JP2589197Y2 - Fatigue monitoring device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fatigue monitoring apparatus applied to a nuclear power plant or the like, and more particularly to a fatigue monitoring apparatus for thermal stratification of pipes for online evaluation of a fatigue damage coefficient and crack stability.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional fatigue monitoring device and its peripheral structure. The fatigue monitoring device 1 includes a fatigue monitoring operation unit 11 and a database unit 12. The database unit 12 stores a green function 12a of stress, a temperature change diagram 12b, and an equivalent thermal bending stress database 12c.

The Green function of stress 12a is calculated in advance by a FEM (finite-element method) using a large-scale computer (not shown).
d) By the analysis 12a1, the stress is obtained as the time change of the stress at the evaluation point of the axisymmetric model with respect to the unit time change (step change) 12a2 of the fluid temperature. Temperature change diagram 1
2b shows the relationship between the time change rate of the outer surface temperature and the data obtained by subtracting the outer surface temperature from the fluid temperature by FEM analysis using the axially symmetric model, as in the case of the Green function 12a of the stress (confirmed that the relationship is almost a straight line). Already). The equivalent adiabatic bending stress database 12c is obtained as a thermal bending stress based on a beam model FEM analysis 12c1 assuming a uniform unit temperature distribution 12c2 in the pipe cross section.

[0004] The fatigue monitoring operation unit 11 inputs fluid temperature data from the fluid temperature sensor 2 or, if the fluid temperature data cannot be obtained, attaches an outer surface temperature sensor 3 near an evaluation point. Input the outer surface temperature data from. The fatigue monitoring calculation unit 11
Further, pressure data is input from the pressure sensor 4.

[0005] That is, the fatigue monitoring calculation unit 11 calculates the pressure change 4a obtained from the pressure sensor 4 and the fluid temperature change 2a obtained from the fluid temperature sensor 2 or the external surface temperature change 3a obtained from the external surface temperature sensor 3. Is input as an input signal, the thermal stress change is evaluated online using the respective data stored in the database 12, and the fatigue damage coefficient and the crack stability are further evaluated.
To be displayed.

FIG. 5 is a functional block diagram showing a detailed configuration of the fatigue monitoring operation unit 11, and FIG. 6 is a block diagram of the database 12 and the fatigue monitoring operation unit 11 in FIG.

[0007] When the outer surface temperature sensor 3 is used, the fatigue monitoring calculation unit 11 obtains an estimated fluid temperature change 11a using a temperature change diagram 12b. When the outer surface temperature change 3a is used, the designated fluid temperature change 11a is used.
When the fluid temperature sensor 2 is used, the measured fluid temperature change 2a is used as an input signal, and a green function 12
A thermal shock stress calculation 11c is performed online by the Green's function method 11b extracted from a.

The fatigue monitoring calculation section 11 calculates an equivalent thermal bending calculation 11 d from the external surface temperature change 3 a obtained from the external surface temperature sensor 3 using an equivalent thermal bending stress database.
Execute The pressure change 4 obtained from the pressure sensor 4
a is multiplied by a predetermined coefficient, and an internal pressure stress calculation 11e is performed.

The fatigue monitoring calculation section 11 calculates the thermal shock stress 11c and the equivalent thermal bending stress 11 described above.
Fatigue damage calculation 11f is performed from each calculation result of d and calculation 11e of internal pressure stress. Calculation of equivalent thermal bending stress 11
Crack stability evaluation based on the net stress concept is performed from d and the calculation 11e of the internal pressure stress.

[0010]

In the conventional method described above, the evaluation means is developed and installed on the assumption that the temperature distribution in the cross section of the pipe is uniform. However, in general, a temperature distribution occurs in the cross section of the pipe, and when this temperature distribution is remarkable, a thermal stratification phenomenon occurs, and the pipe may be damaged by fatigue. Therefore, the conventional method cannot properly evaluate the dominant thermal stress in the case where a temperature distribution occurs in the cross section of the pipe, and cannot perform accurate fatigue damage evaluation.

[0011] The present invention has been made in view of the above circumstances, and has as its object to provide a fatigue monitoring device capable of improving the evaluation accuracy of thermal stress and capable of performing accurate fatigue damage calculation.

[0012]

The fatigue monitoring apparatus according to the present invention subtracts the outer surface temperature from the data measured by the outer surface temperature sensor attached near the evaluation point and the predetermined inner surface temperature. Means for calculating the estimated inner wall temperature distribution and the estimated inner wall temperature change over time in the vicinity of the evaluation point from the data and the rate of change of the outer surface temperature with time, and the local thermal stress and equivalent heat in the pipe cross-section from the estimated inner wall temperature distribution obtained by this means A means for obtaining a bending stress, a means for obtaining a thermal shock stress by using the Green's function method from the estimated inner wall temperature change over time, a means for obtaining an internal pressure stress from data measured by a pressure sensor, Means for realizing fatigue damage evaluation and crack stability evaluation of piping from the stress, the equivalent thermal bending stress, the thermal shock stress, and the internal pressure stress. It is characterized in.

[0013]

The relationship between the external surface temperature temporal change rate prepared in advance and the data obtained by subtracting the external surface temperature from the internal surface temperature is input from a plurality of external surface temperature sensors provided near the evaluation point. The estimated inner wall temperature change near the evaluation point and the inner wall temperature distribution of the evaluation point cross section are obtained using the curve. For this estimated inner wall temperature change, the local thermal stress in the plate thickness direction is evaluated using the Green's function method of the axially symmetric model.

Further, the local thermal stress distributed in the pipe section is obtained from the inner wall temperature distribution by a simple evaluation method. Further, a thermal bending temperature distribution that generates an equivalent thermal bending moment of the entire pipe is obtained from the inner wall temperature distribution, and the thermal bending stress is proportionally multiplied by a unit thermal bending temperature distribution previously obtained by the beam model FEM analysis, and the entire pipe is obtained. Of thermal bending stress. Fatigue damage calculation is performed by adding the thermal stresses of the three components described above.

[0015]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the configuration of the fatigue monitoring device of the present invention and its surroundings. The fatigue monitoring device 6 includes a fatigue monitoring operation unit 61 and a database unit 62. The database unit 62 stores an equivalent thermal bending stress database 62a, a green function of stress 62b, and a temperature change diagram 62c.

The equivalent thermal bending stress database 62a includes a unit linear temperature distribution 62a1 of the inner wall temperature in the section of the pipe to be evaluated.
(Temperature distribution where the temperature difference between the top and bottom of the horizontal pipe is a linear distribution of 1 ° C. when viewed from the side) is obtained by performing beam model FEM analysis 62a2. The Green function 62b of the stress is obtained in advance by an FEM analysis 62b1 of the axially symmetric model by a large-scale computer (not shown).
It is determined for the unit temperature change 62b2 of the inner wall.
Further, the temperature change diagram 62c is obtained as a relationship between a value obtained by subtracting the outer surface temperature from the inner surface temperature and the time change rate of the outer surface temperature.

A plurality of outer surface temperature sensors 3 and pressure sensors 4 are provided near the evaluation points. The fatigue monitoring computing unit 61 of the fatigue monitoring computing device 6 receives the external surface temperature change 3a from the external surface temperature sensor 3 and the pressure change 4a from the pressure sensor 4, and uses the database unit 62 in a procedure as described later. Crack stability evaluation and fatigue damage evaluation are performed. The display device 5 is provided at a predetermined position such as a central control room, and displays an evaluation result. Next, the procedure of crack stability evaluation and fatigue damage calculation will be described. If the fluid temperature in the pipe changes instantaneously as a whole due to thermal shock, the local thermal stress in the plate thickness direction is evaluated using the Green's function method for the conventional axisymmetric model.

The non-axial symmetrical stress component newly added due to the temperature distribution generated in the pipe cross section can be separated into local thermal stress (pipe self-constrained stress) distributed in the pipe cross section and thermal bending stress of the entire pipe. it can. The former can be formulated from the self-balance of moment and force in the pipe cross section from the distribution of the pipe inner wall temperature in the pipe cross section. The latter assumes a region where thermal stratification occurs, models the entire piping system with a beam model, and sets a linear temperature where the temperature difference between the top and bottom of the horizontal pipe is the unit temperature (= 1 ° C) in the assumed thermal stratification generation region. The stress at the evaluation point when the distribution is given is prepared as a database, and the evaluation can be performed using the linear temperature distribution obtained from the temperature distribution in the pipe section.

Next, the operation of this embodiment will be described with reference to a functional block diagram of the fatigue monitoring calculation section 61 shown in FIG. 2 and FIG. 3 in which a graph is added to each block in FIG. The fatigue monitoring calculation unit 61 uses the outer surface temperature change 3a measured by the outer surface temperature sensor 3 as an input signal, and obtains the inner wall temperature distribution 61a of the evaluation point cross section and its time change 61b using the temperature change diagram 62c. The thermal shock stress calculation 61d is performed using the estimated inner wall temperature time change 61b and the Green function method 61c extracted from the stress Green function 62b.

According to the temperature distribution 61a of the inner wall of the cross section at the evaluation point, a calculation 61e of the local thermal stress in the cross section of the pipe is executed for the non-linear temperature distribution component by the self-balancing formula of the moment and force in the cross section of the pipe. Fatigue monitoring calculation unit 61
Performs an equivalent thermal bending stress calculation 61f using the equivalent thermal bending stress database 62a at the same time. Further, the pressure change 4a signal input from the pressure sensor 4 is multiplied by a factor times to perform an internal pressure stress calculation 61g.

Fatigue damage calculation 61h is carried out from the calculation results of the internal pressure stress calculation 61g, the thermal shock stress calculation 61d, the local thermal stress calculation 61e in the pipe cross section, and the equivalent thermal bending stress calculation 61f.

Further, based on the calculation results of the thermal bending stress calculation 61f and the internal pressure stress calculation 61g, a crack stability evaluation 61i based on a net stress concept for an assumed crack is performed, and a comprehensive soundness evaluation is performed online. I do.

[0023]

[Effect of the Invention] As described in detail above, the temperature distribution in the piping cross section is calculated by measuring the outer surface temperature distribution, and a fatigue monitoring calculation unit including a stress evaluation logic capable of coping with the non-axial target temperature distribution is constructed. Thereby, the evaluation accuracy of thermal stress is remarkably improved, and accurate fatigue damage calculation becomes possible.

Further, in the conventional stress evaluation logic which presumes a uniform temperature distribution in a cross section, there is a case where the degree of fatigue damage is estimated to be low, so that a problem arises in safety evaluation. This invention solves such a problem. Is done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a fatigue monitoring device according to an embodiment of the present invention and a peripheral configuration thereof.

FIG. 2 is a block diagram showing details of a fatigue monitoring calculation unit in the embodiment.

FIG. 3 is a diagram showing each block in FIG. 2 using a graph.

FIG. 4 is a block diagram showing the overall configuration of a conventional fatigue monitoring device and its peripheral configuration.

FIG. 5 is a block diagram showing details of a fatigue monitoring calculation unit in a conventional fatigue monitoring device.

FIG. 6 is a diagram showing each block in FIG. 5 using a graph.

[Explanation of symbols]

3 ... outer surface temperature sensor, 4 ... pressure sensor, 5 ... display device, 6 ... fatigue monitoring device, 61 ... fatigue monitoring calculation unit, 62 ... database unit, 62a ... equivalent thermal bending stress database, 62b ... green function of stress, 62
c: temperature change diagram, 62a1: unit linear temperature distribution of the inner wall temperature (non-axial target), 62a2: beam model FEM analysis,
62b1: FEM analysis of the axis-symmetric model;

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Umehara 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Kobe Shipyard, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-59-206751 (JP, A) JP-A-58-211625 (JP, A) JP-A-61-265211 (JP, A) JP-A-61-95212 (JP, A) JP-A-59-128429 (JP, A) -1440839 (JP, A) Japanese Utility Model 63-167299 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01M 13/00 G01N 3/32 G21C 17/003

Claims (1)

(57) [Scope of request for utility model registration] 1. The evaluation point is obtained from data measured by an outer surface temperature sensor attached near an evaluation point, data obtained by subtracting an outer surface temperature from a previously determined inner surface temperature, and a time change rate of the outer surface temperature. Means for calculating an estimated inner wall temperature distribution and an estimated inner wall temperature time change in the vicinity; means for calculating a local thermal stress and an equivalent thermal bending stress in a pipe section from the estimated inner wall temperature distribution obtained by the means; Means for obtaining a thermal shock stress using the Green's function method from the change; means for obtaining an internal pressure stress from data measured by a pressure sensor; and a method for obtaining the local thermal stress in the pipe section, the equivalent thermal bending stress, and the thermal shock stress. Means for realizing the fatigue damage evaluation and the crack stability evaluation of the pipe from the internal pressure stress.