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Single-point method for measuring fatigue S-N curve performance of materials and components

A S-N, single-point method technology, applied in the field of single-point method, can solve the problems of high test consumption and cost, high cost, reducing the number of samples and test time, etc.

Inactive Publication Date: 2014-09-10
BEIHANG UNIV
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Problems solved by technology

Due to the dispersion of fatigue damage, it is often necessary to perform group fatigue tests to obtain fatigue test data of large samples and infer its statistical characteristics. Therefore, the test consumption and cost are huge
In order to reduce the number of samples and test time, the single-point-group method was previously developed to determine the fatigue S-N curve. However, the cost of this method is still high. For aerospace structural parts, sometimes only a few samples can be provided for fatigue test testing For this reason, the present invention proposes a single-point method for measuring the fatigue S-N curves of materials and components. Group tests can meet the requirements of small sample data expected in engineering, and the invention has important academic significance and engineering application value

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  • Single-point method for measuring fatigue S-N curve performance of materials and components

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Embodiment Construction

[0045] figure 1 For the flow chart of the method of the present invention, the present invention is realized in three steps, specifically:

[0046] Step 1. Randomize the three-parameter fatigue S-N curve

[0047] The three-parameter power function of the fatigue S-N curve is

[0048] N(S-S 0 ) m = C (21)

[0049] Randomize equation (21) and take the natural logarithm, after transformation, we get

[0050] lnN=lnC-m·ln(S-S 0 )+lnW(S) (22)

[0051] Then let Y=lnN, b 1 = lnC,b 2 =-m, X=ln(S-S 0 ), Z(S)=lnW(S), then formula (22) becomes

[0052] Y=b 1 +b 2 X+Z(S) (23)

[0053] Equation (23) is the lognormal model of the three-parameter power function of the fatigue S-N curve, where Z(S) is a lognormal random variable dependent on the fatigue stress level S, and its mean and standard deviation are 0 and σ(S).

[0054] It is usually assumed that σ(S) has a linear relationship with the logarithmic fatigue stress lnS, that is

[0055] σ(S)=c+d·lnS (24)

[0056] Let σ(...

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Abstract

A single-point method for measuring fatigue S-N curve performance of materials and components comprises the three steps that first, a three-parameter fatigue S-N curve is randomized, second, an equation set is listed by utilizing the maximum likehood principle, and third, the equation set is solved. The method is simple and practical, only a few of samples need to be measured in a single-point test, the number of samples is greatly reduced, sets of tests are not needed, and the requirement for small-subsample data on engineering is met. The method has good practical value and wide application prospects in the technical field of measurement.

Description

technical field [0001] The invention provides a single-point method for measuring the fatigue S-N curve performance of materials and components, which belongs to the technical field of testing. Background technique [0002] The fatigue S-N curve is a key performance index of materials and structures, and is one of the prerequisites for fatigue life assessment. Due to the dispersion of fatigue damage, it is often necessary to carry out group fatigue tests to obtain fatigue test data of a large sample and infer its statistical characteristics. Therefore, the test consumption and cost are huge. In order to reduce the number of samples and test time, the single-point-group method was previously developed to determine the fatigue S-N curve. However, the cost of this method is still high. For aerospace structural parts, sometimes only a few samples can be provided for fatigue test testing For this reason, the present invention proposes a single-point method for measuring the fati...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F19/00
Inventor 熊峻江王强马阅军
Owner BEIHANG UNIV
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