A steel wire rope tension distribution detection method based on elastic creep

Abstract

The present application belongs to the technical field of hoist monitoring, and relates to a steel wire rope tension distribution detection method based on elastic creep, comprising the following steps: setting a sensor in a hoist gasket to measure the radial deformation δ r and tangential deformation δ t of the gasket at each position under the action of the steel wire rope; calculating the radial pressure, tangential stress and maximum static friction of the gasket; establishing a stick zone tension balance formula and a slip zone tension balance formula of a steel wire rope micro section, and judging the slip of the steel wire rope micro section; and respectively integrating the stick zone tension balance formula and the slip zone tension balance formula to obtain a tension distribution formula. The present application models the steel wire rope traction process considering elastic creep, obtains the tension distribution of the steel wire rope in operation, can help the staff more clearly detect the rope tension condition and the creep micro-slip condition, improves the equipment safety, and provides a new reference basis for the health degree management of the rubber gasket.

Description

Technical Field

[0001] This invention belongs to the field of hoist monitoring technology, and particularly relates to a method for detecting the tension distribution of wire ropes based on elastic creep. Background Technology

[0002] Friction wire rope hoists are mechanical devices that rely on the friction between the wire rope and the rubber pads on the drive wheel to transmit power and achieve vertical lifting of heavy objects. They are widely used in mining, underground construction and other fields.

[0003] Monitoring the wire rope tension of friction-type wire rope hoists is crucial. If the wire rope tension is too low, it will cause the wire rope to slip, or even jump out of the groove due to slack. If the wire rope tension is too high, it will cause local overload, accelerate the fatigue breakage of the wire rope and the wear of the rubber liner.

[0004] Currently, existing technologies typically use pressure sensors embedded in rubber pads to measure rope tension. Chinese patent CN220081912U discloses a friction pad with a built-in sensor, which monitors the pressure of the wire rope on the pad using a pressure sensor installed inside the pad, and promptly corrects or repairs the wire rope based on pressure changes.

[0005] However, the radial pressure sensor can only measure the wire rope tension when it is static. When the wire rope drum drives the load, the wire rope is pulled by the frictional force along the tangential direction of the drum. At this time, the wire rope tension cannot be simply calculated from the radial pressure of the wire rope on the pad. Therefore, this method cannot accurately measure the wire rope tension for a wire rope hoist in operation.

[0006] The rubber liner is an elastomer, capable of radial compression and circumferential shearing, while the wire rope, made of multiple strands of twisted steel wire, possesses a significant elastic modulus and is similarly stretched or springy due to tension changes. Therefore, as the drum rotates, both the rubber liner and the wire rope deform due to tension changes (a phenomenon known as elastic creep), resulting in a constant, slight tangential slippage. While elastic creep has been studied in belt pulley drives, it is not yet relevant in wire rope hoists. Elastic creep leads to wear and temperature increases, and causes the force process to no longer conform to the Euler friction formula. This makes the physical process of the drum driving the wire rope more complex, and the wire rope tension during the drive process more difficult to calculate. Summary of the Invention

[0007] To analyze the tension distribution of the wire rope during the operation of the hoist and to perform in-depth monitoring of the wire rope tension, this invention proposes a wire rope tension distribution detection method based on elastic creep, comprising the following steps: Step S1: Install sensors inside the hoist liner to measure the radial deformation δ of the liner at each location under the force of the wire rope. r and tangential deformation δt ; Step S2: Calculate the radial pressure, tangential stress, and maximum static friction of the gasket; Step S3: Establish the tension balance formulas for the adhesion zone and slip zone of the wire rope micro-segment, and determine the slippage of the wire rope micro-segment. Step S4: Integrate the tension balance formulas for the adhesion zone and the slip zone respectively to obtain the tension distribution formula: ; Where T0 is the initial tension at the starting position of the slack side of the wire rope, and T(θ) s ) represents the tension at the boundary between the slip zone and the adhesion zone, R is the drum radius, b is the equivalent width coefficient of the contact between the pad and the wire rope, μ is the coefficient of friction, and k t k is the equivalent shear stiffness of the pad. r θ is the equivalent radial stiffness of the gasket. s It represents the critical angle at the boundary between the slip zone and the adhesion zone.

[0008] Preferably, step S2 specifically includes: S2.1 Determine the radial pressure p(θ) and radial deformation δ through experimental calibration or empirical formulas. r The corresponding curve of (θ); assuming linear elasticity for the gasket, the radial pressure p(θ) per unit contact length of the gasket at θ is: ; S2.2 Calculate the maximum static friction between the pad and the wire rope: ; Where, τ max This represents the maximum static friction. S2.3 Calculate the tangential stress generated by the tangential deformation of the gasket: ; Where τ(θ) is the tangential stress per unit contact length of the pad located at θ.

[0009] The preferred method for judging slippage of wire rope segments is as follows: The rate of change of local wire rope tension in the micro-segment of the adhesive zone is less than the maximum static friction of the liner. Combining this with the tension balance formula in the adhesive zone, the slippage criterion is obtained: ; If the sensor measurement data of the pad at θ satisfies the above formula, then there is no slight slippage at that position, which is the adhesion zone; if the above formula is not satisfied, then slight slippage occurs at that position due to creep, which is the slippage zone.

[0010] Preferably, the method further includes step S5: calculating the slip zone range index and the wire rope tension imbalance, the specific method of which is as follows: S5.1 Calculate the slip zone range index : ; Where, θ max For the wire rope wrap angle; S5.2 Calculate the tension imbalance coefficient B: The tension distribution T of each wire rope was measured. i (θ), where i represents the wire rope serial number, and the tension imbalance coefficient B is defined as: ; The tension imbalance coefficient B is used to represent the percentage deviation between the maximum single rope tension and the average rope tension.

[0011] The beneficial effects of this invention are: Through the above method, this invention models the wire rope traction process considering elastic creep, and obtains the tension distribution of the wire rope during operation. This helps workers to more clearly detect the rope tension and creep micro-slippage, improves equipment safety, and provides a new reference for the health management of rubber linings. Attached Figure Description

[0012] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 Here is a structural diagram of an existing friction-type wire rope hoist; Figure 2 A schematic diagram illustrating the principle of deformation of rubber gaskets at different positions on the drum; Figure 3 This is a schematic diagram showing the deformation of the rubber gasket before and after being subjected to force. Figure 4 This is a flowchart illustrating the steps of the wire rope tension distribution detection method according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the relationship between the normalized tension T and the position angle θ. In the diagram, 1 is the drum, 2 is the rubber pad, 3 is the load, 4 is the wire rope, 5 is the guide drum one, and 6 is the guide drum two. Detailed Implementation

[0013] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0014] The structure of existing friction wire rope hoists is generally as follows: Figure 1 As shown, the system includes a drum 1 mounted on the ground. A rubber pad 2 is fixedly mounted on the outer periphery of the drum 1. Rope grooves are machined on the outer surface of the rubber pad 2. A steel wire rope 4 passes around the rubber pad 2 (the steel wire rope 4 is secured in the rope grooves on the rubber pad 2) and is rotatably connected to guide drum 1 5 and guide drum 2 6 respectively. After passing through guide drum 1 5, the steel wire rope 4 is connected to a load 3, which may be an elevator car or a cargo transport device. A large motor drives the drum 1 to rotate, which in turn moves the load 3 up and down via the steel wire rope 4.

[0015] When the drum 1 rotates and pulls the load 3 through the wire rope 4, the tension at both ends of the wire rope segment in contact with the rubber pad 2 is different. The side with greater tension is called the tight side, and the side with less tension is called the slack side. Figure 2 As shown, when drum 1 rotates counterclockwise, then Figure 2 The upper section of the steel wire rope on the rubber liner 2 is tightened, resulting in greater tension and radial pressure on the rubber liner 2, while the lower section of the steel wire rope on the rubber liner 2 experiences less tension and radial pressure. For example... Figure 3 As shown, the rubber material of the rubber pad 2 is an elastomer. When its upper side is subjected to the frictional force of the steel wire rope 4, it will undergo lateral compression and oblique deformation. This oblique deformation causes the rotation speeds of the rubber pad 2 and the steel wire rope 4 to be inconsistent, resulting in slight slippage.

[0016] From the tight side to the slack side, the tension in the wire rope must decrease continuously and gradually. Assuming the wire rope 4 is a perfectly flexible body and the pad is a rigid body, the tension distribution conforms to Euler's friction formula T. max = T0×exp(μθ), where T max T0 and T0 represent the tight-side tension and slack-side tension, respectively; exp is an exponential function with the natural logarithm base; μ is the coefficient of friction; and θ is the wrap angle. However, considering the elasticity of the rubber pad 2 and the sliding caused by elastic creep, this physical process is actually quite complex.

[0017] This invention provides a method for detecting the tension distribution of steel wire rope based on elastic creep, comprising the following steps: Step S1: Install sensors inside the hoist liner to measure the radial deformation δ of the liner at each location under the force of the wire rope. r and tangential deformation δ t .

[0018] The radial and tangential directions refer to the radial and tangential directions of the hoist drum. The method of installing a sensor within the hoist liner is existing technology. Typically, a cavity is machined within the liner, and interdigitated capacitive electrodes are placed within this cavity. When the liner deforms, the minute displacement causes a change in capacitance, which, after testing and calibration, reflects the liner's deformation. For specific sensor examples, refer to "Online Monitoring Sensor for Wire Rope Tension of Multi-Rope Friction Hoists" (Chen Xianzhong et al., Journal of Beijing University of Science and Technology, Vol. 20, No. 5, Oct. 1998), or existing products such as dielectric elastomer sensors (DES) can be used.

[0019] Each wire rope of the hoist corresponds to a ring of padding. To ensure measurement accuracy, a sensor can be installed in each ring of padding, or a sensor can be evenly installed at certain angles in a ring of padding, and linear interpolation can be used for approximation.

[0020] For ease of calculation, the embodiment uses a position angle θ to represent the current calculated position of the pad. The initial position where the slack side of the wire rope contacts the pad is recorded as θ=0. For example... Figure 2 The middle drum rotates counterclockwise. The bottom of the drum is the slack side, where θ = 0, and the top of the drum is the tight side, where θ = 180°. δ r (θ) and δ t (θ) represents the radial and tangential deformations located at the rotation angle θ on the drum, respectively, in micrometers.

[0021] Step S2: Calculate the radial pressure, tangential stress, and maximum static friction of the gasket. Specifically: S2.1 Determine the radial pressure p(θ) and radial deformation δ through experimental calibration or empirical formulas. r The corresponding curve of (θ).

[0022] Assuming linear elasticity for the gasket, the radial pressure p(θ) per unit contact length of the gasket at point θ is: ; Where, k r The equivalent radial stiffness is determined by the material properties and structure of the gasket and can be measured through experimental calibration. If other elastic assumptions are adopted for the gasket, the radial pressure p(θ) and radial deformation δ will be... r (θ) shows a positive correlation, and radial pressure p(θ) and radial deformation δ can also be calibrated experimentally. r The corresponding curve of (θ).

[0023] S2.2 Calculate the maximum static friction between the pad and the wire rope: ; Where, τ maxThe maximum static friction is given by μ, which is the coefficient of friction. In practical engineering, the rope grooves on the pad need to be machined periodically, so the coefficient of friction μ can remain basically constant and can be obtained through experimental calibration or empirical data.

[0024] S2.3 Calculate the tangential stress generated by the tangential deformation of the gasket. Specifically: ; Where τ(θ) is the tangential stress per unit contact length of the pad at position θ, and k t This is the equivalent shear stiffness of the pad.

[0025] Step S3: Establish the tension balance formulas for the adhesion zone and slip zone of the wire rope micro-segment, and determine the slippage of the wire rope micro-segment. A wire rope micro-segment refers to a small segment at the location studied by the differential equation, specifically a segment with an angle of θ. Specifically: S3.1 The area on the drum without any slight slippage is called the adhesion zone. The tension balance formula for the wire rope segments in the adhesion zone is constructed as follows: For the adhesion zone, the local rate of change of wire rope tension is equal to the tangential stress of the liner: ; Where T(θ) is the wire rope tension at θ. Let R be the local rate of change of wire rope tension, and b be the drum radius. Since the wire rope contacts the semi-circular groove on the liner, the equivalent contact width coefficient b is needed for conversion. The equivalent contact width coefficient b is a constant and can be obtained through experimental calibration or empirical data.

[0026] Substituting τ(θ) into the equation yields the rate of change of local wire rope tension in the adhesion zone: .

[0027] S3.2. The area with minute slippage on the drum is called the slip zone. The tension balance formula for the wire rope micro-segment in the slip zone is as follows: For the slip zone, the friction between the wire rope and the pad becomes sliding friction. Since the velocity difference between the wire rope and the pad is extremely small during creep, the sliding friction can be approximated as the maximum static friction. Therefore, the tension balance formula for the slip zone is obtained: ; Substitute τ max (θ) yields the rate of change of local wire rope tension in the slip zone: .

[0028] S3.3 Construct a criterion for micro-segment slippage in the wire rope to determine whether slippage has occurred. Specifically: For the wire rope segments in the adhesion zone, the rate of change of local wire rope tension must be less than the maximum static friction of the pad, i.e., it must satisfy: ; By combining the tension balance formula in the adhesion zone, the slip criterion is obtained: ; After simplification, it becomes: ; If the sensor measurement data of the pad at θ satisfies the above formula after calculation, then there is no slight slippage at that position, which is the adhesion zone; if the above formula is not satisfied, then slight slippage occurs at that position due to creep, which is the slippage zone.

[0029] Step S4: Integrate the tension balance formulas for the adhesion zone and the slip zone respectively to obtain the distribution formula for tension T. Specifically: When the drum rotates and drives the load, the tension of the wire rope is greater on the tight side and less on the slack side. A slip zone begins to appear on the tight side and expands towards the slack side, with the rate of change of wire rope tension gradually decreasing. When the slip zone expands to a certain angle, the rate of change of wire rope tension is less than the maximum static friction of the bushing, after which it enters the adhesion zone. There is no slippage between the wire rope and the bushing, and they rotate completely synchronously. The angle at the boundary between the slip zone and the adhesion zone is denoted as the critical angle θ. s The tangential stress of the liner in this local area is exactly equal to the maximum static friction of the liner, that is: ; θ≤θ s The region is the adhesion region, θ>θ s The region is the slip zone. Integrating over the two regions above yields the distribution of tension T: ; T0 is the initial tension at the starting position of the slack side of the wire rope. In actual engineering, it can be calculated by the torque of the drum drive motor, or by setting a wire rope tension measuring device near the slack side (commonly used devices include hydraulic tensioning cylinders, guide wheels with bearings and strain gauges, etc.).

[0030] Through the above method, the present invention solves the problem of calculating the tension distribution of the wire rope during the rotation of the drum, enabling real-time monitoring of the tension at various positions of the wire rope, better understanding of the wire rope's health, and avoiding situations such as multi-rope tension imbalance and abnormal slippage.

[0031] The physical process of the aforementioned pad-driven wire rope was modeled and simulated using ANSYS finite element simulation. The normalized tension T versus position angle θ curve is shown below. Figure 5 As shown. This simulation uses a wrap angle θ. max =180°, the critical angle θ shown in the calculation resultss It is approximately 1.265 radians. It can be seen that in the adhesion zone, the wire rope tension increases almost linearly from the initial tension T0 on the slack side, reaching a critical angle θ. s Subsequently, the shear stress provided by the radial deformation will soon exceed the maximum static friction, after which a small slip occurs, and the radial pressure p(θ) and radial deformation δ r (θ) all rise rapidly; the rotation angle θ approaches θ max At the 180° position, the wire rope is not yet in complete contact with and compressed against the padding, therefore the rate of increase in wire rope tension is... The tension drops rapidly to 0, and the wire rope tension T reaches the maximum value of the tight side tension.

[0032] Furthermore, since there is no relative movement between the wire rope and the pad in the adhesion zone, wear is almost nonexistent. Wear typically occurs only in the slip zone. The larger the slip zone, the higher the wear rate of both the pad and the wire rope, and the more severe the rubber aging caused by frictional heating. Excessively large slip zones can lead to wire rope slippage and derailment, causing serious accidents. Therefore, the detection method of this invention also includes: Step S5: Calculate the slip zone range index and the wire rope tension imbalance.

[0033] S5.1 Calculate the slip zone range index : ; Where, θ max For the wire rope wrap angle, θ s θ is the critical angle at the boundary between the slip region and the adhesion region. s It is calculated based on the slip criterion in step S3.3.

[0034] Slip zone range index It is used to quantitatively represent the proportion of the slip zone of a single wire rope to the overall wire rope wrap angle, thereby reflecting the health of the padding. The smaller the value, the smaller the current slip zone and the better the padding condition. Generally... It should be less than 15% of the target threshold; otherwise, it means that the friction coefficient of the liner is too low, and the liner groove needs to be machined or the liner needs to be made smoother.

[0035] S5.2 Calculate the tension imbalance coefficient B: The tension distribution T of each wire rope in a multi-rope wire rope hoist can be measured using the method described above. i (θ), (i represents the wire rope number) can be used to detect the tension distribution of the wire rope at various locations.

[0036] The tension imbalance coefficient is defined as: ; The tension imbalance coefficient B represents the percentage deviation between the maximum single rope tension and the average rope tension. For a normally operating hoist, the tension in each rope should be evenly distributed. Typically, only the location of maximum tension, θ, needs to be calculated. max The tension imbalance coefficient B is measured at a certain point. When the tension imbalance B exceeds 10%, it means that the tension distribution of the wire rope is significantly unbalanced, and the monitoring system will issue an alarm. Wire ropes with excessive tension will suffer damage such as broken wires due to overload, and may even break completely. Wire ropes with excessive tension are prone to slippage and derailment.

[0037] The tension imbalance coefficient B can also be used for calculations at other angles θ. If the tension imbalance coefficient B is significantly larger at other angles, it usually means that there is an abnormal condition at that location, such as abnormal scratches in the rope groove, broken wires, or hard debris embedded in the rubber, which causes a significant abnormality in the local friction coefficient of the padding in a certain rope groove at that location.

[0038] In the embodiments of the present invention, all technical features not described in detail are existing technologies or conventional technical means, and will not be repeated here.

[0039] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A method for detecting tension distribution in steel wire ropes based on elastic creep, characterized in that, Includes the following steps: Step S1: Install sensors inside the hoist liner to measure the radial deformation δ of the liner at each location under the force of the wire rope. r and tangential deformation δ t ; Step S2: Calculate the radial pressure, tangential stress, and maximum static friction of the gasket; Step S3: Establish the tension balance formulas for the adhesion zone and slip zone of the wire rope micro-segment, and determine the slippage of the wire rope micro-segment. Step S4: Integrate the tension balance formulas for the adhesion zone and the slip zone respectively to obtain the tension distribution formula: ； Where T0 is the initial tension at the starting position of the slack side of the wire rope, and T(θ) s ) represents the tension at the boundary between the slip zone and the adhesion zone, R is the drum radius, b is the equivalent width coefficient of the contact between the pad and the wire rope, μ is the coefficient of friction, and k t k is the equivalent shear stiffness of the pad. r θ is the equivalent radial stiffness of the gasket. s It represents the critical angle at the boundary between the slip zone and the adhesion zone.

2. The method for detecting tension distribution in a wire rope based on elastic creep according to claim 1, characterized in that, Step S2 specifically includes: S2.1 Determine the radial pressure p(θ) and radial deformation δ through experimental calibration or empirical formulas. r The corresponding curve of (θ); assuming linear elasticity for the gasket, the radial pressure p(θ) per unit contact length of the gasket at θ is: ； S2.2 Calculate the maximum static friction between the pad and the wire rope: ； Where, τ max This represents the maximum static friction. S2.3 Calculate the tangential stress generated by the tangential deformation of the gasket: ； Where τ(θ) is the tangential stress per unit contact length of the pad located at θ.

3. The method for detecting tension distribution in a steel wire rope based on elastic creep according to claim 2, characterized in that, The method for judging slippage of small segments of wire rope is as follows: The rate of change of local wire rope tension in the micro-segment of the adhesive zone is less than the maximum static friction of the liner. Combining this with the tension balance formula in the adhesive zone, the slippage criterion is obtained: ； If the sensor measurement data of the pad at θ satisfies the above formula, then there is no slight slippage at that position, which is the adhesion zone; if the above formula is not satisfied, then slight slippage occurs at that position due to creep, which is the slippage zone.

4. A method for detecting the tension distribution of a steel wire rope based on elastic creep according to any one of claims 1-3, characterized in that, It also includes step S5: calculating the slip zone range index and the wire rope tension imbalance, the specific method of which is as follows: S5.1 Calculate the slip zone range index : ； Where, θ max For the wire rope wrap angle; S5.2 Calculate the tension imbalance coefficient B: The tension distribution T of each wire rope was measured. i (θ), where i represents the wire rope serial number, and the tension imbalance coefficient B is defined as: ； The tension imbalance coefficient B is used to represent the percentage deviation between the maximum single rope tension and the average rope tension.

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