the testing-load applying device applies the predetermined testing load to the specimen, and the predetermined testing load to the specimen is changeable with respect to the constant magnitude of the pressing force, and
the equations are following equations (1) to (5):

G
II

=

1

2
⁢
B

⁢

(

c
1

+

c
2

+

h
1
2

4

⁢

d
1

+

h
2
2

4

⁢

d
2

)

⁢

N
c
2

=
0

(
1
)

N
c

=

2

h
1

⁢
ξ

+

2
⁢
η

⁢

{

-

(

ξ
⁢

P
D

+

h
2

⁢

d
2

2

⁢

P
E

2

)

⁢
a

+

(

α
2

-

α
1

)

⁢
Δ
⁢
T

}

Assignees

• Univ Waseda
• Kanagawa Institute Of Industial Science And Tech
• Jp Steel Plantech Co
• Kanagawa Institute Of Industrial Science And Tech

Inventors

• Hosoi Atsushi
• Kawada Hiroyuki
• Harada Kazuki
• Jespersen Kristine Munk

Classifications

• G01N19/04

  Measuring adhesive force between materials, e.g. of sealing tape, of coating · CPC title

• G01N3/24

  by applying steady shearing forces (G01N3/26, G01N3/28 take precedence) · CPC title

• G01N2203/0067

  Fracture or rupture · CPC title

• G01N2203/0066

  Propagation of crack · CPC title

• G01N2203/0017

  Tensile · CPC title