Method for predicting crack initiation stress by combining small taper experiment with simulation

A taper and crack technology, which is applied in the field of small taper experiment combined with simulation to predict crack initiation stress, can solve problems such as time-consuming, and achieve the effect of small result error, saving experimental materials, and reducing experimental period.

Inactive Publication Date: 2021-04-13
UNIV OF SCI & TECH BEIJING
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Obtaining a stress threshold requires at least 6-10 identical specimens, which will take a lot of time

Method used

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  • Method for predicting crack initiation stress by combining small taper experiment with simulation
  • Method for predicting crack initiation stress by combining small taper experiment with simulation
  • Method for predicting crack initiation stress by combining small taper experiment with simulation

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Embodiment example

[0050] In this example, sample dimensions such as figure 2 As shown, put the sample into 0.5mol / L sulfuric acid plus 0.5g / L thiourea for electrochemical hydrogen charging, and the hydrogen charging current density is 2mA / cm 2 , the time is 200h. Applied nominal stress is 600MPa, such as Figure 4 , because the stress at the center of the sample has exceeded its yield strength, the actual stress there is greater than 600MPa, and the specific value is given by the finite element. After the experiment, the sample was cut along the central axis, and the crack depth on the edge of the sample and the distance from the crack to the center of the sample were counted, as shown in Figure 5 shown. The predicted crack initiation distance from the center of the sample is 4173 μm. According to the finite element simulation results, the stress value of crack initiation under this condition is 487.42 MPa.

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Abstract

The invention provides a method for predicting a crack initiation stress by combining a small taper experiment with simulation. The method comprises the following steps: preparing a plurality of groups of small-taper samples and traditional parallel samples; carrying out a tensile experiment on the traditional parallel samples to obtain an engineering stress-strain curve of the samples; setting a required stress under a dead load condition according to the measured yield strength of the material; setting a deadline in a dead load state, then taking out the samples, cutting the samples along a central axis, and counting the depth of the crack and the relative position of the crack to the centers of the samples by using a scanning electron microscope; and deducing the distance from the crack initiation part to the centers of the samples according to the crack depth and the distance to the centers. A stress distribution cloud chart of the samples in a stressed state is simulated by using a finite element to obtain the stress at the crack initiation part so that the stress value of crack initiation can be predicted by using the small-taper samples. According to the invention, an experimental period is greatly shortened, and experimental materials are saved.

Description

technical field [0001] The invention belongs to the field of performance testing, and in particular relates to a method for predicting crack initiation stress by combining small taper experiments with simulation. Background technique [0002] Due to the harsh service environment of submarine platforms, oil and gas pipelines, nuclear power plants, and underground facilities, the steel structures used in large quantities are prone to stress corrosion cracking, which will have a catastrophic impact on the safe operation of the facilities. Therefore, under the designed load-bearing conditions and service environment, it is very important to predict whether and when the crack will open. The traditional method is to obtain the fracture time of standard parallel samples under different external constant load conditions, so as to test the stress threshold value of stress corrosion cracking within a certain period of time. Obtaining a stress threshold requires at least 6-10 identica...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08G01N1/28G06F30/23
CPCG01N1/28G01N3/08G06F30/23
Inventor 高克玮晏倩颜鲁春庞晓露乔利杰宿彦京徐秋发李东东
Owner UNIV OF SCI & TECH BEIJING
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