Method for determining region turning point of titanium alloy fatigue crack growth rate curve Paris
A technology of fatigue crack growth and crack growth, which is applied in the field of fatigue crack growth behavior analysis, can solve the problems of large twists and turns, inconsistencies, and deviations of test data curves, and achieve the effects of sufficient scientific basis, high accuracy, and complete technical solutions
Inactive Publication Date: 2016-11-02
AVIC BEIJING INST OF AERONAUTICAL MATERIALS
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When the visual method determines the position of the turning point of the curve, the error is relatively large, and the result has a large deviation from the actual situation; mathematical methods include intercept method, iteration method and curvature method, which can be used to determine the turning point of the curve with a simple shape. However, the theoretical basis of mathematical methods is insufficient, and the results often do not match the actual situation.
In addition, when the test data is complex and the data are highly dispersed, the test data curve has large twists and turns and often has multiple turning points. At this time, visual inspection and mathematical methods have encountered difficulties in accurately determining the turning point. Judging based on engineering experience, the results often lack authenticity and validity. Therefore, it is necessary to develop an analysis method that can accurately determine the turning point of the fatigue crack growth rate curve
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[0045] Step 1. Get ready to start. In this example, the medium-strength, high-toughness, and high damage-tolerant TC4-DT titanium alloy is used as the object. After conventional two-phase zone forging and quasi-β heat treatment, the obtained microstructure is a typical lamellar structure. The composition and mechanical properties of the material The properties are shown in Table 1 and Table 2.
[0046] Table 1 Material Composition
[0047]
[0048] Table 2 Mechanical properties
[0049]
[0050] Step 2: Carry out fatigue crack growth rate test. The fatigue crack growth rate test is carried out according to the "Metallic Materials Fatigue Crack Growth Rate Test Method" (GB / T 6398-2000), the test environment is room temperature, air, the test frequency f=10Hz, and the maximum load P max =6.4KN, stress ratio R=0.1. Record the i-th load cycle number N during the test i and N i The corresponding crack growth length a i , to obtain all experimental data points (N i ,a ...
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Abstract
The invention belongs to the technical field of material fatigue crack growth behavior analysis, and provides a method for determining a region turning point of a titanium alloy fatigue crack growth rate curve Paris. The method determines the crack growth length during change of a fatigue crack growth mechanism according to the changes of crack growth behavior and fracture mode shown by micro characteristics of the fracture; and solving the stress intensity factors and the fatigue crack growth rate corresponding to the crack propagation length, so as to determine the turning point position of the fatigue crack growth rate curve Paris. The invention has full scientific basis and high accuracy, can satisfy material performance evaluation and damage tolerance design by designers and users, and is beneficial to the application of modern engineering.
Description
technical field [0001] The invention belongs to the technical field of fatigue crack growth behavior analysis and relates to a method for judging the turning point of the Paris zone of the fatigue crack growth rate curve of titanium alloy. Background technique [0002] The common fatigue crack growth rate curve can generally be divided into three stages in the logarithmic coordinate da / dN-ΔK relationship curve, that is, the ΔK in the low ΔK range is close to the threshold value (ΔK th ) stage (I zone), the stable expansion stage in the middle ΔK range (II zone, Paris zone) and the high ΔK range ΔK rapidly tends to fracture toughness (ΔK IC ) stage (Zone III). A large number of research results show that the fatigue crack growth rate curve has a logarithmic linear relationship in the Paris area, that is, the double logarithmic coordinate da / dN-ΔK curve is a straight line in the Paris area. Using this relationship for fatigue life prediction and durability analysis is The fo...
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IPC IPC(8): G01N3/32
CPCG01N3/32G01N2203/0005G01N2203/0066
Inventor 祝力伟朱知寿王新南商国强费跃李静
Owner AVIC BEIJING INST OF AERONAUTICAL MATERIALS
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