METHOD AND SYSTEM FOR DETERMINING A CRITICAL MATERIAL FATIGUE STATE IN CIVIL ENGINEERING MACHINES

Description

[0001] The invention relates to a method for determining a critical material fatigue state in civil engineering machines, which comprise as components an undercarriage, an upper carriage, a mast, a working implement for soil cultivation in civil engineering (in particular mounted on the mast), a main winch for raising and lowering the working implement by means of a main cable along the mast, and / or a feed device for the working implement. Furthermore, data are determined and recorded, at least regarding the forces occurring at the main winch, the forces occurring at the feed device, and / or the torques occurring at the working implement.

[0002] The invention further relates to a system for determining a critical material fatigue state in a civil engineering machine, comprising a civil engineering machine with an undercarriage, a superstructure, a mast, a working attachment for soil cultivation in civil engineering (in particular mounted on the mast), a main winch for raising and lowering the working attachment by means of a main cable along the mast, and / or a feed mechanism. Furthermore, sensors are provided on the civil engineering machine to determine data at least on forces occurring at the main winch, forces occurring at the feed mechanism, and / or torques occurring at the working attachment.

[0003] The main cable typically carries the working attachment, which is not necessarily guided along the mast. A carriage may be provided on the mast, which can be operated by the feed mechanism and, in particular, moved along the mast. If the working attachment has, for example, a Kelly bar and a power swivel head, these can therefore be raised and lowered independently of each other. The mast can be designed, for example, as a standard mast or a telescopic mast. It can also be angled relative to the superstructure.

[0004] To ensure the safe operation of civil engineering machinery, such as specialized rotary drilling rigs, cable excavators, or pile drivers, safety-relevant components of the machinery must be inspected for crack development in the steel components of the entire machine. This crack development occurs due to material fatigue. Typically, fixed inspection intervals are prescribed based on the operating hours of the machinery. However, these intervals must be designed to ensure that even heavily stressed machines are inspected frequently enough.

[0005] The stress placed on a deep-digging machine depends on factors such as soil conditions, the drilling method used, the drilling tool employed, and also the functional demands placed on the machine operator. For example, it's important to consider that a deep-digging machine used only in soft materials, such as sandy soils, is subjected to significantly less stress than one working with hard rock.

[0006] From DE 197 09 445 A1 or DE 103 10 116 A1, methods for motor vehicles are known with which material fatigue states or service intervals can be estimated or determined for components subject to wear or aging processes.

[0007] From US patent 2018 / 058046 A1, a monitoring system for a drilling rig with a mast that can be locked in at least one vertical position and pivoted about an axis on a fixed support by actuating mast lifting cylinders is known. It comprises strain gauges, a data acquisition unit, a processor and memory, and at least one output device. The strain gauges are located at least on the mast, preferably at locations prone to failure. The data acquisition unit records real-time strain data from strain, pressure, and position measuring devices. The processor and memory use the data to calculate the actual load or cumulative damage by means of a rainflow analysis to determine a real-time operating status of the drilling rig.The output device(s) display the instantaneous stress or accumulated damage along with corresponding reference values ​​for the maximum allowable stress or accumulated damage. The reference value for the maximum allowable stress associated with the strain gauge location can be calculated from a stress at which the device is expected to fail, either at the strain gauge location itself or at other unmeasured locations that are expected to be most vulnerable based on a finite element analysis. A warning is issued when the stress or accumulated damage exceeds or approaches the corresponding reference value.

[0008] From PAWLUS WITOLD ET AL: "Mitigation of Fatigue Damage and Vibration Severity of Electric Drivetrains by Systematic Selection of Motion Profiles", IEEE / ASME TRANSACTIONS ON MECHATRONICS, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, Vol. 21, No. 6, December 6, 2016 (2016-12-06), pages 2870-2880, XP011633543, it is known to determine damage figures of a motor-driven drive of a grab for assembling offshore drill strings, taking into account S-N curves, using the Rainflow method based on measured motion profiles with torques and speeds of the drive.

[0009] The invention is based on the Task The aim is to specify a method and a system that enable efficient prediction of material fatigue in underground construction machinery.

[0010] This problem is solved according to the invention by a method for determining a critical material fatigue state in underground construction machinery with the features of claim 1 and a system for determining a critical material fatigue state in an underground construction machine with the features of claim 12.

[0011] Preferred embodiments of the invention are specified in the dependent claims, in the figures and their explanations.

[0012] According to the invention, damage values ​​are determined from the obtained data using a rainflow method. These damage values ​​are accumulated over a period of time to obtain a current damage value. The current damage value is compared with a calculated permissible damage value for at least one component, and a critical material fatigue state is identified when the current damage value approaches the calculated permissible damage value. For the purposes of the invention, permissible damage value can be understood as a damage value that describes a state at which the component is just barely sufficiently stable.

[0013] A fundamental aspect of the invention is the explicit determination and recording of data on forces occurring at the main winch, forces occurring at the feed mechanism, and / or torques occurring at the working tool. According to the invention, it has been recognized that data (initial data) from just one of these three possible sources is sufficient to reliably determine damage values ​​that allow conclusions to be drawn about material fatigue conditions in underground construction machinery. Although a significantly larger amount of data can theoretically be collected during the operation of an underground construction machine, the invention has identified these three data sources as the most relevant, and the evaluation of even just one of these sources is sufficient to determine a critical material fatigue condition.

[0014] According to the invention, a rainflow method or rainflow analysis is performed based on the collected data to determine damage values. The rainflow method is also alternatively referred to as rainflow counting or rainflow counting method. The damage values ​​determined in this way are summed so that a current damage value can be determined. This can, in principle, be carried out separately for each component, depending on the underlying data. However, it can also be carried out for a group of components or for the entire excavation equipment.

[0015] The currently determined damage value is compared with a permissible damage value for the component or component group. This permissible damage value is a calculated value. A critical material fatigue state is then determined when the current damage value approaches the previously determined and / or defined permissible damage value.

[0016] In this way, it is achieved that fixed inspection intervals no longer have to be observed, but that, based on the damage occurring, a maintenance time can be predicted flexibly, and an inspection only has to be carried out when a threshold of critical material fatigue is reached.

[0017] It is advantageous to use a corresponding S-N curve or S-N curve to determine the damage coefficient for each component. This allows conclusions to be drawn about the damage of the respective component or component group based on the damage coefficients. The S-N curve commonly used in mechanical engineering is based on so-called S-N tests, which provide information about fatigue strength and long-term fatigue strength. These tests take into account factors such as the material of the assembly, as well as other details like the precise design.

[0018] The determined permissible damage value that a component may exhibit before a material fatigue state is detected is calculated for each component using a nonlinear finite element method. In this way, with a certain computational effort, a corresponding threshold value or permissible damage value can be determined for any component of a deep-construction machine, which can then be used in the method according to the invention.

[0019] In principle, the data, such as those relating to forces at the main winch, the feed mechanism, and / or torques at the working tool, can be evaluated separately or correlated with each other. The advantage of separate evaluation is that it requires less computing power, but the results are also less precise. In contrast, the required computing time increases significantly for correlated evaluation. However, it provides more accurate damage figures.

[0020] In other words, the damage number calculation can be performed either uniaxially or multiaxially.

[0021] As already described, for the inventive method it is sufficient to use data on forces occurring at the main winch, data on forces occurring at the feed device, and / or data on torques occurring at the working tool for further evaluation. However, an even more precise determination of the damage coefficients and thus of the occurrence of a material fatigue state can be achieved if further data (secondary data) are used. This data can relate, for example, to the position of the working tool, in particular to the mast, the slewing acceleration of the superstructure, the travel acceleration of the underground construction machine, the tractive force of the undercarriage, forces occurring at an auxiliary winch, the mast inclination, the reach, the angle of rotation between the superstructure and undercarriage, the slope of the subgrade, and the path of the drilling axis.In other words, data for one, several, or all of the listed elements can be used for further analysis. The main winch, the feed mechanism, and the auxiliary winch can each be operated independently.

[0022] In principle, the collected data can be recorded in any way desired. It is advantageous to transmit this data wirelessly to an external storage device, either continuously or discontinuously. However, wired transmission is also possible. Wireless transmission is preferred, as it allows data to be collected at any given time, thus enabling the most accurate prediction of when a critical material fatigue state will be reached.

[0023] The data itself can also be recorded locally in the excavation machine and transmitted wirelessly at fixed intervals or read out using a data retrieval device. Data analysis can be performed by a processing unit located within the excavation machine or by a processing unit located remotely. A combined analysis is also possible.

[0024] In a training course, based on the approach of the current damage value to the determined permissible damage value, a time period until the critical material fatigue state is reached can be determined or predicted. Furthermore, it is possible for at least one person from a group consisting of a user or operator, an owner, a manufacturer, a service company, and a lessor of the construction machinery to be informed a specified time before the critical material fatigue state is reached. In other words, a prediction can be made based on the development of the damage value as to how long it will take until the critical material fatigue state is reached. The relevant operator, for example, can then be informed in good time before this state is reached. However, other persons or organizations can also be informed.For example, the manufacturer of the construction equipment, who is responsible for maintenance, the rental company, or a service company can be informed. The timeframe for this can be predetermined by the manufacturer of the construction equipment. However, it is also possible for the timeframe to be defined individually. Individually defined in this context could mean that the timeframe can be specified for each component or, for example, for each area of ​​application.

[0025] Furthermore, when the current damage value approaches the determined permissible damage value, the excavation machine can be locked for certain work procedures. This can mean that the execution of these procedures is prevented via the machine's control system or is only possible after a warning that must be acknowledged. Such work procedures may be those that, based on experience, cause particularly high damage values, such as drilling into hard rock. These procedures can be identified, for example, by measuring the required torque or by selecting specific tools mounted on the machine. The lock may only be lifted after an inspection has taken place. However, during the lock, it may still be possible to execute other work procedures with expected lower damage values.

[0026] The critical material fatigue condition refers specifically to cracking in the steel components of the underground construction machine. Material fatigue is clearly distinct from maintenance conditions, such as the necessary replacement of engine, transmission, or hydraulic oil.

[0027] In a system according to the invention, an evaluation device is provided which is designed to determine damage numbers from the determined data using a rainflow method, to accumulate the damage numbers over a period of time to a current damage value, to compare the current damage value with a determined and / or stored permissible damage value for at least one component, and to identify a critical material fatigue state when the current damage value approaches the determined permissible damage value.

[0028] In other words, the system according to the invention relates to a civil engineering machine which has corresponding sensors to determine data on forces occurring at the main winch, data on forces occurring at the feed device and / or data on torques occurring at the working tool.

[0029] Furthermore, the system has an evaluation unit which is designed to carry out the essential steps of the inventive method in order to detect a critical material fatigue state before it occurs.

[0030] It is preferable for the evaluation unit to be located remotely from the excavation machine and for the data to be transferable to the evaluation unit directly or indirectly. For example, the evaluation unit could be located on central servers of a service company or the manufacturer of the excavation machine. This makes it possible to monitor multiple excavation machines with a single evaluation unit, thus enabling the determination of corresponding damage values ​​and critical material fatigue conditions. Alternatively, the evaluation unit could be integrated directly into the excavation machine, eliminating the need for further data transmission.

[0031] The data required by the evaluation unit can be sent directly from the excavation machine to the evaluation unit via a suitable communication network. Alternatively, this data can also be actively queried by the evaluation unit from a database that exists for other purposes related to the excavation machine.

[0032] In a training course, the evaluation system is designed to inform at least one person from a defined group—a user, an operator, a manufacturer, an owner, a service company, and a lessor of the construction machinery—about a critical material fatigue condition within a specified time period before its detection. It is essential that at least one, a large majority, or all persons or organizations relevant to the maintenance and operational safety of the construction machinery are informed that a critical material fatigue condition is imminent. This ensures that necessary maintenance is only carried out when the critical material fatigue condition is nearly reached, rather than according to predetermined intervals that are often too short for safety reasons.

[0033] The invention is explained in more detail below with reference to a preferred embodiment. The drawings show: Fig. 1 is a schematic representation of a deep-construction machine; and Fig. 2 is a flowchart to illustrate the method according to the invention.

[0034] A civil engineering machine 10, which is specifically designed as a drilling rig, is in Fig. 1 As shown, a superstructure 14 is preferably rotatably mounted on a substructure 12 with a chassis, which may be designed as a crawler chassis. A mast 20 can be arranged on the front of the superstructure 14, which has an operator's cabin 16, via a linkage mechanism 22. The mast 20 can be designed as a mast with a front linear guide 24, along which a carriage 26 with a drilling drive 28 can be vertically moved and guided by means of a feed device, which may be designed as a feed winch 27, and / or a main winch 25.

[0035] To form a working tool 30, a drilling tool 34 is preferably arranged on the underside of a Kelly bar 32. The Kelly bar 32 is rotatably driven, in particular via the drilling drive 28, and is vertically adjustable on the mast 20 by means of a cable 36. Counterweights 15 can be arranged at the rear 40 of the superstructure 14.

[0036] The training of a civil engineering machine 10 as a drilling rig according to Fig. 1 This is merely an example, whereby the civil engineering machine 10 can also be designed in other ways, in particular with other work equipment 30 for civil engineering, such as a diaphragm wall cutter, a ram or a vibrator.

[0037] Referring to the flowchart according to Fig. 2 The inventive method for determining a critical material fatigue state in underground construction machinery will now be explained in more detail.

[0038] In step 1, the operation of the civil engineering machine 10, which may be, for example, a drilling rig or a pile driver, is started.

[0039] During operation, data on operating parameters are determined in step 2. This data can include forces occurring at the main winch 25, for example, when raising or lowering the working tool 30, or forces occurring at the feed unit, for example, when applying pressure to the working tool. Data on torques occurring at the working tool, for example, due to rotation against ground resistance during drilling, can also be measured and recorded. The feed unit can consist of a feed winch 27 or a cylinder unit, so the forces involved can be either tensile or, in the case of a cylinder unit, compressive. This force can be determined using a force measuring axis, for example, at a pulley of the cable.

[0040] If torques need to be determined, this can be done, for example, using a torque measuring flange.

[0041] Furthermore, additional or alternative data can also be determined and recorded regarding the position of the rotary head of the working tool 30, the slewing acceleration of the superstructure 14 during slewing, the general travel acceleration of the excavation machine 10, in particular the acceleration during starting and braking, the resulting vehicle tractive force, which can also be referred to as the undercarriage tractive force, the tractive forces on an auxiliary winch, the absolute mast inclination, the reach (meaning the mast position relative to the undercarriage 12), the rotational position of the superstructure 14 relative to the undercarriage 12, in particular the angle of rotation between these two, the slope of the subgrade (which can be defined as the absolute slope of the superstructure to the horizontal), the drilling axis, in particular with respect to the mast, and the currently used soil cultivation method. In principle, it is possible to use some, all, or any combination of this data.

[0042] In step 3, the collected data is then transferred to an evaluation unit. This unit can be integrated into or attached to the excavation machine 10. However, it is also possible to locate it externally. Data transmission to an external evaluation unit is preferably wireless. However, it is also possible to temporarily store the data in the excavation machine 10 and periodically transfer it to the evaluation unit via a data transfer that is at least partially wired.

[0043] In step 4, the evaluation unit calculates a current damage value for selected components of the underground construction machine 10. Preferably, a damage number is determined from the data using a rainflow method, which is then summed over a period of operation to obtain a current damage value.

[0044] In step 5, the evaluation unit compares the current damage value with a previously determined permissible damage value for the component. This permissible damage value is calculated, for example, using a nonlinear finite element method.

[0045] In step 6, the result of the comparison between the determined current damage value and the permissible damage value is evaluated. If the permissible damage value has not yet been reached, the procedure continues from step 2. If it has been reached, or if the determined current damage value is approaching the permissible damage value, the procedure continues in step 7. It is not absolutely necessary that the permissible damage value has already been reached; decisions can also be made accordingly if there is still a certain safety margin between the current damage value and the permissible damage value, allowing sufficient time to carry out appropriate maintenance and inspection steps.

[0046] In step 7, a user, operator, owner, manager, manufacturer, lessor, service company, or other relevant person or organization is informed. In principle, several persons or organizations can also be informed jointly or simultaneously about reaching the critical material fatigue state, which can be determined by comparing the current damage value with the permissible damage value. This can be done, for example, via an electronic message. This information can also be displayed additionally or exclusively in the operator's cabin, e.g., together with a calculated remaining time until the critical material fatigue state is reached.

[0047] It is also possible that the excavation machine will be blocked for certain work processes that are expected to cause a particularly high amount of damage until an inspection has taken place, while other work processes that are known to cause low amounts of damage are still permitted.

[0048] Subsequently, in step 8, the underground construction machine is checked for material fatigue such as cracks, especially in steel components.

[0049] Thus, using the method and system according to the invention, a critical material fatigue state can be predicted and a corresponding inspection can be carried out in good time, without the inspection taking place much too early.

Claims

1. Method for determining a critical material fatigue state in civil-engineering machines (10), which comprises, as components, an undercarriage (12), an upper structure (14), a mast (20), a work device (30), in particular mounted on the mast (20), for ground working in civil engineering, a main winch (25) for raising and lowering the work device (30) by means of a main cable (36) along the mast (20), and / or a feed means for the work device (30), wherein first data relating to - forces arising on the main winch (25), - forces arising on the feed means, and / or - torques arising on the work device (30) are determined and recorded, wherein damage figures are determined from the obtained first data by means of a Rainflow Method, wherein the damage figures are cumulated over a time period to a current damage value, wherein the current damage value is compared with a previously determined allowable damage value for at least one of the components, wherein the previously determined allowable damage value per component is determined for the at least one of the components with the aid of a nonlinear Finite Element Method, and wherein a critical material fatigue state is identified when the current damage value is approached the determined allowable damage value.

2. Method according to claim 1, characterised in that a corresponding Wöhler curve is taken into account for determining the damage figures per component.

3. Method according to claim 1 or 2, characterised in that the first data are evaluated separately in each case.

4. Method according to claim 1 or 2, characterised in that the first data are evaluated in a manner correlated with one another.

5. Method according to any one of claims 1 to 4, characterised in that the damage figures are determined from the obtained first data alone, by means of the Rainflow Method.

6. Method according to any one of claims 1 to 4, characterised in that at least second data relating to one element from the following group are also determined and recorded, and used in the determination of the damage figures by means of the Rainflow Method: position of the work device (30), pivot acceleration of the upper structure (14), travel acceleration of the civil-engineering machine (10), tractive force of the chassis of the undercarriage (12), forces arising on an auxiliary winch, mast inclination, radial range, rotational angle between the upper structure (14) and undercarriage (12), planum slope, course of a drilling axis.

7. Method according to any one of claims 1 to 6, characterised in that the determined data are transmitted wirelessly to an external memory, for recording, wherein the transmission is carried out continuously and / or discontinuously.

8. Method according to any one of claims 1 to 7, characterised in that the determined data are recorded locally.

9. Method according to any one of claims 1 to 8, characterised in that a time period until the critical material fatigue state is reached is determined based on the current damage value approaching the determined allowable damage value, and in that a fixed time period before the critical material fatigue state is reached, at least one of a group comprising user, operator, manufacturer, owner, service company and lessor is informed thereof.

10. Method according to any one of claims 1 to 9, characterised in that when the current damage value approaches the determined allowable damage value, the civil-engineering machine (10) is blocked for certain work methods that cause a particularly high damage value.

11. Method according to any one of claims 1 to 10, characterised in that the critical material fatigue state is a crack formation in the steel construction components of the civil-engineering machine.

12. System for determining a critical material fatigue state in a civil-engineering machine (10), comprising, as components an undercarriage (12), an upper structure (14), a mast (20), a work device (30), in particular mounted on the mast (20), for ground working in civil engineering, a main winch (25) for raising and lowering the work device (30) by means of a main cable (36) along the mast (20), and / or a feed means, wherein sensors are provided on the civil-engineering machine (10), for determining first data relating to - forces arising on the main winch (25), - forces arising on the feed means, and / or - torques arising on the work device (30), wherein an evaluation means is provided, which is configured - to determine damage figures from the determined first data, by means of a Rainflow Method, - to cumulate the damage figures over a time period to a current damage value, - to compare the current damage value with a previously determined allowable damage value for at least one component, wherein the previously determined allowable damage value per component is determined for the at least one of the components with the aid of a nonlinear Finite Element Method, and - to identify a critical material fatigue state when the current damage value approaches the determined allowable damage value.

13. System according to claim 12, characterised in that the damage figures are determined from the obtained first data alone, by means of the Rainflow Method.

14. System according to claim 12 or 13, characterised in that the evaluation means is provided remotely from the civil-engineering machine, and in that the data can be transmitted directly or indirectly to the evaluation means.

15. System according to claim 12, 13 or 14, characterised in that the evaluation means is configured, a fixed time period before a critical material fatigue state is identified, to inform at least one of a group comprising user, operator, manufacturer, owner, service company and lessor of the civil-engineering machine, of this.