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Creep-damage lifetime forecast method of material under multi-axial stress state

A stress state and life prediction technology, applied in special data processing applications, instruments, electrical and digital data processing, etc., can solve the problems of uneven temperature distribution, inability to achieve life prediction, and difficulty in convergence, and achieve a simple and clear prediction process. Meaning, result accurate effect

Inactive Publication Date: 2017-04-05
CHINA UNIV OF PETROLEUM (EAST CHINA)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

At the same time, an excessively large ratio also makes convergence difficult in the finite element simulation process.
Although there is no such expression in the classic K-R creep damage model, due to the structure of the constitutive model itself, the convergence in the finite element calculation process is poor, and a large amount of calculation time is required
In addition, when performing life analysis on equipment components under actual working conditions, the temperature distribution in the equipment is usually not uniform, and the current creep-damage model usually performs life prediction under the condition of uniform temperature, which cannot realize the existence of temperature gradient conditions. Life Prediction under

Method used

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  • Creep-damage lifetime forecast method of material under multi-axial stress state

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Embodiment 1

[0050] Such as figure 1 Shown: A creep-damage life prediction method for materials under multiaxial stress states based on the stress-damage criterion. When the cumulative value of creep damage reaches the critical value of damage, a crack is considered to appear in the material. The prediction of creep life is realized by defining different crack lengths as the judgment conditions of material failure. The creep-strain damage model is based on the fact that the material reaches the failure strain under the multiaxial stress state as the basis for the complete damage of the material. The multiaxial creep failure strain is usually converted from the uniaxial creep failure strain using a certain conversion relationship such as the Cocks and Ashby model, and the conversion results are relatively conservative. The creep-damage life prediction method of the material under the multiaxial stress state includes the following steps:

[0051] Step (1), establishing a creep-damage cons...

Embodiment 2

[0108] The difference between embodiment 2 and embodiment 1 is that the creep crack growth of the brazed joint Inconel625 / BNi-2 at 650° C. is selected. The creep test curve of solder BNi-2 at 650 °C is as follows Figure 7 shown. Since the creep strain of the solder in the first stage of creep accounts for about 10% of the total failure strain, for the solder, the three stages of creep should be considered in the creep-damage analysis. Using the creep curves of solder under different stress states, the parameters obtained by fitting are =3.28e4, =333, n =2.92, p =2.70, =3.2307, , , m =0.29, Q =223kJ / mol. The material parameters of the Inconel 625 alloy are the same as those in Example 1. The comparison between the creep life of solder BNi-2 and the test value under the uniaxial stress state predicted by the present invention is as follows: Figure 8 It can be seen that the two are in good agreement. For the multiaxial creep performance parameters of nickel-ba...

Embodiment 3

[0111] The difference between embodiment 3 and embodiment 2 is that the creep crack growth of the brazed joint Inconel625 / BNi-2 under the condition of non-uniform temperature is selected. Such as Figure 12 As shown: the highest temperature of the sample is 650°C, the lowest temperature is about 535°C, and the whole sample has a large gradient. Such as Figure 13 Shown: The creep crack growth of the brazed joint after creeping for 3200 hours under the temperature distribution state. The invention can successfully predict the creep crack expansion of the equipment components under the condition of uneven temperature, and realize the life prediction of the equipment according to the variation trend of the crack expansion.

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Abstract

A creep-damage lifetime forecast method of a material under a multi-axial stress state belongs to the field of material lifetime forecast. The method of the material under the multi-axial stress state is characterized by comprising the following steps of (1) building a creep-damage constitutive model which can represent different temperatures under the multi-axial stress state; (2) building a creep constitutive equation describing different temperatures under the multi-axial stress state; (3) building a damage equation of the material during the creep process; (4) embedding the creep-damage equations in the steps (2) and (3) into a finite element for lifetime analysis; and (5) forecasting creep lifetime of the material under the multi-axial stress state according to an analysis result of the infinite element. By the method of the material under the multi-axial stress state, the lifetime forecast of the material under a high-temperature condition can be achieved better, the forecast process is simple, and a result is accurate.

Description

technical field [0001] The invention relates to a creep-damage life prediction method for materials under a multiaxial stress state, which belongs to the field of material life prediction. Background technique [0002] In the fields of nuclear power, petrochemical and aerospace, many structural components such as heat exchangers work under high temperature and high pressure for a long time, and the entire structure is in a complex multiaxial stress state. Creep and the damage caused by it are the main failure modes of the structure one. Creep-damage failure research under multiaxial stress state is one of the most important links in structural integrity assessment. The forecast is positive. [0003] In recent years, domestic and foreign scholars have carried out a lot of research work on creep-damage failure behavior under multiaxial stress state, and have proposed a variety of creep-damage life prediction models. Currently, there are mainly two kinds of creep-strain dama...

Claims

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Application Information

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IPC IPC(8): G06F17/50
CPCG06F30/23G06F2119/04
Inventor 张玉财蒋文春罗云赵慧琴葛磊
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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