Method for measuring high-temperature creep crack growth threshold value of material

A technology of crack growth and high temperature creep, which is applied in the test field of high temperature prestressed creep crack growth test to determine the threshold value of creep crack growth, and achieves the effects of high cost, promotion of crack growth and reduction of test cost

Active Publication Date: 2013-07-24
BEIHANG UNIV
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Problems solved by technology

[0005] According to the current method, the difficulty in testing the creep crack growth of materials is reflected in the following two aspects: (1) it i

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  • Method for measuring high-temperature creep crack growth threshold value of material
  • Method for measuring high-temperature creep crack growth threshold value of material
  • Method for measuring high-temperature creep crack growth threshold value of material

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Embodiment Construction

[0026] like figure 1 Shown, the specific implementation steps of the present invention are as follows:

[0027] 1. Processing specimens: For the specific materials studied, process a batch (at least 6 pieces) of standard compact tension (CT) specimens according to the requirements of the creep crack growth test. The initial incision height is 2 mm; the initial incision length is 0.45 times the width of the test piece; the surface of the test piece is first polished with 300-grit sandpaper and then with 2000-grit fine sandpaper to make the surface roughness and finish as high as possible so that the crack propagation path can be observed. Process a batch (at least 6 pieces) of wedges with different thicknesses. The thickness of the wedges starts from 2.1mm. The thickness difference between the wedges is 0.05mm. The width of the wedges is consistent with the width of the test piece. The distance to the left side of the specimen is 2mm larger.

[0028] 2. Prefabricated cracks: ...

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Abstract

The invention discloses a method for measuring high-temperature creep crack growth threshold value of material. The method comprises the following steps of: for a specific material, according to the creep crack growth test requirement, processing at least 6 standard compact tension specimens, performing crack prefabrication for the well processed at least 6 specimens on a fatigue performance tester, wherein the prefabricated crack length is 0.5 times of the width of each specimen; wedging a wedge-shaped block into an initial notch of each specimen, placing the headmost end of the straight part of the wedge-shaped block at the position of a loading line, providing displacement for the loading line, forming a stress-strain field characterized by a stress strength factor at the tip of the specimen crack, and providing a driving force for the creep crack growth, wherein the specimens with different initial stress strength factors grow after certain time under creep effect in high-temperature environment, and in the same time interval, the crack growth lengths are different; drawing for the different stress strength factors and the corresponding crack growth rates, and solving the creep crack growth threshold value of the material through an extrapolation method. According to the method provided by the invention, multiple specimens can be tested for one time, and thus, the test cost is greatly reduced and the test time is greatly shortened.

Description

technical field [0001] The invention relates to a method for measuring a fracture mechanical property parameter of a material, specifically a test method for determining a threshold value of creep crack growth by using a high-temperature prestressed creep crack growth test. technical background [0002] Creep crack growth is a very complex mechanical behavior, and the creep crack growth curve is described by the relationship between the crack length a and time t. For low ductility alloys, the crack growth behavior can be determined by the crack growth rate da / dt and the stress intensity factor K I to describe. Usually creep crack growth is divided into three stages: the first stage, da / dt increases with K I The value rises and increases rapidly, the starting point of this stage is usually called the threshold value of stress intensity factor, denoted as K th ; In the second stage, da / dt varies with K I The value rises and increases steadily; in the third stage, da / dt inc...

Claims

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Application Information

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IPC IPC(8): G01N3/28
Inventor 鲍蕊刘浩张建宇
Owner BEIHANG UNIV
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