JP3886865B2 - Metal material damage evaluation method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal material damage evaluation method and apparatus, and more particularly to brittleness generated in welds of low alloy steel used as various pipes using high-temperature pressure-resistant metal members such as thermal power plants and nuclear power plants. The present invention relates to a damage evaluation method and apparatus for a metal material suitable for use in evaluating the progress of microscopic damage such as creep damage and diagnosing the life of the metal material.
[0002]
[Prior art]
In recent years, in thermal power plants, maintenance management that fully considers thermal fatigue due to equipment deterioration due to long-term use, frequent start / stop, rapid load fluctuations, etc. is becoming more and more important as the operation time becomes longer. It has become to.
For example, in large-diameter thick-walled pipes that use high-temperature pressure-resistant metal members, cracks and other scratches often occur inside the weld, but this scratch can be detected only by inspection of the outer surface. Therefore, there is a demand for the development of a crack monitoring method by early detection of this scratch and accurate measurement of its size.
Conventionally, in order to estimate the remaining life (time to break), the MLAS method that estimates the remaining life by directly inspecting the surface damage and the TOFD method (Time Of Flight Diffraction) that inspects the internal damage It has been.
[0003]
The MLAS method is a method of taking a replica of a surface by transferring the surface of a pipe to a plastic film, and observing the replica using an optical microscope. And the distribution state thereof, and the life is diagnosed by comparing with the reference data of the relationship between these and the life.
[0004]
The TOFD method is based on the following measurement principle. FIG. 14 is an explanatory diagram for explaining the measurement principle of the TOFD method. A transmitting probe 1 for transmitting ultrasonic waves and a receiving probe 2 for receiving ultrasonic waves are placed on the surface of the metal material 3. The crack (defect) 4 generated inside the metal material 3 is placed at an equal distance, the ultrasonic wave 5 is transmitted into the metal material 3 by the transmission probe 1, and the crack is generated by the reception probe 2. The diffracted wave 6 from the upper end and the lower end of 4 is detected, the propagation time thereof is measured, and the height of the crack 4 is obtained by equation (1). In the figure, 7 is a surface wave, and 8 is a bottom surface reflected wave.
[0005]
L = Zb-Zt
= √ (tb2 · V2 / 4−S2) −√ (tt2 · V2 / 4−S2) (1)
Where L: crack height
Zb: Depth of crack tip
Zt: Depth of crack bottom
D: Distance between the transmission probe 1 and the reception probe 2
S: D / 2
V: Speed of diffracted wave
tt: Diffraction wave propagation time from crack tip
tb: Diffraction wave propagation time from crack bottom
Since the TOFD method described above uses a diffracted wave from a defect to detect flaws, it is less affected by the inclination of the defect than the conventional ultrasonic flaw detection method, and the possibility of overlooking a directional defect is reduced. The defect detection performance is improved.
[0006]
However, since the crack propagation calculation assumes that a single crack grows and propagates, for example, in the case of damage where multiple microscopic cracks grow and repeat coalescence. However, there is a possibility that the remaining life diagnosis by the above method may not correspond to the actual damage state, and as a result, the remaining life diagnosis may be inaccurate.
Therefore, Japanese Patent Application No. 2000-367017 proposes an evaluation method capable of predicting the remaining life even in a metal material in which a plurality of microscopic cracks are internally generated and damaged in such a manner that they grow while repeating coalescence. Has been.
[0007]
In this evaluation method, initial damage is first estimated based on the measurement results of the replica method and the TOFD method, and the stress distribution is estimated from the initial damage. Next, a grain boundary model in the welded portion of the high-temperature pipe 11 is created, and a microscopic damage progress simulation is performed based on FIGS. 15 and 16. In this analysis model, the grain boundary length group is [L], the average is Lm, the standard deviation is LS, the fracture resistance value of the grain boundary is R, the average is Rm, and the standard deviation is RS.
[0008]
The crack generation driving force F determined by the stress σ acts on each grain boundary model, and at the stage where no crack is generated, assuming that the grain boundary fracture driving force is D, the damage progress rate dR / dt = −D = −F.
When the damage progresses as time passes and the fracture resistance value R of the grain boundary becomes negative (R <0), the grain boundary breaks and a crack occurs. At the grain boundary adjacent to the crack, the grain boundary fracture driving force D is equal to the sum of the crack generation driving force F and the product of the crack propagation driving force K and the crack length a adjacent to the grain boundary. (D = F + a · K).
[0009]
As time progresses, the number of cracks gradually increases and the length of each crack increases.
[0010]
[Problems to be solved by the invention]
However, the above evaluation method has many points to be improved.
One of the problems is related to the time distribution of the stress distribution. The pipe welded portion to be subjected to the remaining life diagnosis has a portion having a large stress and a portion having a small stress (having a stress distribution) depending on the shape of the weld bead. The growth rate of microscopic damage depends on the stress, and the damage progresses faster as the stress increases. The portion where the damage has progressed has a reduced apparent rigidity, resulting in a decrease in stress. The part of the stress that has been lowered will still be handled by the part with small damage, and the stress at this part will increase. Therefore, damage of this part progresses. To repeat this, the stress distribution changes from moment to moment as the damage progresses. However, in the conventional microscopic damage progress calculation, the stress distribution does not change from the initial state to the fracture, so the damage progress can be accurately predicted in the latter half of the life (after about 80%) where the stress distribution is different from the initial state. Therefore, the break time could not be estimated accurately. For this reason, the accuracy of the life diagnosis up to the subsequent fracture was insufficient.
[0011]
This invention is made | formed in view of said situation, Comprising: It aims at providing the damage evaluation method and apparatus of a metal material which can estimate a remaining life more correctly.
[0012]
[Means for Solving the Problems]
The damage evaluation method for a metal material according to claim 1 is a method for evaluating a flaw in a metal material, wherein an internal damage state of the metal material is inspected to obtain a damage distribution, and the metal is determined based on the damage distribution. By estimating the internal shape of the material and further expressing the interior of the metal material with a grain boundary model, and applying a stress calculated based on the internal shape of the metal material to each of the grain boundary models, It is characterized by calculating the destruction process of the boundary model.
[0013]
In the present invention, the fracture progress process can be calculated more accurately by applying stress to the grain boundary model in consideration of the shape inside the metal material.
[0014]
According to a second aspect of the present invention, in the damage evaluation method for a metal material according to the first aspect, the estimated internal shape of the metal material is changed variously, the estimated probability of the shape, and the fracture progress of each grain boundary model. The remaining life probability of the metal material is calculated in correspondence with the remaining life obtained by the calculation of the process.
[0015]
In the present invention, the remaining life of the metal material can be probabilistically evaluated by variously estimating the inside of the metal material and comparing the probability with the remaining life of the analysis result.
[0016]
The invention according to claim 3 is a method for evaluating scratches on a metal material, wherein a grain boundary model of an internal shape of the metal material is created, and an initial stress acting on each grain boundary model is set, and then a predetermined value is set. Calculate the fracture progress after a lapse of time, recalculate the stress acting on each grain boundary model based on the damage of the grain boundary model obtained as a result, and based on the stress after the recalculation Furthermore, it is characterized in that a fracture progress process after a predetermined time has elapsed is calculated.
[0017]
According to a fourth aspect of the present invention, in the damage evaluation method for a metal material according to the first or second aspect, a grain boundary model of the internal shape of the metal material is created, and initial stress acting on each of the grain boundary models is determined. After the setting, calculate the progress of fracture after a predetermined time, and recalculate the stress acting on each grain boundary model based on the damage of the grain boundary model obtained as a result. Further, the fracture progressing process after a predetermined time has been calculated based on the stress.
[0018]
In the inventions according to the third and fourth aspects, it is possible to perform a simulation in consideration of a stress that changes due to damage.
[0019]
According to a fifth aspect of the present invention, in the damage assessment method for a metal material according to the third or fourth aspect, the calculation of the progress of the fracture is repeated until the fracture of the metal material.
[0020]
In the present invention, it is possible to continue the calculation until the time of fracture by sequentially recalculating the stress acting on the grain boundary model.
[0021]
The invention according to claim 6 is the metal material damage evaluation method according to any one of claims 1 to 5, wherein the grain boundary model damage site obtained by calculation of a fracture progress process of the grain boundary model is represented by the grain boundary. It is characterized by being displayed on the screen or printed in superposition with the model.
[0022]
In the present invention, by displaying the grain boundary model and the void generated in the grain boundary model together, the analysis result can be represented in a state that is easy to understand visually. The dimension of the grain boundary model is not particularly limited. For example, it is conceivable that a grain boundary model created by a computer is displayed on the screen, and a damaged part is indicated by a bold line on the grain boundary model.
[0023]
The invention according to claim 7 is the damage evaluation method for a metal material according to any one of claims 1 to 6, wherein the internal shape of the metal material is displayed or printed on the screen, and the fracture progress process of the grain boundary model is calculated. The degree of damage of the obtained grain boundary is shown superimposed on the internal shape of the metal material.
[0024]
In the present invention, for example, a structure inside a metal is displayed on a screen, and a portion having a large degree of damage obtained by analysis in the structure is shown by changing its color and density. By doing in this way, an analysis result can be expressed in a state that is easy to understand visually.
[0025]
According to an eighth aspect of the present invention, in the damage evaluation method for a metallic material according to the seventh aspect, the result of actually inspecting the damaged state of the metallic material is simultaneously displayed on a screen or printed.
[0026]
In the present invention, the validity of the analysis result can be determined by comparing the analysis result and the actual inspection result, and the degree of damage is determined by combining the analysis result and the actual inspection result. be able to.
[0027]
The invention according to claim 9 is an apparatus for evaluating a flaw in a metal material, the internal shape estimating means for estimating the internal shape of the metal material based on the internal damage distribution of the metal material, and the inside of the metal material An analysis means for calculating the progress of fracture of each grain boundary model by applying a stress calculated based on the internal shape of the metal material to each grain boundary model. It is characterized by having.
[0028]
In the present invention, the fracture progress process can be calculated more accurately by applying stress to the grain boundary model in consideration of the shape inside the metal material.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a metal material damage evaluation method and apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a metal material damage evaluation apparatus shown as an embodiment of the present invention.
In the figure, reference numeral 10 is an internal inspection means for inspecting the internal damage state of the metal material to obtain a damage distribution, 11 is a stress estimation means for calculating the internal average stress of the metal material based on the damage distribution, and 12 is estimated. Bead shape estimation means (internal shape estimation means) for estimating the internal shape of the metal material based on the average stress. Reference numeral 13 denotes a grain boundary model based on the internal shape of the metal material, and calculates the grain boundary average stress acting on the grain boundary model from the internal shape of the metal material. It is an analysis means for calculating the progress process. Reference numeral 14 denotes evaluation means for evaluating the bead shape estimated by the bead shape estimation means 12 and the analysis result of the analysis means 13.
As the internal inspection means 10, an inspection apparatus using the TOFD method shown in FIG. 14 can be adopted, but not limited to this, a phased array method or the like can also be adopted.
[0030]
FIG. 2A is a cross-sectional view showing a welded portion of a high-temperature pipe which is an example of the metal material 3. In the figure, reference numeral 21 is a high-temperature pipe made of a low alloy steel pipe or the like, and the low alloy steel plate 22 is cylindrical. Bending is performed, and end faces 22 a and 22 b along the longitudinal direction are joined by a welded portion 23. A HAZ part (weld heat affected zone) 24 to be detected is generated in the welded part 23. Reference numeral 25 denotes a replica of the surface of the metal material 3.
[0031]
The composition of the welded portion 23 is composed of, for example, 2.2% Cr-1% Mo-0.12% C-balance Fe, and impurities greatly related to the creep damage progress rate of the welded portion 23 are, for example, P ( Phosphorus), As (arsenic), Sn (tin), and Sb (antimony).
The creep damage degree (lifetime consumption rate) of the welded portion 23 has a substantially normal distribution as shown in FIG. 2 (b), and this is the concentration of the impurity Sb obtained by the impurity analysis of the welded portion 23. It almost matches the distribution.
[0032]
Next, the metal material damage evaluation method of the present embodiment will be described with reference to FIG. 3, taking the high-temperature pipe 21 shown in FIG. 2 as an example.
1. Ultrasonic flaw detection by the TOFD method and classification of flaws
(1) Ultrasonic flaw detection by TOFD method
The HAZ portion 24 generated inside the high-temperature pipe 21 is placed at a position where the transmission probe 1 and the reception probe 2 shown in FIG. 14 are sandwiched by the welded portion 23 along the circumferential direction of the surface of the high-temperature pipe 21. The ultrasonic probe 5 is transmitted in the high-temperature pipe 21 by the transmission probe 1 and the diffracted wave 14 from the HAZ unit 24 is detected by the reception probe 2. Detect the presence of damage. Here, when damage is detected, values of the position, height, and length of the damage are obtained. The damage position is identified by scanning both the transmission probe 1 and the reception probe 2 along the weld line.
[0033]
(2) Classification of detected flaws
This damage is classified into any one of three types from the values of the position, height, and length of the damage position.
Scratches detected by the TOFD method are classified into the following three types.
A wound (crowded wound)
It is estimated that several small damages are dense. For example, this is the case when two damages estimated to be at the same depth are adjacent and the distance between the damages is shorter than the length of the damage.
B wound (planar wound)
It is estimated that the damage spreads in a plane in the thickness direction.
C wound (volumetric wound)
Presumed to be three-dimensional damage such as slag entrainment.
[0034]
2. Judgment by MLAS method
(1) Collecting replicas
A replica 25 of the surface of the high temperature pipe 21 is collected by a method of transferring the surface of the high temperature pipe 21 to a plastic film.
For example, rough polishing and fine polishing are sequentially applied to the surface, the surface is finished to a mirror surface, the inspection target portion of the mirror surface is selectively removed by etching, and a plastic film for replica is pressed and etched on the etched portion. The surface irregularities are transferred to a plastic film.
[0035]
(2) Observation and determination of replica
The replica 25 is observed using an optical microscope, and the presence or absence of vacancies (creep voids) due to creep damage and the distribution state thereof are examined. Here, it is roughly determined whether or not the damage is caused by creep damage.
Next, the presence or absence of creep voids and their distribution state are precisely observed using a scanning electron microscope (SEM). For example, the number of creep voids generated is measured, the creep void surface density is calculated based on this measured value, and the relationship between the previously obtained life evaluation diagram (creep void surface density and creep damage degree (lifetime consumption rate) is shown. The creep damage degree is estimated from the graph), and whether or not the damage is caused by the creep damage is determined based on the creep damage degree.
[0036]
As described above, when creep damage is recognized in the replica 25, it is determined that the detected damage is a damage due to creep damage. When the damage due to creep is not recognized in the replica 25, the detected damage is creep. It can be determined that the scratch is not due to damage (scratch during manufacturing).
[0037]
3. Judgment by chemical component analysis
(1) Impurity analysis
The oxide film on the surface of the sampling region of the weld 23 is removed by grinding until a metallic luster is obtained, and the exposed metal portion is further ground to collect chips. Next, the contents of P, As, Sn, and Sb are analyzed using the chips.
The analysis method of each element is as follows.
P: Atomic absorption method (Japanese Industrial Standard; JIS G 1257)
As, Sn, Sb: Hydride generation ICP emission spectrometry
[0038]
(2) Creep property evaluation
Next, from these impurity analysis results, a creep embrittlement coefficient (CEF) is obtained based on the following formula (2).
CEF = P (wt.%) + 2.4 As (wt.%) + 3.6 Sn (wt.%)
+ 8.2Sb (wt.%) (2)
The creep damage degree (lifetime consumption rate) is estimated from the CEF value and the separately calculated piping stress calculation result, and it is determined whether or not the damage detected by the creep damage degree is due to creep damage.
[0039]
Now, based on the creep damage detected as described above and the damage detected by the TOFD method, the stress estimation means 11 estimates the internal average stress of the actual machine. Specifically, the stress estimation means 11 estimates that the part with a lot of damage is a part with a large stress, and further calculates the average stress in consideration of the use conditions, use time, internal pressure and plate thickness, pipe bending stress, and the like. presume.
Next, the bead shape estimation means 12 estimates the bead shape (the shape of the weld metal 23) based on the stress. For example, the part where the stress is large is a recess as indicated by reference numeral 18 in FIG. 2A, and it can be estimated that the stress is concentrated for this reason.
However, since the bead shape is not necessarily accurately determined, the variation in bead size and shape is probabilistically estimated, and the following microscopic damage progress simulation is performed in various ways.
[0040]
Next, the analysis means 13 performs a microscopic damage progress simulation based on the bead shape.
First, as shown in FIGS. 4 and 5, a grain boundary model in the HAZ portion 24 of the high-temperature pipe 21 made of the FEM element Mi is created. In this example, it is a one-dimensional model. In this analysis model, the set of grain boundary lengths is [L], the average is Lm, the standard deviation is LS, the set of fracture resistance values at the grain boundaries is [R], the average is Rm, and the standard deviation is RS. .
The stress (grain boundary average stress) σi acting on each FEM element Mi is determined. This is determined by analysis such as FEM analysis based on the bead shape. For example, since stress concentrates in the concave portion of the bead, the stress σi has a large value.
Subsequently, a crack generation driving force Fi and a crack propagation driving force Ki, which are parameters in Mi represented by the symbol i as an i-th dividing element, for example, are determined. Fi and Ki are values determined by temperature and stress σi as shown in FIG.
Further, in the simulation, data such as material characteristics and load characteristics of the high temperature pipe 21 are also used. For these data, in order to consider the influence of impurities, the material characteristics and load characteristics of the high-temperature pipe 21 are corrected based on the quantification result of the impurity content by chemical component analysis.
[0041]
A load model of the high temperature pipe 21 corresponding to this stress load is created. Each grain boundary in the FEM element Mi receives a crack generation driving force Fi due to the stress σi. When the simulation is started, cracks are generated with time. In FIG. 5, when each grain boundary receives a grain boundary fracture driving force Di, the fracture resistance Ri decreases with time, and when it becomes negative (Ri <0), the grain boundary breaks and a crack is generated. At the grain boundary adjacent to the crack, the grain boundary fracture driving force Di is equal to the sum of the crack generation driving force Fi and the product of the crack propagation driving force Ki and the crack length ai adjacent to the grain boundary. (Di = Fi + ai / Ki). That is, at the grain boundary adjacent to the crack, the damage progress rate dRi / dt = −Di = Fi + ai · Ki, and at the grain boundary not adjacent to the crack, the damage progress rate dRi / dt = −Di = Fi.
[0042]
In this way, damage (creep void) to each divided element after a certain period of time is obtained.
The simulation is performed until the actual machine usage time, and the analysis condition is confirmed by comparing the actual inspection with the analysis result. If the actual inspection and the analysis result differ greatly, recalculation is performed with different analysis conditions.
The above is performed for a predetermined time (for example, 60% of the life expected by the conventional method based on the number of creep voids), and the fracture determination process is performed.
[0043]
Whether or not the fracture has occurred is determined by whether or not the total sum Σa of all the cracks in the entire weld has reached a certain threshold value. This threshold is determined as follows.
(1) When the effective stress σeff exceeds values such as tensile limit and yield stress
The stress supported by the grain boundary where no creep void is formed is the effective stress. When the height of the HAZ portion 24 is h and the load acting on the HAZ portion is P, the effective stress σeff is σeff = P / (h−Σa). Σa when this effective stress exceeds a certain value (for example, yield stress of material, tensile limit, elastic limit) is determined as a threshold value.
(2) When the effective stress σeff exceeds the value corresponding to a given creep rupture life
Based on the known correspondence between the effective stress σeff and the creep rupture time shown in FIG. 7, for example, the creep rupture life is determined to be ruptured when Σa giving σeff which is the remaining 100 hours. When it becomes, it is judged as a fracture.
(3) When the total crack length exceeds a certain value
When there is only one crack, the remaining life can be obtained by crack propagation calculation using C *. Assuming a case where there is virtually one crack of length Σa, a crack propagation calculation by C * is performed, and Σa when the remaining lifetime is 100 hr is set as a threshold value. C * is a fracture mechanics parameter that depends on the stress and creep characteristics of the material.
In addition, it is conceivable that the fracture Σa is determined based on conditions for determining fracture regardless of Σa and methods other than the above three methods.
It should be noted that if any one of these conditions is satisfied, it may be determined as a fracture, and if a plurality of conditions are satisfied in combination, it may be determined as a fracture.
[0044]
When the fracture has not been reached, the simulation is continued. As described above, creep voids are generated in each grain boundary model element Mi. The portion where the void is generated cannot support the stress, and accordingly, the other grain boundary model element Mi ′ where the void is not generated supports the stress, so that the grain boundary average stress within the element becomes large. For this reason, a change in stress distribution caused by void generation is added to the simulation conditions.
Specifically, as shown in FIG. 9, the relationship between the void number density and “Young's modulus of damaged material / Young's modulus of undamaged material” is used. In the damaged material, the rigidity decreases as the void number density increases. Using this rigidity, the stress is obtained by FEM analysis or the like. Based on the new stress σi, the crack generation driving force Fi and the crack propagation driving force Ki are obtained again, and the simulation is performed again.
This is followed by 60%, 70%, 80%, etc. of the assumed life, and the simulation is performed while successively updating the stress σi until finally breaking.
[0045]
In the case of rupture, the evaluation means 14 aggregates many simulation results of the rupture time with respect to the probability (probability) of variously estimated bead sizes and shapes, and the remaining life as shown in FIG. Calculate probabilistic life assessment based on cumulative failure probability.
[0046]
Thus, in this embodiment, since the simulation is performed by sequentially recalculating the stress acting on the grain boundary model, a more accurate remaining life can be calculated.
It should be noted that the microscopic damage progress simulation shown in the present embodiment is an example to which the present invention is applied, and it goes without saying that the present invention can be applied to other analyses.
[0047]
Further, screen display may be performed as follows.
For example, the grain boundary model shown in FIGS. 4 and 5 is set to about 30 rows in the thickness direction. The grain boundary model at this time is set at random based on a predetermined normal distribution. Here, pseudo two-dimensional data is obtained by two-dimensionally arranging a one-dimensional grain boundary model that is easy to analyze (to easily and accurately grasp the phenomenon that actually occurs by performing such processing) be able to). This is shown in FIG. In the figure, reference numeral 20 represents a grain boundary, and a thick line indicated by reference numeral 21 represents a void (damage).
In this way, by displaying the two-dimensional grain boundary model 20 constructed in a pseudo manner and the void 21 generated in the grain boundary model, the analysis result can be expressed in a state that is easy to understand visually. .
[0048]
Furthermore, it can also be displayed as shown in FIG.
In FIG. 12, reference numeral 25 indicates the state of occurrence of voids for the entire internal shape of the metal material. In the internal shape 25, a damage state 25a in which the color density and color are changed in accordance with the void density is displayed in an overlapping manner. For example, a crack of 3 mm or more estimated from the analysis and an area of damage of 50% or more are displayed in red, for example, so that they can be easily understood. Reference numeral 26 is a partially enlarged view and is the same grain boundary model as FIG. When the cursor is moved to an arbitrary position of the internal shape of the reference numeral 25, the enlarged state of the reference numeral 26 can be seen.
Reference numeral 27 denotes an estimated stress, and reference numeral 28 denotes a degree of damage. These can be displayed on one screen, and the analysis result can be expressed in a state that is easy to visually understand.
[0049]
Furthermore, it may be displayed as shown in FIG.
In FIG. 13, reference numeral 30 indicates a void generation state for the entire internal shape, and is the same as reference numeral 25 in FIG. 12.
Reference numeral 31 is a photograph of a replica collected by the MLAS method, reference numeral 32 is an inspection result by the TOFD method, and reference numeral 33 is an inspection result by the phased array method.
The analysis result 30 and the nondestructive inspection results 31 to 33 are displayed on the screen. The analysis result 30, the inspection result 32 by the TOFD method, and the inspection result 33 by the phased array method may be displayed separately as shown in FIG.
By displaying in this way, the validity of the analysis result can be determined, and the degree of damage can be determined by combining the analysis result and the actual inspection result.
11 to 13 show the pseudo-configured two-dimensional grain boundary model, the same analysis and display may be performed for one and three dimensions.
In the above description, the image is displayed on the screen. However, it may be printed out.
[0050]
【The invention's effect】
As described above, the following effects can be obtained in the present invention.
According to the first aspect of the present invention, a more accurate fracture progress process can be calculated by using the stress distribution and the shape inside the metal material. Therefore, the remaining life can be predicted more accurately.
According to the second aspect of the present invention, it is possible to probabilistically evaluate the remaining life of the metal material by variously estimating the inside of the metal material and comparing the probability with the remaining life of the analysis result. it can.
According to the third and fourth aspects of the invention, since a simulation taking into account the stress that changes due to damage is possible, an accurate remaining life can be predicted.
According to the fifth aspect of the present invention, it is possible to continue the calculation until the breakage by sequentially recalculating the stress acting on the grain boundary model.
According to the invention described in claim 6, by displaying the grain boundary model and the void generated in the grain boundary model together, the analysis result can be expressed in a state that is easy to understand visually.
According to the seventh aspect of the present invention, by displaying the internal structure of the metal material and the damage state together, the analysis result can be expressed in a state that is easy to understand visually.
According to the invention described in claim 8, the validity of the analysis result can be determined by comparing the analysis result with the actual inspection result, and the analysis result and the actual inspection result are combined. The degree of damage can be determined.
According to the ninth aspect of the invention, a more accurate fracture progress process can be calculated by using the stress distribution and the shape inside the metal material. Therefore, the remaining life can be predicted more accurately.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a damage evaluation apparatus for a metal material shown as an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a weld portion of a high-temperature pipe to which the damage evaluation apparatus is applied.
FIG. 3 is a flowchart showing a part of a damage evaluation method realized by the damage evaluation apparatus.
FIG. 4 is a diagram in which a HAZ portion is represented by a grain boundary model in a pipe thickness direction.
FIG. 5 is a schematic diagram showing a grain boundary fracture resistance distribution model by the damage evaluation apparatus.
6A is a diagram showing a relationship between stress and a crack generation driving force, and FIG. 6B is a diagram showing a relationship between stress and a crack propagation driving force K. FIG.
FIG. 7 is a diagram showing the relationship between creep rupture time and effective stress.
FIG. 8 is a diagram showing the relationship between remaining life and effective stress.
FIG. 9 is a diagram showing a void number density and a decrease in Young's modulus.
FIG. 10 is a diagram showing a remaining life and a cumulative failure probability.
FIG. 11 shows a state in which a pseudo two-dimensional grain boundary model and a damaged part are displayed in an overlapping manner.
FIG. 12 is a diagram showing a state in which the state of occurrence of voids is displayed for the entire internal shape together with the estimated stress and the degree of damage.
FIG. 13 is a diagram showing a state in which an analysis result and a nondestructive inspection are both displayed.
FIG. 14 is an explanatory diagram for explaining the measurement principle of the TOFD method.
FIG. 15 is a flowchart showing a microscopic damage progress simulation.
FIG. 16 is a schematic diagram showing a grain boundary fracture resistance distribution model of a microscopic damage progress simulation.
[Explanation of symbols]
10 Internal inspection means
11 Stress estimation means
12 Bead shape estimation means (internal shape estimation means)
13 Analysis means
14 Evaluation means

Claims (9)

A method for evaluating scratches on a metal material,
The internal damage state of the metal material is inspected to determine the damage distribution, the internal shape of the metal material is estimated based on the damage distribution, the interior of the metal material is represented by a grain boundary model, and each of these grain boundary models A damage evaluation method for a metal material, wherein the fracture progress process of each grain boundary model is calculated by applying a stress calculated based on the internal shape of the metal material. In the metal material damage evaluation method according to claim 1,
The estimated internal shape of the metal material is variously changed, and the estimated life probability of the metal material is calculated by corresponding the estimated probability of the shape and the remaining life obtained by calculating the fracture progress of each grain boundary model. A method for evaluating damage of a metal material, comprising: A method for evaluating scratches on a metal material,
Create a grain boundary model of the internal shape of the metal material, set the initial stress acting on each grain boundary model, calculate the fracture progress process after a predetermined time, and further, the grain boundary obtained as a result The metal material damage characterized by recalculating the stress acting on each grain boundary model based on the model damage, and further calculating the progress of fracture after a predetermined time based on the stress after the recalculation Evaluation methods. The damage evaluation method for a metal material according to claim 1 or 2,
Create a grain boundary model of the internal shape of the metal material, set the initial stress acting on each grain boundary model, calculate the fracture progress process after a predetermined time, and further, the grain boundary obtained as a result The metal material damage characterized by recalculating the stress acting on each grain boundary model based on the model damage, and further calculating the progress of fracture after a predetermined time based on the stress after the recalculation Evaluation methods. In the metal material damage evaluation method according to claim 3 or 4,
A method for evaluating damage to a metal material, wherein the calculation of the progress of the fracture is repeated until the metal material is broken. In the metal material damage evaluation method according to claim 1,
A damage evaluation method for a metal material, characterized in that a damaged part of a grain boundary model obtained by calculation of a fracture progress process of the grain boundary model is displayed on a screen or printed while being superimposed on the grain boundary model. In the metal material damage evaluation method according to claim 1,
The internal shape of the metal material is displayed or printed on the screen, and the degree of damage of the grain boundary obtained by calculation of the fracture progress process of the grain boundary model is superimposed on the internal shape of the metal material. To evaluate damage to metallic materials. In the metal material damage evaluation method according to claim 7,
A method for evaluating damage of a metal material, wherein the result of actually inspecting the damaged state of the metal material is simultaneously displayed on a screen or printed. An apparatus for evaluating scratches on metal materials,
Internal shape estimation means for estimating the internal shape of the metal material based on the distribution of internal damage of the metal material, and the inside of the metal material is represented by a grain boundary model, and the interior of the metal material with respect to each grain boundary model An apparatus for evaluating damage of a metal material, comprising: an analysis unit that calculates a fracture progression process of each grain boundary model by applying a stress calculated based on a shape.

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