Accelerated reproduction method for fatigue crack fault of cover plate type structure

Abstract

The invention belongs to the technical field of structural fatigue test verification, and particularly relates to an accelerated reproduction method for a fatigue crack fault of a cover plate type structure. The method comprises the following steps: establishing a product overall modal simulation model containing a cover plate type structure, determining a measuring point, then replacing other parts except a cover plate with a mass block, determining the weight of an equivalent mass block by modal simulation, finally adding the equivalent mass block to the middle of the cover plate type structure, and carrying out a sweep frequency test on the cover plate type structure. And a residence test is carried out according to a frequency sweep test result, and the reproduction of a fatigue crack fault is rapidly realized. By adopting the method provided by the invention, the fatigue test of the cover plate type structure can be accelerated, the test period is greatly shortened, and the fault reproduction efficiency is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of structural fatigue testing and verification technology, specifically relating to a method for accelerating the reproduction of fatigue crack failures in cover plate structures. Background Technology

[0002] Cover plate structures refer to structures that are symmetrically distributed, bolted together, relatively lightweight, and commonly used for dustproofing and sealing containers. Under complex operating conditions, local modalities in cover plate structures are easily excited, leading to fatigue cracks at the bolted connections and causing severe consequences such as fracture and detachment. Due to limited simulation accuracy and the large number of bolts, accurate fault location for these fatigue cracks is often difficult. Furthermore, the development of fatigue cracks requires the product to undergo a long period of operation; reproducing the fault through testing is time-consuming and costly, hindering the investigation of the fault's cause and the improvement and verification of subsequent products. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings in the prior art by providing an accelerated reproduction method for fatigue crack failures in cover plate structures. By establishing a modal simulation model of the product containing the cover plate structure, and after determining the measurement points, other components except the cover plate are replaced with mass blocks to accelerate fatigue testing of the cover plate structure, shorten the test cycle, and significantly improve the failure reproduction efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: an accelerated reproduction method for fatigue crack failures in cover plate-like structures. The method involves establishing an overall modal simulation model of the product including the cover plate-like structure, determining the measurement points, replacing other components except the cover plate with mass blocks, determining the weight of the equivalent mass blocks using modal simulation, adding the equivalent mass blocks to the middle of the cover plate-like structure, performing a frequency sweep test on the cover plate-like structure, and conducting a dwell test based on the results of the frequency sweep test, thereby rapidly reproducing fatigue crack failures.

[0005] Furthermore, a modal simulation model of the product including cover plate-like structures is established based on the geometric model; parts with less influence such as seals, oil and gaskets in the hydraulic oil tank are deleted and applied to the product in the form of equivalent mass, a mesh is drawn, and a modal simulation model of the hydraulic oil tank as a whole is established.

[0006] Furthermore, based on the overall modal simulation model of the hydraulic tank, the individual component models are assembled into a whole using either bound contact or non-separating contact, while fixed constraints are added. The local modal modes of the cover plate structure are calculated to determine the locations of the cover plate structure with larger vibration responses.

[0007] Furthermore, binding contacts are added between the housing and the main end cover, the housing and the bolts, the bolts and the gaskets, and the gaskets and the cover plate. Non-separation contacts are added between the housing and the cover plate. Fixed constraints are set on the bottom surface of the support. Simulation calculations are performed to obtain the modal vibration mode of the real cover plate.

[0008] Furthermore, the method for determining the weight of the equivalent mass block is as follows: replace all components except the cover plate with the mass block, and add binding contact between the mass block and the cover plate; add a fixture model, add non-separating contact between the cover plate and the fixture, add fixed constraints on the bottom surface of the fixture, and calculate the mode shape of the replaced cover plate; determine the weight of the equivalent mass block by making the mode shape of the cover plate basically consistent with the calculated results in the mode shape of the real cover plate.

[0009] Furthermore, the external shape of the mass block includes, but is not limited to, a hexagonal nut.

[0010] Furthermore, frequency sweep tests were conducted on cover plate structures: a. The locations with the largest vibration response in the modal vibration modes of the actual cover plate are used as monitoring points; b. After installing the equivalent mass block in the middle of the cover plate structure to make it a whole, conduct a frequency sweep test on the cover plate structure.

[0011] Furthermore, in the frequency sweep test results, the frequency point with the largest vibration response amplitude below 1 kHz was selected for the dwell test.

[0012] The beneficial effects of this invention are: This invention calculates the weight of the equivalent mass block through modal simulation and frequency sweep test of the entire product, and then adds the mass block to the middle of the cover plate structure. Frequency sweep test and dwell test are carried out on the cover plate structure to achieve rapid reproduction of fatigue crack failure, which helps and supports fault location, fault cause analysis and subsequent product improvement and verification. Traditional fault reproduction methods rely on real structures for experimental reproduction, which typically takes hundreds of hours. However, the accelerated reproduction method for fatigue crack faults in cover plate structures proposed in this invention can complete the reproduction in just over ten hours, greatly improving the efficiency of fault reproduction. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the workflow of the method of the present invention; Figure 2 This is a product overall modal simulation model built using Ansys; Figure 3 This is a schematic diagram showing the equivalent mass block weight calculated through modal simulation. Figure 4 This is a schematic diagram showing the addition of a mass block in the middle of a cover plate-like structure. Figure 5 A schematic diagram for conducting a frequency sweep test on a cover plate structure after adding a mass block; Figure 6 The image shows the result of fatigue crack fault reproduction. Detailed Implementation

[0014] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific design details are set forth in the following detailed description to provide a more complete understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setup and method set forth below, but covers any improvements, substitutions, and modifications to the structures, methods, and devices without departing from the spirit of the invention. In the drawings and the following description, any parts not exhaustively described are considered to be common knowledge or conventional practices in the art.

[0015] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0016] See appendix Figures 1-6 The method of this invention rapidly reproduces fatigue cracks at the bolts of a hydraulic oil tank cover plate through modal simulation, frequency sweep test, and dwell test, providing assistance and support for fault location, fault cause analysis, and subsequent product improvement and verification. The specific implementation steps are as follows: (1) Establish a modal simulation model: Remove parts such as seals, oil and gaskets that have a small impact in the hydraulic tank, apply them to the product in the form of equivalent mass, draw a mesh, and establish a modal simulation model of the hydraulic tank as a whole; the drawn mesh is easier to converge and the simulation calculation efficiency is higher. (2) Calculate the mode shape of the cover plate: Add binding contact between the box and the main end cover, the box and the bolt, the bolt and the gasket, and the gasket and the cover plate. Add non-separation contact between the box and the cover plate. Set fixed constraints on the bottom surface of the support and perform simulation calculations to obtain the mode shape of the cover plate. (3) Calculate the equivalent mass block weight: The model in (2) is reduced, and the other parts except the cover plate are replaced with mass blocks. A binding contact is added between the mass block and the cover plate. A fixture model is added, and a non-separating contact is added between the cover plate and the fixture. A fixed constraint is added to the bottom surface of the fixture. The mode shape of the cover plate is calculated. The weight of the equivalent mass block is determined by making the mode shape of the cover plate basically consistent with the calculation results in (2). This can ensure that the fault reproduction results are closer to the actual fault results. (4) Conduct a sweep frequency test: After installing the equivalent mass block in the middle of the cover plate to make it a whole, install the cover plate on the fixture; take the position of the cover plate with the larger vibration response obtained in (2) as the monitoring point and conduct a sweep frequency test on the cover plate.

[0017] (5) Conduct a dwell test: In the results of (5), select the frequency point with the largest vibration response amplitude below 1kHz and conduct a dwell test on the cover plate to realize the rapid reproduction of fatigue crack failure.

[0018] Example 1 like Figures 2 to 6 As shown, the specific implementation process of the accelerated reproduction method for fatigue crack failure in cover plate structures according to the present invention is as follows: Step 1: Establish a modal simulation model of the entire hydraulic oil tank, such as... Figure 2 As shown; Step 2: Calculate the locations of the cover plate with the largest vibration response using the model from Step 1; Step 3: Determine the weight of the equivalent mass block through modal simulation, such as... Figure 3 As shown; Step 4: Add the mass block to the middle of the cover plate to make it a whole, and then install the cover plate onto the fixture, such as... Figure 4 As shown; Step 5: Conduct a frequency sweep test on the entire cover plate as described in Step 4, such as... Figure 5 As shown; Step 6: Based on the test results of Step 5, conduct a dwell test on the cover plate to achieve rapid reproduction of fatigue crack failure, such as... Figure 6 As shown.

[0019] The method proposed in the above specific implementation of the present invention can accelerate fatigue testing of cover plate structures, significantly shorten the testing cycle, and significantly improve the efficiency of fault reproduction.

[0020] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for accelerated reproduction of fatigue crack failure of a cover plate type structure, characterized by, The method comprises the following steps: establishing a modal simulation model of a product containing a cover plate type structure; replacing other components except the cover plate with a mass block; determining the weight of the equivalent mass block by modal simulation; adding the equivalent mass block to the middle of the cover plate type structure; conducting a sweep frequency test on the cover plate type structure; and conducting a dwell test according to the sweep frequency test results, thereby quickly realizing the reproduction of the fatigue crack fault.

2. The method of claim 1, wherein the fatigue crack failure of the cover plate structure is accelerated by, A modal simulation model of the product containing the cover plate type structure is established based on a geometric model; the sealing ring, oil and gasket and other parts that have less influence on the hydraulic oil tank are deleted and applied to the product in the form of equivalent mass; a grid is drawn; and a modal simulation model of the whole hydraulic oil tank is established.

3. The method of claim 2, wherein the fatigue crack failure of the cover plate structure is accelerated by, Based on the modal simulation model of the whole hydraulic oil tank, the part models are assembled into a whole by using bound contact or non-separation contact, and a fixed constraint is added, so as to calculate the local modal vibration mode of the cover plate type structure and determine the position with greater vibration response of the cover plate type structure.

4. The method of claim 3, wherein the fatigue crack failure of the cover plate structure is accelerated by, Bound contact is added between the tank and the main end cover, the tank and the bolt, the bolt and the gasket, the gasket and the cover plate, non-separation contact is added between the tank and the cover plate, a fixed constraint is arranged on the bottom surface of the bracket, and simulation calculation is performed, so as to obtain the modal vibration mode of the real cover plate.

5. The method of claim 4, wherein the fatigue crack failure of the cover plate structure is accelerated by, The method for determining the weight of the equivalent mass block is as follows: other components except the cover plate are replaced with a mass block, and bound contact is added between the mass block and the cover plate; a clamp model is added, non-separation contact is added between the cover plate and the clamp, and a fixed constraint is added to the bottom surface of the clamp, so as to calculate the modal vibration mode of the replaced cover plate; the weight of the equivalent mass block is determined by making the vibration mode of the cover plate substantially consistent with the calculation result in the modal vibration mode of the real cover plate.

6. The method of claim 5, wherein the fatigue crack failure of the cover plate structure is accelerated by, The shape structure of the mass block includes but is not limited to a hexagonal nut.

7. The method of claim 5, wherein the fatigue crack failure of the cover plate structure is accelerated by, The sweep frequency test is conducted on the cover plate type structure as follows: a. The position with greater vibration response in the modal vibration mode of the real cover plate is taken as a monitoring point; b. The equivalent mass block is added to the middle of the cover plate type structure, so that the sweep frequency test is conducted on the cover plate type structure.

8. The method of claim 7, wherein the fatigue crack failure of the cover plate structure is accelerated by, In the sweep frequency test results, the frequency point with the maximum vibration response amplitude below 1 kHz is selected for the dwell test.

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