Quantitative characterization method for early-stage propagation rate of single crystal ultrahigh-cycle fatigue internal crack

A technology of growth rate and internal crack, applied in the field of fatigue crack testing, can solve the problem of measuring crack growth rate, etc., to achieve the effect of increasing complexity

Active Publication Date: 2021-01-29
BEIHANG UNIV
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Problems solved by technology

Due to the ultra-high cycle fatigue crack initiation of single crystal superalloys in the interior, the conventional surface observation method, potential drop method and flexibility method cannot be used to measure the crack growth rate
Moreover, in the first stage of the single crystal expansion process, there are no typical features such as fatigue bands, and the fracture quantitative inversion method based on fatigue bands cannot be used

Method used

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  • Quantitative characterization method for early-stage propagation rate of single crystal ultrahigh-cycle fatigue internal crack
  • Quantitative characterization method for early-stage propagation rate of single crystal ultrahigh-cycle fatigue internal crack
  • Quantitative characterization method for early-stage propagation rate of single crystal ultrahigh-cycle fatigue internal crack

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Embodiment 1

[0030] Taking DD6 single crystal as an example, the specific steps of quantitative characterization of the early growth rate of internal cracks in ultra-high cycle fatigue of single crystal based on fracture notch are as follows:

[0031] (1) Design and process the DD6 single crystal ultrasonic fatigue specimen, which is marked as specimen 1. Ultrasonic fatigue testing machine is used to conduct ultra-high cycle fatigue test on specimen 1. The test temperature is 1000°C, the test frequency is 20kHz, and the load spectrum is : 200MPa / 120ms+20MPa / 360ms, the fatigue life data and fatigue fracture of specimen 1 were obtained after the test;

[0032] (2) Utilize scanning electron microscope to observe the fatigue fracture that obtains in step (1), figure 1 (a) is the overall morphology of the fatigue fracture (the white box shows the fatigue source area), the fatigue cracks initiate from the loose part of the internal casting, and there is a fatigue arc near the fatigue source area...

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Abstract

The invention discloses a method for quantitatively characterizing the early growth rate of an ultrahigh-cycle fatigue internal crack of a single crystal, and realizes fracture nicking based on an ultrasonic fatigue test of a specific load spectrum and establishes a set of fracture backstepping-based model for quantitatively characterizing the growth rate of the internal fatigue crack. The model does not need to pay attention to the test process, the relationship between the fatigue crack propagation rate and the stress intensity factor amplitude can be quickly calculated only according to thefatigue fracture and the test conditions, and then the change of the propagation rate in the fatigue crack propagation process is analyzed.

Description

technical field [0001] The invention belongs to the field of fatigue crack testing and relates to a method for quantitatively characterizing the early growth rate of internal cracks in single crystal ultra-high cycle fatigue. Background technique [0002] Nickel-based single crystal superalloys have the advantages of high high temperature strength, strong oxidation resistance, and excellent fatigue resistance. They are the materials of choice for advanced aeroengine turbine blades at this stage. Ultra-high cycle fatigue failure is an important problem faced by turbine blades in the middle and late stages of service. The ultra-high cycle fatigue cracks of single crystal superalloys mainly originate from internal defects such as casting pores, loose structures, carbides, and eutectic structures, and most of the cracks propagate along the same plane. Studies have shown that the initiation and early propagation stages of ultra-high cycle fatigue cracks consume most of the fatig...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N23/2251G01N3/32
CPCG01N23/2251G01N3/32
Inventor 赵子华张福禄李茜
Owner BEIHANG UNIV
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