CN-122016453-A - Duplex self-centering device for fatigue test and double-parameter progressive testing method

Abstract

The invention discloses a duplex self-centering device for a fatigue test and a double-parameter progressive testing method, wherein the duplex self-centering device is provided with two bearing plates at the center of a fatigue tester, and the bearing plates are fixed through bolts and nuts; the concave spherical surface of the bearing plate is sequentially provided with a spherical surface backing plate, a polytetrafluoroethylene ring and a steel wire anchoring piece, the steel wire anchoring piece consists of a casting body and a steel wire, and the steel wire penetrates through holes in the centers of the polytetrafluoroethylene ring, the spherical surface backing plate and the concave spherical surface of the bearing plate and is connected to a clamp of the fatigue testing machine for clamping. The fatigue test adopts the device and utilizes the stress amplitude and the anchoring length to carry out progressive cumulative test. According to the invention, the synchronous test of two steel wire anchoring test pieces is realized through the duplex structural design, the test precision is ensured, the test efficiency is greatly improved, and the test cost is reduced, so that the batch test is satisfied to obtain the actually required steel wire anchoring S-N curve, and the basis is provided for the fatigue-resistant design of the steel wire anchoring of the bridge cable.

Inventors

• ZENG SHUKANG
• LI XITONG
• Zou Xuwei
• HUANG ZHUOYUN
• SHEN XIUWEN
• WANG LU
• SHEN RUILI
• ZHOU PING
• GU SONG
• GU YING
• REN SONGBO
• KONG CHAO
• HUANG GUANG

Assignees

• 西南科技大学

Dates

Publication Date

20260512

Application Date

20260210

Claims (6)

1. 1. A duplex self-centering device for a steel wire anchoring fatigue test is characterized in that two bearing plates (2) are vertically arranged in the center of a fatigue tester (1), four corners of each bearing plate (2) penetrate through four bolts (5) and are fixed through nuts (3), a concave spherical surface is formed in the middle of each bearing plate (2), a central opening is formed in the middle of each bearing plate, a spherical base plate (7), a polytetrafluoroethylene ring (6) and a steel wire anchoring piece (4) are sequentially arranged on the concave spherical surface of each bearing plate (2), each steel wire anchoring piece (4) consists of a casting body (401) and a steel wire (402), each steel wire (402) penetrates through a hole in the center of the concave spherical surface of each polytetrafluoroethylene ring (6), each spherical base plate (7) and each bearing plate (2) and is connected to a lower clamp of the fatigue tester (1), and the other bearing plates (2) are identical in arrangement, but the steel wires (402) are connected to the upper clamp of the fatigue tester (1).
2. 2. The duplex self-centering device for steel wire anchoring fatigue test according to claim 1, wherein the hole diameters of the centers of the bearing plate (2) and the spherical backing plate (7) are slightly larger than the diameter of the steel wire (402).
3. 3. A duplex self-centering device for steel wire anchoring fatigue test according to claim 1, wherein the hole diameter in the center of the polytetrafluoroethylene ring (6) is identical to the diameter of the steel wire (402).
4. 4. The duplex self-centering device for steel wire anchoring fatigue test according to claim 1, wherein the two ends of the bolt (5) are threaded and the middle is smooth.
5. 5. A double-parameter progressive testing method for a steel wire anchoring fatigue test, which is characterized by using the double-connection type self-centering device according to any one of claims 1-5, and comprises the following specific experimental steps: Step 1, preparing a batch of steel wire anchoring pieces (4), grouping and numbering according to the stress amplitude and the anchoring length from small to large, wherein each group of test starts from the test piece with the smallest number, and each group of test pieces is provided with a plurality of copies; Step 2, assembling the tool according to the requirement, and setting a stress amplitude; Step 3, clamping the free end steel wire (402) of the steel wire anchoring member with a longer anchoring length by an upper clamp of the fatigue testing machine (1), and clamping the free end steel wire (402) of the steel wire anchoring member with a smaller anchoring length by a lower clamp; Step4, starting the fatigue testing machine (1), loading fatigue load in a circulating way until a test piece is damaged, and recording the load circulation times C; Step 5, taking down and disassembling the tool, taking out two test pieces, replacing the damaged steel wire anchoring piece (4) with the next steel wire anchoring piece (4) of the same group, assembling and inverting the tool, and continuing loading until all the steel wire anchoring pieces (4) of the same group except the last steel wire anchoring piece (4) are subjected to loading damage; step 6, completing the test of the replication group, recording the load cycle times, and completing the discrete processing of test data; step 7, setting the stress amplitude of the next stage, and repeating the steps 3-5 until each group is completely destroyed except the last test piece; Step 8, summarizing the fatigue load cycle times C, and converting the fatigue load cycle times C into the fatigue life N of the test piece under different stress amplitudes and different anchoring lengths according to the fatigue load cycle times C; and 9, drawing a fatigue curve under different anchoring lengths, namely an S-N curve, by taking a stress amplitude sigma as an ordinate and a logarithm lgN of the fatigue life of the test piece as an abscissa.
6. 6. The method for testing the double parameters of the steel wire anchoring fatigue test according to claim 5, wherein the installing step in the step 2 is as follows: step 2.1, one of the bearing plates (2) is penetrated through 4 bolts (5), wherein the concave spherical surface side of the bearing plate (2) faces inwards, and then an inner side nut (3) is installed; step 2.2, sequentially penetrating 1 steel wire anchoring piece (4) to be detected through the polytetrafluoroethylene ring (6), the spherical backing plate (7) and the bearing plate (2); step 2.3, screwing another group of inner nuts (3) at the position of the threads at the other end of the bolt (5), sequentially penetrating a steel wire anchoring piece (4) to be detected through a polytetrafluoroethylene ring (6), a spherical backing plate (7) and another bearing plate according to the method of step 2.2, penetrating the bearing plate through the bolt, properly leveling the bearing plate by adjusting the inner nuts, and screwing the nuts (3) at the outer side of the top plate (2); and 2.4, setting the stress amplitude of the fatigue testing machine (1).

Description

Duplex self-centering device for fatigue test and double-parameter progressive testing method Technical Field The invention belongs to the technology of testing the anchoring performance of bridge cable steel wires, and particularly relates to a duplex self-centering device for a fatigue test and a double-parameter progressive testing method. Background The deep implementation of national ' national traffic and ' national manufacturing ' strategy continuously promotes the construction of large channels in river-crossing, sea-crossing and mountain areas, and drives the cable-bearing bridge to develop towards a larger span direction. At present, the main span of the established world maximum span cable-stayed bridge-Chang Tai Yangtze river bridge reaches 1208m, and the main span of the established world maximum span suspension bridge-Zhang Jinggao Yangtze river bridge reaches 2300m. As a core load-bearing member of such a bridge, a cable composed of a large number of steel wires, including a main cable, a sling, and a stay cable, has a strength to be lifted in synchronization with span growth. In recent ten years, the bridge cable strength of China realizes leading rapid jump, the steel wire strength of the stay cable of the established Changtai Yangtze river bridge reaches 2100MPa, and the steel wire strength of the main cable of the established Zhang Jinggao Yangtze river bridge reaches 2200MPa. Meanwhile, the cable realizes force transmission through the anchoring systems at the two ends of the cable, so that the improvement of the strength of the steel wire of the cable puts the same high requirements on the safety of cable anchoring, and the cable mainly comprises two layers of anchoring bearing and fatigue resistance. In the bearing layer, the anchor bearing capacity is generally improved by developing novel anchor materials or lengthening anchor length and the like, and safety inspection is carried out by using anchor pull-out tests, so that the research in the industry is relatively mature. On the other hand, in the bridge operation process, due to alternating actions of vehicles, wind, temperature and the like, accumulated damage is very easy to occur at the cable anchoring position, and finally fatigue damage is likely to occur, so that the safety of the full-bridge structure is affected. Therefore, the method has important practical significance in accurately testing and evaluating the anchoring fatigue performance of the cable wire. However, current test analysis of cable anchoring fatigue performance also lacks effective means, resulting in lack of direct data support for related theoretical research and engineering applications. The main reason is that a plurality of parameters exist in the cable wire anchoring test piece, and different parameter combinations can generate more working conditions, namely the sample size of the test to be tested is often larger. Secondly, the fatigue test has long period and high cost, and the traditional one-by-one test method cannot bear the test requirements of a large number of test pieces. Thirdly, the fatigue test is extremely sensitive, and the test piece needs to be kept centered to avoid the influence of additional bending moment, so that the requirement on the assembly precision of the test device is very high. Therefore, aiming at a large number of cable steel wire anchoring fatigue test pieces, it is necessary to develop a test device and a test method capable of improving test efficiency, saving test cost and guaranteeing centering of the test pieces. Disclosure of Invention The invention provides a duplex self-centering device for a fatigue test and a double-parameter progressive test method, which aims to solve the problems of insufficient device precision and low test efficiency in the steel wire anchoring fatigue test. The invention discloses a duplex self-centering device for a steel wire anchoring fatigue test, wherein two bearing plates are vertically arranged in the center of a fatigue tester, four corners of each of the two bearing plates penetrate through four bolts and are fixed by nuts, a concave spherical surface is formed in the middle of one bearing plate, a central opening is formed in the middle of the bearing plate, a spherical surface base plate, a polytetrafluoroethylene ring and a steel wire anchoring piece are sequentially arranged on the concave spherical surface of the bearing plate, the steel wire anchoring piece consists of a casting body and a steel wire, the steel wire penetrates through holes in the centers of the polytetrafluoroethylene ring, the spherical surface base plate and the concave spherical surface of the bearing plate and is connected to a clamp on the fatigue tester for clamping, and the other bearing plates are identical in arrangement, but the steel wire is connected to the clamp on the fatigue tester for clamping. Further, the diameters of the holes in the centers of the bearing plate and the spherical back