A method for evaluating hydrogen damage life of shock tube

Abstract

The present invention belongs to the technical field of hypersonic test equipment, and discloses an online evaluation method for hydrogen damage life of a shock wave tube. The online evaluation method for hydrogen damage life of a shock wave tube of the present invention collects the service condition parameters of the tube, and calculates the radial strain value and radial hydrogen concentration distribution of the current tube online; the influence of hydrogen concentration on elongation is fitted by test data to obtain the fracture strain value under the current hydrogen concentration of the tube; the hazard coefficient is obtained by the ratio of the current strain value to the fracture strain value; and the tube life is predicted by the historical hazard coefficient. The online evaluation method for hydrogen damage life of a shock wave tube of the present invention evaluates the strength of the tube by hydrogen concentration, and the degree of hydrogen damage to the tube online; the hydrogen damage life of the tube is evaluated online by the time fitting relationship of the historical hazard coefficient; the economical and timely performance is good, and the tube is suitable for engineering promotion.

Description

Technical Field

[0001] The invention belongs to the technical field of hypersonic test equipment, and in particular relates to an online evaluation method for hydrogen loss life of a shock tube. Background Art

[0002] A shock tunnel is a pulsed wind tunnel that uses shock waves to compress the test gas and then expand it steadily through a nozzle to produce a hypersonic test airflow. Hydrogen drive is the main drive method for shock tunnels. Using hydrogen drive can produce stronger shock waves and obtain higher test parameters. Heating the hydrogen can also obtain stronger driving capabilities.

[0003] In actual use, the shock wave tube is in direct contact with hydrogen, and the material will produce hydrogen damage such as hydrogen embrittlement and hydrogen corrosion, which will have an adverse effect on the service life of the tube. However, this cannot be directly judged from the appearance, which poses a major hidden danger to service safety. In addition, the shock wave tube has high service pressure and a wide temperature range, and the dangers of hydrogen leakage are huge. It is impossible to judge the service life of the tube, which poses a greater safety risk.

[0004] Currently, there is an urgent need to develop an online evaluation method for the hydrogen loss life of the shock tube in a hydrogen-driven shock tunnel. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an online evaluation method for hydrogen loss life of a shock tube.

[0006] The method for online evaluation of hydrogen loss life of a shock tube of the present invention comprises the following steps:

[0007] Step 1: The sensor installed on the pipe body collects the outer layer temperature, inner layer temperature and inner layer pressure of the pipe body;

[0008] Step 2: Establish a one-dimensional axisymmetric finite element model;

[0009] Step 3: In a one-dimensional axisymmetric finite element model, the collected outer layer temperature, inner layer temperature and inner layer pressure of the tube body are introduced to calculate the radial stress distribution of the current tube body and obtain the radial strain value of the current tube body;

[0010] Step 4: Use Sieverts' law to calculate the current inner layer saturated hydrogen concentration of the pipe body through the collected inner layer temperature and inner layer pressure of the pipe body;

[0011] Step 5: In the one-dimensional axisymmetric finite element model, the inner saturated hydrogen concentration of the current tube is introduced, and the radial hydrogen concentration distribution of the current tube is calculated according to the historical hydrogen concentration of the tube;

[0012] Step 6: Introduce test data of materials with different hydrogen contents, fit the radial elongation threshold of the tube under the current hydrogen concentration distribution condition, and then calculate the fracture strain value under the current hydrogen concentration distribution condition;

[0013] Step 7: Calculate the ratio of the radial strain value of the current pipe body to the fracture strain value of the current pipe body to obtain the current risk factor;

[0014] Step 8: Use historical hazard coefficient fitting to predict the pipe life under the current hazard coefficient.

[0015] The shock tube hydrogen loss life online evaluation method of the present invention has the following advantages:

[0016] a. Only a small amount of conventional parameters can be collected to evaluate the hydrogen loss life of the pipe;

[0017] b. The degree of hydrogen damage to the pipe material can be evaluated online without sampling and testing the pipe material.

[0018] c. The pipe life can be predicted online to guide the maintenance and management of the pipe.

[0019] The shock tube hydrogen loss life online evaluation method of the present invention is based on the following four basic works: 1. Collecting the service condition data of the tube; 2. Establishing the calculation model of the tube strain distribution and hydrogen concentration distribution; 3. Obtaining the test data of the influence of hydrogen concentration on the elongation of the material; 4. Obtaining the historical hazard coefficient.

[0020] The shock wave tube hydrogen loss life online evaluation method of the present invention collects the service condition parameters of the tube body, calculates the radial strain value of the current tube body and the radial hydrogen concentration distribution of the current tube body online; uses the influence of hydrogen concentration on elongation fitted by test data to obtain the fracture strain value of the current tube body under the radial hydrogen concentration distribution of the current tube body; obtains the current risk factor through the ratio of the radial strain value of the current tube body to the fracture strain value of the current tube body; and finally predicts the tube life under the current risk factor through the historical risk factor.

[0021] In short, the shock tube hydrogen damage life online evaluation method of the present invention evaluates the tube strength through hydrogen concentration and the degree of hydrogen damage to the tube online; the hydrogen damage life of the tube is evaluated online through the time fitting relationship of the historical hazard coefficient; it is economical and timely, and is suitable for engineering promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a flow chart of the on-line evaluation method of hydrogen loss life of a shock tube body of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1

[0025] like Figure 1 As shown, the online evaluation method for hydrogen loss life of the shock tube body of this embodiment includes the following steps:

[0026] Step 1: The sensor installed on the pipe body collects the outer layer temperature T of the pipe body 0 , inner layer temperature of the tube body T i And the inner layer pressure P of the pipe body;

[0027] Step 2: Establish a one-dimensional axisymmetric finite element model;

[0028] Step 3: In the one-dimensional axisymmetric finite element model, introduce the collected outer layer temperature T of the tube 0 , inner layer temperature of the tube body T i and the inner layer pressure P of the pipe body, calculate the radial stress distribution of the current pipe body, and obtain the radial strain value ε of the current pipe body r ;

[0029] The specific process is to take the outer layer temperature T 0 and the inner temperature of the tube body T i As boundary conditions, the heat conduction equation Perform discrete solution to obtain the thermal strain value ε of the current pipe body th , expressed as in, is the output heat flux, λ is the thermal conductivity, α is the linear expansion coefficient, r is the radius of the tube, and T is the temperature;

[0030] The outer layer pressure is 0, and the inner layer pressure P of the pipe body is used as the boundary condition. By solving the equations of force balance, deformation coordination and physical equations, the radial strain value ε of the current pipe body is obtained. r and hoop strain value ε θ ; The system of equations for force balance, deformation coordination and physical equations is:

[0031]

[0032] Among them, σ r , σ θ are radial stress, hoop stress, ε r , ε θ are radial strain and hoop strain respectively, σ and ε are equivalent stress and equivalent strain, K and n are material constants.

[0033] Step 4: Use Sieverts' law to obtain the inner temperature T of the pipe body i Calculate the current inner layer saturated hydrogen concentration C of the pipe body by using the inner layer pressure P of the pipe body H ;

[0034] CH The calculation formula is: A is a constant, R is a gas constant, and ΔH is the heat of solution;

[0035] Step 5: In the one-dimensional axisymmetric finite element model, introduce the inner saturated hydrogen concentration C of the current tube H The radial hydrogen concentration distribution C of the current tube body is calculated by the historical hydrogen concentration of the tube body H (r);

[0036] The specific method is: take the radial hydrogen concentration distribution of the current tube body calculated at the previous acquisition time as the initial condition, and solve the diffusion equation The inner boundary condition is the inner saturated hydrogen concentration C of the current tube at the current moment. H ; Where C is the hydrogen concentration, τ is the time, and D is the diffusion coefficient.

[0037] Step 6: Introduce the test data of materials with different hydrogen contents, fit the radial elongation threshold of the tube under the current hydrogen concentration distribution conditions, and then calculate the fracture strain value ε under the current hydrogen concentration distribution conditions f ;

[0038] That is, the test data of the effect of hydrogen concentration on the elongation of the material is introduced into the radial hydrogen concentration distribution of the current pipe body, and the fracture strain value ε of the current pipe body is calculated. f =ln(1+A * (C)), where A * (C) is the radial elongation of the current tube under the corresponding hydrogen concentration obtained by fitting;

[0039] Step 7: Calculate the radial strain value ε of the current tube body r and the current fracture strain value ε of the tube f The ratio of , obtain the current risk factor;

[0040] ζ r =(ε r +ε th ) / ε f

[0041] Among them, r is the current radial risk factor;

[0042] Step 8: Use historical risk factor fitting to predict the pipe life under the current risk factor;

[0043] By fitting the relationship between the historical hazard factor and time, the hazard threshold is defined, and the time required for the current hazard factor to reach the threshold is fitted to predict the pipe life.

[0044] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments, and they can be applied to various fields suitable for the present invention. For those familiar with the art, other improvements and modifications can be easily realized without departing from the principles of the present invention, and the present invention is not limited to the specific details and the legends shown and described here.

Claims

1. A shock tube hydrogen loss life online evaluation method, characterized in that: The following steps are involved: Step 1: The sensor installed on the pipe body collects the outer layer temperature, inner layer temperature and inner layer pressure of the pipe body; Step 2: Establish a one-dimensional axisymmetric finite element model; Step 3: In a one-dimensional axisymmetric finite element model, the collected outer layer temperature, inner layer temperature and inner layer pressure of the tube body are introduced to calculate the radial stress distribution of the current tube body and obtain the radial strain value of the current tube body; Step 4: Use Sieverts' law to calculate the current inner layer saturated hydrogen concentration of the pipe body through the collected inner layer temperature and inner layer pressure of the pipe body; Step 5: In the one-dimensional axisymmetric finite element model, the inner saturated hydrogen concentration of the current tube is introduced, and the radial hydrogen concentration distribution of the current tube is calculated according to the historical hydrogen concentration of the tube; Step 6: Introduce test data of materials with different hydrogen contents, fit the radial elongation threshold of the tube under the current hydrogen concentration distribution condition, and then calculate the fracture strain value under the current hydrogen concentration distribution condition; Step 7: Calculate the ratio of the radial strain value of the current pipe body to the fracture strain value of the current pipe body to obtain the current risk factor; Step 8: Use historical hazard coefficient fitting to predict the pipe life under the current hazard coefficient.

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