JP2021187663A - Device, program, and method for evaluating fatigue damage of mobile crane - Google Patents

Abstract

To provide a fatigue damage evaluation device that can accurately evaluate fatigue damage of components of a mobile crane.SOLUTION: A fatigue damage evaluation device AA comprises: a moment measuring device 41 that measures a falling moment acting on a boom; a turning angle measuring device 42 that measures a turning angle of the boom; and an arithmetic unit 40 to which measured values of the moment measuring device 41 and the turning angle measuring device 42 are input. The arithmetic unit 40 obtains a stress amplitude ratio which is a ratio of a fluctuation range of stress generated in an evaluation object portion to the total amplitude of rated stress on the basis of the measured values of the falling moment and the turning angle, for each work from the lift-off to the landing of a suspended load, obtains a one-work fatigue damage value from the stress amplitude ratio, integrates the one-work fatigue damage value in a predetermined period, and obtains a cumulative fatigue damage value.SELECTED DRAWING: Figure 5

Description

The present invention relates to a fatigue damage evaluation device for a mobile crane, a fatigue damage evaluation program, and a fatigue damage evaluation method. More specifically, the present invention relates to devices, programs and methods for assessing fatigue damage to the substructure of a mobile crane.

The arrival of maintenance time for the components of mobile cranes may be determined based on the amount of work. For example, Patent Document 1 discloses that the amount of damage to the lower traveling body of a wheel crane is calculated. When carrying out port cargo handling, the crane device repeats the work within a turning range of about 90 degrees. Therefore, four turning ranges are provided around the turning center of the upper turning 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 for each turning range is uniform. By doing so, it is possible to prevent the member at a specific position of the lower traveling body from being fatigued and broken at an early stage.

Japanese Unexamined Patent Publication No. 2013-107762

In the case of a mobile crane, the stress generated in the member supporting the swivel table varies greatly depending on the swivel angle of the boom. However, in the prior art, fatigue damage is not evaluated in consideration of the turning angle of the boom, and the evaluation accuracy is low.

In view of the above circumstances, it is an object of the present invention to provide a fatigue damage evaluation device, a fatigue damage evaluation program, and a fatigue damage evaluation method capable of accurately evaluating fatigue damage of components of a mobile crane.

The fatigue damage evaluation device of the first invention evaluates fatigue damage of a mobile crane having a substructure including an evaluation target portion, a swivel mounted on the substructure, and a boom provided on the swivel. In the device, a moment measuring device for measuring the lodging moment acting on the boom, a turning angle measuring device for measuring the turning angle of the boom, and measured values of the moment measuring device and the turning angle measuring device are input. The calculation device is provided with a calculation device, and the calculation device has a fluctuation range of stress generated in the evaluation target portion based on the measured values of the lodging moment and the turning angle for each operation from the ground cutting to the landing of the suspended load. The feature is that the stress amplitude ratio, which is the ratio to the total rated stress amplitude, is obtained, the one-work fatigue damage value is obtained from the stress amplitude ratio, and the one-work fatigue damage value in a predetermined period is integrated to obtain the cumulative fatigue damage value. And.
In the first invention, the fatigue damage evaluation device of the second invention obtains a load factor, which is a ratio of the measured value of the lodging moment to the rated value, from the change of the turning angle in the one work period. It is characterized in that the amplitude ratio of the stress generated in the evaluation target portion is obtained, and the stress amplitude ratio is obtained by multiplying the load factor by the amplitude ratio.
In the first or second invention, the fatigue damage evaluation device of the third invention obtains the cumulative fatigue damage value from the start of use of the evaluation target site to the present, and the cumulative fatigue damage value is the said. It is characterized in that it is determined that the life of the evaluation target site has reached the end when the life threshold determined for the evaluation target site is exceeded.
The fatigue damage evaluation device of the fourth invention is characterized in that, in any one of the first to third inventions, the evaluation target portion is a front portion or a rear portion of a frame on which the swivel table is mounted.
In any one of the first to third inventions, the fatigue damage evaluation device of the fifth invention indicates that the evaluation target portion is a bolt that fixes a swivel bearing interposed between the swivel table and the frame to the frame. It is a feature.
The fatigue damage evaluation program of the sixth invention is a fatigue damage evaluation of a mobile crane having a substructure including an evaluation target site, a swivel mounted on the substructure, and a boom provided on the swivel. It is a fatigue damage evaluation program to make the computer function so that the measured values of the lodging moment acting on the boom and the turning angle of the boom are input, and each work from the ground cutting to the landing of the suspended load is performed. Based on the measured values of the lodging moment and the turning angle, the stress amplitude ratio, which is the ratio of the fluctuation range of the stress generated in the evaluation target site to the total rated stress amplitude, is obtained, and the one-work fatigue damage value is obtained from the stress amplitude ratio. It is characterized in that the computer functions so as to accumulate the one-work fatigue damage values in a predetermined period and obtain the cumulative fatigue damage values.
In the sixth invention, the fatigue damage evaluation program of the seventh invention obtains a load factor which is a ratio of the measured value of the lodging moment to the rated value, and changes the turning angle during the one work period to the evaluation target portion. It is characterized in that the computer functions so as to obtain the amplitude ratio of the generated stress and to obtain the stress amplitude ratio by multiplying the load factor by the amplitude ratio.
In the sixth or seventh invention, the fatigue damage evaluation program of the eighth invention obtains the cumulative fatigue damage value from the start of use of the evaluation target site to the present, and the cumulative fatigue damage value is the evaluation target site. It is characterized in that the computer functions so that it is determined that the life of the evaluation target portion has reached the end of the life when the life threshold defined above is exceeded.
The fatigue damage evaluation method of the ninth invention is a fatigue damage evaluation of a mobile crane having a substructure including an evaluation target portion, a swivel mounted on the substructure, and a boom provided on the swivel. In the method, the lodging moment acting on the boom is measured, the turning angle of the boom is measured, and the measured values of the lodging moment and the turning angle are used for each operation from the ground cutting to the landing of the suspended load. Based on this, the stress amplitude ratio, which is the ratio of the fluctuation range of the stress generated in the evaluation target site to the total rated stress amplitude, is obtained, the one-work fatigue damage value is obtained from the stress amplitude ratio, and the one-work fatigue damage value in a predetermined period is integrated. Then, the cumulative fatigue damage value is obtained.
In the ninth invention, the fatigue damage evaluation method of the tenth invention obtains a load factor which is a ratio of the measured value of the lodging moment to the rated value, and changes in the turning angle during the one work period to the evaluation target portion. It is characterized in that the amplitude ratio of the generated stress is obtained, and the stress amplitude ratio is obtained by multiplying the load factor by the amplitude ratio.
In the ninth or tenth invention, the fatigue damage evaluation method of the eleventh invention obtains the cumulative fatigue damage value from the start of use of the evaluation target site to the present, and the cumulative fatigue damage value is the evaluation target site. It is characterized in that it is determined that the life of the evaluation target portion has reached the end of the life when the life threshold defined above is exceeded.

According to the first and second inventions, since the cumulative fatigue damage value is obtained based on the stress amplitude ratio in consideration of the turning angle of the boom, the fatigue damage of the evaluation target portion can be evaluated accurately.
According to the third invention, since it is possible to detect that the life of the evaluation target portion has reached the end of its life, maintenance can be promoted at an appropriate time.
According to the fourth invention, the fatigue damage of the front portion or the rear portion of the frame can be accurately evaluated.
According to the fifth invention, the fatigue damage of the bolt fixing the swivel bearing can be accurately evaluated.
According to the sixth and seventh inventions, since the cumulative fatigue damage value is obtained based on the stress amplitude ratio in consideration of the turning angle of the boom, the fatigue damage of the evaluation target portion can be evaluated accurately.
According to the eighth invention, since it is possible to detect that the life of the evaluation target portion has reached the end of its life, maintenance can be promoted at an appropriate time.
According to the ninth and tenth inventions, since the cumulative fatigue damage value is obtained based on the stress amplitude ratio in consideration of the turning angle of the boom, the fatigue damage of the evaluation target portion can be evaluated accurately.
According to the eleventh invention, since it is possible to detect that the life of the evaluation target portion has reached the end of its life, maintenance can be promoted at an appropriate time.

It is a side view of a loading type truck crane. It is a front view of the outrigger device. It is a top view of the outrigger device. It is a vertical sectional view of a swivel bearing. It is a block diagram of the fatigue damage evaluation apparatus which concerns on 1st Embodiment. It is explanatory drawing of the coordinate system used for the calculation of fatigue damage evaluation. It is explanatory drawing of the coordinate system used for the calculation of the fatigue damage evaluation in another example. It is a flowchart of the fatigue damage evaluation process in 1st Embodiment. It is a flowchart of stress amplitude ratio calculation. It is a flowchart of the fatigue damage evaluation process in 2nd Embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
(Mobile crane)
The fatigue damage evaluation device according to the first embodiment of the present invention is used to evaluate the 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 loaded truck cranes. Hereinafter, the case of a loaded truck crane will be described as an example.

As shown in FIG. 1, the load-type truck crane CR has a general-purpose truck 10. A driver's cab 11 is provided in the front portion of the general-purpose truck 10, and a loading platform 12 is provided in the rear portion. 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 provided on the frame 21 so as to be swivelable. A boom 23 is provided on the upper end of the swivel table 22 so as to be undulating. A winch is built in the swivel table 22. The wire rope extended from this winch is guided to the tip of the boom 23. The wire rope is hung around a pulley provided at the tip of the boom 23 and the hook 24. As a result, the hook 24 is suspended from the tip of the boom 23. A suspended 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 an operating lever group 25 for operating a hydraulic circuit. The operator can operate the small crane 20 by using the operation lever group 25.

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

The small crane 20 may have a remote control terminal capable of bidirectional communication with the control device 26. The remote control terminal may be a wireless control terminal such as a so-called radio-controlled transmitter, or may be a wired control terminal. The operator can operate the small crane 20 by using the remote control terminal.

The small crane 20 has an outrigger device 30. As shown in FIG. 2, the frame 21 has a horizontally arranged tubular portion. The tubular portion is a tubular member having a substantially rectangular cross section, and both ends are open. Outrigger inner boxes 31 are inserted into the openings at both ends of the cylinder. 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 the left and right sides of the loaded truck crane CR.

The outrigger device 30 is projected when the crane work is performed. To project the outrigger device 30, the outrigger inner box 31 is pulled out from the cylinder 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 part of the weight of the loaded truck crane CR is applied to the outrigger device 30. This supports the loaded 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 pulled into the cylinder.

As shown in FIG. 4, a swivel bearing 27 is interposed between the frame 21 and the swivel base 22. The swivel 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 turn with respect to the inner ring 27b.

The swivel base 22 is fixed to the outer ring 27a by a plurality of bolts. Further, the inner ring 27b is fixed to the top plate 21a of the frame 21 by 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 swivel with respect to the frame 21.

The swivel bearing 27 is provided with a drive device 28. The drive device 28 has a hydraulic motor 28a. The rotating shaft of the hydraulic motor 28a is connected to the pinion gear 28c via the speed reducer 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 meshed with each other. When the hydraulic motor 28a is driven, the pinion gear 28c rotates and the outer ring 27a turns with respect to the inner ring 27b. As a result, the swivel table 22 turns.

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, if the pinion gear 28c is meshed with the gear formed on the inner peripheral surface of the inner ring 27b, the swivel base 22 can be swiveled by the drive of the hydraulic motor 28a.

The "frame" described in the claims may be any part as long as it is a part on which the swivel is mounted, and is not limited to the frame 21 of the loading type truck crane CR. For example, a frame of a lower traveling body such as an all-terrain crane, a rough terrain crane, or a truck crane also corresponds to the "frame" described in the claims.

The "substructure" described in the claims may be a structure on which a swivel base is mounted. In the case of the present embodiment, in addition to the frame 21, the outrigger device 30 is also a part of the lower structure. Lower traveling bodies such as all-terrain cranes, rough terrain cranes, and truck cranes also correspond to the "substructure" described in the claims.

The "swivel table" described in the claims is not limited to the swivel table 22 of the present embodiment. The swivel table 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 the present embodiment will be described.
As shown in FIG. 5, the fatigue damage evaluation device AA has an arithmetic unit 40. The arithmetic unit 40 is a computer composed of a CPU, a memory, and the like. By installing the fatigue damage evaluation program on the computer, the function as the arithmetic unit 40 is realized. The fatigue damage assessment program can be stored in a variety of computer-readable storage media. The arithmetic unit 40 may be realized as one function of the control device 26 for controlling the hydraulic circuit of the small crane 20. Further, the arithmetic unit 40 and the control device 26 may be different devices.

The fatigue damage evaluation device AA has a moment measuring device 41 for measuring 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 own weight of the boom 23. The configuration of the moment measuring device 41 is not particularly limited, and examples thereof include a configuration in which the hydraulic pressure in the hydraulic cylinder that raises and lowers the boom 23 is measured by a pressure sensor. Further, a load measuring device that obtains the load W of the suspended load LO from the tension of the wire rope that suspends the hook 24, a length measuring device that measures the length L of the boom 23, and an undulating angle measurement that measures the undulating angle φ of the boom 23. The moment measuring device 41 may be configured from the device. The lodging moment M can be obtained from the load W of the suspended load LO, the length L of the boom 23, and the undulation angle φ.

The fatigue damage evaluation device AA has a turning angle measuring device 42 for measuring the turning angle Θ of the boom 23. The configuration of the swivel angle measuring instrument 42 is not particularly limited, and examples thereof include a configuration in which the swivel angle Θ of the boom 23 is discretely detected by a plurality of proximity switches provided on the frame 21 or the swivel table 22. Further, there is a configuration in which the rotation angle of the swivel table 22 is read by a potentiometer.

The measured values M and Θ of the moment measuring device 41 and the turning angle measuring device 42 are input to the arithmetic unit 40. The arithmetic unit 40 evaluates fatigue damage based on the lodging moment M and the turning angle Θ.

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

The front portion of the frame 21 is, for example, the portion of 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 by the lodging moment M acting on the boom 23. For example, when the boom 23 turns forward, compressive stress is generated in the front portion P1. When the boom 23 turns backward, tensile stress is generated in the front portion P1. The opposite may be true depending on the position of the front portion P1.

A load is also generated on the rear portion P2 of the frame 21 by the lodging moment M acting on the boom 23. For example, when the boom 23 turns forward, tensile stress is generated in the rear portion P2. When the boom 23 turns backward, compressive stress is generated in the rear portion P2. The opposite may be true depending on the position of the rear portion P2.

As shown in FIG. 4, a selected bolt 27c for fixing the swivel bearing 27 to the frame 21 can be used as the evaluation target portion P3. Tensile stress generated by fastening is generated in the bolt P3. When the boom 23 turns to the side opposite to the position of the bolt P3, the tensile stress generated in the bolt P3 becomes large. When the boom 23 turns 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 the calculation of fatigue damage evaluation is defined with reference to the position of the evaluation target portion P in the horizontal plane. Let O be the turning center of the boom 23. The horizontal line passing through the turning center O of the boom 23 and the evaluation target portion P is defined as the reference line BL. The horizontal line passing through the turning center O of the boom 23 and perpendicular to the reference line BL is defined as the fractionation line DL. The region on the evaluation target site P side from the fraction line DL is defined as the anterior region FA. The region opposite to the evaluation target site P from the fraction line DL is designated as the posterior region RA.

Let θ be the turning angle of the boom 23 in this coordinate system. The direction of the evaluation target portion P with respect to the turning center O of the boom 23 is referred to as "directly in front". The direction opposite to the evaluation target portion P with respect to the turning center O of the boom 23 is referred to as "immediately behind". The turning angle θ is 0 ° when the boom 23 faces directly in front.

Note that FIG. 6 shows a coordinate system when the evaluation target portion P is the front portion of the frame 21. The front and back in this coordinate system coincide with the front and back with respect to the loaded truck crane CR. However, the front and back in the coordinate system used for the calculation of fatigue damage evaluation and the front and back of the mobile crane do not always match.

For example, a plurality of bolts 27c of the swivel bearing 27 are provided around the swivel center O. The coordinate system changes depending on which bolt 27c is targeted for evaluation. As shown in FIG. 7, when the bolt 27c arranged at the position P3 is used as the evaluation target site, the front and rear in the coordinate system used for the calculation of fatigue damage evaluation and the front and back of the loaded truck crane CR do not match.

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 loaded truck crane CR. Therefore, the turning angle θ in the coordinate system used for the calculation of fatigue damage evaluation and the turning angle Θ measured by the turning angle measuring device 42 do not always match. Therefore, the arithmetic unit 40 converts the turning angle Θ measured by the turning angle measuring device 42 into the turning angle θ in the coordinate system based on the relationship between the coordinate system and the direction of the mobile crane.

As shown in FIG. 8, the arithmetic unit 40 roughly evaluates the fatigue damage of the evaluation target portion P by the following procedure.
Step S1: Obtain the stress amplitude ratio of the stress generated in the evaluation target site for each work.
Step S2: Obtain one work fatigue damage value from the stress amplitude ratio for each work.
Step S3: One work fatigue damage value is integrated to obtain the cumulative fatigue damage value.

Here, "one work" means a crane work from the ground cutting to the landing of the suspended load LO. The ground cutting of the suspended load LO means that the suspended load LO slung on the hook 24 is lifted from the state where it is placed on the ground, the loading platform, or the like. The landing of the suspended load LO means that the suspended load LO suspended from the hook 24 is placed on the ground, a loading platform, or the like. Therefore, it can be said that one work is a work while the load of one suspended load LO is applied to the boom 23.

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

Hereinafter, each process of steps S1 to S3 will be described in detail.

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) First, the arithmetic unit 40 obtains the stress amplitude ratio r _i of the stress generated in the evaluation target portion P for each work. Here, the “stress amplitude ratio r _i ” is, as shown in the equation (1), a ratio of _{the fluctuation range Δσ i} of the stress generated in the evaluation target portion P to the rated stress total amplitude σ _pp. "Rated stress total amplitude σ _pp " is the total amplitude (peak to peak) of the stress generated in the evaluation target site P when the boom 23 is swiveled 360 ° under the condition that the rated moment is acting on the boom 23. Is.

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

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

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) First, the arithmetic unit 40 _{obtains the load factor f i} of the boom 23. As shown in the equation (2), the load factor f _i is a 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 a lodging moment M generated in the boom 23 when the suspended load LO of the rated load is suspended.

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

The load factor f _i means the ratio of the actual load to the maximum value of the 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 can be obtained by the equation (2).

(Step S12) Next, the arithmetic unit 40 obtains _{the amplitude factor a i of the} stress generated in the evaluation target portion P from the change in the turning angle θ in one work period. The specific calculation method of the amplitude factor a _i differs depending on whether the boom 23 has swiveled in both the front region FA and the rear region RA, or one of them. Hereinafter, the calculation method of the amplitude factor a _i will be described 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 swivels in both the anterior and posterior regions When the boom 23 swivels across both the anterior region FA and the posterior region RA during a period of work, the amplitude factor is based on equation (3). a _i can be obtained.

Here, a _i is the amplitude factor in the i-th work, θ (t) is the turning angle at time t during the i-th work, max {cos θ (t)} is the maximum value of cos θ (t), and min {cos θ. (t)} is the minimum value of cos θ (t), σ _f is the absolute value of the rated stress (rated compressive stress or rated tensile stress) generated at the evaluation target site P when the boom 23 faces directly in front, and σ _r is the boom. It means the absolute value of the rated stress (rated tensile stress or rated compressive stress) generated in the evaluation target portion P when 23 faces directly behind.

When the evaluation target portion P is the front portion of the frame 21 or the like, in FIG. 3 (when the evaluation target portion P is the front portion P1 of the frame 21, the left side of FIG. 3 is the front region FA and the right side is the rear region. RA.) When the tip of the boom 23 is in the front region FA, compressive stress is generated in the evaluation target portion P1. Further, when the tip portion of the boom 23 is in the rear region RA, tensile stress is generated in the evaluation target portion P1. The opposite may be true depending on the site.

The maximum value of the compressive stress that can occur in the evaluation target portion P is called "rated compressive stress". The rated compressive stress is the maximum value of the compressive stress generated in the evaluation target portion P when the boom 23 is swiveled by 360 ° under the condition that the _{rated moment Mc is acting on the boom 23.} The maximum value of the tensile stress that can occur in the evaluation target portion P is called "rated tensile stress". The rated tensile stress is the maximum value of the tensile stress generated in the evaluation target portion P when the boom 23 is swiveled by 360 ° under the condition that the _{rated moment Mc is acting on the boom 23.}

Case B: When the boom turns in the front region The load of the suspended load LO is not applied to the boom 23 at the start and end of one work. The load applied to the boom 23 changes from the no-load state to the loaded state in which the suspended load LO is applied. _{Therefore, in order to obtain the amplitude factor ai of the} stress generated in the evaluation target portion P, it is necessary to consider the change in stress from the no-load state. Therefore, in Case B, the amplitude factor a _i is obtained as follows.

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

Case C: When the boom turns in the rear region Even when the boom turns in the rear region, it is necessary to consider the change in stress from the no-load state. Therefore, in Case C, the amplitude factor a _i is obtained as follows.

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

Equations (3) to (5) also assume that the absolute values of the rated compressive stress and the rated tensile stress of the evaluation target portion P are different. For example, when the evaluation target portion P is a front portion, a rear portion, or the like of the frame 21, the absolute values of the rated compressive stress and the rated tensile stress may differ. Further, the bolt 27c of the swivel bearing 27 has a tensile stress due to the lodging moment M acting on the boom 23, but no compressive stress.

As described above, the absolute values of the rated compressive stress and the rated tensile stress may differ depending on the evaluation target portion P. That is, the absolute value may differ between the compressive stress (or tensile stress) when the boom 23 is directed directly in front and the tensile stress (or compressive stress) when the boom 23 is directed directly behind.

The fluctuation of stress generated in the evaluation target portion P includes so-called double swing and single swing. The double swing means that when the boom 23 is swiveled, compressive stress and tensile stress are alternately generated in the evaluation target portion P. In the case of one-sided swing, the stress generated in the evaluation target portion P is either compressive stress or tensile stress. When the boom 23 is swiveled, a state in which stress is generated in the evaluation target portion P and a state in which the stress is released alternately occur. For example, the bolt 27c of the swivel bearing 27 has a tensile stress but no compressive stress. In the case of such a one-sided swing, any one of σ _f and σ _r is set to 0 in the equations (3), (4), and (5).

Further, depending on the evaluation target portion P, the absolute values of the rated compressive stress and the rated tensile stress may be the same. That is, the absolute value may be the same between the compressive stress (or tensile stress) when the boom 23 is directed directly in front and the tensile stress (or compressive stress) when the boom 23 is directed directly behind. That is, the condition _{is σ f} = σ _r.

_{As shown below, if} σ f = σ _r in the equation (3), the equation (6) is derived.

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

(Step S13) A description will be given by returning to FIG. As shown in the equation (9), the arithmetic unit 40 _{multiplies the load factor f i} by the amplitude factor a _i to obtain the stress amplitude ratio r _i .

The total amplitude of the rated stress is σ _pp . Therefore, the total amplitude of the stress generated in the evaluation target portion P when the boom 23 is swiveled 360 ° under the load factor f _i (the lodging moment M _{i acts on the boom 23) is f i} σ _pp . Assuming that the amplitude factor is a _i , the stress fluctuation width Δσ _i is expressed by Eq. (10).

As shown below, _{by substituting the equation (10) into Δσ i} of the equation (1), the equation (9) is obtained. That is, the equation (1) and the equation (9) are synonymous.

The method described in the above steps S11 to S13 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 obtained in consideration of 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) Return to FIG. 8 for explanation. The arithmetic unit 40 obtains one work fatigue damage value d _{i from the stress amplitude ratio r i} . (1) The work fatigue damage value is obtained, for example, based on the equation (11).

Here, d _i one work fatigue damage value in the i-th task, alpha denotes a predetermined constant.

JIS B 8822-1: The 2001, when determining the load spectrum factor _{K p} of the crane, the maximum load (rating magnitude of individual loads during use of the crane (load level) P _i is expected that the crane is handled (Load) It is described that the value obtained by dividing by _{P max (P i} / P _{max) is cubed.} If this is followed, α = 3 may be set. However, α may be set to another value in consideration of the test result, the safety factor, and the like.

(Step S3) Then, the arithmetic unit 40, as shown in equation (12), obtains the cumulative fatigue damage value D by integrating one work fatigue damage value d _i in a predetermined period. That is, from the m-th work to the n-th work, the one-work fatigue damage value d _i obtained for each work is integrated to obtain the cumulative fatigue damage value D.

(1) The period for accumulating the work fatigue damage value d _i (at the start and at the end) can be arbitrarily determined. For example, the accumulation period can be set to 1 hour, 1 day, 1 month or 1 year. The arithmetic unit 40 performs the processes of steps S1 to S3 for each work, and repeats this process during the integration period. As a result, the cumulative fatigue damage value D accumulated in the evaluation target site P during the integration period can be obtained.

The obtained cumulative fatigue damage value D may be displayed on the screen or may be transferred to another device as data.

_{According to the present embodiment, since the cumulative fatigue damage value D is obtained based on the stress amplitude ratio r i} considering the turning angle θ of the boom, the fatigue damage of the evaluation target portion P can be evaluated accurately. If the front part or the rear part of the frame is selected as the evaluation target part P, the fatigue damage of the front part or the rear part of the frame can be evaluated accurately. If the tip of the outrigger outer box is selected as the evaluation target portion P, the fatigue damage of the outrigger outer box can be evaluated accurately. If a bolt for fixing the swivel bearing to the frame is selected as the evaluation target portion P, the fatigue damage of the bolt can be evaluated accurately.

[Second Embodiment]
Next, the fatigue damage evaluation device AA according to the second embodiment of the present invention will be described.
The various members that make up a mobile crane accumulate fatigue damage as they are used, which in turn leads to damage. If it is possible to detect the end of life before the member is damaged, maintenance such as repair and replacement can be performed. The fatigue damage evaluation device AA of the present embodiment detects the end of the life of the evaluation target portion P.

As shown in FIG. 10, the arithmetic unit 40 performs a stress amplitude ratio calculation (step S1), a one-work fatigue damage value calculation (step S2), and a cumulative fatigue damage value calculation (step S3). Since these are the same as those of the first embodiment, the description thereof will be omitted.

In the present embodiment, the arithmetic unit 40 obtains the cumulative fatigue damage value D from the start of use of the evaluation target portion P to the present. That is, the arithmetic unit 40 performs the processes of steps S1 to S3 for each work, and repeats this from the start of use of the evaluation target portion P to the present.

Every time determining cumulative fatigue damage value D (time for adding the new one work fatigue damage value d _i), and compares the cumulative fatigue damage value D and life threshold value T (step S4). The life threshold T is a predetermined value for the evaluation target portion P. The life threshold T is determined by a test or the like. If the cumulative fatigue damage value D does not exceed the life threshold T, the process returns to step S1.

When the cumulative fatigue damage value D exceeds the life threshold value T, the arithmetic unit 40 determines that the life of the evaluation target portion P has reached the end. In this case, the arithmetic unit 40 issues an alarm to notify the user of the end of the service life (step S5). The means of the alarm is not particularly limited, and examples thereof include lighting of an indicator lamp, screen display, and voice.

According to the present embodiment, since it is possible to detect that the life of the evaluation target portion P has reached the end of its life, maintenance can be promoted at an appropriate time according to the usage state of the mobile crane. Therefore, the user can perform effective maintenance to maintain the quality of the mobile crane.

CR loading type truck crane 10 general-purpose truck 20 small crane 21 frame 22 swivel table 23 boom 27 swivel bearing 30 outrigger device 31 outrigger inner box 32 outrigger jack AA fatigue damage evaluation device 40 arithmetic unit 41 moment measuring device 42 swivel angle measuring device

Claims (11)

A fatigue damage evaluation device for a mobile crane having a substructure including an evaluation target site, a swivel mounted on the substructure, and a boom provided on the swivel.
A moment measuring device that measures the lodging moment acting on the boom,
A swivel angle measuring device that measures the swivel angle of the boom,
The moment measuring device and the arithmetic unit for inputting the measured values of the turning angle measuring device are provided.
The arithmetic unit is
For each work from ground cutting to landing of the suspended load, the stress amplitude ratio, which is the ratio of the fluctuation range of the stress generated in the evaluation target site to the total rated stress amplitude, is obtained based on the measured values of the lodging moment and the turning angle. , Obtain one work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation device characterized in that the cumulative fatigue damage value is obtained by integrating the one-work fatigue damage values in a predetermined period. The arithmetic unit is
Obtain the load factor, which is the ratio of the measured value of the lodging moment to the rated value.
The amplitude factor of the stress generated in the evaluation target site was obtained from the change in the turning angle during the one work period.
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 unit is
The cumulative fatigue damage value from the start of use of the evaluation target site to the present is obtained.
The fatigue damage according to claim 1 or 2, wherein when the cumulative fatigue damage value exceeds the life threshold determined for the evaluation target site, it is determined that the life of the evaluation target site has reached the end. 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 base is mounted. The fatigue damage evaluation device according to any one of claims 1 to 3, wherein the evaluation target portion is a bolt that fixes a swivel bearing interposed between the swivel table and the frame to the frame. Fatigue for making a computer function to evaluate fatigue damage of a mobile crane having a substructure including an evaluation target site, a swivel mounted on the substructure, and a boom provided on the swivel. It ’s a damage assessment program.
The measured values of the lodging moment acting on the boom and the turning angle of the boom are input.
For each work from ground cutting to landing of the suspended load, the stress amplitude ratio, which is the ratio of the fluctuation range of the stress generated in the evaluation target site to the total rated stress amplitude, is obtained based on the measured values of the lodging moment and the turning angle. , Obtain one work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation program characterized in that a computer is operated to integrate the one-work fatigue damage values in a predetermined period to obtain a cumulative fatigue damage value. Obtain the load factor, which is the ratio of the measured value of the lodging moment to the rated value.
The amplitude factor of the stress generated in the evaluation target site was obtained from the change in the turning angle during the one work period.
The fatigue damage evaluation program according to claim 6, wherein the computer functions to obtain the stress amplitude ratio by multiplying the load factor by the amplitude factor. The cumulative fatigue damage value from the start of use of the evaluation target site to the present is obtained.
6. Claim 6 characterized by having a computer function so that when the cumulative fatigue damage value exceeds the life threshold set for the evaluation target site, it is determined that the life of the evaluation target site has reached the end. Or the fatigue damage assessment program described in 7. A method for evaluating fatigue damage of a mobile crane having a substructure including a site to be evaluated, a swivel mounted on the substructure, and a boom provided on the swivel.
The lodging moment acting on the boom is measured and
Measure the turning angle of the boom and
For each work from ground cutting to landing of the suspended load, the stress amplitude ratio, which is the ratio of the fluctuation range of the stress generated in the evaluation target site to the total rated stress amplitude, is obtained based on the measured values of the lodging moment and the turning angle. , Obtain one work fatigue damage value from the stress amplitude ratio,
A fatigue damage evaluation method, characterized in that the cumulative fatigue damage value is obtained by accumulating the one-work fatigue damage values in a predetermined period. Obtain the load factor, which is the ratio of the measured value of the lodging moment to the rated value.
The amplitude factor of the stress generated in the evaluation target site was obtained from the change in the turning angle during the one work period.
The fatigue damage evaluation method according to claim 9, wherein the stress amplitude ratio is obtained by multiplying the load factor by the amplitude factor. The cumulative fatigue damage value from the start of use of the evaluation target site to the present is obtained.
The fatigue damage according to claim 9 or 10, wherein when the cumulative fatigue damage value exceeds the life threshold determined for the evaluation target site, it is determined that the life of the evaluation target site has reached the end. Evaluation method.

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