JP2003065921A - Method for evaluating integrity in structure material, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the integrity of a structure material without greatly damaging an evaluation site. SOLUTION: The method for evaluating integrity in structure materials comprises a process (S2) for measuring hardness at a site to be evaluated or the corresponding hardness, a process (S3) for calculating at least one of material characteristic values other than hardness by fitting a hardness measurement value obtained in the hardness measurement process to a master curve where the material characteristic value other than hardness is expressed as a function of hardness to the material characteristic value (breakdown stress, tensile strength, and the like) obtained for a material having the equivalent material characteristic as a site to be evaluated, and a process (S4) for evaluating the breakdown of equipment by a material characteristic value other than hardness obtained in the material characteristic value calculation process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus used under conditions such that the strength of constituent materials changes with the passage of time and has defects such as cracks and cracks on the surface or inside of the apparatus. Structural material integrity evaluation method and its evaluation program.

[0002]

2. Description of the Related Art In materials constituting chemical plants, power plants, etc., cracks may occur as a result of material damage accumulated on the surface or inside of equipment as time passes during actual operation. In addition to such cracks that occur due to the operating load of actual equipment, there are originally small cracks that cannot be detected by inspection during plant construction, and they may grow gradually during plant operation. is there. If an excessive external load due to an earthquake or the like is applied to a device having these cracks, the cracks may rapidly progress and may be destroyed.

The materials constituting the above-mentioned plant are
Material characteristic values such as strength may change with time due to temperature, stress load, etc. during actual operation, and may be different from the initial values at the time of plant construction.

In order to accurately evaluate the structural soundness by accurately calculating the fracture strength in the presence of cracks in plant equipment under operating conditions involving such material changes, the material changes It is essential to know the material property values of the formed members.

This material change depends on the initial value of the material characteristic value at the time of plant construction and the subsequent operating state. Generally, even if the operation history of the equipment is known, it is difficult to grasp or measure the local load history of the equipment, and it is difficult to estimate the accurate material change. Or, the structural material soundness on the safety side is evaluated by overestimating the material change.

[0006] Further, depending on the evaluation equipment and parts,
In some cases, it may be possible to cut out a part of the member from the site where a defect such as a crack was discovered or assumed, or its vicinity.
Tensile strength, stress-strain relationship, fracture toughness value, or JR
It is possible to produce material test pieces of various shapes and dimensions according to material characteristic values required for structural material soundness evaluation such as curves, and obtain those values. According to this method, even if the material changes, the change can be captured as the value of the material characteristic value, and the soundness of the structural material can be accurately evaluated.

[0007]

In the conventional sampling method for highly accurate structural material soundness evaluation in consideration of the material change occurring in the constituent materials with the passage of plant operation time, the material characteristic values required for the evaluation are Accordingly, it is necessary to collect material test pieces of various shapes and sizes from the surface or inside of the equipment. As a result, the surface of the equipment will be significantly destroyed, and repair such as backfilling is required before the plant restarts after the collection.

It is an object of the present invention to provide a method and a program therefor for performing a highly accurate structural material integrity evaluation without giving a large damage to an evaluation site. Even if the hardness, the yield stress, the tensile strength, or the stress-strain relationship changes, whether or not the change is liable to cause a failure depends on the failure mode. That is, in order to perform an accurate structural material integrity evaluation for equipment that is operated under conditions where deterioration of plant constituent materials over time is expected,
It is necessary to quantitatively grasp the changes in each material property value and evaluate the structural material integrity according to the usage conditions and fracture mode of the equipment.

Here, since the above-mentioned material characteristic values are events related to the microscopic deformation resistance of the material, there is a correlation between the respective values. In particular, since hardness is relatively easy to measure, the correlation between hardness and other material property values is calculated and made into a master curve, and the hardness measurement value of actual equipment is used for equipment damage diagnosis. There is a method of calculating necessary material data using the master curve, and using the material data to perform accurate life diagnosis according to the aged state of the actual machine.

Particularly in the case of high temperature equipment, the metallographic changes of the constituent materials are large and the hardness and creep strength often change greatly. By formulating the relationship between the two, the creep strength can be calculated from the measured hardness value. A method of estimating is known (see, for example, JP-A-60-67838 and JP-A-11-326578).

The object of evaluation of the present invention is a device which is operated at a temperature, load, etc., which does not assume damage due to creep, and the present invention evaluates the structural soundness in the presence of defects such as cracks and cracks. In this case, yield stress, tensile strength, stress-strain relationship, fracture toughness value, JR curve, etc. required for the calculation are estimated from hardness measurement values, and the structural integrity of the equipment is evaluated using those values. Suggest methods and programs.

[0012]

In order to achieve the above object, the invention of claim 1 provides a method for evaluating the integrity of a structural material of a device which may have a defect in the structural material. Hardness measurement step of measuring the hardness corresponding to, the material property value other than the hardness obtained for the material having the same material properties as the evaluation target site, the material property value other than the hardness To the master curve represented as a function of, the hardness measurement value obtained in the hardness measurement step is applied, a material property value calculation step of calculating at least one of the material property values other than the hardness, and And a destructive evaluation step of performing destructive evaluation of the device by using the material characteristic values other than the hardness obtained in the material characteristic value calculating step.

According to the first aspect of the present invention, the material characteristic value of the plant equipment constituent material required for highly accurate structural material integrity evaluation can be calculated from the hardness measurement value. As a result, it becomes possible to perform a highly accurate structural material soundness evaluation that directly reflects the material change of the constituent material that occurs during the operation of the plant equipment, without seriously damaging the evaluation target part.

The invention described in claim 2 is the same as claim 1
In the structural material integrity evaluation method according to, the material property values other than the hardness include at least one of yield stress, tensile strength, stress-strain relationship, fracture toughness value, and JR curve, Is characterized by.

According to the invention of claim 2, in addition to the effects and advantages of the invention of claim 1, yield stress, tensile strength, stress-strain relationship, fracture toughness value, JR curve, etc. can be utilized. it can.

The invention described in claim 3 is the same as claim 1
Alternatively, in the structural material soundness evaluation method according to the second aspect, the hardness corresponding to the hardness of the evaluation target site is the hardness of the evaluation target site.

According to the third aspect of the invention, in addition to obtaining the action and effect of the first aspect of the invention, the hardness of the evaluation target portion is directly measured, so that the accuracy is high. In some cases, the indentation mark for hardness measurement may remain on the device to be evaluated, but this is minute, and repair after measurement is unnecessary or necessary, but very slight and easy.

The invention described in claim 4 is the same as claim 1.
Alternatively, in the structural material integrity evaluation method according to the second aspect, the hardness corresponding to the hardness of the evaluation target part is a hardness of a part of the device different from the evaluation target part, The hardness of the part where the hardness can be estimated,
Is characterized by.

According to the invention of claim 4, in addition to obtaining the action and effect of the invention of claim 1 or 2, when it is difficult to measure the hardness of the evaluation target portion, the hardness value at a position different from that is determined. The hardness of the evaluation target part can be estimated.

The invention described in claim 5 is the same as claim 1.
In the structural material soundness evaluation method according to any one of items 1 to 4, the hardness corresponding to the hardness of the evaluation target portion is the hardness of the sample collected from the device.

According to the invention of claim 5, in addition to obtaining the operation and effect of the invention of any one of claims 1 to 4, it is possible to bring in a hardness measuring instrument and measure the hardness at the actual plant site. On the other hand, since the sample for measurement can be brought back to a laboratory or the like in which the environment is prepared and measured, more accurate hardness measurement can be performed, and as a result, the accuracy of structural material integrity evaluation can be improved.

The invention according to claim 6 is the same as claim 1.
5. The structural material soundness evaluation method according to any one of 1 to 5, wherein the shape of the defect is virtually set in the fracture evaluation step, and a numerical value representing the shape dimension of the virtual defect is used. .

According to the invention of claim 6, in addition to the effects and advantages of the invention of claims 1 to 5, when cracks, cracks or the like cannot be detected by inspection, or when inspection is omitted, Alternatively, the structural material integrity can be evaluated even when cracks and cracks are expected to occur by analysis or the like.

The invention described in claim 7 is the same as claim 1.
7. The structural material integrity evaluation method according to any one of 1 to 6 is characterized in that, in the destruction evaluation step, the shape dimension of the defect is set to a value larger than an actual value.

According to the invention of claim 7, the operation and effect of any one of the inventions of claims 1 to 6 can be obtained, and in addition, the soundness of the structural material, that is, the conservative evaluation, can be evaluated.

The invention described in claim 8 is the same as claim 1.
In the structural material soundness evaluation method according to any one of 1 to 7, the hardness is calculated by using the indentation depth and the load of the indenter of the hardness tester in the hardness measurement step.

According to the invention of claim 8, in addition to obtaining the action and effect of the invention of any one of claims 1 to 7, the hardness (called universal hardness) obtained by using the pushing depth and the load of the indenter is obtained. Compared to the conventional hardness measurement method that measures the size of the indentation after unloading the indenter by using it, it is more accurate and more sensitive to the changes in the material of the equipment to be evaluated, which better reflects the mechanical properties of the material. It enables structural material integrity evaluation.

The invention described in claim 9 is the same as claim 1.
In the structural material soundness evaluation method according to any one of 1 to 8, at least the fracture toughness value, the JR curve and the stress-strain relationship are calculated in the material characteristic value calculating step, and the brittleness parameter and the ductility parameter are calculated in the fracture evaluating step. On a fracture evaluation diagram with the relationship of as a coordinate plane, the fracture evaluation point calculated using the fracture toughness value and the JR curve is below the fracture evaluation curve calculated using the stress-strain relationship, It is characterized in that it is used as a criterion for not breaking. According to the invention of claim 9, the action and effect of the invention of any one of claims 1 to 8 can be obtained, and in addition, it becomes possible to evaluate the structural material soundness with high accuracy reflecting the material change.

According to a tenth aspect of the present invention, a computer is provided with at least one of the hardnesses other than the hardness determined for a material having the same material properties as the evaluation target site of the device which may have a defect in the structural material. A function of storing a master curve representing a material characteristic value as a function of hardness, a function of inputting a measured value of hardness corresponding to the hardness of the evaluation target site, and the measured value of the master curve and the hardness It is a program for realizing the function of calculating the at least one material characteristic value of the evaluation target region from the above and the function of performing the destructive evaluation of the device using the at least one material characteristic value.

According to the tenth aspect of the present invention, it is possible to realize a highly accurate structural material soundness evaluation by a computer, which directly reflects the material changes of the constituent materials that occur during the operation of the plant equipment.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a flow chart according to the first embodiment of the present invention. First, the conditions of the evaluation site are set (step S1). In the present embodiment, the case where the shape of the evaluation site is tubular, the defect is a circumferential crack, and a bending load is applied will be described as an example. The defect shape shall be modeled as a semi-elliptical shape or a fan shape existing on the inner surface of the pipe, or a fan shape penetrating the pipe plate thickness,
The structural material integrity evaluation is executed using the values of the defect depth and the defect length of these model defects.

The modeling is performed based on the defect shape measured by the defect inspection of the actual machine. Even if the defect is not found, the existence of the defect is virtually assumed and the shape is set. Also include things. For example, these cases are applicable when it is assumed that a minute defect having a detection accuracy of the defect detection apparatus or less is present, or when the defect size is predicted by analysis or the like for a portion that the defect detection apparatus cannot spatially approach. Even if a defect is actually measured, if a larger value than the actually measured dimension is used for evaluation, the defect in the evaluation will progress even if the load is lower than it actually is, and it is conservative from the viewpoint of safety. It is possible to perform various structural material integrity evaluations. Next, hardness measurement or setting is performed (step S2). The hardness is measured or set by any of the following methods.

The hardness of the site to be evaluated is directly measured by bringing the hardness measuring device into contact with or close to the surface of the evaluation device and pressing an indenter for measuring hardness against the surface to be measured. The hardness of the evaluation target site is calculated without measuring the hardness of the evaluation target site directly by measuring the hardness of the site away from the evaluation site and using the conversion relationship with the hardness of the evaluation site obtained separately. .

Here, as the hardness test method used for measurement, the size of the indentation left on the surface of the object to be measured after unloading the indenter for measurement is measured as in the conventional hardness test represented by Vickers hardness. Any of a method and a method called universal hardness, which is obtained by using an indenter indentation depth and a load, may be used.

The latter universal hardness has been reported to be a measuring method that more reflects the mechanical properties of the material than the conventional method such as Vickers hardness (Reference: Yasuda).
Et al, A new method for evaluating stress-strain prope
rties of metals using ultra-microhardness techniqu
e, Journal of Nuclear Materials, Vol.187, p.109, 1
992).

Next, the yield stress, tensile strength, stress-strain relationship, fracture toughness value, JR curve, etc. are calculated (step S3). The relationship between the hardness and the yield stress σ _y and the tensile strength σ _u can be expressed by a function that includes temperature as a variable. That is, the hardness test is generally carried out at room temperature, but the operating temperature of the equipment to be evaluated is often different from room temperature, and the temperature is included in the variables (1) and (2) below. Form. σ _y = f (hardness, temperature) (1) σ _u = g (hardness, temperature) (2)

Here, there is also a method in which the hardness test is carried out at a high temperature equal to the temperature of the equipment to be evaluated to obtain the high temperature hardness. Furthermore, if the evaluation target state is always a constant temperature, the yield stress σ _y and tensile strength σ _u at that temperature are _calculated by the following equations (3), (4)
It can also be expressed simply as a function of hardness only. σ _y = f (hardness) (3) σ _u = g (hardness) (4)

In the present embodiment, in order to simplify the explanation,
Including the stress-strain relationship, the fracture toughness value, and the JR curve, the temperature factor will be omitted as in the above equation. The fracture toughness value J _IC can also be expressed as a function of hardness as in the following equation (5), like the yield stress σ _y and the tensile strength σ _u . J _IC = h (hardness) (5)

On the other hand, regarding the stress-strain relationship and the JR curve, the former is the relationship between the stress σ and the strain ε, and the latter is the relationship between the elasto-plastic fracture toughness value J and the crack growth amount Δa. ) And equation (7) may be used for approximation. σ = α (ε) ⁿ (6) J = β (Δa) ^m (7)

Here, the coefficients α and β and the index n in the above equation,
m can be expressed as a function of hardness like the following expressions (8) to (11). α = i (hardness) (8) n = j (hardness) (9) β = k (hardness) (10) m = l (hardness) (11)

Finally, destructive evaluation is performed (step S
4). The destructive evaluation method is, for example, the R6 method developed by the Central Electricity Authority of the United Kingdom (for example, reference: I. Milne et al., CEGB Re
p., R / H / R6-Rev.3, 1986) or the Japan Society for Opportunity Society maintenance standard (Nuclear Power Generation Equipment Standard JSME S NA1-2000, 2000)
May follow the two-parameter method stipulated in (May). The two-parameter method is a method in which a linear fracture mechanics criterion and a plastic collapse criterion are combined to perform fracture evaluation on a fracture evaluation diagram.

FIG. 2 shows the flow until the destructive evaluation by the two-parameter method. The radius and wall thickness of the pipe, the size of the defect, and the load condition (here, the bending moment) are input as the shape of the evaluation portion described in FIG. 1 (step S21). Next, the yield stress, the tensile strength and the stress-strain curve are calculated using the measured values of hardness similarly described in FIG. 1 (step S22). Instead of calculating some or all of these values from the hardness, values obtained by literature or analysis may be used.

Next, a destruction evaluation curve showing the limit of destruction of the equipment to be evaluated is obtained from the above values (step S23). There are several types of relational expressions that display the fracture evaluation curve. As an example,
The equation defined by the R6 method option 2 which is the two-parameter method is shown in the following equation (12). Kr = [(E · ε _ref ) / (Lr · σ _y ) + (Lr ³ σ _y ) / (2E · ε _ref )] ^−1/2 (12)

Here, Kr is a brittleness parameter and Lr is a ductility parameter. Further, E is a longitudinal elastic modulus, and since this value is not treated as a function of hardness in the present embodiment, it is necessary to cite a value in literatures or the like. ε _ref is the strain corresponding to the stress Lr · σ _y on the stress-strain curve, and σ _y is the yield stress. In the above equation, Lr is discontinued by the plastic collapse criterion σ _f / σ _y . Here, σ _f is a flow stress obtained by (yield stress + tensile strength) / 2.

Next, the fracture toughness value and the JR curve are calculated using the hardness according to the present invention (step S24). Here, instead of calculating some or all of these values from the hardness, the values obtained by literature or analysis may be used. Destruction evaluation points are obtained from the above values (step S2
5). Here, the case of a pipe with a through crack that undergoes bending is shown. _{Lr = M / M C (a} 0, σ y) (13) Kr = [J e (a 0) / J IC] 1/2 (14)

Here, M is a load moment, and M _C is a limiting moment of a pipe having a through crack of length 2a ₀ assuming a perfect elasto-plastic body. J _e (a ₀ ) is the elastic component of the J integral, and J _IC is the fracture toughness value.

Further, the fracture evaluation points when the crack propagates by Δa with a constant moment are obtained by the equations (13) and (14). However, J _{IC in the} equation (14) is replaced with J integral corresponding to the crack growth amount Δa on the JR curve. By connecting with the fracture evaluation point before the virtual propagation, the fracture evaluation point is displayed as a curve (crack propagation locus) on the fracture evaluation diagram. Compare the fracture evaluation curve obtained as above and the fracture evaluation points,
If one or more of the fracture evaluation points is below the fracture evaluation curve, it is determined that the defect progresses (step S26).

According to the present embodiment, the physical property value of the material required for the fracture evaluation of the device having the defects such as cracks and cracks can be obtained by measuring the hardness of the evaluation target member. When the material changes during the operation of the plant equipment, the structural integrity evaluation of the equipment can be performed with high accuracy reflecting the material change.

In the above embodiment, a program is used to calculate the material characteristic value from the hardness measurement value and the master curve and to perform the destructive evaluation of the equipment based on the material characteristic value. It can be executed by a computer.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. Here, parts that are the same as or similar to those in the first embodiment are assigned the same reference numerals and duplicate explanations are omitted.

In the second embodiment, similar to the first embodiment, the material characteristic value is calculated based on the hardness.
This hardness measurement is not performed on the target site of the evaluation target device, but is performed on a sample sampled from the evaluation target device for hardness measurement. Therefore, the sampling step of the hardness measurement sample (step S31) is provided before the hardness measurement (step S2). Others are the same as those in the first embodiment.

Compared to carrying out the measurement work by bringing in a hardness measuring device to the site of the actual plant, the sampled sample can be taken back to a laboratory or the like in an environment where it can be measured, so that more accurate hardness measurement is possible. As a result, the accuracy of structural material integrity evaluation can be improved. In addition, if physical property values other than hardness can be measured with the size of the sampling sample, it can be carried out as necessary.

[0053]

According to the present invention, with respect to a device that is operated under conditions where the material changes during use, cracks, cracks, etc. on the surface or inside of the device constituent material during its manufacture or use When assessing the structural integrity of a device in the presence of defects, it is possible to calculate material property values that correlate with hardness from the measured hardness values as indicators of material changes, and use those values. Thus, even if the material change in the actual machine is complicated, it is possible to accurately evaluate the structural material soundness reflecting the change.

Since the hardness test is a semi-non-destructive test method in which damage to the object to be measured during measurement is small, the surface of the object to be measured is not largely destroyed. Even if it is necessary to sample a sample for measurement from the device to be evaluated, the size of the sample is larger than that of a test piece required when determining material property values other than hardness by a conventional test method. It can be very small. Therefore, even if it is necessary to repair the cutout traces due to sampling by welding, backfilling, etc., the work is extremely minor. As described above, according to the present invention, inexpensive and highly accurate structural material soundness evaluation can be performed.

[Brief description of drawings]

FIG. 1 is a flow chart of a first embodiment of a structural material soundness evaluation method according to the present invention.

FIG. 2 is a flow chart when the fracture evaluation step in FIG. 1 is performed by a two-parameter method.

FIG. 3 is a flow chart of a second embodiment of a structural material soundness evaluation method according to the present invention.

Claims (10)

[Claims] 1. A hardness measuring step of measuring hardness corresponding to hardness of a portion to be evaluated in a structural material soundness evaluation method for a device having a possibility that a structural material has a defect; For material property values other than the hardness obtained for materials having equivalent material properties, a master curve expressing the material property values other than the hardness as a function of the hardness is added to the hardness obtained in the hardness measurement step. Material characteristic value calculation step of applying at least one of the material characteristic values other than the hardness, and the material characteristic values other than the hardness obtained in the material characteristic value calculation step are used. And a destructive evaluation step of performing destructive evaluation of the device. 2. The structural material soundness evaluation method according to claim 1, wherein the material property values other than the hardness include yield stress, tensile strength, stress-strain relationship, fracture toughness value, and J
A structural material integrity evaluation method comprising at least one of R curves. 3. The structural material soundness evaluation method according to claim 1 or 2, wherein the hardness corresponding to the hardness of the evaluation target portion is the hardness of the evaluation target portion. Structural material integrity evaluation method. 4. The structural material integrity evaluation method according to claim 1, wherein the hardness corresponding to the hardness of the evaluation target site is a hardness of a site of the device different from the evaluation target site. Then, the structural material soundness evaluation method is characterized in that it is the hardness of a portion where the hardness of the evaluation target portion can be estimated. 5. The structural material integrity evaluation method according to claim 1, wherein the hardness corresponding to the hardness of the evaluation target portion is the hardness of a sample collected from the device. A structural material integrity evaluation method characterized by: 6. The structural material integrity evaluation method according to claim 1, wherein in the destruction evaluation step,
A structural material soundness evaluation method, wherein the shape of the defect is virtually set and a numerical value representing the shape dimension of the virtual defect is used. 7. The structural material integrity evaluation method according to claim 1, wherein in the destruction evaluation step,
A structural material soundness evaluation method, characterized in that the shape dimension of the defect is set to a value larger than an actual value. 8. The structural material soundness evaluation method according to claim 1, wherein in the hardness measuring step,
A method for evaluating the integrity of a structural material, wherein hardness is calculated using the indentation depth of an indenter of a hardness tester and a load. 9. The structural material soundness evaluation method according to claim 1, wherein in the material characteristic value calculating step, at least a fracture toughness value,
A JR curve and a stress-strain relationship are calculated, and in the fracture evaluation step, a fracture calculated using the fracture toughness value and the JR curve on a fracture evaluation diagram having a relationship between brittleness parameter and ductility parameter as a coordinate plane. A structural material integrity evaluation method, characterized in that the evaluation point is below a fracture evaluation curve calculated using the stress-strain relationship as a criterion of non-destruction. 10. A computer is provided with at least one material characteristic value other than the hardness obtained for a material having the same material characteristics as an evaluation target part of an equipment which may have a defect in a structural material, as a function of hardness. A function of storing the master curve represented, a function of inputting a measurement value of hardness corresponding to the hardness of the evaluation target portion, the at least the evaluation target portion from the master curve and the measurement value of the hardness A program for realizing a function of calculating one material characteristic value, and a function of performing destructive evaluation of the device using the at least one material characteristic value.