Method of Measuring Fatigue Crack Growth Rate Using Asymmetric Crack
A technique of fatigue crack growth and asymmetry, which is applied in the direction of applying repeated force/pulsation force to test the strength of materials, measuring devices, instruments, etc., and can solve the problems of different fatigue crack growth rates, stress intensity factor variation, and increase in effective data volume, etc. question
Active Publication Date: 2019-02-12
BEIHANG UNIV +1
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[0005] The object of the present invention is to provide a kind of method that adopts asymmetric crack test fatigue crack growth rate, not only can solve the problem that can't effectively utilize M(T) specimen asymmetric crack growth data in existing test standard; And, left, right The stress intensity factor of the crack tip is different, and the fatigue crack growth rate is also different. Compared with the symmetrical crack of the M(T) specimen, the effective data volume of the asymmetric crack is doubled, and the effective information is significantly increased, which can save the specimen and manpower, Financial resources; by reasonably configuring the position and size of the asymmetric notch, the test of the fatigue crack growth rate in the whole range can be realized
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[0047] The present invention will be described in further detail below through specific embodiments in conjunction with the accompanying drawings.
[0048] Considering that there is no method for testing the fatigue crack growth rate by using asymmetric cracks, the invention provides a method for testing the fatigue crack growth rate by using asymmetric cracks.
[0049] The method includes:
[0050] Adopt straight strip specimens of equal thickness, and process asymmetrical notches along the X axis in the working section of the specimens;
[0051] Clamp the specimen with an asymmetric notch on the upper and lower chucks of the fatigue testing machine. The distance from the notch to the upper and lower chucks is the same, so that the loading direction is perpendicular to the surface of the notch, that is, the loading direction is parallel to the Y axis. Then apply a constant amplitude fatigue load with a stress ratio of R to carry out the fatigue crack growth test;
[0052] M...
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The invention relates to a fatigue crack propagation testing technology, in particular to a method for testing fatigue crack propagation rates with asymmetric cracks. The method comprises steps as follows: asymmetric notches are processed at test piece working sections along an X axis; test pieces provided with the asymmetric notches are clamped on a fatigue testing machine for a fatigue crack propagation test; left and right crack tip propagation information of the asymmetric cracks is measured; fatigue fracture propagation rates of left and right crack tips are estimated respectively, and stress intensity factor ranges of the left and right crack tips of the asymmetric cracks under the clamping boundary condition are calculated; fatigue crack propagation rate parameters CA, nA, CB and nB of a material are obtained respectively. According to the method, the problem that data are invalidated after the asymmetric cracks are generated on M (T) test pieces is solved; the stress intensity factor ranges of the left and right crack tips are different, so that the fatigue crack propagation rates are different, and compared with symmetric cracks of the M (T) test pieces, the data volume is increased and effective information is increased; positions and sizes of the asymmetric notches can be reasonably configured, and a full-range fatigue crack propagation rate test is realized.
Description
technical field [0001] The invention relates to a fatigue crack growth test technology, in particular to a method for testing a fatigue crack growth rate by using an asymmetric crack. Background technique [0002] Fatigue / fracture under repeated load is the main failure mode of aircraft structure. In order to ensure the safety and economy of the structure, modern advanced aircraft structures generally adopt the idea of durability / damage tolerance for structural design. According to the requirements of this design idea, in the structural design stage, fatigue crack growth analysis and damage tolerance test should be carried out to determine the structural maintenance interval, and the fatigue crack growth rate of the material is the basic performance parameter for fatigue crack growth analysis. For this reason, since the 1950s, a large number of researches on the test methods of fatigue crack growth rate of materials have been carried out at home and abroad, and the standar...
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IPC IPC(8): G01N3/32G01N3/06
CPCG01N3/068G01N3/32G01N2203/0073G01N2203/0641
Inventor 贺小帆董颖豪杨博霄李玉海
Owner BEIHANG UNIV