Fatigue limit rapid prediction method based on strain increment

A fatigue limit and strain increment technology, which is applied in the direction of testing material strength by applying repetitive force/pulsation force, and can solve problems such as narrow application range and poor accuracy.

Active Publication Date: 2016-03-02
ACADEMY OF ARMORED FORCES ENG PLA
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Problems solved by technology

[0017] Since the fatigue limit and static parameters have different physical meanings, these empirical prediction formulas are all based on s...

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  • Fatigue limit rapid prediction method based on strain increment
  • Fatigue limit rapid prediction method based on strain increment
  • Fatigue limit rapid prediction method based on strain increment

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Embodiment Construction

[0064] In order to verify the feasibility and accuracy of the strain-based rapid prediction fatigue limit theory, we carried out strain and infrared experiments on two different common materials for blower impellers (precipitation hardening martensitic stainless steel FV520B and KMN-I) under an average stress of 700MPa. Synchronous online monitoring of thermal signals, comparing and verifying the prediction results of strain-based fatigue limit with the prediction results of Luong method in the currently recognized infrared thermal imaging method. The test results are described in detail below.

[0065] Two common compressor impeller materials, FV520B and KMN-I, were selected as raw materials and their simulated overspeed preloading process (test average stress σ’ mean Set to 900MPa to simulate ultra-speed centrifugal force, stress amplitude Δσ' to 10MPa to simulate airflow forced vibration, test frequency to 30HZ, and fatigue loading 5000 times) to prepare samples from pre-st...

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Abstract

A fatigue limit rapid prediction method based on strain increment belongs to the field of rapid prediction of material fatigue limit. The invention discovers that under gradient stress load, the variation rule of strain capacity is very similar to the variation rule of temperature. Since the Luong method can use corresponding stable temperature rise value under gradient load to predict the fatigue limit, the strain capacity under gradient load can theoretically be used for rapid prediction of fatigue limit. The method utilizes a fatigue testing machine and an extensometer thereof (no dependence on expensive high-precision thermal infrared imager), and theoretically only uses one specimen to rapidly and economically predict a reliable fatigue limit of the material or a simple member in a day time according to variation rule of strain capacity under gradient load. The traditional lifting method and grouping method spend a few months and consume a large amount of human and financial resources, therefore the present invention has high engineering practical value and significant economic benefits.

Description

Technical field: [0001] The invention belongs to the field of rapid prediction of material fatigue limit. Background technique: [0002] At present, there is no mature theoretical model that can reveal the physical nature of the fatigue limit of materials, so it is difficult to obtain it through theoretical calculations. For strain-age hardening materials, under constant amplitude loading conditions, it is found from their S-N curves that usually more than about 10 6 A "plateau" occurs after the fatigue cycle. When the stress amplitude is lower than the platform stress, the sample can withstand infinite fatigue cycles without failure, and the platform stress is called the fatigue limit σ e (or endurance limit). However, for some materials such as high-strength steel and aluminum alloys that do not have strain age hardening, there may be no fatigue limit. With the increase of cycle times, the stress range they can withstand continues to decrease. At this time, the sample c...

Claims

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Application Information

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IPC IPC(8): G01N3/32
Inventor 王海斗张玉波徐滨士王桂阳范博楠邢志国
Owner ACADEMY OF ARMORED FORCES ENG PLA
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