JP2016156630A - Fatigue limit evaluation method and fatigue limit evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate fatigue limit of an evaluation target member having a non-periodic surface roughness profile.SOLUTION: A fatigue limit evaluation device 10 comprises: a peak coordinate value extraction part 12 for extracting peak coordinate values of mountains and valleys contained in measurement values of a surface profile of an evaluation target member; an evaluation profile data creation part 13 for, with respect to the extracted peak coordinate values, when a height difference between the adjacent mountain and valley is smaller than a predetermined threshold, performing filtering processing for removing one or both of the peak coordinate values, for creating evaluation profile data in which, the height difference between the adjacent mountain and valley becomes equal to or more than the predetermined threshold; a surface roughness index value calculation part 14 for, by using depth of each valley, and distance between adjacent mountains, or distance between adjacent valleys obtained from the evaluation profile, for calculating surface roughness index values; and a fatigue limit estimation value calculation part 15 for calculating a fatigue limit estimation value of the evaluation target member by using a maximum value of the calculated surface roughness index values.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fatigue limit evaluation method and a fatigue limit evaluation apparatus for members constituting a device.

  Many of the causes of equipment damage are destruction of members constituting the equipment due to metal fatigue. Metal fatigue is a phenomenon in which a minute crack (crack) generated on the surface of a member of a device develops inside the member due to repeated application of a load, and eventually breaks through the member. . In such metal fatigue, it is known that a fatigue limit, which is a limit stress at which a member does not break, is affected by the surface state of the member.

  By the way, as the surface state of the actual device member, it is necessary to consider not only the surface state of the member at the time of design and production but also the effects of unexpected scratches and corrosion attached during the service period. That is, the surface state of the member of an apparatus changes every moment during the service period of an apparatus. Therefore, it is important to establish a technology that quantitatively measures the surface condition of a member and evaluates the fatigue limit based on the measurement result in order to determine whether or not the equipment can be continuously operated when the surface condition of the member changes over time. Become.

  Non-Patent Document 1 discloses a method for quantitatively evaluating the fatigue limit of a member having a periodic minute notch profile (periodic surface roughness) such as a lathe machining trace. That is, in Non-Patent Document 1, a periodic minute notch formed on the surface of a member is regarded as a crack on the surface of the member, and √area which is a governing factor of the fatigue limit is determined from the stress intensity factor of the periodic crack. A method for obtaining and calculating the fatigue limit of the member is shown.

Murakami Takayoshi, Takahashi Koji, Yamashita Yasuo, "Quantitative evaluation of the effect of surface roughness on fatigue strength (effect of roughness depth and pitch)", Japan Society of Mechanical Engineers, A, August 1997, No. 63, 612, p. 1612-1619

  However, even though the fatigue limit evaluation method disclosed in Non-Patent Document 1 is effective for evaluating the fatigue limit of a member having a periodic surface roughness profile, the non-periodic surface roughness profile is used. It is not always effective for the evaluation of the fatigue limit of a member.

  Therefore, an object of the present invention is to provide a fatigue limit evaluation method and a fatigue limit evaluation apparatus that can be applied to a member having an aperiodic surface roughness profile.

In the fatigue limit evaluation method according to the present invention, a computer connected to a surface roughness measuring device for measuring a surface profile of an evaluation target member obtains a measured value of the surface profile of the evaluation target member from the surface roughness measurement device. The step of acquiring, the step of extracting the peak coordinate value of the mountain and the peak coordinate value of the valley included in the measurement value of the acquired surface profile, and the data comprising the peak coordinate value of the extracted mountain and the peak coordinate value of the valley When the height difference between adjacent peaks and valleys is smaller than a predetermined threshold, a filtering process is performed to remove the peak coordinate values of one or both peaks or valleys, and the heights of adjacent peaks and valleys Generating evaluation profile data such that the difference is greater than or equal to the predetermined threshold; and including the evaluation profile in the evaluation profile. Calculating the surface roughness index value of the evaluation profile using the obtained value, and determining the depth of each valley and the distance between the adjacent mountain and mountain or valley and valley Calculating a fatigue limit estimated value of the evaluation target member using a relatively large value among the surface roughness index values.
And more preferably, the surface roughness index value used in the step of calculating the fatigue limit estimated value is the surface obtained for each valley included in the evaluation profile in the step of calculating the surface roughness index value. It is the maximum value of the roughness index value.

  According to the present invention, a fatigue limit evaluation method and a fatigue limit evaluation apparatus applicable to a member having an aperiodic surface roughness profile are provided.

The figure which showed the example of the function structure of the fatigue limit evaluation apparatus which concerns on embodiment of this invention. (A) is the figure which showed typically the example of the surface profile of the evaluation object member, (b) The figure which showed the example of the data structure of the surface profile measurement value. (A) is the figure which showed typically the example of the peak point in the surface profile of an evaluation object member, (b) The figure which showed the example of the data structure of a peak coordinate value. (A) is the figure which showed the example of the profile for evaluation typically, (b) is the figure which showed the example of the data structure of the profile data for evaluation. The figure which showed the example of the surface profile for demonstrating the parameters a and 2b which evaluate the magnitude | size of the crack (valley) required in order to calculate the surface roughness index value √areaA concerning this embodiment. The figure which showed the example of the profile for evaluation produced | generated from the surface profile actually measured with the evaluation object member, and the surface profile. It is a figure showing the example of the relationship between the fatigue limit estimated value of various evaluation object members, and the fatigue limit measured value, (a) is fatigue when the constant C = 0.1 of the threshold value H (= CR) The figure showing the relationship between a limit estimated value and a fatigue limit measured value, (b) is the figure showing the relationship between the fatigue limit estimated value and the fatigue limit measured value when the constant C = 0.3. The figure which showed the example of the test | inspection procedure at the time of applying the fatigue limit evaluation apparatus which concerns on this embodiment to the periodic inspection of the fatigue limit of the evaluation object member. The figure which showed the example of the function structure of the fatigue limit evaluation apparatus which concerns on the 1st modification of embodiment of this invention. The figure which showed the example of the function structure of the fatigue limit evaluation apparatus which concerns on the 2nd modification of embodiment of this invention. The figure which showed the example of the function structure of the fatigue limit evaluation apparatus which concerns on the 3rd modification of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a functional configuration of a fatigue limit evaluation apparatus 10 according to an embodiment of the present invention. As shown in FIG. 1, a fatigue limit evaluation apparatus 10 includes a surface profile measurement value acquisition unit 11, a peak coordinate value extraction unit 12, an evaluation profile data generation unit 13, a surface roughness index value calculation unit 14, and a fatigue limit estimated value. The calculation unit 15, the fatigue limit diagnosis unit 16, the surface profile measurement value storage unit 21, the peak coordinate value storage unit 22, the evaluation profile data storage unit 23, the input device 25, and the output device 26 are configured to include functional blocks. .

  The fatigue limit evaluation device 10 having the above-described functional configuration is realized in terms of hardware by a general computer including a central processing unit (CPU) and a storage device (not shown). In that case, each of the surface profile measurement value acquisition unit 11, the peak coordinate value extraction unit 12, the evaluation profile data generation unit 13, the surface roughness index value calculation unit 14, the fatigue limit estimated value calculation unit 15, and the fatigue limit diagnosis unit 16 The function is realized by the central processing unit of the computer executing a predetermined program stored in the storage device. Further, the surface profile measurement value storage unit 21, the peak coordinate value storage unit 22, and the evaluation profile data storage unit 23 are realized as a storage area allocated to a part of the storage device. The input device 25 includes a keyboard, a mouse, a touch panel, and the like, and is used by a user of the fatigue limit evaluation device 10 to input various information to the central processing unit. The output device 26 is constituted by a liquid crystal display device or the like, and is used for displaying a result obtained by the central processing unit executing a predetermined program.

  Further, the fatigue limit evaluation device 10 includes a surface roughness measurement device 31 that measures a surface profile of an evaluation target member (not shown), a hardness measurement device 32 that measures the hardness of the evaluation target member, and a residual stress of the evaluation target member. Is connected via a communication cable to a residual stress measuring device 33 or the like. Note that the communication cable may be anything such as a LAN (Local Area Network) cable or a USB (Universal Serial Bus) cable as long as it enables information communication with the computer.

  Hereinafter, the function of each functional block of the fatigue limit evaluation apparatus 10 will be described in detail with reference to FIG. 2 and subsequent drawings in addition to FIG. In the following description, the surface roughness profile is referred to as a surface profile or simply a profile.

  FIG. 2A is a diagram schematically showing an example of the surface profile of the evaluation target member, and FIG. 2B is a diagram showing an example of the data structure of the surface profile measurement value. The surface profile of the evaluation target member means a cross-sectional shape in the height direction of the unevenness of the surface of the evaluation target member, and the measurement value (surface profile measurement value 211) is usually parallel to the surface of the evaluation target member. It is represented by the coordinate value in the x-axis direction and the coordinate value in the y-axis direction perpendicular to the surface of the evaluation target member.

That is, the surface roughness measuring device 31 has a predetermined interval (for example, 10 μm interval) along a straight line (x-axis) parallel to the surface of the evaluation target member, and a direction (y-axis) perpendicular to the surface of the evaluation target member. (Direction) surface position (measurement point position) is measured. In the example of FIG. 2A, the cross-sectional shape in the height direction (y-axis direction) of the unevenness of the surface of the evaluation target member is represented by a solid line, and the measurement points p ₁ , p ₂ , p ₃ ,. It is represented by a black circle.

Therefore, the surface profile measurement value acquisition unit 11 (see FIG. 1) executes the following processes [1] and [2].
[1] From the surface roughness measuring device 31, coordinate values (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y) of measured points p ₁ , p ₂ , p ₃ ,. ₃ ), ... are acquired.
[2] Coordinate values (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ) of the acquired measurement points p ₁ , p ₂ , p ₃ ,. Is stored in the surface profile measurement value storage unit 21 as the surface profile measurement value 211 of the evaluation target member (see FIG. 2B).

FIG. 3A is a diagram schematically illustrating an example of peak points in the surface profile of the evaluation target member, and FIG. 3B is a diagram illustrating an example of a data structure of peak coordinate values. Here, the peak point refers to a point corresponding to a peak of an uneven valley or mountain in the surface profile represented by the surface profile measurement value 211. That is, whether the coordinate value _{y n} in the y-axis direction of the measurement point _{p n} is greater than any of the adjacent the measurement point _{p n-1, p n + 1} of coordinate values _y n-1 in the y-axis _{direction, y n + 1} Or the measured point _{pn is referred} to as a peak point _PN . In FIG. 3A, the peak points P ₁ , P ₂ , P ₃ ,... Are represented by white circles.

Therefore, the peak coordinate value extraction unit 12 (see FIG. 1) executes the following processes [1] to [3].
[1] Coordinate values (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y) of the measured points p ₁ , p ₂ , p ₃ ,. ₃ ) Read out.
[2] Coordinate values (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ) of the read measurement points p ₁ , p ₂ , p ₃ ,. From the coordinate values (X ₁ , Y ₁ ), (X ₂ , Y ₂ ), (X ₃ , Y ₃ ),... Corresponding to the peak points P ₁ , P ₂ , P ₃ ,. Extract.
[3] The extracted coordinate values (X ₁ , Y ₁ ), (X ₂ , Y ₂ ), (X ₃ , Y ₃ ),... Are stored as peak coordinate values 221 in the peak coordinate value storage unit 22. (See FIG. 3B).

FIG. 4A is a diagram schematically showing an example of an evaluation profile, and FIG. 4B is a diagram showing an example of the data structure of evaluation profile data. Here, as shown in FIG. 4A, the evaluation profile is a predetermined threshold value H that is a difference in height between adjacent peak points P _N and P _{N + 1} in the surface profile measured by the surface roughness measuring device 31. Is smaller than the peak point P _N , P _{N + 1} is ignored, and the peak points Q ₁ , Q ₂ , Q ₃ ,... Refers to the surface profile to be applied. In FIG. 4A, the evaluation profile is represented by a thick solid line, and the surface profile measured by the surface roughness measuring device 31 is represented by a broken line. As shown in FIG. 4B, the evaluation profile data 231 includes coordinate values (X ′ ₁ , Y ′ ₁ ) of peak points Q ₁ , Q ₂ , Q ₃ ,. (X ′ ₂ , Y ′ ₂ ), (X ′ ₃ , Y ′ ₃ ),...

Therefore, the evaluation profile data generation unit 13 (see FIG. 1) executes the following processes [1] to [4].
[1] The coordinate values (X ₁ , Y ₁ ), (X ₂ , Y ₂ ), (X ₃ , Y ₃ ) of the peak points P ₁ , P ₂ , P ₃ ,. , ... are read out.
[2] When the height difference between the peak points P _i , P _{i + 1} adjacent to the read peak points P ₁ , P ₂ , P ₃ ,... Filtering processing is performed to remove one or both of the coordinate values (X _i , Y _i ) and (X _{i + 1} , Y _{i + 1} ) of P _i and P _{i + 1} .
[3] The evaluation profile data 231 is generated so that the height difference between the peak points Q _N and Q _{N + 1} adjacent to each other after the filtering process is equal to or greater than a predetermined threshold value H.
[4] The coordinate values (X ′ ₁ , Y ′ ₁ ), (X ′ ₂ , Y ′ ₂ ) of the peak points Q ₁ , Q ₂ , Q ₃ ,. (X ′ ₃ , Y ′ ₃ ),... Are stored in the evaluation profile data storage unit 23.

In the present embodiment, the threshold value H used in the above processing is a value obtained by multiplying the surface roughness parameter R obtained from the surface profile measurement value 211 of the evaluation target member by a positive constant C, that is, H = C · It shall be expressed as R. The surface roughness parameter R is, for example, a Japanese Industrial Standard (JIS B0601 “Product Geometric Specification (GPS) —Surface Properties: Contour Curve Method—Terms, Definitions, and Surface Property Parameters”) It is preferable to select one from ten-point average roughness R _zjis , arithmetic average roughness R _a , maximum height R _{z and the} like.

When the 10-point average roughness R _zjis or the maximum height R _z is adopted as the surface roughness parameter R, the value of the constant C is usually 1 or less, but the arithmetic average roughness _Ra is If it is adopted, it may exceed 1. In any case, an appropriate value of the constant C is determined experimentally or empirically depending on the type of the surface roughness parameter R.

Further, in the Japanese Industrial Standard (JIS B0601), the calculation method of the ten-point average roughness R _zjis is mentioned, but for example, the 8-point average roughness, the 20-point average roughness, etc. are not mentioned. However, the n-point average roughness such as the 8-point average roughness and the 20-point average roughness can be calculated in the same manner as the ten-point average roughness R _zjis . Therefore, as the surface roughness parameter R, an n-point average roughness may be used instead of the ten-point average roughness R _zjis . However, n here is a positive integer.

  By the way, according to Non-Patent Document 1, the surface roughness index value √area of a member to be evaluated having a periodic crack (concave portion) has the periodic crack pitch 2b and the crack depth a as variables. The function f is expressed by That is, √area = f (a, 2b).

ここで、σ_ｗ：疲労限度の推定値
Ｈｖ：ビッカース硬さ
Ｒｏ：応力比（＝σ_ｍｉｎ／σ_ｍａｘ）
σ_ｍａｘ：最大応力
σ_ｍｉｎ：最小応力
Further, in Non-Patent Document 1, if this surface roughness index value √area is used, the fatigue limit σ _w is accurately estimated by the following equation (1).

Where σ _w : Estimated fatigue limit
Hv: Vickers hardness
Ro: Stress ratio (= σ _min / σ _max )
σ _max : Maximum stress
σ _min : Minimum stress

Therefore, in this embodiment, the surface roughness index value calculation unit 14 (see FIG. 1) calculates a surface roughness index value √areaA corresponding to the surface roughness index value √area referred to in Non-Patent Document 1. Next, the fatigue limit estimated value calculation unit 15 calculates the fatigue limit estimated value σ _w using the surface roughness index value √areaA calculated as described above. Hereinafter, processing of the surface roughness index value calculation unit 14 and the fatigue limit estimated value calculation unit 15 will be described.

  FIG. 5 is a view showing an example of a surface profile for explaining parameters a and 2b for evaluating the size of a crack (valley) necessary for calculating the surface roughness index value √areaA according to the present embodiment. It is. In FIG. 5, a broken line represents a surface profile measured by the surface roughness measuring device 31, and a thick solid line represents an evaluation profile.

  Here, the surface roughness index value calculation unit 14 obtains data corresponding to the parameters a and 2b in the evaluation profile using the evaluation profile data 231, and then uses these data to determine the surface roughness index value. √AreaA is calculated.

That is, the surface roughness index value calculation unit 14 calculates the surface roughness index value √areaA according to the following procedures [1] to [4].
[1] With reference to the evaluation profile data 231, peak points Q _N and Q _{N + 2} of the peaks in the evaluation profile (thick solid line drawn in FIG. 5) are extracted, and further, peak points Q _{N + 1} and Q _{N + 3 of the} valleys are extracted. To extract. Here, N is an even number starting from 2 (N = 2, 4,...) (Hereinafter the same).
[2] The pitch 2b _N in the x direction of the two peaks is calculated using the coordinate values in the x direction of the peak points Q _N and Q _{N + 2} of the extracted peaks. That is, 2b _N = X ′ _{N + 2} −X ′ _N is calculated.
[3] Using the coordinate values in the y direction of the peak points Q _N and Q _{N + 2 of the} extracted peaks and the peak point Q _{N + 1} of the valley between them, the depth a _N of each valley is calculated. At this time, it is assumed that the depth a _N of the valley is a difference in height between the higher mountain and the valley among the adjacent mountains. That is, the valley depth a _N = max (Y ′ _N , Y ′ _{N + 2} ) −Y ′ _{N + 1} at the peak point Q _{N + 1} of the valley is calculated. Here, max represents a function for obtaining the maximum value.
[4] Using {(a _N , 2b _N ): N = 2, 4,...} Obtained as described above, √areaA is calculated according to the following equation (2).
√area A = max {f _A (a _N , 2b _N ): N = 2, 4,...} (2)

In Equation (2), the maximum value is obtained from the value set {f _A (a _N , 2b _N ): N = 2, 4,... For example, an average value of the maximum value and the second largest value may be taken.

When the surface roughness index value √areaA is obtained by the above procedure, the fatigue limit estimated value calculation unit 15 follows the formula (1) or a modified formula that actually matches a part of the formula (1), The fatigue limit estimated value σ _w is calculated. In addition, when formula (1) is used, √area = √areaA.

Also, when calculating the fatigue limit estimate sigma _w, it is necessary to stress ratio Ro added to hardness (Vickers hardness Hv) and evaluated member evaluated member. In that case, the value measured by the hardness measuring device 32 is used as the hardness of the evaluation target member. In addition, as the residual stress in the evaluation target member necessary for calculating the stress ratio Ro, a value measured by the residual stress measuring device 33 is used.

  FIG. 6 is a diagram illustrating an example of a surface profile actually measured on the evaluation target member and an evaluation profile generated from the surface profile. In FIG. 6, the thin solid line represents the actually measured surface profile, and the thick solid line represents the evaluation profile. Further, the white square mark represents the peak point of the peak or valley of the evaluation profile, and the black circle mark represents the peak point of the valley where √areaA is maximum.

In the example of FIG. 6, as the surface roughness parameter R serving as a reference for the threshold value H (= C · R) for determining the height difference between adjacent peak points in the actually measured surface profile (thin solid line), The ten-point average roughness R _zjis referred to in the Japanese Industrial Standard is used, and the value of the constant C is 0.3 (that is, C = 0.3).

As can be seen from the example of FIG. 6, the evaluation profile is obtained by removing small peaks and valleys from the measured surface profile by filtering, that is, the actually measured micro-surface profile is divided into large peaks and valleys. It can be said that it has been converted to a macro surface profile consisting of Furthermore, according to FIG. 6, equation (2), etc., the fatigue limit estimated value σ _w calculated by the fatigue limit estimated value calculating unit 15 is a macro valley (crack) where √areaA is maximum and its adjacent It is assumed that it is determined by the influence of the valley.

  This means that a value considering the interference of the stress of the valley adjacent to the valley of the valley having the largest stress concentration among the valleys in the evaluation profile is a determining factor of the fatigue limit. Normally, when stress concentration parts such as notches are adjacent to each other, the stress is dispersed by interference, and the influence of the stress concentration becomes relatively small, so this interpretation can be said to be natural. However, if the small peaks and valleys in the actually measured surface profile cannot be appropriately filtered, an appropriate evaluation profile cannot be obtained. Therefore, the inventors conducted various evaluation tests as shown below. Here, only the result is shown.

FIG. 7 is a diagram showing an example of the relationship between estimated fatigue limit values and measured fatigue limit values of various evaluation target members. FIG. 7A shows a constant C of a threshold value H (= C · R) of 0.1. The figure showing the relationship between the fatigue limit estimated value and the fatigue limit measured value at the time of (b), (b) is the figure showing the relationship between the fatigue limit estimated value and the fatigue limit measured value when the constant C is 0.3 It is. The surface roughness parameter R employed at this time is the ten-point average roughness R _zjis .

  In the graphs of FIGS. 7A and 7B, the horizontal axis represents the actual fatigue limit value, the vertical axis represents the estimated fatigue limit value, and the values are relativized. Further, a straight line drawn diagonally from the lower left to the upper right of the graph means that the actual fatigue limit value matches the estimated fatigue limit value. In addition, the alternate long and short dash line drawn along the straight line indicates that the fatigue limit estimated value deviates by plus or minus 10% from the fatigue limit measured value.

In the graphs of FIGS. 7A and 7B, white or black circles, squares, and triangles indicate evaluation test results when different stresses are applied to different surface states of different evaluation target members. It is shown. Here, the surface state refers to a state determined by the material of the evaluation target member, processing conditions (for example, grinder processing, blast processing), and the like. Further, here, only the stress conditions where the stress ratio Ro (= σ _min / σ _max ) is 0 and −1 are evaluated.

  In FIG. 7A, that is, when C = 0.1, the estimated fatigue limit value and the measured fatigue limit value deviate by 10% or more for the surface condition and stress condition of most of the evaluation target members. Yes. On the other hand, in FIG. 7B, that is, when C = 0.3, the deviation between the fatigue limit estimated value and the fatigue limit measured value is 10 for the surface condition and stress condition of most of the evaluation target members. It is within%. This means that in order to improve the estimation accuracy of the fatigue limit estimation value, an appropriate threshold value H (= CR) for obtaining an appropriate evaluation profile, that is, an appropriate constant according to the surface roughness parameter R It can be seen that it is important to determine the value of C or its range.

  In the fatigue limit evaluation apparatus 10 according to the present embodiment, the value of the constant C is determined based on the surface roughness parameter R obtained from the surface profile measurement value 211 of the evaluation target member. This brings about the effect that the standard to be clarified. That is, if the value of constant C or its range is obtained experimentally or empirically in advance, the user of fatigue limit evaluation apparatus 10 measures the surface profile of the evaluation target member and obtains the surface roughness parameter. Thus, anyone can easily determine the threshold value H. Therefore, any user can obtain an appropriate evaluation profile by the fatigue limit evaluation apparatus 10 according to the present embodiment, and can estimate the fatigue limit with high accuracy.

By adding a fatigue limit diagnostic unit 16 (see FIG. 1) to the fatigue limit evaluation apparatus 10 as described above, the fatigue limit evaluation apparatus 10 can be used as a fatigue limit inspection apparatus. In that case, the fatigue limit diagnosis unit 16 executes, for example, the following processes [1] to [3].
[1] The load stress value received by the separately evaluated evaluation target member is read through the input device 25 such as a keyboard.
[2] The fatigue limit estimated value of the evaluation target member calculated by the fatigue limit estimated value calculating unit 15 is compared with the read load stress value.
[3] As a result of the comparison, when the load stress value is equal to or less than the fatigue limit estimated value, the output device 26 such as a liquid crystal display device displays that the evaluation target member is “continuous use is possible” Further, when the load stress value exceeds the fatigue limit estimated value, the similar output device 26 displays that the member to be evaluated should be “repaired” or “replaced”.

  FIG. 8 is a diagram illustrating an example of an inspection procedure when the fatigue limit evaluation apparatus 10 according to the present embodiment is applied to the periodic evaluation of the fatigue limit of a member to be evaluated. However, this inspection procedure is mainly shown as an inspector's work procedure, and the processing executed by the fatigue limit evaluation apparatus 10 is particularly surrounded by a broken line.

  As shown in FIG. 8, the inspector first measures the surface profile of the evaluation target member using the surface roughness measuring device 31 (step S21). At this time, the surface profile may be measured with a portable roughness meter, or a surface roughness measuring device in which the surface of the replica, which is a transfer of the surface shape of the evaluation target member, is installed in an inspection room or the like. You may measure by 31.

  Next, the inspector measures the hardness of the evaluation target member using the hardness measurement device 32 (step S21), and further measures the residual stress of the evaluation target member using the residual stress measurement device 33 (step S21). S23). Subsequently, the inspector separately inputs a load stress value received by the evaluation target member obtained by an evaluation such as an experiment or a simulation to the fatigue limit evaluation device 10 via the input device 25 such as a keyboard (step S24). .

  When the work by the inspector as described above is performed, as the work proceeds, the fatigue limit evaluation apparatus 10 includes a surface profile measurement value acquisition unit 11, a peak coordinate value extraction unit 12, an evaluation profile data generation unit 13, a surface Processing to be performed by the roughness index value calculation unit 14 and the fatigue limit estimated value calculation unit 15 is sequentially executed, and a fatigue limit estimated value is calculated as a result of these processing (step S25).

  Hereinafter, as the processing of the fatigue limit diagnosis unit 16, the fatigue limit evaluation apparatus 10 compares the calculated fatigue limit estimated value with the load stress value input in step S24 (step S26). As a result of the comparison, when the load stress value is equal to or less than the fatigue limit estimated value (Yes in step S26), the fatigue limit evaluation device 10 indicates that the evaluation target member is “continuous use is possible”. Are displayed on the output device 26 such as a liquid crystal display device (step S27). Further, when the load stress value exceeds the fatigue limit estimated value (No in step S26), a message indicating that the member to be evaluated should be “repaired” or “replaced” is displayed on the liquid crystal display device or the like. Is displayed on the output device 26 (step S28). In this case, the output device 26 may notify the “repair” or “replacement” by voice or a warning lamp.

  As described above, when the fatigue limit evaluation apparatus 10 according to the present embodiment is applied to the periodic inspection of the fatigue limit of the evaluation target member, the inspector does not have to perform an operation that particularly requires judgment. The work efficiency can be improved, and an inspection result independent of the worker can be obtained.

  In the embodiment described above, the profile data generator for evaluation 13 of the fatigue limit evaluation device 10 filters and removes small peaks and valleys in the surface profile of the evaluation target member measured by the surface roughness measuring device 31. In other words, an evaluation profile representing the macro roughness of the evaluation target member is generated. Then, the surface roughness index value calculation unit 14 calculates the maximum one of the surface roughness index values calculated for all cracks (valleys) included in the evaluation profile as the surface roughness index value √areaA. The fatigue limit estimated value calculation unit 15 calculates the fatigue limit estimated value using the surface roughness index value √areaA.

  Therefore, in the fatigue limit evaluation apparatus 10 according to the present embodiment, even if the surface profile measurement value 211 obtained from the evaluation target member represents a non-periodic surface roughness profile, the surface profile measurement value 211 determines that The estimated fatigue limit value of the member to be evaluated can be calculated. Therefore, according to the present embodiment, a fatigue limit evaluation method and a fatigue limit evaluation apparatus that can be applied to a member of a device having an aperiodic surface roughness profile are provided.

(First Modification of Embodiment)
FIG. 9 is a diagram illustrating an example of a functional configuration of the fatigue limit evaluation apparatus 10a according to the first modification of the embodiment of the present invention. The fatigue limit evaluation apparatus 10a according to the first modified example includes a hardness / residual stress database 24 inside instead of the external hardness measurement apparatus 32 and the residual stress measurement apparatus 33. 1 is different from the fatigue limit evaluation apparatus 10 shown in FIG.

  In general, the hardness and residual stress of the evaluation target member are determined almost uniquely depending mainly on the material of the member and the processing conditions of the surface. Therefore, the fatigue limit evaluation apparatus 10a according to the present modification includes the material of the member, A hardness / residual stress database 24 is provided in which information configured by associating the surface processing conditions with the hardness and residual stress of the member is registered. And it is assumed that the hardness measuring device 32 and the residual stress measuring device 33 do not need to be connected to the fatigue limit evaluation device 10a.

  In the fatigue limit evaluation apparatus 10 a configured as described above, it is not necessary to perform the work of measuring the hardness of the evaluation target member using the hardness measurement apparatus 32 or the work of measuring the residual stress using the residual stress measurement apparatus 33. . As a result, the efficiency of the fatigue limit evaluation work for calculating the fatigue limit estimated value and the periodic inspection work for the fatigue limit are improved.

(Second Modification of Embodiment)
FIG. 10 is a diagram illustrating an example of a functional configuration of the fatigue limit evaluation device 10b according to the second modification of the embodiment of the present invention. The fatigue limit evaluation device 10b according to the second modification is different from the fatigue limit evaluation device 10 shown in FIG. 1 in that a surface roughness measuring device 31 is incorporated therein.

  That is, the fatigue limit evaluation apparatus 10 shown in FIG. 1 is configured only by a so-called computer in terms of hardware, but the fatigue limit evaluation apparatus 10b according to this modification is connected to a computer and the computer. The surface roughness measuring device 31 is configured. Since recent computers have advanced in performance and miniaturization, the present modified example has a surface roughness having a fatigue limit evaluation function rather than the fatigue limit evaluation device 10b incorporating the surface roughness measuring device 31. It can be said that the measurement device can be realized.

(Third Modification of Embodiment)
FIG. 11 is a diagram illustrating an example of a functional configuration of a fatigue limit evaluation apparatus 10c according to a third modification of the embodiment of the present invention. The fatigue limit evaluation apparatus 10c according to the third modification is shown in FIG. 1 in that a hardness measurement apparatus 32 and a residual stress measurement apparatus 33 are incorporated in addition to the surface roughness measurement apparatus 31 therein. This is different from the fatigue limit evaluation apparatus 10.

  In other words, it can be said that this modification example realizes the fatigue limit evaluation apparatus 10c having an all-in-one function. Therefore, in the fatigue limit evaluation apparatus 10c according to this modification, even when the hardness or residual stress of the evaluation target member changes due to, for example, a change over time, the hardness or residual stress can be measured quickly, so that the accuracy is higher. A fatigue limit estimate can be obtained quickly.

  The present invention is not limited to the above-described embodiments and modifications, and further includes various modifications. For example, the above-described embodiments and modifications have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, a part of the configuration of an embodiment or modification can be replaced with the configuration of another embodiment or modification, and the configuration of another embodiment or modification can be replaced with another embodiment or modification. It is also possible to add the following configuration. In addition, with respect to a part of the configuration of each embodiment or modification, the configuration included in another embodiment or modification may be added, deleted, or replaced.

10, 10a, 10, b, 10c Fatigue limit evaluation apparatus 11 Surface profile measurement value acquisition unit 12 Peak coordinate value extraction unit 13 Profile data generation unit for evaluation 14 Surface roughness index value calculation unit 15 Fatigue limit estimation value calculation unit 16 Fatigue Limit diagnosis unit 21 Surface profile measurement value storage unit 22 Peak coordinate value storage unit 23 Profile data storage unit for evaluation 24 Hardness / residual stress database 25 Input device 26 Output device 31 Surface roughness measurement device 32 Hardness measurement device 33 Residual stress Measuring device 211 Surface profile measurement value 221 Peak coordinate value 231 Profile data for evaluation

Claims (14)

A computer connected to a surface roughness measuring device for measuring a surface profile of a member to be evaluated,
Obtaining a measurement value of the surface profile of the evaluation target member from the surface roughness measuring device;
Extracting a peak coordinate value of a mountain and a peak coordinate value of a valley included in the measurement value of the acquired surface profile;
When the height difference between adjacent peaks and valleys is smaller than a predetermined threshold with respect to the data consisting of the peak coordinate values of the extracted peaks and valley peak coordinates, the peak coordinates of one or both peaks or valleys Performing a filtering process to remove a value, and generating data of an evaluation profile such that a height difference between adjacent peaks and valleys is equal to or greater than the predetermined threshold;
For the valleys included in the evaluation profile, the depth of each valley and the distance between the adjacent mountains and mountains or the valley and valley are obtained, and the surface roughness index value of the evaluation profile is calculated using the obtained values. Steps,
Calculating a fatigue limit estimated value of the evaluation target member using a relatively large value among the calculated surface roughness index values;
Fatigue limit evaluation method characterized by performing The surface roughness index value used in the step of calculating the fatigue limit estimated value is the maximum of the surface roughness index value obtained for each valley included in the evaluation profile in the step of calculating the surface roughness index value. It is a value. The fatigue limit evaluation method of Claim 1 characterized by the above-mentioned. The fatigue limit evaluation method according to claim 1, wherein the predetermined threshold is a value obtained by multiplying a surface roughness parameter obtained from a measured value of a surface profile of the evaluation target member by a positive constant. The computer
The load stress value received by the evaluation target member input via the input device is compared with the calculated fatigue limit estimated value. When the load stress value exceeds the fatigue limit estimated value, the evaluation target The fatigue limit evaluation method according to claim 1, further comprising a step of outputting a message for prompting repair or replacement of the member to the output device. The computer
In the step of calculating the fatigue limit estimate of the evaluation object member,
In addition to the surface roughness index calculated in the step of calculating the surface roughness index value, the evaluation value measured by the hardness value of the evaluation object member measured by the hardness measurement device and the residual efficacy measurement device The fatigue limit evaluation method according to claim 1, wherein an estimated fatigue limit value of the evaluation target member is calculated using a value of a residual stress of the member. The computer
Further comprising a hardness / residual stress database configured by associating hardness and residual stress with the processing conditions of the evaluation target member;
In the step of calculating the fatigue limit estimate of the evaluation object member,
In addition to the surface roughness index calculated in the step of calculating the surface roughness index value, the hardness and residual of the evaluation target member obtained from the hardness / residual stress database according to the processing conditions of the evaluation target member The fatigue limit evaluation method according to claim 1, wherein an estimated fatigue limit value of the evaluation target member is calculated using stress. From a surface roughness measuring device that measures the surface profile of the evaluation target member, a surface profile measurement value acquisition unit that acquires a measurement value of the surface profile of the evaluation target member;
A peak coordinate value extraction unit for extracting a peak coordinate value of a mountain and a peak coordinate value of a valley included in the measurement value of the acquired surface profile;
When the height difference between adjacent peaks and valleys is smaller than a predetermined threshold with respect to the data consisting of the peak coordinate values of the extracted peaks and valley peak coordinates, the peak coordinates of one or both peaks or valleys An evaluation profile data generation unit that performs filtering processing to remove values and generates evaluation profile data such that the height difference between adjacent peaks and valleys is equal to or greater than the predetermined threshold;
For the valleys included in the evaluation profile, the depth of each valley and the distance between the adjacent mountains and mountains or the valley and valley are obtained, and the surface roughness index value of the evaluation profile is calculated using the obtained values. A surface roughness index value calculator,
A fatigue limit estimated value calculating unit that calculates a fatigue limit estimated value of the evaluation target member using a relatively large value among the calculated surface roughness index values;
A fatigue limit evaluation apparatus comprising: The surface roughness index value used in the fatigue limit estimated value calculation unit is the maximum value of the surface roughness index value obtained for each valley included in the evaluation profile in the surface roughness index value calculation unit. The fatigue limit evaluation apparatus according to claim 7. The fatigue limit evaluation apparatus according to claim 7, wherein the predetermined threshold is a value obtained by multiplying a surface roughness parameter obtained from a measured value of a surface profile of the evaluation target member by a positive constant. The load stress value received by the evaluation target member input via the input device is compared with the calculated fatigue limit estimated value. When the load stress value exceeds the fatigue limit estimated value, the evaluation target The fatigue limit evaluation device according to claim 7, further comprising a fatigue limit diagnosis unit that outputs a message for prompting repair or replacement of a member to the output device. The fatigue limit estimated value calculation unit,
In addition to the surface roughness index calculated by the surface roughness index calculation unit, the hardness value of the evaluation target member measured by a hardness measurement device and the residual of the evaluation target member measured by a residual efficacy measurement device The fatigue limit evaluation apparatus according to claim 7, wherein a fatigue limit estimated value of the evaluation target member is calculated using a stress value. Further comprising a hardness / residual stress database configured by associating hardness and residual stress with the processing conditions of the evaluation target member;
The fatigue limit estimated value calculation unit,
In addition to the surface roughness index calculated by the surface roughness index calculation unit, the hardness and residual stress of the evaluation target member obtained from the hardness / residual stress database according to the processing conditions of the evaluation target member are used. The fatigue limit estimation device according to claim 7, wherein an estimated fatigue limit value of the member to be evaluated is calculated. A surface roughness measuring device for measuring a surface profile of a member to be evaluated;
From the surface roughness measuring device, a surface profile measurement value acquisition unit that acquires a measurement value of the surface profile of the evaluation target member;
A peak coordinate value extraction unit for extracting a peak coordinate value of a mountain and a peak coordinate value of a valley included in the measurement value of the acquired surface profile;
When the height difference between adjacent peaks and valleys is smaller than a predetermined threshold with respect to the data consisting of the peak coordinate values of the extracted peaks and valley peak coordinates, the peak coordinates of one or both peaks or valleys An evaluation profile data generation unit that performs filtering processing to remove values and generates evaluation profile data such that the height difference between adjacent peaks and valleys is equal to or greater than the predetermined threshold;
For the valleys included in the evaluation profile, the depth of each valley and the distance between the adjacent mountains and mountains or the valley and valley are obtained, and the surface roughness index value of the evaluation profile is calculated using the obtained values. A surface roughness index value calculator,
A fatigue limit estimated value calculating unit that calculates a fatigue limit estimated value of the evaluation target member using a relatively large value among the calculated surface roughness index values;
A fatigue limit evaluation apparatus comprising: A hardness measuring device for measuring the hardness of the evaluation target member, and a residual efficacy measuring device for measuring the residual stress of the evaluation target member,
The fatigue limit estimated value calculation unit,
In addition to the surface roughness index calculated by the surface roughness index calculation unit, the hardness value of the evaluation target member measured by the hardness measurement device and the evaluation target member measured by the residual efficacy measurement device The fatigue limit evaluation apparatus according to claim 13, wherein an estimated fatigue limit value of the evaluation target member is calculated using a residual stress value of the above.

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