Calibration method for the brittle fracture assessment parameters for materials based on the Beremin model

Patent metadata

Field	Value
Publication number	US-9810615-B2
Application number	US-201214365273-A
Country	US
Kind code	B2
Filing date	Nov 27, 2012
Priority date	Dec 13, 2011
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

A calibration method for brittle fracture assessment parameters for pressure vessel materials based on the Beremin model includes selecting at least two types of specimens of different constraints, and calculating the fracture toughness values K 0 corresponding to 63.2% failure probability for each type of specimens at a same calibration temperature by using the respective fracture toughness data. The method proceeds by obtaining the stress-strain curve of the material at the calibration temperature, generating finite element models for each type of specimens, and calculating the maximum principal stress and element volume of every element at K=K 0 in each model. A series of values of m are assumed to compute a group of σ u values for each type of specimens, and then m˜σ u curves are plotted for each type of specimens. Brittle fracture assessment parameters are then determined for the material according to the coordinates of the intersection of the m˜σ u curves.

First claim

What is claimed is:

1. A calibration method for the brittle fracture assessment parameters for materials based on the Beremin model, the method comprises the following steps:
(1) Selecting at least two types of specimens made of a same material but with different constraints, and calculating the fracture toughness value K 0 corresponding to 63.2% failure probability for each type of specimens at a same calibration temperature by using the respective fracture toughness data;
(2) Constructing finite element models for each type of specimens using the stress-strain curve of the material measured at the same calibration temperature, and calculating the maximum principal stress σ 1,i and element volume Vi of each element at K=K 0 in each model, where K is a stress intensity factor that describes the intensity of far field loading on the crack front, and i is an order number of elements;
(3) Assuming a series of values of the Weibull slope m and calculating a set of values of the Weibull scale parameter σ u for each type of specimens according to the following equation, and plotting the Beremin's parameters characteristic curves for each type of specimens with the curves representing the relationship between m and σ u for each type of specimens;

σ
u

=

∑
i
n

⁢

(

σ

1
,
i

)

m

⁢

V
i

V
0

m

wherein, n represents the number of elements in the fracture process region, V 0 represents a reference volume;
(4) Determining the brittle fracture assessment parameters for the material according to the coordinates of the intersection of the Beremin's parameters characteristic curves;
(5) using the brittle fracture assessment parameters in safety engineering.

2. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 1 , wherein, in the step (1), fracture toughness tests on each type of specimens are carried out at the same calibration temperature to obtain the fracture toughness data.

3. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 1 wherein, in the step (1), fracture toughness tests are carried out on each type of specimens at different temperatures to obtain the fracture toughness data, and calculating the fracture toughness value K 0 corresponding to 63.2% failure probability at the same calibration temperature by using the predetermined master curve.

4. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 3 wherein, in the step (1), the same calibration temperature is the lowest of the different temperatures.

5. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 1 wherein, in the step (2), the uniaxial tensile test is carried out at the same calibration temperature to obtain the stress-strain curve.

6. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 5 wherein, in the step (3), the values of m are taken as integers larger than 5 and less than 40.

7. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 6 wherein, in the step (3), the fracture process region is defined as the volume inside the loci σ 1,i ≧λσ ys , wherein λ is a constant, σ ys is the yield strength of the material at the calibration temperature.

8. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 7 wherein, in the step (3), the value of λ is 1 or 2.

9. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 1 wherein, in the step (1), at least six fracture toughness data are obtained for each type of specimens are required.

10. The calibration method for the brittle fracture assessment parameters for materials based on the Beremin model according to claim 9 wherein, in the step (1), at least fifteen fracture toughness data are obtained for each type of specimens are required.

Assignees

• Univ East China Science & Tech

Inventors

• Xuan Fuzhen
• Cao Yupeng
• Hui Hu
• Li Penning
• Wang Guozhen

Classifications

• G01N3/62 Primary

  Manufacturing, calibrating, or repairing devices used in investigations covered by the preceding subgroups · CPC title

• G01N2203/021

  Treatment of the signal; Calibration · CPC title

• G01N2203/0218

  Calculations based on experimental data · CPC title

• G01N3/40

  Investigating hardness or rebound hardness · CPC title

• G01N2203/0067

  Fracture or rupture · CPC title