Loading mechanism and testing device for fatigue testing of welded joints of bushing structural components

Abstract

This utility model relates to the field of fatigue testing technology for welded joints, specifically disclosing a loading mechanism for fatigue testing of welded joints of bushing structures. The mechanism includes a loader and a loading head. The loading head includes a mounting frame, rollers, and a loading block. The mounting frame is connected to the output end of the loader. The rollers are mounted on the mounting frame, which has a limiting structure, allowing the rollers to move horizontally. The loading block is placed above the bushing under test. The rollers roll on the loading block and transfer the load to the test piece when the loader applies the load. A fatigue testing device for welded joints of bushing structures includes a clamp assembly for holding the upper side plate of the test piece, and a loading mechanism for fatigue testing of welded joints of bushing structures. This solution addresses the problems in existing cantilever loading tests where lateral forces generated by specimen deformation damage the loading equipment, and the inability of traditional loading methods to realistically simulate the actual stress state of the bushing.

Description

Technical Field

[0001] This utility model relates to the field of fatigue testing technology for welded joints, specifically to a loading mechanism and testing device for fatigue testing of welded joints of bushing pipe structures. Background Technology

[0002] Dump trucks, used under specific conditions, primarily engage in short-distance transportation. Their frequent unloading operations and harsh working environments necessitate extremely high safety performance requirements. The dump truck's cargo box tipping axle is connected to the subframe via a lifting axle sleeve support, a key component of the dump truck's lifting mechanism. The lifting axle sleeve support is typically welded to the side plate of the subframe, while the tipping axle is inserted into the axle sleeve of the support. During cargo box lifting, the axle sleeve and tipping axle are often in a state of dry friction. Overloading the vehicle drastically exacerbates wear at this point, severely impacting the service life of the lifting axle sleeve support and posing a serious safety hazard. Therefore, the performance of the welded joint between the axle sleeve and the subframe is a core issue of primary concern in the overall vehicle safety design.

[0003] Traditional fatigue tests on welded joints mostly target common joints such as butt joints, T-joints, corner joints, and lap joints, and standard specimens are fabricated for testing. However, for a bushing structure consisting of a bushing tube, side plates, and possibly reinforcing retaining rings, the welded joint needs to simulate the force transmission path of "rotational shaft stress - bushing tube - side plate." Due to its structural specificity, it cannot be directly loaded on a standard fatigue testing machine and must be connected using a special fixture. Currently, the lack of dedicated fatigue testing fixtures for this type of joint significantly hinders the testing and evaluation of its fatigue performance.

[0004] To verify the performance of such joints, existing technologies have used a "bridge" support system for testing, where both side plates of the bushing are fixed to a fixture, and a load is applied between the two plates. However, to improve load-bearing capacity, modern heavy-duty dump trucks often employ a reinforced design: the bushing and side plates are connected by a retaining ring, with the inner ring of the retaining ring forming a circumferential weld with the outer circumference of the bushing, and the outer ring of the retaining ring then undergoing a large-area weld to the end face of the side plate. This results in extremely high structural strength. To induce cracks in the weld, an extremely high load must be applied, leading to two serious problems: first, the tonnage requirements for the testing equipment are extremely high, resulting in high costs; second, and more problematic, the loading limit of conventional fatigue testing machines is typically no more than 200 kN. Under this bridge support system, even when loaded to the equipment's ultimate load, it is often impossible to induce cracks in the high-strength weld, making it impossible to test the true fatigue limit of the weld joint, effectively assess its safety margin, and rendering the test meaningless.

[0005] To reduce the tonnage requirements of the equipment, existing technologies have explored a "cantilever loading" method, which involves clamping only one side plate and applying a load to the cantilever side of the bushing. This method can significantly reduce the required load, but it presents new challenges to the loading mechanism. Specifically, when a vertical load is applied to a horizontally positioned cantilever bushing, the tested structure will flex under the load, generating a significant lateral force on the load-applying output rod, which can damage the equipment. Taking the hydraulic cylinder used for applying the load as an example, the piston rod of the hydraulic cylinder will be subjected to a lateral force. This lateral force can force the piston rod and cylinder barrel to become misaligned, easily causing damage and oil leakage to the hydraulic cylinder. This not only affects the smooth progress of the test and the lifespan of the equipment, but also prevents the test from accurately simulating the actual stress state of the bushing.

[0006] In summary, there is an urgent need in this field for a new type of loading mechanism that can adapt to cantilever loading methods, effectively reduce loading load requirements, and avoid damage to the loading equipment by lateral forces. Utility Model Content

[0007] This utility model aims to provide a loading mechanism for fatigue testing of welded joints of bushing structural components, in order to solve the problems of damage to the loading equipment caused by lateral force generated by specimen deformation in existing cantilever loading tests, and the inability of traditional loading methods to truly simulate the actual stress state of the bushing.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A loading mechanism for fatigue testing of welded joints of bushing structural components includes a loader and a loading head. The loading head includes a mounting frame, rollers, and a loading block arranged sequentially from top to bottom. The mounting frame is connected to the output end of the loader. The rollers are mounted on the mounting frame, which is equipped with a limiting structure. The rollers can move horizontally within the limiting area of ​​the limiting structure. The loading block is used to be placed above the bushing under test. The rollers are used to roll on the loading block and transfer the load to the test piece when the loader applies the load.

[0009] The principle and advantages of this scheme are as follows: This scheme transforms traditional rigid loading into flexible rolling loading through a "roller-loading block" contact method. When the loader presses down on the roller through the mounting frame, the roller transfers the load to the loading block below, which then acts on the bushing being tested. During the frequent alternating loading in the test process, the roller can move horizontally within the restricted area of ​​the limiting structure. This allows the roller to slide dynamically within the restricted area when the bushing structure undergoes bending deformation under stress, automatically compensating for the change in loading position caused by this bending. This avoids harmful lateral forces on the loader piston rod caused by structural deformation, effectively preventing damage and oil leakage to the loader, and ensuring the continuity of the test and equipment safety.

[0010] Furthermore, the way the rollers in this design roll on the loading block to apply force is highly similar to the dry friction rolling condition between the tipping shaft and the bushing in actual operation of a dump truck. This can more realistically reproduce the actual stress state of the bushing welded joint, thus making the obtained fatigue test data more accurate and reliable.

[0011] In addition, because this solution is used in conjunction with the cantilever loading method for fatigue testing, the load required for weld cracks to appear in the test is reduced, which helps to reduce the requirements for the loader and reduce the cost of the loader.

[0012] Preferably, as an improvement, the limiting structure is at least a pair of strip-shaped limiting grooves, and the central shaft of the roller is slidably connected to the strip-shaped limiting grooves. This solution forms a limitation on the slippage of the roller with a simple structure.

[0013] Preferably, as an improvement, the loading block includes a loading pad block and a loading block body with an arc-shaped mating surface that mates with the shaft sleeve structure being measured, wherein the loading pad block is detachably connected to the top of the loading block body.

[0014] Beneficial effects: The split design makes the loading pad a consumable and adaptable part. When the pad wears out or different load conditions need to be tested, only the loading pad of different specifications needs to be replaced, without replacing the entire loading block. This reduces the cost of use and maintenance time, and improves the versatility and flexibility of the mechanism.

[0015] Preferably, as an improvement, it also includes a height adjustment component disposed between the loader output end and the mounting bracket.

[0016] Beneficial effects: The height adjustment component allows for flexible adjustment of the initial height of the loading head, enabling rapid and accurate adaptation to different sizes and specifications of the tested shaft sleeve structure, thus improving the versatility of the test and the clamping efficiency.

[0017] Preferably, as an improvement, the height adjustment component is a linear drive mechanism.

[0018] Beneficial effects: The linear drive mechanism not only enables precise height adjustment but also functions as a rigid force transmission unit. During test loading, this mechanism works in conjunction with the loader to jointly bear and transmit the load, effectively sharing the force borne by the loader. This significantly enhances the ultimate loading capacity of the entire test setup, enabling it to meet the fatigue test requirements of higher tonnage units.

[0019] Preferably, as an improvement, the linear drive mechanism is a hydraulic regulating cylinder, the cylinder body of which is connected to the mounting bracket, the piston inside the hydraulic regulating cylinder is connected to the output end of the loader, and the cylinder body is provided with a control oil port.

[0020] Beneficial effects: Utilizing a hydraulic adjusting cylinder and the incompressible nature of hydraulic oil, it achieves stable, slippage-free rigid support and force transmission. Its compact structure and high load-bearing capacity enable dual functions of height adjustment and auxiliary loading. The oil circuit can be locked by controlling the oil port, rigidly connecting the cylinder body and piston into one unit, making operation simple and reliable.

[0021] In addition, the presence of the hydraulic adjusting cylinder allows the mounting bracket on the loading head to be made shorter, thereby increasing the strength of the mounting bracket.

[0022] Preferably, as an improvement, the control port includes an inlet and an outlet. The outlet communicates with the rodless chamber of the cylinder near the mounting bracket, and the inlet communicates with the rod chamber of the cylinder. This facilitates height adjustment and load adjustment.

[0023] Preferably, as an improvement, the mounting bracket is detachably connected to the cylinder body of the hydraulic regulating cylinder.

[0024] Preferably, as an improvement, a force sensor is also included, which is disposed between the output end of the loader and the loading head to monitor and provide feedback on the load force applied to the specimen in real time and accurately.

[0025] This utility model also provides a fatigue testing device for welded joints of bushing structures, including a clamp assembly for clamping and fixing the upper side plate of the bushing structure under test, and a loading mechanism for fatigue testing of welded joints of bushing structures. Attached Figure Description

[0026] Figure 1 This is a three-dimensional structural schematic diagram of the fatigue testing device for the welded joint of the bushing tube structure according to an embodiment of the present invention.

[0027] Figure 2 for Figure 1 A schematic diagram of the three-dimensional structure after rotating 90 degrees.

[0028] Figure 3 for Figure 1 The main view.

[0029] Figure 4 for Figure 1 A partial right-side cross-sectional view (to illustrate the relationship between the hydraulic adjusting cylinder, which is a height adjustment component, the loading head, and the test piece).

[0030] Figure 5 In this embodiment, the clamping assembly clamps the side plate of the test piece, while the loading chuck is in an exploded view.

[0031] Figure 6 for Figure 5 A schematic diagram of the three-dimensional structure after rotating 90 degrees.

[0032] The reference numerals in the accompanying drawings include: test bench 1, fixed bracket 11, fixture assembly 2, front clamping baffle 21a, rear clamping baffle 21b, reinforcing plate 22, fixed base plate 23, locking element 24, loading mechanism 3, loader 31, hydraulic cylinder 31, piston rod 311, force sensor 32, linear drive mechanism 33, hydraulic adjusting cylinder 33, piston 331, oil inlet 332, oil outlet 333, mounting block 334, loading head 34, fork 341, roller 342, loading block 343, anti-loosening nut 344, loading pad 343a, loading block body 343b, test piece 100, bushing 10, side plate 20, and retaining ring 30. Detailed Implementation

[0033] The following detailed description illustrates the specific implementation methods: The basic implementation examples are as follows: Figures 1 to 6 As shown.

[0034] Combination Figure 1 A fatigue testing device for welded joints of bushing structures includes a test bench 1, a fixture assembly 2 mounted on the test bench 1, and a loading mechanism 3 for fatigue testing of welded joints of bushing structures mounted on the test bench 1.

[0035] The clamp assembly 2 is used to clamp and fix the upper side plate 20 of the shaft sleeve structure under test. The clamp assembly 2 includes a front clamping baffle 21a, a rear clamping baffle 21b, a reinforcing plate 22, a fixed base plate 23, and a locking element 24. The front clamping baffle 21a and the rear clamping baffle 21b form a pair, and the front clamping baffle 21a and the rear clamping baffle 21b are respectively welded to the two fixed base plates 23. The clamping baffle 21a is perpendicular to the fixed base plate 23. Then, the front and rear baffles are clamped and fixed to the side plate 20 of the test piece 100 by the locking element 24 (such as a locking bolt).

[0036] The reinforcing plate 22 is installed between the clamping baffle and the fixed base plate 23 to make the clamp assembly 2 more secure. The fixed base plate 23 is fixed to the test bench 1 by anchor bolts.

[0037] The loading mechanism 3 for fatigue testing of welded joints of bushing structure components includes a loader 31, a force sensor 32, a linear drive mechanism 33, and a loading head 34 arranged from top to bottom.

[0038] The loader 31 is fixedly installed on the test bench 1 by a fixed bracket 11. In this embodiment, it is a hydraulic cylinder 31. The output rod of the hydraulic cylinder 31 is a piston rod 311. A force sensor 32 is fixedly installed at the downward-extending end of the piston rod 311 of the loader 31 to more accurately sense the magnitude of the force.

[0039] The linear drive mechanism 33 is a hydraulic regulating cylinder 33. The bottom of the cylinder body of the hydraulic regulating cylinder 33 is connected to the loading head 34. The piston 331 inside the hydraulic regulating cylinder 33 is connected to the cylinder body that passes through the top of the cylinder body of the hydraulic regulating cylinder 33 and is fixed to the bottom of the force sensor 32.

[0040] The hydraulic regulating cylinder 33 has a control oil port on its cylinder body. The control oil port includes an oil inlet 332 and an oil outlet 333. The oil outlet 333 is connected to the rodless cavity of the cylinder body near the loading head 34, and the oil inlet 332 is connected to the rod cavity of the cylinder body.

[0041] The loading head 34 includes a mounting bracket 341, a roller 342, and a loading block 343 arranged sequentially from top to bottom. In this embodiment, the mounting bracket 341 is fork-shaped and is therefore called a fork bracket 341. The bottom of the cylinder body of the hydraulic adjusting cylinder 33 is fixed with a mounting block 334. The mounting block 334 is threaded, and the fork bracket 341 is threadedly connected to the mounting block 334 to facilitate the replacement of the loading head 34.

[0042] The roller 342 is mounted on the fork carriage 341, which is provided with a limiting structure. The roller 342 can move horizontally within the limiting area of ​​the limiting structure. Specifically, the limiting structure is a pair of strip-shaped limiting grooves opened on the fork carriage 341. The central shaft of the roller 342 is slidably connected to the strip-shaped limiting grooves, and an anti-loosening nut 344 is installed at the end of the central shaft.

[0043] The loading block 343 is used to be placed above the sleeve of the shaft under test; the roller 342 is used to roll on the loading block 343 and transfer the load to the test piece 100 when the loader 31 loads.

[0044] The loading block 343 includes a loading pad 343a and a loading block body 343b with an arc-shaped mating surface that mates with the shaft sleeve structure being measured. The loading pad 343a is detachably connected to the top of the loading block body 343b. In this embodiment, the loading block 343 is bolted to the loading block body 343b. The surface roughness of the top surface of the loading pad 343a is 0.1~1.6μm.

[0045] When roller 342 applies load on loading pad 343a, the load is transferred to the welded joint of the tested bushing structure through loading block body 343b. The main purpose of using roller 342 for loading is to decompose the lateral force applied by the vertical load, and to prevent the piston rod 311, which serves as the output rod of the loader 31, from becoming misaligned, which could lead to damage and oil leakage of the loader 31. At the same time, the rolling loading of roller 342 and loading block 343 and the dry friction force on the bushing of the lifting and tilting shaft are more closely similar, accurately replicating the actual stress state of the bushing.

[0046] In this embodiment, the fatigue test is conducted using the following steps: S1. Clamping steps: Fix the side plate 20 of the shaft sleeve structure to be measured by the clamp assembly 2, so that the shaft sleeve is in a cantilever state. S2. Alignment step: Place the loading block 343 at the predetermined position of the bushing of the test piece 100, and adjust the hydraulic adjusting cylinder 33 on the loading mechanism 3 for fatigue test of the welded joint of the bushing structure to make the roller 342 contact the upper surface of the loading block 343. S3. Loading steps: Control the loader 31 to apply an alternating load to the loading block 343; the load ratio of the alternating load is R=0.1, the loading waveform is a sine wave, and the loading frequency is 1Hz~10Hz; during the loading process, record the test data.

[0047] In this embodiment, the tested bushing structure is clamped and fixed to the side plate 20 by the fixture assembly 2. Then, the loading mechanism 3 for fatigue testing of the welded joint of the bushing structure is used to perform flexible rolling loading on the loading block 343 through the contact method of "roller 342-loading block 343". When the loader 31 presses down on the roller 342 through the fork 341, the roller 342 transfers the load to the loading block 343 below, and then acts on the bushing under test. During the frequent alternating loading in the test process, the roller 342 can move horizontally within the restricted area of ​​the limiting structure. This allows the roller 342 to slide dynamically within the restricted area when the bushing structure is subjected to bending deformation, automatically compensating for the change in loading position caused by this bending. This avoids harmful lateral forces on the piston rod 311 of the loader 31 due to structural deformation, effectively preventing damage and oil leakage to the loader 31, and ensuring the continuity of the test and equipment safety.

[0048] Furthermore, the way the roller 342 rolls on the loading block 343 in this embodiment is highly similar to the dry friction rolling condition between the tipping shaft and the bushing in actual operation of a dump truck. This can more realistically reproduce the actual stress state of the bushing welded joint, thereby making the obtained fatigue test data more accurate and reliable.

[0049] Furthermore, in this embodiment, the hydraulic adjusting cylinder 33 is positioned between the loader 31 and the loading head 34. Utilizing the incompressible nature of hydraulic oil, it achieves stable, slippage-free rigid support and force transmission. Its compact structure and high load-bearing capacity enable it to perform both height adjustment and auxiliary loading functions. The oil circuit can be locked by controlling the oil port, rigidly connecting the cylinder body of the hydraulic adjusting cylinder 33 and the piston 331 into a single unit, making operation simple and reliable.

[0050] In addition, because this embodiment uses a cantilever loading method for fatigue testing, the load required for weld cracks to appear in the test is reduced, which helps to reduce the requirements for the loader 31 and reduce the cost of the loader 31.

[0051] The above descriptions are merely embodiments of this utility model. Commonly known technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solution of this utility model. These modifications and improvements should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A loading mechanism for fatigue testing of welded joints of bushing structural components, comprising a loading machine and a loading head, characterized in that, The loading head includes a mounting frame, rollers, and a loading block arranged sequentially from top to bottom. The mounting frame is connected to the output end of the loader. The rollers are mounted on the mounting frame, which is equipped with a limiting structure. The rollers can move horizontally within the limiting area of ​​the limiting structure. The loading block is used to be placed above the sleeve of the shaft being tested. The rollers are used to roll on the loading block and transfer the load to the test piece when the loader is loading.

2. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 1, characterized in that, The limiting structure is at least one pair of strip-shaped limiting grooves.

3. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 1, characterized in that, The loading block includes a loading pad block and a loading block body with an arc-shaped mating surface that mates with the shaft sleeve structure being measured. The loading pad block is detachably connected to the top of the loading block body.

4. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 1, characterized in that, It also includes a height adjustment component located between the loader output and the mounting bracket.

5. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 4, characterized in that, The height adjustment component is a linear drive mechanism.

6. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 5, characterized in that, The linear drive mechanism is a hydraulic regulating cylinder. The cylinder body of the hydraulic regulating cylinder is connected to the mounting bracket, and the piston inside the hydraulic regulating cylinder is connected to the output end of the loader. The cylinder body is provided with a control oil port.

7. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 6, characterized in that, The control port includes an oil inlet and an oil outlet. The oil outlet is connected to the rodless chamber of the cylinder near the mounting bracket, and the oil inlet is connected to the rod chamber of the cylinder.

8. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 6, characterized in that, The mounting bracket is detachably connected to the cylinder body of the hydraulic regulating cylinder.

9. The loading mechanism for fatigue testing of welded joints of bushing structural components according to claim 1, characterized in that, It also includes a force sensor, which is disposed between the output end of the loader and the loading head.

10. A fatigue testing device for welded joints of a bushing structure, comprising a clamp assembly for holding and fixing the upper side plate of the bushing structure under test, characterized in that, It also includes a loading mechanism for fatigue testing of welded joints of bushing structures as described in any one of claims 1 to 9.

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