CN104567739A

CN104567739A - Method for measuring open angle of crack tip

Info

Publication number: CN104567739A
Application number: CN201410852013.1A
Authority: CN
Inventors: 曹宇光; 甄莹; 贺娅娅; 黄小光; 林红; 徐国强; 张士华; 孙晓瑜; 胡雪扬; 聂文俊
Original assignee: China University of Petroleum East China
Current assignee: Wuxi Hongtai Inspection Technology Co Ltd
Priority date: 2014-12-31
Filing date: 2014-12-31
Publication date: 2015-04-29
Anticipated expiration: 2034-12-31
Also published as: CN104567739B

Abstract

The invention relates to a method for measuring the open angle of a crack tip. The method comprises the following steps that an upper fracture face and a lower fracture face of a fracture failure component are scanned and detected; height data of the upper fracture face and height data of the lower fracture face are typed in, and a fracture three-dimensional model is established based on the fracture surface height data; the upper fracture face is overturned in the width direction; the upper fracture face is mirrored and matched with the lower fracture face, artificial initial cracks, stretching plastic deformation and compression plastic deformation can be obtained through accurate matching, the matched fractures are projected, and fracture face projections can be obtained; the cross section of a fracture is extracted, the section profile of the upper fracture and the section profile of the lower fracture are obtained, and an upper fracture pre-crack matched with the cross section should be completely matched with a lower fracture pre-crack; the section profile of the upper fracture and the section profile of the lower fracture are rotated and moved, and accordingly the crack expanding process is simulated. According to the method, using is convenient, operation is easy, and engineering technicians can grasp and use the method easily.

Description

A kind of method measuring crack tip ope ning angle

Technical field

The invention belongs to mechanical engineering and fracture failure fault diagnosis field, particularly, relate to a kind of method measuring crack tip ope ning angle.

Background technology

In recent years, China's oil and gas pipes transport fast development, while providing energy supply powerful guarantee to country, pipeline break failure accidents bring serious threat safely may to the people's lives and property, and the reason of fracture failure of therefore must clarifying a diagnosis also takes measures to prevent the generation of fracture accident.

The criterion describing Crack Extension is varied, wherein crack tip ope ning angle because it is directly perceived, explicit physical meaning and there is very strong attractive force, especially for pipeline crack, in its steady propagation process, crack tip ope ning angle is tending towards this key character of definite value and more makes crack tip ope ning angle criterion receive much concern.So-called crack tip ope ning angle is exactly the angles of two rupture surface at crack tip place.The measurement of crack tip ope ning angle is generally obtained by fracture mechanics experiments, takes pictures and then measure in crack propagation process.But be not easy because crack propagation velocity is difficult to obtain clear pictures, crack tip soon reasons such as finding and determine, accurately obtaining crack tip ope ning angle is a difficult problem always.Meanwhile, because picture pick-up device can only photograph the outside surface of sample, the most advanced and sophisticated open-angle of test specimen underbead crack therefore more cannot be obtained.The crack tip ope ning angle be difficult in Obtaining Accurate crack extesion process greatly limit the application of this fracture criterion.From the documents and materials of consulting, not yet have at present and utilize fracture to carry out the relevant report of crack tip ope ning angle measurement.

Summary of the invention

For overcoming the defect that prior art exists, the invention provides a kind of method measuring crack tip ope ning angle, utilize the three-dimensional fracture of computer reconstruction and reverse simulation fracture process, crack tip ope ning angle is measured, to solve in experimental fragmentation protocol the difficult problem being difficult to accurately obtain crack tip ope ning angle when fracture process is simulated.

For achieving the above object, the present invention adopts following proposal:

Measure the method for crack tip ope ning angle, comprise the steps:

1, non-contact 3-D laser microscope is utilized to carry out Scanning Detction to the upper fracture face of fracture failure component and lower fracture face;

2, fracture face and lower fracture face altitude information in typing, and based on fracture surface altitude information, set up fracture three-dimensional model;

3, upper fracture face is overturn in the width direction;

4, it is mated with lower fracture face by upper fracture face mirror image, by accurate match, artificial initial crack, stretching plastic sex change and compressive plastic deformation can be obtained, the fracture of pairing is carried out projection and can obtain rupture surface projection;

5, extract fracture xsect and obtain fracture cross section profile and lower fracture cross section profile, xsect preparing the right pre-crackle of upper fracture should fit like a glove with the pre-crackle of lower fracture;

6, respectively upper fracture cross section profile and lower fracture cross section profile are rotated, move thus simulating crack expansion process.

Relative to prior art, the present invention has following beneficial effect:

(1), easy to use, simple to operate, be easy to numerous engineering technical personnel grasp and use.

(2), without the need to observing fracture process in experimental fragmentation protocol and making a video recording, only after fracture accident occurs, three-dimensional values need be carried out to fracture, extract fracture surface information.

(3), avoid owing to being difficult to get a distinct image and accurately cannot judge the crack tip ope ning angle numerical bias that the reasons such as crack tip actual position cause.

(4), by extracting midsection can obtain crack tip ope ning angle in the middle part of test specimen, this utilizes conventional method to obtain.

(5), by coding, the intellectuality of whole process, standardization can be realized, also can avoid the interference of human factor.

Accompanying drawing explanation

Fig. 1 is fracture three-dimensional model schematic diagram;

Fig. 2 a, Fig. 2 b, Fig. 2 c, Fig. 2 d, Fig. 2 e are fracture process simulation schematic diagram;

Fig. 3 is crack tip ope ning angle instrumentation plan;

In figure: 1, upper fracture face, 2, lower fracture face, 3, artificial initial crack, 4, rupture surface projection, 5, stretching plastic deformation, 6, xsect, 7, compressive plastic deformation, 8, upper fracture cross section profile, 9, the pre-crackle of upper fracture, 10, lower fracture cross section profile, 11, the pre-crackle of lower fracture, 12, crack tip ope ning angle, 13, crack tip, 14, predetermined distance, 15, crack initiation is most advanced and sophisticated.

Embodiment

As shown in Figure 1, Figure 2 shown in a, Fig. 2 b, Fig. 2 c, Fig. 2 d, Fig. 2 e, Fig. 3, measure the method for crack tip ope ning angle, comprise the steps:

1, non-contact 3-D laser microscope is utilized to carry out Scanning Detction to the upper fracture face 1 of fracture failure component and lower fracture face 2;

2, fracture face 1 and lower fracture face 2 altitude information in typing, and based on fracture surface altitude information, set up fracture three-dimensional model, as shown in Figure 1;

3, upper fracture face 1 is overturn in the width direction;

4, it is mated with lower fracture face 2 by upper fracture face 1 mirror image, as shown in Figure 1, by accurate match, artificial initial crack 3, stretching plastic sex change 5 and compressive plastic deformation 7 can be obtained, the fracture of pairing is carried out projection and can obtain rupture surface projection 4;

5, extract fracture xsect 6 and obtain fracture cross section profile 8 and lower fracture cross section profile 10, xsect 6 preparing the right pre-crackle of upper fracture 9 should fit like a glove with the pre-crackle 11 of lower fracture, as shown in Figure 2 c;

6, respectively upper fracture cross section profile 8 and lower fracture cross section profile 10 rotated, move thus simulating crack expansion process, as shown in Figure 2 d;

In crack propagation process simulation process, first intersection point and the crack tip 13 of upper fracture cross section profile 8 and lower fracture cross section profile 10 is determined, then the point on fracture cross section profile 8 and lower fracture cross section profile 10 in predetermined distance 14 place is determined after crack tip 13 respectively, by these 2 respectively with crack tip 13 line, between two lines, angle is crack tip ope ning angle 12, as shown in Figure 3, so far, the measurement to crack tip ope ning angle 12 is realized.

Based on method described in step 6, in the different phase of Crack Extension, as shown in Figure 2 d, calculate crack tip ope ning angle 12, the Changing Pattern of crack tip ope ning angle 12 with Crack Extension can be obtained;

By intercepting the xsect 6 at sample diverse location place in the width direction, as shown in Figure 1, repeating step 5 to step 8, can obtain along the Changing Pattern of diverse location place, specimen width direction crack tip ope ning angle 12 with Crack Extension.

Claims

1. measure a method for crack tip ope ning angle, it is characterized in that, comprise the steps:

(1), non-contact 3-D laser microscope is utilized to carry out Scanning Detction to the upper fracture face of fracture failure component and lower fracture face;

(2), fracture face and lower fracture face altitude information in typing, and based on fracture surface altitude information, set up fracture three-dimensional model;

(3), upper fracture face is overturn in the width direction;

(4), by upper fracture face mirror image it is mated with lower fracture face, by accurate match, artificial initial crack, stretching plastic sex change and compressive plastic deformation can be obtained, the fracture of pairing is carried out projection and can obtain rupture surface projection;

(5), extract fracture xsect and obtain fracture cross section profile and lower fracture cross section profile, xsect preparing the right pre-crackle of upper fracture should fit like a glove with the pre-crackle of lower fracture;

(6), respectively upper fracture cross section profile and lower fracture cross section profile are rotated, move thus simulating crack expansion process.

2. the method for measurement crack tip ope ning angle according to claim 1, it is characterized in that, in crack propagation process simulation process, first intersection point and the crack tip of upper fracture cross section profile and lower fracture cross section profile is determined, then the point on fracture cross section profile and lower fracture cross section profile in predetermined distance place is determined after crack tip respectively, by these 2 respectively with crack tip line, between two lines, angle is crack tip ope ning angle.

3. the method for the measurement crack tip ope ning angle according to claim 1-2, is characterized in that, in the different phase of Crack Extension, calculates crack tip ope ning angle, can obtain the Changing Pattern of crack tip ope ning angle with Crack Extension.

4. the method for the measurement crack tip ope ning angle according to claim 1-2, it is characterized in that, by intercepting the xsect at sample diverse location place in the width direction, repeat step 5 to step 6, can obtain along the Changing Pattern of diverse location place, specimen width direction crack tip ope ning angle with Crack Extension.