Method for testing fatigue crack growth rate of three-point bending sample in T-shaped wave load holding test

A technology of fatigue crack growth and crack growth rate, which is applied in the direction of testing the strength of materials by applying a stable bending force, which can solve the problem that the fatigue crack growth rate of materials cannot be directly measured, and achieve the effect of accurate data support.

Pending Publication Date: 2022-04-12
INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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Problems solved by technology

[0008] Existing test software can only measure the fatigue crack growth rate of materials under the condition that the loading waveform is a triangular wave or a sine wave, and cannot directly measure the fatigue crack growth rate of a material whose loading waveform is a T-shaped wave. Therefore, it is necessary to develop a new test method to Accurately simulate the force state of the deep submersible during the process of diving or surfacing

Method used

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  • Method for testing fatigue crack growth rate of three-point bending sample in T-shaped wave load holding test
  • Method for testing fatigue crack growth rate of three-point bending sample in T-shaped wave load holding test
  • Method for testing fatigue crack growth rate of three-point bending sample in T-shaped wave load holding test

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Embodiment 1

[0042] The present embodiment is the test method of the fatigue crack growth rate of the T-type wave load test three-point bending (SEB) sample, specifically as follows:

[0043] (1) Process the three-point bending (SEB) sample to be tested, and the sample size is as follows figure 1 Shown; measure and record B (sample thickness), W (sample width) and other dimensional information.

[0044] (2) Determine the stress intensity factor range △K corresponding to the crack propagation of the material, and calculate the required test load range △F according to the stress intensity factor range △K and formula (1);

[0045]

[0046] In the formula (1), △F is the test load range; B is the thickness of the sample; S is the span; W is the distance from the loading hole of the sample to the root of the sample; f(a / W) is the calculation parameter;

[0047]

[0048] (3) Use the software on the electro-hydraulic servo fatigue testing machine to edit the test loading program, use the T-sh...

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Abstract

The invention discloses a method for testing the fatigue crack growth rate of a three-point bending sample in a T-shaped wave load holding test, and belongs to the technical field of material fatigue testing. The method comprises the following steps: processing an SEB sample to be detected; determining a stress intensity factor range K and a test load range F; editing a test loading program, and taking a T-shaped wave as a loading waveform; prefabricating cracks and measuring the elasticity modulus E of the sample according to a flexibility method; starting a test according to a test loading program, collecting original data such as time, load, displacement, COD gauge dependent variable, cycle life and the like until the sample is completely fractured, and then substituting the obtained original data into a flexibility method calculation formula to calculate the crack length of the sample; performing data processing on the obtained fatigue life Nf and crack length a data of the plurality of samples to obtain the steady-state crack growth rate of the material under the trapezoidal wave loading condition; and taking the corresponding cycle life when the crack propagation amount is 0.5 mm as the initiation life of the sample under the T-ladder wave loading condition.

Description

technical field [0001] The invention relates to the technical field of material fatigue testing, in particular to a method for testing the fatigue crack growth rate of a three-point bending specimen in a T-shaped wave holding test. Background technique [0002] The ocean accounts for 70% of the total area of ​​the earth and more than 90% of the earth's living space. In the vast ocean world, the ocean affects the climate and weather phenomena on land, and a large number of marine animals and plants are an important source of food for human beings. The ocean has abundant natural resources for human development and utilization, including water resources, biological resources, mineral resources, space resources, and energy resources. Although humans began to explore and develop the ocean very early, from the earliest diving to the current deep-sea probes gradually increase their understanding of the ocean. However, humans have only been able to explore about 5% of the ocean fl...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/20
Inventor 王学刚段启强张哲峰
Owner INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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