Development of self-lubricating spherical plain bearings for key nodes of space self-anchored suspension bridges of Hangzhou Jiangdong Bridge

Development of self-lubricating spherical plain bearings for key nodes of space self-anchored suspension bridges of Hangzhou Jiangdong Bridge

1.Project background

Hangzhou Jiangdong Bridge is an important part of the Hangzhou Qiantang River Crossing Project. As the most novel structure and the most difficult construction bridge on the Qiantang River, Jiangdong Bridge is the only space cable self-anchored suspension bridge and prestressed concrete continuous beam combination in the country. system. The structure of the bridge is unique, the bridge is multi-type, the process is complex, the technical difficulty is high, and a large number of new processes need to be applied. Among them, the main navigation hole self-anchored suspension bridge has a unique shape.

It is a three-span space cable self-anchored suspension bridge. The main span of the suspension bridge is 260 meters. There is no precedent for this type of suspension bridge in China. In this space self-anchored suspension bridge, the suspension cables are inclined transversely in the bridge stage, and the slope is relatively large, about 2.9:1, which requires that the suspension cables must adapt to the longitudinal and transverse bidirectional deformation. Generally, the pin-connected slings of traditional suspension bridges can only adapt to one-way deformation, so the bridge must be innovatively designed and developed a new type of sling ball joint. The principals of the Shanghai Engineering Design and Research Institute and the Shanghai Materials Research Institute, the project design units, have visited our company for many times, and entrusted our company to develop the spherical plain bearings used in the ball joints.

2. Project implementation plan

2.1 Preliminary work of the project

Through technical exchanges with the main design personnel of Shanghai Engineering Design and Research Institute in the early stage, it is initially assumed that the upper end of the sling is connected with the main cable clamp by a radial spherical plain bearing, and the lower end is connected with the steel box girder by an angular contact spherical bearing, so that the sling can not only Adapt to the deformation along the bridge, but also adapt to the deformation of the transverse bridge. For the engineering requirements to ensure a service life of 50 years, it is preliminarily determined to use self-lubricating spherical plain bearings and stainless steel materials, and it is determined to first make samples for full-scale tests.

2.2 Main contents and objectives of project R&D or construction

Pin-connected sling features (technical indicators): It can adapt to vertical and horizontal two-way deformation, the friction coefficient of the upper and lower joints is small (set index value), and it can adapt to ±6° rotation angles.

Main contents and objectives of project R&D or construction

2.2.1 Basic requirements of the project:

The bearings of this project must meet the requirements of anti-aging and corrosion resistance, self-lubrication, wear resistance and long life under the harsh working conditions of the ring, and at the same time, they must have the ability to adjust the deflection, buffer vibration, and do not need maintenance. In order to meet these requirements, the self-lubricating radial spherical plain bearings for the key nodes of the Jiangdong Bridge space self-anchored suspension bridge adopt the following structural forms: The outer ring is made of stainless steel 4Cr13, quenched, and the outer ring is split. The inner spherical surface is chrome-plated and fixed with a lock ring. The end face of the outer ring is embedded in the sealing ring material using PTFE; the inner ring is made of stainless steel 4Cr13, and the spherical surface is inlaid with uniform solid self-lubricating material. The main technical key points that need to be solved for this type of bearing are: (1) Research on friction properties of spherical inlaid solid self-lubricating materials; (2) Research on inlaying spherical surface technology of solid self-lubricating materials; (3) Research on technological performance of PTFE sealing ring; (4) Research on manufacturing process of inner and outer rings; ( 5) Research on matching technology of inner ring and outer ring.

2.2.2 The product structure diagram is shown in Figure

The bearing of this structure breaks the limit of the service life of the general radial spherical plain bearing with a sealing ring of 20 to 30 years, and reaches the service life of 50 years. Bear high radial load, small swing angle, self-lubrication, maintenance-free, wear-resistant and other special conditions such as space cable self-anchored suspension bridge.

2.2.3 Key technology research contents:

(1) Research on product structure design (maintenance-free self-lubricating structure design);

(2) Research on friction and wear performance of solid self-lubricating materials under low speed and heavy load;

(3) Research on uniform inlay of stainless steel. Lubrication principle and law of solid self-lubricating materials;

(4) Research on the uniform mosaic processing technology of solid self-lubricating materials;

(5) Research on the processing technology and use of PTFE sealing rings;

(6) Stainless steel outer ring spherical surface chrome plating process.

2.2.4 Key technical principle:

dry wear mechanism. When two non-lubricated surfaces are rubbed against each other, the uneven peaks on the two surfaces are subjected to shearing, local bonding and plastic deformation, thereby causing friction and wear. Conventional lubricants can significantly reduce these effects, however at standstill, especially under heavy load conditions, the oil and grease are squeezed out, effectively leaving the bearing unlubricated, which is often lost on the next movement. Shows a high coefficient of static friction. Radial spherical plain bearings with solid self-lubricating material in the inner ring do not dislodge under these conditions, so the material does not increase the coefficient of friction during subsequent movement. This type of bearing always provides a lubricating film on the bearing surface, thus ensuring always low friction and wear, even under heavy static load conditions, the solid lubricant film remains on the bearing surface. As wear occurs, more solid lubricant will be released to the bearing surfaces where lubricant is required.


2.3 Product innovation points

Therefore, the innovation of this project product is:

2.3.1 Structural innovation:

(1) The product of this project adopts stainless steel inlaid solid self-lubricating material and spherical chrome plating to replace the original steel-to-steel or steel-to-copper friction pair. It also has the function of maintenance-free self-lubrication, so as to realize zero failure of the key nodes of the space self-anchored suspension bridge, and avoid the pollution to the environment caused by the original oiling and lubrication. At the same time, because the stainless steel inner ring is used to replace the copper inner ring, it can save a lot of copper materials, improve the overall strength of the inner ring, etc., and achieve sustainable innovation and development.

(2) PTFE sealing ring is used to replace the traditional graphite nylon or polyurethane sealing ring, so that the service life of the sealing ring is increased to 50 years, and the working temperature is expanded from -30℃~130℃ to -50℃~200℃, greatly enhancing Anti-aging and anti-corrosion properties.

2.3.2 Process innovation:

(1) The processing of the spherical surface of the inner ring evenly inlaid with solid self-lubricating materials is a difficult point in the processing of domestic spherical plain bearings. Now our company has basically overcome this problem, and specially designed and equipped such special machine tools; this technology can double the internal The original processing specifications and capabilities of the solid self-lubricating material are evenly embedded in the ring spherical surface.

(2) The self-lubricating material with a coverage rate of Z% can effectively reduce wear, reduce friction and prevent seizure, and can significantly improve the service life of the bearing during operation. It can gradually distribute the solid lubricant to the friction surface through the heat generated by friction under the condition of no oil, so as to achieve the effect of small friction coefficient and good wear resistance. In terms of uniform array arrangement: all inlaid holes are arranged in a cross in the direction of movement, and the distance between the holes in the axial or radial direction (in terms of the direction of movement) should be kept in a close ratio to ensure that the lubrication covers the entire sliding direction and form a complete Solid lubricating film.

Process innovation

(3) It is difficult to accurately process and control the spherical surface interference due to the use of PTFE sealing rings in this project, so as to achieve the sealing effect on the inside of the bearing; our company has basically mastered this technology and can be stably applied in small batch production. The project will become the company's know-how when it is completed.

2.4 Comparison of product technical performance with similar products at home and abroad

At present, there are no similar product manufacturers at home and abroad, so the products of this project are original at home and abroad. The advanced nature of its product technical performance is reflected in:

2.4.1 Product advancement:

The product of this project needs to pass the comprehensive performance assessment test of the upper and lower nodes of the sling under fatigue load and the 1 million swing test of the upper and lower nodes of the sling by the Shanghai Institute of Materials. The overall performance can reach the domestic level. leading level.

2.4.2 Advanced structure:

The product of this project is maintenance-free due to its self-lubricating structure. At the same time, it saves copper resources and realizes sustainable development.

2.4.3 Technological advancement:

The inner ring spherical surface evenly inlaid solid self-lubricating material processing technology and PTFE sealing ring control technology adopted in this project are in the leading domestic and international advanced level.

3.Project maturity

(1) The self-lubricating spherical plain bearings at the key nodes of the space self-anchored suspension bridge have passed the pilot test, and a small batch production process technology has been formed. It has the characteristics of high strength, high wear resistance and high impact resistance, which ensures that the spherical plain bearing can still be intact when subjected to a large radial and axial combined load, and at the same time, compared with the original bearing, it saves a lot of non-ferrous metals. Metal, but also solve the bearing installation and maintenance problems.

(2) The products of this project have passed the appraisal of the company's technical appraisal committee, and are original at home and abroad. Due to the strong R&D team of the company, complete production equipment, process tooling and testing methods, the quality system and environmental system have been established according to ISO/TS16949 and ISO14001, which can meet the requirements of mass production and product quality and environmental protection, and the product quality is stable and reliable; the products of this project After the test of Shanghai Institute of Materials Research, the performance indicators have been recognized. At the same time, the company always takes value engineering as a guide in the process of transforming technological achievements, and strives to improve the cost performance of products, which has won unanimous praise from users.

(3) Intellectual property rights of core technologies: The core technologies of this project are all developed and mastered by the company. For the self-lubricating spherical plain bearings of key nodes of space self-anchored suspension bridges, the company has applied for relevant patent technology protection. As the company is in a leading position in the domestic and international advanced level in spherical plain bearing technology, one of the main research projects of the company's post-doctoral workstation is the research and development of solid self-lubricating materials, which has a strong ability of continuous innovation and improvement. Therefore, it can meet the diverse needs of users in different occasions, so that our company's bearings in this project are always at the highest level in the domestic industry, and strive to surpass the international advanced level.

4. Results

Trial-produced samples and passed the Shanghai Materials Research Institute: performance assessment test of the upper and lower nodes of the sling under fatigue load and 1 million swing tests of the upper and lower nodes of the sling; the service life of the PTFE sealing ring can meet the requirements of 50 years; The temperature reaches and meets the requirements of -50℃~200℃.

Time: 2022-07-18