JP7419977B2 - Mobile crane fatigue damage evaluation device, fatigue damage evaluation program, and fatigue damage evaluation method - Google Patents

Description

The present invention relates to a fatigue damage evaluation device, a fatigue damage evaluation program, and a fatigue damage evaluation method for a mobile crane. More particularly, the present invention relates to an apparatus, program, and method for evaluating fatigue damage of a mobile crane undercarriage.

The timing of maintenance of components of a mobile crane may be determined based on the amount of work. For example, Patent Document 1 discloses calculating the amount of damage to an undercarriage of a wheel crane. When carrying out cargo handling at a port, the crane device repeatedly performs operations within a turning range of about 90 degrees. Therefore, four turning ranges are provided around the turning center of the upper rotating body, and the amount of damage is calculated for each turning range. The operator appropriately changes the orientation of the wheel crane with respect to the quay so that the amount of damage in each turning range is uniform. By doing so, it is possible to suppress early fatigue failure of members at specific locations on the lower traveling body.

Japanese Patent Application Publication No. 2013-107762

In the case of a mobile crane, the stress generated in the members supporting the swivel base varies greatly depending on the swing angle of the boom. However, in the conventional technology, fatigue damage was not evaluated in consideration of the swing angle of the boom, and the evaluation accuracy was low.

In view of the above circumstances, an object of the present invention is to provide a fatigue damage evaluation device, a fatigue damage evaluation program, and a fatigue damage evaluation method that can accurately evaluate fatigue damage of structural members of a mobile crane.

The fatigue damage evaluation device of the first invention is a fatigue damage evaluation device for a mobile crane having a lower structure including a portion to be evaluated, a swivel mounted on the lower structure, and a boom provided on the swivel. The device includes a moment measuring device for measuring a lodging moment acting on the boom, a swinging angle measuring device for measuring a swinging angle of the boom, and the measurement values of the moment measuring device and the swinging angle measuring device are inputted. a calculation device, the calculation device calculates the fluctuation range of stress occurring in the evaluation target portion based on the measured values of the lodging moment and the turning angle for each operation from the lifting of the suspended load to the landing. A stress amplitude ratio, which is a ratio to the total amplitude of rated stress, is determined, a one-work fatigue damage value is determined from the stress amplitude ratio, and the one-work fatigue damage value is integrated over a predetermined period to obtain a cumulative fatigue damage value. shall be.
In the fatigue damage evaluation device of a second aspect of the invention, in the first aspect, the calculation device calculates a load factor that is a ratio of the measured value of the lodging moment to the rated value, and calculates the load factor from the change in the turning angle during the period of the one work. The present invention is characterized in that an amplitude rate of stress occurring in the evaluation target region is determined, and the stress amplitude ratio is determined by multiplying the load rate by the amplitude rate.
In the fatigue damage evaluation device of a third invention, in the first or second invention, the calculation device calculates the cumulative fatigue damage value from the start of use of the evaluation target part to the present, and the cumulative fatigue damage value is calculated from the cumulative fatigue damage value. The present invention is characterized in that it is determined that the lifespan of the evaluation target region has reached when the lifespan threshold value determined for the evaluation target region is exceeded.
A fatigue damage evaluation device according to a fourth invention is characterized in that, in any one of the first to third inventions, the evaluation target region is a front portion or a rear portion of a frame on which the swivel table is mounted.
A fatigue damage evaluation device according to a fifth aspect of the invention is characterized in that, in any one of the first to third aspects, the evaluation target part is a bolt that fixes a slewing bearing interposed between the swivel base and the frame to the frame. Features.
The fatigue damage evaluation program of the sixth invention is a fatigue damage evaluation program for a mobile crane having a lower structure including a portion to be evaluated, a swivel base mounted on the lower structure, and a boom provided on the swivel base. This is a fatigue damage evaluation program for operating a computer to perform a fatigue damage evaluation program, in which the measured values of the lodging moment acting on the boom and the swing angle of the boom are input, and the program calculates the fatigue damage evaluation program for each operation from the lifting of the suspended load to the landing. , based on the measured values of the lodging moment and the turning angle, determine a stress amplitude ratio, which is the ratio of the fluctuation range of stress occurring in the evaluation target part to the total amplitude of rated stress, and determine a one-work fatigue damage value from the stress amplitude ratio. The present invention is characterized in that the computer is operated to calculate a cumulative fatigue damage value by integrating the fatigue damage values for one work over a predetermined period.
A fatigue damage evaluation program according to a seventh aspect of the present invention, in the sixth aspect, calculates a load factor that is a ratio of the measured value of the lodging moment to the rated value, and calculates the load factor that is the ratio of the measured value of the lodging moment to the rated value, The present invention is characterized in that the computer is operated to determine the amplitude ratio of the generated stress, and to calculate the stress amplitude ratio by multiplying the load ratio by the amplitude ratio.
A fatigue damage evaluation program according to an eighth aspect of the present invention, in the sixth or seventh aspect, calculates the cumulative fatigue damage value from the start of use of the evaluation target part to the present, and determines the cumulative fatigue damage value for the evaluation target part. The present invention is characterized in that the computer is operated so as to determine that the lifespan of the evaluation target region has reached when the lifespan threshold value determined by the evaluation target region has been exceeded.
A fatigue damage evaluation method according to a ninth aspect of the invention is a fatigue damage evaluation method for a mobile crane having a lower structure including a portion to be evaluated, a swivel base mounted on the lower structure, and a boom provided on the swivel base. The method includes measuring the lodging moment acting on the boom, measuring the swing angle of the boom, and calculating the measured values of the lodging moment and the swing angle for each operation from the lifting of the suspended load to the landing. Based on the above, find the stress amplitude ratio which is the ratio of the range of stress fluctuation occurring in the evaluation target part to the total amplitude of rated stress, find the one-work fatigue damage value from the stress amplitude ratio, and integrate the one-work fatigue damage value for a predetermined period. The method is characterized in that the cumulative fatigue damage value is determined.
In the fatigue damage evaluation method of the tenth invention, in the ninth invention, a load factor that is a ratio of the measured value of the lodging moment to the rated value is determined, and the load rate is determined based on the change in the turning angle during the period of the one work. The present invention is characterized in that the amplitude ratio of the generated stress is determined, and the stress amplitude ratio is determined by multiplying the load rate by the amplitude ratio.
In the fatigue damage evaluation method of an eleventh invention, in the ninth or tenth invention, the cumulative fatigue damage value is determined from the start of use of the evaluation target part to the present, and the cumulative fatigue damage value is determined for the evaluation target part. It is characterized in that it is determined that the lifespan of the evaluation target region has reached when the lifespan threshold value determined by the evaluation target region has been exceeded.

According to the first and second aspects of the invention, since the cumulative fatigue damage value is determined based on the stress amplitude ratio in consideration of the swing angle of the boom, it is possible to accurately evaluate the fatigue damage at the evaluation target site.
According to the third invention, it is possible to detect that the life of the evaluation target region has come to an end, so that maintenance can be prompted at an appropriate time.
According to the fourth invention, it is possible to accurately evaluate fatigue damage in the front portion or rear portion of the frame.
According to the fifth invention, it is possible to accurately evaluate fatigue damage of a bolt that fixes a swing bearing.
According to the sixth and seventh inventions, since the cumulative fatigue damage value is determined based on the stress amplitude ratio in consideration of the swing angle of the boom, it is possible to accurately evaluate the fatigue damage at the evaluation target site.
According to the eighth invention, it is possible to detect that the life of the evaluation target region has come to an end, so that maintenance can be prompted at an appropriate time.
According to the ninth and tenth aspects, since the cumulative fatigue damage value is determined based on the stress amplitude ratio in consideration of the swing angle of the boom, it is possible to accurately evaluate fatigue damage at the evaluation target site.
According to the eleventh invention, it is possible to detect that the life of the evaluation target region has come to an end, so that maintenance can be prompted at an appropriate time.

It is a side view of a loading type truck crane. It is a front view of an outrigger device. It is a top view of an outrigger device. FIG. 3 is a longitudinal cross-sectional view of the swing bearing. FIG. 1 is a block diagram of a fatigue damage evaluation device according to a first embodiment. FIG. 3 is an explanatory diagram of a coordinate system used for calculation of fatigue damage evaluation. It is an explanatory view of the coordinate system used for calculation of fatigue damage evaluation in other examples. It is a flowchart of fatigue damage evaluation processing in a 1st embodiment. It is a flowchart of stress amplitude ratio calculation. It is a flow chart of fatigue damage evaluation processing in a 2nd embodiment.

Next, embodiments of the present invention will be described based on the drawings.
[First embodiment]
(mobile crane)
The fatigue damage evaluation device according to the first embodiment of the present invention is used to evaluate fatigue damage of a mobile crane. The type of mobile crane is not particularly limited. Examples of mobile cranes include all-terrain cranes, rough terrain cranes, truck cranes, and load-bearing truck cranes. Hereinafter, the case of a loading type truck crane will be explained as an example.

As shown in FIG. 1, the load-bearing truck crane CR has a general-purpose truck 10. As shown in FIG. A driver's cab 11 is provided in the front part of the general-purpose truck 10, and a loading platform 12 is provided in the rear part. A small crane 20 is mounted in a portion of the vehicle frame 13 of the general-purpose truck 10 between the driver's cab 11 and the loading platform 12.

The small crane 20 has a frame 21 fixed on the vehicle frame 13. A swivel base 22 is rotatably provided on the frame 21. A boom 23 is provided at the upper end of the swivel base 22 so as to be able to rise and fall. The swivel base 22 has a built-in winch. A wire rope extended from this winch is guided to the tip of the boom 23. The wire rope is wrapped around a pulley provided at the tip of the boom 23 and the hook 24. Thereby, the hook 24 is suspended from the tip of the boom 23. A hanging load LO is suspended from the hook 24.

The small crane 20 is hydraulically driven by a hydraulic circuit. The small crane 20 is provided with a group of operating levers 25 for operating a hydraulic circuit. The operator can operate the small crane 20 using the control lever group 25.

The small crane 20 has a control device 26 that controls the hydraulic circuit. The control device 26 is a computer composed of a CPU, memory, and the like. The hydraulic circuit operates based on a control signal from the control device 26. Thereby, the control device 26 controls the operation of the small crane 20.

The small crane 20 may have a remote control terminal that can communicate bidirectionally with the control device 26. The remote control terminal may be a wireless control terminal such as a so-called radio-controlled transmitter, or a wired control terminal. An operator can operate the small crane 20 using a remote control terminal.

The small crane 20 has an outrigger device 30. As shown in FIG. 2, the frame 21 has a horizontally arranged cylindrical portion. The cylindrical portion is a cylindrical member having a substantially rectangular cross section and is open at both ends. Outrigger inner boxes 31 are inserted into the openings at both ends of the cylindrical portion, respectively. The outrigger inner box 31 is a beam member having a substantially rectangular cross section. An outrigger jack 32 is provided at the tip of the outrigger inner box 31. The outrigger jack 32 is composed of a hydraulic cylinder. The outrigger jacks 32 are arranged on both left and right sides of the loading type truck crane CR.

When performing crane work, the outrigger device 30 is extended. To extend the outrigger device 30, the outrigger inner box 31 is pulled out from the cylindrical portion, the outrigger jack 32 is extended, and the float 33 is brought into contact with the ground. When the outrigger jack 32 is grounded, a portion of the weight of the loaded truck crane CR is applied to the outrigger device 30. This supports the loading type truck crane CR. After the crane work is completed, the outrigger device 30 is stored. To store the outrigger device 30, the outrigger jack 32 is retracted and the outrigger inner box 31 is drawn into the cylindrical portion.

As shown in FIG. 4, a swing bearing 27 is interposed between the frame 21 and the swing base 22. The swing bearing 27 has an outer ring 27a and an inner ring 27b fitted inside the outer ring 27a. A plurality of bearing balls are interposed between the outer ring 27a and the inner ring 27b, and the outer ring 27a can rotate relative to the inner ring 27b.

The swivel base 22 is fixed to the outer ring 27a with a plurality of bolts. Further, the inner ring 27b is fixed to the top plate 21a of the frame 21 with bolts 27c. A plurality of bolts 27c are provided along the circumferential direction of the inner ring 27b. The swivel bearing 27 allows the swivel base 22 to rotate relative to the frame 21 .

The swing bearing 27 is provided with a drive device 28 . The drive device 28 has a hydraulic motor 28a. A rotating shaft of the hydraulic motor 28a is connected to a pinion gear 28c via a reduction gear 28b. A gear is formed on the outer peripheral surface of the outer ring 27a. The gear of the outer ring 27a and the pinion gear 28c are engaged. When the hydraulic motor 28a is driven, the pinion gear 28c rotates, and the outer ring 27a turns relative to the inner ring 27b. As a result, the swivel base 22 rotates.

Note that the outer ring 27a of the swivel bearing 27 may be fixed to the frame 21, and the inner ring 27b may be fixed to the swivel base 22. In this case, by meshing the pinion gear 28c with a gear formed on the inner peripheral surface of the inner ring 27b, the swivel base 22 can be rotated by driving the hydraulic motor 28a.

The "frame" described in the claims may be any part on which a swivel base is mounted, and is not limited to the frame 21 of the loading truck crane CR. For example, frames of undercarriage bodies such as all-terrain cranes, rough terrain cranes, and truck cranes also correspond to the "frame" described in the claims.

The "lower structure" described in the claims may be any structure on which a swivel table is mounted. In this embodiment, in addition to the frame 21, the outrigger device 30 is also part of the lower structure. Undercarriage bodies such as all-terrain cranes, rough terrain cranes, and truck cranes also correspond to the "underbody structure" described in the claims.

The "swivel base" described in the claims is not limited to the swivel base 22 of this embodiment. The swivel base may be provided with a driver's seat or the like.

(Fatigue damage evaluation device)
Next, the configuration of the fatigue damage evaluation device of this embodiment will be explained.
As shown in FIG. 5, the fatigue damage evaluation apparatus AA includes a calculation device 40. The arithmetic unit 40 is a computer composed of a CPU, memory, and the like. By installing a fatigue damage evaluation program into the computer, the function as the arithmetic device 40 is realized. The fatigue damage evaluation program can be stored in various types of computer readable storage media. The computing device 40 may be realized as one function of the control device 26 that controls the hydraulic circuit of the small crane 20. Further, the arithmetic device 40 and the control device 26 may be separate devices.

The fatigue damage evaluation device AA has a moment measuring device 41 that measures the lodging moment M acting on the boom 23. The lodging moment M is generated by the load of the suspended load LO and the dead weight of the boom 23. The configuration of the moment measuring device 41 is not particularly limited, but may include a configuration in which the hydraulic pressure in a hydraulic cylinder that raises and lowers the boom 23 is measured using a pressure sensor. In addition, there is a load measuring device that measures the load W of the suspended load LO from the tension of the wire rope that hangs the hook 24, a length measuring device that measures the length L of the boom 23, and a undulation angle measurement device that measures the undulation angle φ of the boom 23. The moment measuring device 41 may be configured from a device. The lodging moment M can be determined from the load W of the suspended load LO, the length L of the boom 23, and the heave angle φ.

The fatigue damage evaluation device AA has a swing angle measuring device 42 that measures the swing angle Θ of the boom 23. Although the configuration of the turning angle measuring device 42 is not particularly limited, it may be configured to discretely detect the turning angle Θ of the boom 23 using a plurality of proximity switches provided on the frame 21 or the rotating base 22. Another example is a configuration in which the rotation angle of the swivel base 22 is read by a potentiometer.

Measured values M and Θ from a moment measuring device 41 and a turning angle measuring device 42 are input to the calculation device 40 . The calculation device 40 performs fatigue damage evaluation based on the lodging moment M and the turning angle Θ.

(Fatigue damage evaluation method)
Next, a fatigue damage evaluation method will be explained.
The fatigue damage evaluation device AA evaluates fatigue damage of a specific part included in the lower structure of a mobile crane. Hereinafter, the site to be evaluated for fatigue damage will be referred to as "evaluation target site P." The evaluation target site P is not particularly limited as long as it is a site included in the lower structure, but a site where stress changes due to work using a boom is preferably selected. For example, in the case of a load-bearing truck crane CR, the parts P to be evaluated include the front part, the rear part of the frame 21, the bolt 27c that fixes the swing bearing 27 to the frame 21, and the like.

The front portion of the frame 21 is, for example, a portion P1 shown in FIG. The frame 21 is a member that supports the swivel base 22. Therefore, a load is generated on the front portion P1 due to the lodging moment M acting on the boom 23. For example, when the boom 23 pivots forward, compressive stress is generated in the front portion P1. When the boom 23 pivots backward, tensile stress is generated in the front portion P1. Note that the opposite may occur depending on the position of the front portion P1.

A load is also generated on the rear portion P2 of the frame 21 due to the lodging moment M acting on the boom 23. For example, when the boom 23 pivots forward, tensile stress is generated in the rear portion P2. When the boom 23 pivots rearward, compressive stress is generated in the rear portion P2. Note that the opposite may occur depending on the position of the rear portion P2.

As shown in FIG. 4, a selected one of the plurality of bolts 27c fixing the swing bearing 27 to the frame 21 can be set as the evaluation target part P3. A tensile stress is generated in the bolt P3 due to fastening. When the boom 23 turns to the side opposite to the position of the bolt P3, the tensile stress generated in the bolt P3 increases. When the boom 23 pivots to the position of the bolt P3, the tensile stress generated in the bolt P3 becomes smaller.

As shown in FIG. 6, a coordinate system used for calculation of fatigue damage evaluation is defined based on the position of the evaluation target part P in the horizontal plane. Let O be the turning center of the boom 23. A horizontal line passing through the rotation center O of the boom 23 and the evaluation target site P is defined as a reference line BL. A horizontal line passing through the rotation center O of the boom 23 and perpendicular to the reference line BL is defined as a dividing line DL. The area on the side of the evaluation target site P from the dividing line DL is defined as the anterior area FA. The region on the opposite side of the evaluation target site P from the dividing line DL is defined as a rear region RA.

The turning angle of the boom 23 in this coordinate system is assumed to be θ. The direction of the evaluation target region P with respect to the rotation center O of the boom 23 is referred to as "directly ahead." The direction opposite to the evaluation target region P with respect to the rotation center O of the boom 23 is referred to as "straight behind." The turning angle θ is 0° when the boom 23 faces straight ahead.

Note that FIG. 6 shows a coordinate system when the evaluation target site P is the front part of the frame 21. The front and back in this coordinate system correspond to the front and rear with respect to the loading type truck crane CR. However, the front and back in the coordinate system used for fatigue damage evaluation calculations and the front and back of the mobile crane do not necessarily match.

For example, a plurality of bolts 27c of the swing bearing 27 are provided around the swing center O. The coordinate system changes depending on which bolt 27c is to be evaluated. As shown in FIG. 7, when the bolt 27c placed at position P3 is the evaluation target part, the front and back in the coordinate system used for fatigue damage evaluation calculations do not match the front and back of the loading truck crane CR.

Generally, the turning angle Θ measured by the turning angle measuring device 42 is set to 0° when the boom 23 faces directly in front of the loading type truck crane CR. Therefore, the turning angle θ in the coordinate system used for calculation of fatigue damage evaluation does not necessarily match the turning angle Θ measured by the turning angle measuring device 42. Therefore, the calculation device 40 converts the turning angle Θ measured by the turning angle measuring device 42 into a turning angle θ in the coordinate system based on the relationship between the coordinate system and the orientation of the mobile crane.

As shown in FIG. 8, the arithmetic device 40 performs fatigue damage evaluation of the evaluation target site P in the following steps.
Step S1: Find the stress amplitude ratio of the stress generated in the evaluation target site for each task.
Step S2: Obtain the fatigue damage value for each work from the stress amplitude ratio for each work.
Step S3: Integrate the fatigue damage values for one work to obtain the cumulative fatigue damage value.

Here, "one work" means the crane work from the lifting of the suspended load LO to the landing. The lifting of the suspended load LO means that the suspended load LO hung from the hook 24 rises from a state placed on the ground, loading platform, or the like. Landing of the suspended load LO means that the suspended load LO suspended from the hook 24 is placed on the ground, loading platform, or the like. Therefore, one work can be said to be work while the load of one hanging load LO is applied to the boom 23.

At the start of one work, the boom 23 changes from an unloaded state to a state where the load of the suspended load LO is applied. Further, at the end of one work, the boom 23 changes from the state where the load of the suspended load LO is applied to the no-load state. Therefore, the period of one work can be determined by the change in the lodging moment M measured by the moment measuring device 41.

Each process of steps S1 to S3 will be explained in detail below.

ここで、ｒ_iはｉ番目作業における応力振幅比、Δσ_iはｉ番目作業における評価対象部位Ｐに生じる応力の変動幅、σ_ppは定格応力全振幅を意味する。 (Step S1) The calculation device 40 first calculates the stress amplitude ratio r _i of the stress generated in the evaluation target site P for each task. Here, the "stress amplitude ratio r _i " is the ratio of the fluctuation width Δσ _i of the stress occurring in the evaluation target site P to the total rated stress amplitude σ _pp , as shown in equation (1). "Total amplitude of rated stress _σpp " is the total amplitude (peak-to-peak) of stress that occurs in the evaluation target part P when the boom 23 is rotated 360 degrees under the condition that the rated moment is acting on the boom 23. It is.

Here, r _i is the stress amplitude ratio in the i-th work, Δσ _i is the fluctuation range of stress occurring in the evaluation target part P in the i-th work, and σ _pp is the total amplitude of the rated stress.

The stress amplitude ratio r _i can be determined based on the measured values of the lodging moment M acting on the boom 23 and the swing angle θ of the boom 23 . The stress amplitude ratio r _i is determined by steps S11 to S13 shown in FIG. 9, for example.

ここで、ｆ_iはｉ番目作業における負荷率、Ｍ_iはｉ番目作業における倒伏モーメント、Ｍ_ｃは定格モーメントを意味する。 (Step S11) The calculation device 40 first determines the load factor _fi of the boom 23. As shown in equation (2), the load factor f _i is the ratio of the measured value M _i of the lodging moment to the rated value M _c . Here, the rated moment M _c is the maximum value of the lodging moment M that can act on the boom 23. Generally, the rated moment M _c is the lodging moment M that occurs in the boom 23 when the suspended load LO with the rated load is suspended.

Here, f _i means the load factor in the i-th work, M _i means the lodging moment in the i-th work, and M _c means the rated moment.

The load factor _fi means the ratio of the actual load to the maximum load applied to the boom 23. The maximum value of the load applied to the boom 23 is the load applied when the rated moment _Mc is acting on the boom 23. Therefore, the load factor f _i is determined by equation (2).

(Step S12) Next, the arithmetic device 40 calculates the amplitude rate a _i of the stress generated in the evaluation target region P from the change in the turning angle θ during one work period. The specific calculation method for the amplitude rate a _i differs depending on whether the boom 23 has turned in both the front area FA and the rear area RA, or whether it has turned in one. Hereinafter, the method for calculating the amplitude ratio a _i will be explained in order for each case.

ここで、ａ_iはｉ番目作業における振幅率、θ(t)はｉ番目作業の期間中の時刻ｔにおける旋回角、max{cosθ(t)}はcosθ(t)の最大値、min{cosθ(t)}はcosθ(t)の最小値、σ_fはブーム２３が真正面に向いたときに評価対象部位Ｐに生じる定格応力（定格圧縮応力または定格引張応力）の絶対値、σ_rはブーム２３が真後ろに向いたときに評価対象部位Ｐに生じる定格応力（定格引張応力または定格圧縮応力）の絶対値を意味する。 Case A: When the boom rotates in both the front area and the rear area If the boom 23 rotates in both the front area FA and the rear area RA during one work period, based on equation (3), the amplitude rate a _i can be found.

Here, a _i is the amplitude rate in the i-th work, θ(t) is the turning angle at time t during the i-th work, max{cosθ(t)} is the maximum value of cosθ(t), min{cosθ (t)} is the minimum value of cosθ(t), σ _f is the absolute value of the rated stress (rated compressive stress or rated tensile stress) that occurs in the evaluation target part P when the boom 23 faces directly ahead, and σ _r is the boom It means the absolute value of the rated stress (rated tensile stress or rated compressive stress) that occurs in the evaluation target site P when 23 faces directly backward.

When the evaluation target site P is the front part of the frame 21, etc., in FIG. RA), when the tip of the boom 23 is in the front area FA, compressive stress is generated in the evaluation target region P1. Further, when the tip of the boom 23 is located in the rear region RA, tensile stress is generated in the evaluation target region P1. Note that the opposite may be true depending on the location.

The maximum value of compressive stress that can occur in the evaluation target site P is referred to as "rated compressive stress." The rated compressive stress is the maximum value of the compressive stress that occurs in the evaluation target portion P when the boom 23 is rotated 360° under the condition that the rated moment _Mc is acting on the boom 23. The maximum value of tensile stress that can occur in the evaluation target site P is referred to as "rated tensile stress." The rated tensile stress is the maximum value of the tensile stress that occurs in the evaluation target portion P when the boom 23 is rotated 360° under the condition that the rated moment _Mc is acting on the boom 23.

Case B: When the boom rotates in the front area The load of the suspended load LO is not applied to the boom 23 at the start and end of one operation. The load applied to the boom 23 changes from a no-load state to a loaded state in which the load of the suspended load LO is applied. Therefore, in order to obtain the amplitude rate a _i of the stress occurring in the evaluation target site P, it is necessary to consider the change in stress from the no-load state. Therefore, in case B, the amplitude ratio a _i is determined as follows.

When the boom 23 turns only in the front area FA during one work period, the amplitude rate a _i can be determined based on equation (4).

Case C: When the boom rotates in the rear area Even when the boom rotates in the rear area, it is necessary to consider the change in stress from the no-load state. Therefore, in case C, the amplitude rate a _i is determined as follows.

When the boom 23 turns only in the rear region RA during one work period, the amplitude rate a _i can be determined based on equation (5).

Equations (3) to (5) also assume that the absolute values of the rated compressive stress and rated tensile stress of the evaluation target site P are different. For example, when the evaluation target site P is the front portion, rear portion, etc. of the frame 21, the absolute values of the rated compressive stress and the rated tensile stress may be different. Furthermore, although tensile stress is generated in the bolt 27c of the swing bearing 27 due to the lodging moment M acting on the boom 23, no compressive stress is generated.

In this way, depending on the evaluation target site P, the absolute values of the rated compressive stress and the rated tensile stress may differ. That is, the compressive stress (or tensile stress) when the boom 23 is facing directly forward and the tensile stress (or compressive stress) when the boom 23 is facing directly behind may have different absolute values.

It should be noted that the variations in stress occurring in the evaluation target site P include so-called double swings and single swings. Double swinging means that compressive stress and tensile stress are alternately generated in the evaluation target region P when the boom 23 is rotated. In the case of unilateral swing, the stress generated in the evaluation target site P is either compressive stress or tensile stress. When the boom 23 is rotated, a state in which stress is generated in the evaluation target region P and a state in which the stress is released are alternately generated. For example, tensile stress is generated in bolt 27c of swing bearing 27, but compressive stress is not generated. In the case of such a one-sided swing, either σ _f or σ _r is set to 0 in equations (3), (4), and (5).

Further, depending on the evaluation target site P, the absolute values of the rated compressive stress and the rated tensile stress may be the same. That is, the compressive stress (or tensile stress) when the boom 23 is facing directly forward and the tensile stress (or compressive stress) when the boom 23 is facing directly behind may have the same absolute value. In other words, the condition is σ _f =σ _r .

As shown below, if σ _f =σ _r in equation (3), equation (6) is derived.

Furthermore, as shown below, when σ _f =σ _r , formula (7) is derived from formula (4), and formula (8) is derived from formula (5).

(Step S13) Returning to FIG. 9, explanation will be given. The calculation device 40 multiplies the load factor f _i by the amplitude factor a _i to obtain the stress amplitude ratio r _i , as shown in equation (9).

Note that the total amplitude of rated stress is σ _pp . Therefore, the total amplitude of the stress generated in the evaluation target region P when the boom 23 is rotated 360 degrees under the load factor f _i (the lodging moment M _i is acting on the boom 23) is f _i σ _pp . When the amplitude rate is a _i , the stress fluctuation range Δσ _i is expressed by equation (10).

As shown below, by substituting equation (10) for Δσ _i in equation (1), equation (9) is obtained. That is, equation (1) and equation (9) are synonymous.

The method described in steps S11 to S13 above is based on the premise that the lodging moment M _i acting on the boom 23 does not change during one work period. However, when the working radius of the boom 23 changes, the lodging moment M _i increases or decreases. Therefore, the stress amplitude ratio r _i may be calculated by taking into account the time change of the lodging moment M _i during one work period.

ここで、ｄ_iはｉ番目作業における一作業疲労損傷値、αは所定の定数を意味する。 (Step S2) Returning to FIG. 8, explanation will be given. The calculation device 40 calculates the one-work fatigue damage value d _i from the stress amplitude ratio r _i . The one-work fatigue damage value is determined based on, for example, equation (11).

Here, d _i means a one-work fatigue damage value in the i-th work, and α means a predetermined constant.

JIS B 8822-1:2001 stipulates that when calculating the load spectrum coefficient K _p of a crane, the magnitude of each load (load level) P _i during use of the crane is calculated from the maximum load (rated) that the crane is expected to handle. Load) It is described that the value obtained by dividing the value (P _i /P _max ) by P _max to the third power is used. If we follow this example, we should set α=3. However, considering test results, safety factors, etc., α may be set to other values.

(Step S3) Next, the calculation device 40 calculates the cumulative fatigue damage value D by integrating the one-work fatigue damage values d _i in a predetermined period, as shown in equation (12). That is, the cumulative fatigue damage value D is determined by integrating the fatigue damage values d _i obtained for each work from the m-th work to the n-th work.

The period (at the start and at the end) for accumulating the fatigue damage value d _i for one work can be arbitrarily determined. For example, the accumulation period can be set as one hour, one day, one month, or one year. The arithmetic unit 40 performs steps S1 to S3 for each task, and repeats this process during the integration period. Thereby, the cumulative fatigue damage value D accumulated in the evaluation target site P during the integration period can be determined.

The calculated cumulative fatigue damage value D may be displayed on a screen, or may be transferred as data to another device.

According to the present embodiment, since the cumulative fatigue damage value D is determined based on the stress amplitude ratio r _i that takes into account the swing angle θ of the boom, the fatigue damage of the evaluation target region P can be evaluated with high accuracy. If the front part or the rear part of the frame is selected as the evaluation target part P, fatigue damage in the front part or the rear part of the frame can be evaluated with high accuracy. If the tip of the outrigger outer box is selected as the evaluation target site P, fatigue damage to the outrigger outer box can be evaluated with high accuracy. If the bolt that fixes the swing bearing to the frame is selected as the evaluation target part P, fatigue damage of the bolt can be evaluated with high accuracy.

[Second embodiment]
Next, a fatigue damage evaluation apparatus AA according to a second embodiment of the present invention will be explained.
The various members that make up a mobile crane accumulate fatigue damage as they are used, and eventually breakage occurs. If it is possible to detect the end of a member's lifespan before it is damaged, maintenance such as repair or replacement can be performed. The fatigue damage evaluation apparatus AA of this embodiment detects the end of the life of the evaluation target site P.

As shown in FIG. 10, the calculation device 40 calculates the stress amplitude ratio (step S1), the one-work fatigue damage value (step S2), and the cumulative fatigue damage value (step S3). Since these are the same as those in the first embodiment, their explanation will be omitted.

In this embodiment, the calculation device 40 calculates the cumulative fatigue damage value D of the evaluation target site P from the start of use to the present. That is, the arithmetic device 40 performs the processing from steps S1 to S3 for each task, and repeats this process from the time the evaluation target site P starts to be used until the present time.

Then, each time the cumulative fatigue damage value D is calculated (each time a new one-work fatigue damage value d _i is added), the cumulative fatigue damage value D is compared with the life threshold T (step S4). The lifespan threshold T is a value predetermined for the evaluation target site P. The lifespan threshold T is determined by tests and the like. If the cumulative fatigue damage value D does not exceed the lifespan threshold T, the process returns to step S1.

When the cumulative fatigue damage value D exceeds the lifespan threshold T, the calculation device 40 determines that the lifespan of the evaluation target part P has come. In this case, the arithmetic device 40 issues an alarm to notify the user that the life span has come to an end (step S5). The warning means is not particularly limited, but examples include lighting of an indicator lamp, screen display, and sound.

According to the present embodiment, it is possible to detect that the life of the evaluation target part P has come to an end, so that maintenance can be prompted at an appropriate time depending on the usage state of the mobile crane. Therefore, the user can perform effective maintenance to maintain the quality of the mobile crane.

CR Loading truck crane 10 General-purpose truck 20 Small crane 21 Frame 22 Swivel base 23 Boom 27 Swing bearing 30 Outrigger device 31 Outrigger inner box 32 Outrigger jack AA Fatigue damage evaluation device 40 Arithmetic device 41 Moment measuring device 42 Swivel angle measuring device

Claims (11)

A fatigue damage evaluation device for a mobile crane, comprising a lower structure including a portion to be evaluated, a swivel mounted on the lower structure, and a boom provided on the swivel,
a moment measuring device that measures the lodging moment acting on the boom;
a swing angle measuring device that measures the swing angle of the boom;
an arithmetic device into which the measured values of the moment measuring device and the turning angle measuring device are input,
The arithmetic device is
For each operation from the lifting of the suspended load to the landing, calculate the stress amplitude ratio, which is the ratio of the range of stress variation occurring in the evaluation target area to the total amplitude of the rated stress, based on the measured values of the lodging moment and the turning angle. , determine the one-work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation device characterized in that a cumulative fatigue damage value is obtained by integrating the fatigue damage values for one work over a predetermined period. The arithmetic device is
Determine the load factor, which is the ratio of the measured value of the lodging moment to the rated value,
Determining the amplitude rate of stress occurring in the evaluation target part from the change in the turning angle during the period of the one work,
2. The fatigue damage evaluation device according to claim 1, wherein the stress amplitude ratio is obtained by multiplying the load factor by the amplitude factor. The arithmetic device is
Determining the cumulative fatigue damage value from the start of use of the evaluation target part to the present,
Fatigue damage according to claim 1 or 2, characterized in that it is determined that the life of the evaluation target region has reached when the cumulative fatigue damage value exceeds a life threshold value determined for the evaluation target region. Evaluation device. The fatigue damage evaluation device according to any one of claims 1 to 3, wherein the evaluation target portion is a front portion or a rear portion of a frame on which the swivel table is mounted. 4. The fatigue damage evaluation device according to claim 1, wherein the evaluation target portion is a bolt that fixes a slewing bearing interposed between the swivel base and the frame to the frame. Fatigue for making a computer function to evaluate fatigue damage of a mobile crane that has a lower structure including a part to be evaluated, a swivel mounted on the lower structure, and a boom installed on the swivel. A damage assessment program, comprising:
measurements of a lodging moment acting on the boom and a swing angle of the boom are input;
For each operation from the lifting of the suspended load to the landing, calculate the stress amplitude ratio, which is the ratio of the range of stress variation occurring in the evaluation target area to the total amplitude of the rated stress, based on the measured values of the lodging moment and the turning angle. , determine the one-work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation program characterized by causing a computer to function so as to calculate a cumulative fatigue damage value by integrating the fatigue damage values for one work over a predetermined period. Determine the load factor, which is the ratio of the measured value of the lodging moment to the rated value,
Determining the amplitude rate of stress occurring in the evaluation target part from the change in the turning angle during the period of the one work,
7. The fatigue damage evaluation program according to claim 6, wherein the computer is operated to calculate the stress amplitude ratio by multiplying the load rate by the amplitude rate. Determining the cumulative fatigue damage value from the start of use of the evaluation target part to the present,
Claim 6, characterized in that the computer is operated to determine that the life span of the evaluation target region has reached when the cumulative fatigue damage value exceeds a life threshold value determined for the evaluation target region. or the fatigue damage evaluation program described in 7. A fatigue damage evaluation method for a mobile crane having a lower structure including a portion to be evaluated, a swivel mounted on the lower structure, and a boom provided on the swivel, the method comprising:
measuring the lodging moment acting on the boom;
measuring the swing angle of the boom;
For each operation from the lifting of the suspended load to the landing, calculate the stress amplitude ratio, which is the ratio of the range of stress variation occurring in the evaluation target area to the total amplitude of the rated stress, based on the measured values of the lodging moment and the turning angle. , determine the one-work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation method, characterized in that a cumulative fatigue damage value is determined by summing the fatigue damage values for one work over a predetermined period. Determine the load factor, which is the ratio of the measured value of the lodging moment to the rated value,
Determining the amplitude rate of stress occurring in the evaluation target part from the change in the turning angle during the period of the one work,
10. The fatigue damage evaluation method according to claim 9, wherein the stress amplitude ratio is determined by multiplying the load rate by the amplitude rate. Determining the cumulative fatigue damage value from the start of use of the evaluation target part to the present,
Fatigue damage according to claim 9 or 10, characterized in that it is determined that the life of the evaluation target region has come when the cumulative fatigue damage value exceeds a life threshold value determined for the evaluation target region. Evaluation method.