JP4373881B2 - Multiple crack growth analysis method and apparatus - Google Patents

Description

  The present invention relates to a multiple crack growth analysis method and apparatus for analyzing the crack propagation of a structure.

  Since crack evaluation is an important index in determining the strength of a structure, the progress of cracks has been analyzed by various analysis methods and analyzers. None of these conventional analysis methods and apparatuses have performed the analysis of the growth of three or more cracks, and in general, analysis is performed only for the case of two cracks.

  In the case of multiple crack growth analysis methods and devices for two cracks, first, the crack growth analysis evaluation is performed separately for each crack, and the relationship between time and crack size is arranged side by side. If it is determined that any of the adjacent cracks have joined together, replace with one large crack at that point and continue the growth analysis. To do.

The following are examples of conventional crack analysis methods (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-204789

  However, the conventional multiple crack growth analysis means as described above performs the individual crack growth analysis one after another, and the results are arranged side by side so that the intervals between adjacent cracks are merged. It is determined whether or not the value is below the reference value for determination. Therefore, the calculation after the time point determined to be merged is wasted. Therefore, since these useless times are accumulated, there is a problem that it takes a lot of time to analyze the entire structure.

  In addition, in the conventional crack analysis method, there was no reference to a method for handling cracks after coalescence after judging the occurrence of multiple cracks in the structure and the progress of coalescence.

  The present invention has been made in order to solve the above-described problems, and in a crack analysis of a structure, an analysis can be performed for progress due to generation of multiple cracks and repetition of coalescence, and the progress can be made in a short time. An object of the present invention is to provide a method and an apparatus for analyzing the propagation of a plurality of cracks, which can provide an analysis result.

In order to solve the above-described problem, the method for analyzing the growth of a plurality of cracks according to the present invention is a member of the structure input to the data input unit when a plurality of crack-like defects are detected in the structure. The stress intensity factor calculation unit calculates the stress intensity factor for each crack from the size, stress and crack size, and the crack growth characteristic data of the material constituting the structure input to the data input unit and the Based on the stress intensity factor, the crack growth amount calculation unit calculates the size of each crack after a minute time increment, and the coalescence judgment unit compares the interval between adjacent cracks with a predetermined reference value. If the interval between adjacent cracks is equal to or less than the reference value, the two corresponding cracks are considered to be combined and replaced by a single crack at the crack replacement part, and the crack after the next minute time a multi-how to calculate the dimensions, said-out裂同workers When the interval is larger than the reference value and falls below the reference value after a minute time increment, the amount less than the reference value is divided by the sum of the growth rates of the cracks between the cracks. Find the time width of the minute, subtract the time width of this excess from the time after the minute time increment to determine the time when the interval between the cracks just reached the reference value and the coalescence time, By subtracting the excess amount of the crack growth increment, which is obtained by multiplying the time width of the excess by the growth rate of each crack, from the size of the crack after the minute time increment, the crack time at the coalescence time is subtracted. It is a method characterized by determining each dimension and further replacing the cracks with one crack .

Further, in order to solve the above-described problem, the multiple crack growth analysis device of the present invention is configured such that when a plurality of crack-like defects are detected in the structure, the member dimensions and stress and crack dimensions of the structure are detected. And a stress intensity factor calculator for calculating a stress intensity factor for each crack from the member dimensions and stress and crack dimensions of the structure input to the data input part, and Based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each crack size after a minute time increment is calculated, and the interval between adjacent cracks Ki replaced when the coalescence judging unit for comparing the predetermined reference value, it is assumed that the interval of Ki fit adjacent cleft coalesced two crack corresponding to the case is less than the reference value into one crack and cleft replacement unit, you after the next minute time A development apparatus for analyzing multiple Crack a Ruki crack propagation amount calculation unit to calculate the dimensions of Ruki裂, spacing of the-out裂同mechanic greater than the reference value, after a small time increment When the amount is less than the reference value, the amount of time less than the reference value is divided by the sum of the growth rates of the cracks between the cracks to obtain an excess time width. Subtract from the time after the minute time increment to determine the time when the interval between the cracks has just reached the reference value and set it as the coalescence time, and the growth rate of each of the cracks in the excess time width Is subtracted from the crack size after the minute time increment to obtain the respective dimensions of the cracks at the coalescence time. those characterized by be replaced with crack A.

  According to the multiple crack growth analysis method and apparatus of the present invention, the progress of multiple cracks in a structure and the progress due to repeated coalescence are analyzed in a short time, so that the calculation result of the strength of the structure can be obtained quickly. It becomes possible.

  Hereinafter, embodiments of a method and an apparatus for analyzing crack propagation according to the present invention will be described with reference to the drawings.

  With reference to FIG. 1, a multiple crack growth analysis apparatus according to the first embodiment will be described. The multiple crack growth analysis apparatus 10 of the first embodiment includes a data input unit 1 and a multiple crack growth calculation unit 2. The data input unit 1 includes, for example, member data such as dimensions used in analysis determination, Crack data such as position and size, stress data, and material data such as crack propagation speed are input. The multiple crack growth calculation unit 2 includes a stress intensity factor calculation unit 5, a crack growth amount calculation unit 6, a coalescence determination unit 7, and a crack replacement unit 8.

  FIG. 2 is a model diagram of a crack analyzed in this example. FIG. 2 illustrates a crack 21, a crack 22, a crack 23, a crack 24, and a crack 25 on the surface of the structure 20, and the longitudinal direction of FIG. .

  Here, the subscript a represents the crack depth at the deepest crack point. The subscript c represents a surface point, and the symbol 2 c represents the length of the crack on the surface of the structure 20 in the X-axis direction. The subscript i indicates the crack number. When the crack growth mechanism is fatigue, the stress intensity factors Ka and Kc are read as stress intensity factor ranges ΔKa and ΔKc, respectively, and the minute time Δt is interpreted as the minute repetition number ΔN for analysis.

The data input unit 1 includes dimensions of members constituting the structural material, stresses, semi-elliptical surface crack positions x _i and initial dimensions (crack depth a _i , crack length 2c _i ), and material cracks. Crack growth characteristic data is input. In the stress intensity factor calculation unit 5, the stress intensity factors Ka and Kc of individual cracks are calculated from the stress, the member size, and the crack size. On the other hand, in the crack growth amount calculation unit 6, the crack growth amounts Δa _i and Δ2c _i in a minute time Δt are all cracks from the stress intensity factor and crack growth characteristic data calculated by the stress intensity factor calculation unit 5. Are simultaneously calculated and added to the original crack size. The coalescence determination unit 7 checks all adjacent cracks to see if there is anything whose distance between the cracks is equal to or less than a reference value. In the crack replacement part 8, when the coalescence of cracks is detected, those cracks are replaced with one crack. Here, the minute time is a time width arbitrarily set as a time width for analysis in the method and apparatus for analyzing the propagation of multiple cracks according to the present invention.

  FIG. 3 illustrates the mechanism of coalescence determination in the multiple crack propagation analysis method of the present embodiment.

  In the coalescence determination unit 7, the distance between all two adjacent cracks (crack 31 and crack 32) is compared with the reference value s by the method shown in FIG. When it is determined that the distance d between the cracks is less than the reference value s at time t + Δt (FIG. 3B), which is equal to or less than the reference value s at time t (FIG. 3B). 8, one of these two cracks having the same depth as that of the deeper crack 32, and one large having the same length as that of the two cracks 31 and connecting both ends of the crack 32. Replace with the crack 33 (FIG. 3C).

  In FIG. 3B, a dotted line represents a crack at time t, and in FIG. 3C, a dotted line represents a crack at time t + Δt.

  In this embodiment configured as described above, the amount of progress of a plurality of cracks at every minute time is calculated simultaneously, and the progress analysis is performed while comparing the interval between adjacent cracks at the same time with the reference value at each step. To implement. In other words, it is an algorithm that performs crack growth analysis while constantly monitoring the coalescence determination.

  Therefore, according to the multiple crack growth analysis apparatus 10 of the present embodiment, a plurality of crack growth analyzes are performed at a time while constantly monitoring the coalescence determination of the cracks. It is possible to perform crack growth analysis.

  Next, a second embodiment of the method and apparatus for analyzing crack propagation according to the present invention will be described with reference to FIGS.

At time t, as shown in FIG. 4 (A), the distance d between two adjacent cracks 41 and 42 is larger than the reference value s for merging determination, so that they are treated as independent cracks. However, after a minute time increment Δt, it is assumed that the interval between both cracks is less than the reference value s by s _ov as shown in FIG. In addition, the dotted line in FIG.4 (B) has shown the dimension of both the cracks at the time t. In this case, the following formula (1)

By going back the time by Δt ′ obtained by the above, it is possible to obtain the time when the interval between the two cracks has just become the reference value s (FIG. 4C). This time is defined as the coalescence time. Here, the expressions (1) dc / dt _i and dc / dt _{i + 1} are the respective propagation speeds on the surface of the crack 41 (crack number i) and the crack 42 (crack number i + 1).

  Thus, by defining the excess time width Δt ′ from the coalescence time, the dimensions of the crack 41 and the crack 42 at the coalescence time t + Δt−Δt ′ are determined from the respective crack dimensions at the time t + Δt. It is possible to determine by subtracting dc / dt × Δt ′ for the crack and da / dt × Δt ′ for the crack depth. The two cracks 41 and the cracks 42 subject to the merge determination are replaced with one crack at the merge time. When the reference value s for determining the coalescence is 0, the two adjacent cracks 41 and 42 are just in contact at time t + Δt−Δt ′.

  FIG. 5 shows an algorithm of a method for analyzing the growth of a plurality of cracks according to the second embodiment. As shown in FIG. 5, in the multiple crack growth analysis method of the present embodiment, the crack size at time t is defined in step 51, and the crack at time t + Δt after a minute time is defined in step 52. Calculate the dimensions. Next, in step 53, the interval between adjacent cracks is compared with a reference value. If it is determined in step 54 that the interval between cracks is equal to or less than the reference value, the excess time width Δt ′ is determined in step 55. Calculate Next, at step 56, the crack size at the coalescence time t + Δt−Δt ′ is calculated. Next, the end condition is determined in step 57. If the end condition is not reached, the crack size is updated and the next minute time increment is started. On the other hand, if it is determined in step 54 that the interval between the cracks is larger than the reference value, the end condition is directly determined in step 57.

When the crack size is updated in step 58 and the crack interval is equal to or smaller than the reference value in step 54, _ai in step 51 is set to a _i ′, and 2c _{i is set} to 2c _i ′. Update. On the other hand, if it is determined that the crack interval is larger than the reference value, a _i in step 51 is updated to a _i ″ and 2c _i to 2c _i ″.

  Next, a third embodiment of the method and apparatus for analyzing crack propagation according to the present invention will be described with reference to FIGS.

In the multiple crack growth analysis method of the third embodiment, as in the second embodiment, at time t (FIG. 4A), the interval d between the two adjacent cracks 41 and the crack 42 is determined as a unity determination. Since it is larger than the reference value s, each crack is treated as an independent crack. However, it is assumed that the interval d between both cracks is less than the reference value s by s _ov after a minute time increment Δt (FIG. 4B). Δt ′ is defined by equation (1).

  Next, the corrected minute time increment Δt ″ is defined as Δt ″ = Δt−Δt ′. By adding the corrected minute time increment Δt ″ to the time t before the minute time increment, the time when the distance d between the two cracks 41 and the crack 42 is exactly the reference value s can be obtained.

  FIG. 6 shows an algorithm of a method for analyzing the growth of a plurality of cracks according to the third embodiment. By defining the corrected minute time increment Δt ″ in this way, as shown in FIG. 6, the dimensions of the cracks at the coalescence time t + Δt ″ are changed to the crack size at the time t in step 61. It can be determined by adding dc / dt × Δt ″ for, and da / dt × Δt ″ for crack depth. In FIG. 6, the same components as those in FIG.

  The two cracks 41 and the cracks 42 subjected to the merge determination are replaced with one crack at the merge determination time. Further, in the present embodiment, when the reference value s for merging determination is 0, the two adjacent cracks 41 and 42 are just in contact at time t + Δt ″.

  Next, a fourth embodiment of the multiple crack propagation analysis method and apparatus according to the present invention will be described with reference to FIG.

  According to the configuration of this embodiment, the crack growth characteristic data of the material is recorded in the storage medium as a database 71 separate from the data input unit. According to the multiple crack growth analysis apparatus 70 of this embodiment configured as described above, the analysis is performed by inputting the material name in the data input unit 1 or selecting the material name from the material name list. It is possible to easily analyze the growth of multiple cracks without investigating the crack propagation characteristics of the material each time and entering numerical values.

  Next, a fifth embodiment of the method and apparatus for analyzing the propagation of multiple cracks according to the present invention will be described with reference to FIG.

  The multiple crack growth analysis apparatus 80 of this embodiment has a data storage unit 81 that stores input data and calculation results in a recording medium. With such a configuration, when referring to the calculation result at a later date, it is possible to draw out the calculation result at any time without performing the calculation by inputting the same data again. Note that only input data can be saved when the calculation is interrupted.

  Next, Embodiment 6 of the multiple crack propagation analysis method and apparatus according to the present invention will be described with reference to FIG.

  When analyzing the same member shape, stress distribution, and crack shape in the analysis of a structure, there may be a plurality of applicable stress intensity factor calculation formulas. For example, for a semi-elliptical surface crack in a flat plate subjected to simple tensile stress and bending stress, there are Newman & Raju's formula, Shiratori's formula, API standard formula, and the like. Therefore, the multiple crack propagation analysis method 90 of this embodiment stores these applicable stress intensity factor calculation formulas in the database 71 which is a storage medium, and the data input unit 1 calculates the stress intensity factor calculation formulas. In this configuration, the evaluator can select an optimal calculation formula by inputting only the identification name of the name or selecting from the list. According to the multiple crack growth analysis apparatus having such a configuration, it is possible to select a stress intensity factor calculation formula according to the analysis system and purpose.

1 is a configuration diagram of a multiple crack growth analysis apparatus according to the present invention. FIG. The schematic diagram which illustrates the example of a model of multiple cracks. The schematic diagram which shows the unification determination and replacement | exchange of multiple cracks. The schematic diagram which shows determination of coalescence time of multiple cracks. The figure which shows the algorithm of the several crack growth analysis method of Example 2. FIG. The figure which shows the algorithm of the several crack growth analysis method of Example 3. FIG. FIG. 6 is a configuration diagram of a multiple crack growth analysis apparatus according to a fourth embodiment. FIG. 6 is a configuration diagram of a multiple crack growth analysis apparatus according to a fifth embodiment. The block diagram of the multiple crack growth analysis means of Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Data input part 2 Multiple crack growth calculation part 5 Stress intensity factor calculation part 6 Crack growth amount calculation part 7 Coalition determination part 8 Crack replacement part 10 Multiple crack growth analysis apparatus 21, 22, 23, 24, 25 Crack 31, 32, 33 Crack 41, 42 Crack 51, 52, 53, 54, 55, 56, 57, 58 Step 61 Step 70 Multiple crack propagation analysis device 71 Database 80 Multiple crack propagation analysis device 81 Data storage unit 90 Multiple crack growth analyzer

Claims (6)

When multiple crack-like defects are detected in the structure, the stress intensity factor calculation unit calculates the stress for each crack from the structure member dimensions and stress and crack size input to the data input unit. A coefficient is calculated, and based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each of the crack growth amount calculation unit after a minute time increment The crack size is calculated, and the coalescence judgment unit compares the interval between adjacent cracks with a predetermined reference value, and the two cracks corresponding to the case where the interval between adjacent cracks is equal to or less than the reference value. replaced by a crack in crack replacement unit has assumed coalesced a crack, a progress analysis method-out multiple dimensions you calculate crack after the next minute time cracks,
When the interval between the cracks is greater than the reference value and falls below the reference value after a minute time increment, the amount below the reference value is the sum of the growth rates of the cracks between the cracks. The time width of the excess is calculated by dividing the time width by subtracting the time width of the excess from the time after the minute time increment to obtain the time when the interval between the cracks has just reached the reference value. And subtracting the excess amount of the crack growth increment obtained by multiplying the time width of the excess by the respective growth rate of the crack from the size of the crack after the minute time increment, the-out determine the respective dimensions of the crack progress analysis in more than one way cracks further characterized by replacing the-out裂同mechanic to one of a crack. When multiple crack-like defects are detected in the structure, the stress intensity factor calculation unit calculates the stress for each crack from the structure member dimensions and stress and crack size input to the data input unit. A coefficient is calculated, and based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each of the crack growth amount calculation unit after a minute time increment The crack size is calculated, and the coalescence judgment unit compares the interval between adjacent cracks with a predetermined reference value, and the two cracks corresponding to the case where the interval between adjacent cracks is equal to or less than the reference value. replaced by a crack in crack replacement unit has assumed coalesced a crack, a progress analysis method-out multiple dimensions you calculate crack after the next minute time cracks,
When the interval between the cracks is larger than the reference value and falls below the reference value after a minute time increment, the amount below the reference value is reduced by the amount of growth of each crack between the cracks. Divide by the sum to obtain the excess time width, subtract the excess time width from the minute time increment to obtain the corrected minute time increment, and add this corrected minute time increment to the time before the minute time increment. As a result, the time when the interval between the cracks has just reached the reference value is obtained and set as the coalescence time, and the dimension of the crack at the time before the minute time increment is set to the corrected minute time increment. Adding crack growth increments obtained by multiplying the respective growth rates of the cracks to determine the respective dimensions of the cracks at the coalescence time, and further replacing the cracks with one crack. -out multiple Way of progress analysis. When multiple crack-like defects are detected in the structure, the stress intensity factor calculation unit calculates the stress for each crack from the structure member dimensions and stress and crack size input to the data input unit. A coefficient is calculated, and based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each of the crack growth amount calculation unit after a minute time increment The crack size is calculated, and the coalescence judgment unit compares the interval between adjacent cracks with a predetermined reference value, and the two cracks corresponding to the case where the interval between adjacent cracks is equal to or less than the reference value. A crack growth analysis method that considers cracks to be combined and replaces them with a single crack at the crack replacement part, and calculates the crack dimensions after the next minute time,
Assuming a multiple crack model larger than the defects actually detected in the structure, each crack model after a minute time increment is determined based on the crack growth characteristic data of the material constituting the structure. The size is obtained by calculation at the same time, and when the distance between the crack models is equal to or less than the reference value, the crack models are considered to be combined with each other and replaced with one crack model, while the crack models A method for analyzing the propagation of a plurality of cracks, characterized in that if the interval does not reach the reference value, the dimensions of the crack model after the next minute time are calculated simultaneously . When a plurality of crack-like defects are detected in the structure, a data input section for inputting the member dimensions, stress and crack dimensions of the structure;
And the stress intensity factor calculation unit for calculating stress intensity factors for individual crack from the member dimensions and stress when裂寸method of the structure that has been input to the data input unit,
Based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each crack size after a minute time increment is calculated, and A coalescence determination unit that compares the interval with a predetermined reference value ;
A crack replacement portion that considers that two corresponding cracks are combined when the interval between adjacent cracks is equal to or less than the reference value, and replaces the crack with one crack ;
A development apparatus for analyzing multiple Crack a Ruki crack propagation amount calculation unit to calculate the dimensions of the crack after the next minute time,
When the interval between the cracks is greater than the reference value and falls below the reference value after a minute time increment, the amount below the reference value is the sum of the growth rates of the cracks between the cracks. The time width of the excess is calculated by dividing the time width by subtracting the time width of the excess from the time after the minute time increment to obtain the time when the interval between the cracks has just reached the reference value. And subtracting the excess amount of the crack growth increment obtained by multiplying the time width of the excess by the respective growth rate of the crack from the size of the crack after the minute time increment, the crack determine the respective dimensions, further wherein-out裂同mechanic evolution analyzer of multiple cracks and replaces the one crack of. When a plurality of crack-like defects are detected in the structure, a data input section for inputting the member dimensions, stress and crack dimensions of the structure;
And the stress intensity factor calculation unit for calculating stress intensity factors for individual crack from the member dimensions and stress when裂寸method of the structure that has been input to the data input unit,
Based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each crack size after a minute time increment is calculated, and A coalescence determination unit that compares the interval with a predetermined reference value ;
A crack replacement portion that considers that two corresponding cracks are combined when the interval between adjacent cracks is equal to or less than the reference value, and replaces the crack with one crack ;
A development apparatus for analyzing multiple Crack a Ruki crack propagation amount calculation unit to calculate the dimensions of the crack after the next minute time,
When the interval between the cracks is larger than the reference value and falls below the reference value after a minute time increment, the amount below the reference value is reduced by the amount of growth of each crack between the cracks. Divide by the sum to obtain the excess time width, subtract the excess time width from the minute time increment to obtain the corrected minute time increment, and add this corrected minute time increment to the time before the minute time increment. As a result, the time when the interval between the cracks has just reached the reference value is obtained and set as the coalescence time, and the dimension of the crack at the time before the minute time increment is set to the corrected minute time increment. Adding crack growth increments obtained by multiplying the respective growth rates of the cracks to determine the respective dimensions of the cracks at the coalescence time, and further replacing the cracks with one crack. -out multiple Progress analysis device. When a plurality of crack-like defects are detected in the structure, a data input section for inputting the member dimensions, stress and crack dimensions of the structure;
A stress intensity factor calculator that calculates a stress intensity factor for each crack from the member dimensions and stress and crack dimensions of the structure input to the data input part;
Based on the crack growth characteristic data of the material constituting the structure input to the data input unit and the stress intensity factor, each crack size after a minute time increment is calculated, and A coalescence determination unit that compares the interval with a predetermined reference value;
A crack replacement portion that considers that two corresponding cracks are combined when the interval between adjacent cracks is equal to or less than the reference value, and replaces the crack with one crack;
A crack growth analysis device comprising a crack growth amount calculation unit for calculating a crack size after the next minute time,
Assuming a multiple crack model larger than the defects actually detected in the structure, each crack model after a minute time increment is determined based on the crack growth characteristic data of the material constituting the structure. The size is obtained by calculation at the same time, and when the distance between the crack models is equal to or less than the reference value, the crack models are considered to be combined with each other and replaced with one crack model, while the crack models A multi-crack growth analysis apparatus that calculates the size of a crack model after the next minute time at the same time if the interval does not reach the reference value .

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