In recent years, with the development of the railway passenger car industry, the safety and comfort of the train and the airtightness of the whole vehicle are required to be higher and higher. The mechanical connection structure is replaced by the adhesive structure in the window installation. The adhesive structure can play the role of shock absorption, deformation absorption, noise reduction and so on. Usually, there are two ways to bond the window, one is to bond the glass to the window profile frame in advance, and then the window frame profile to the body structure; the other is the windowband structure, the glass directly bonded to the body structure. At present, the most widely used kinds of rubber are polyurethane and modified silicone. This paper makes a brief analysis of adhesive used for railway vehicle windows from the aspects of adhesive structure design, test and construction technology.
1 adhesive structure design
The design of bonding structure is carried out by finite element analysis software. The maximum load of bonding joint is calculated by the performance index of bonding joint under the combined action of mechanical and dielectric. Spring element is used to simulate bonding. Firstly, the bonding position is cut off and meshed on the geometric model of the car window. Then the spring element is used to connect the car window and the corresponding nodes on the car body to simulate bonding. The internal force of the spring is calculated. The internal force of the spring is divided by the bonding area, that is, the bonding stress. ANSYS software can be used for bonding strength analysis.
2 bonding validation test
According to the strength requirement of the adhesives calculated, it is necessary to test the adhesives performance and the adhesion of the substrate.
2.1 performance test
Performance tests include shear strength, tensile strength, hardness, shrinkage, UV resistance and other performance indicators. Typical adhesive adhesives commonly used in track industry.
2.2 substrate adhesion test
The test is used to determine the durability of adhesives on different adhesive substrates.
The test process: the size of the substrate is A4 paper. First, the substrate surface is treated by grinding, cleaning, activation, brushing and priming. Then, the tape adhesive is coated on the substrate surface with manual or pneumatic gun, and the length is at least 50 mm. Each substrate is coated with at least five strips of adhesive. The strips are scraped to a thickness of 5 mm by a scraper, then cured and aged. After each test condition is completed, the strips are destroyed obliquely by a wallpaper knife. The strips are clamped with a pointed nipper (peeling angle 130 to 160 degrees). When the bonding surface is topcoat and / or primer, cut the lacquer surface for inspection. In the process of destruction, the adhesive strip should be cut horizontally 5~10 mm apart from the adhesive surface. When the adhesive strip is subjected to further load, each cutting should last for about 3 s. The test length should be at least 50 mm. The test results show that the cohesive failure of > 95% adhesive is qualified.
2.3 fatigue test
According to the requirements of operation, EMU windows need to carry out physical fatigue vibration tests of whole windows. According to the structure and process of the existing car, the window is glued to the small side wall with the window, and the fatigue test is carried out after the curing is completed. The test vibration frequency and test standard are carried out according to UIC564. The main tests include vibration, extreme pressure change, high and low temperature rain, etc.
3 bonding process
3.1 preparation for environment and preparation
There is a need for separate areas for bonding and polishing, and area marking is necessary.
The temperature range is 15~35 degrees Celsius.
Relative humidity: 20% to 70%.
Dust: Dust load in the air must be small (there is no visible dust on the bonding surface after cleaning and activation after ventilation).
The bonding area should be far away from welding, sandblasting, painting and other operations that can produce flue gas, dust, suspended solids, etc.
Ventilation requirements: ensure ventilation in workplaces (no drafts are allowed).
Sufficient lighting should be provided during the work.
Prior to bonding, personal safety protection should be done according to the requirements of product safety instructions such as cleaning, activation and priming. Gloves and other protective articles must not contain silicon, talcum powder, and fluff.
- the waste should be disposed according to the relevant regulations.
Check whether compressed air is contaminated by water or oil.
Adhesives and associated cleaners need to be transported to the work site before the start-up, season below 5 degrees Celsius needs to be 24 hours ahead of schedule, season above 5 degrees Celsius needs to be 12 hours ahead of schedule, and stored as required.
Preparation of tooling, tools and auxiliary materials for surface treatment, cleaning, coating and installation.
Prepare warning signs for curing period, such as alarm, blockade, label, etc.
Check whether the adhesives and cleaning agents match, and ensure that the cleaning agent is opened within the shelf life, the bottle need to be marked with the opening date, and in accordance with the requirements of the product specifications to mark the maximum life. The cleaning agent used should be tightly sealed.
3.2 bonding surface cleaning
Surface treatment: bonding metal substrate surface needs no oxide layer and rust layer, if necessary with sandpaper or industrial cleaning cloth for grinding and cleaning.
Wipe the adhesive surface with a non-wool wiping cloth or paper wiping agent. When wiping the dirty paper, it needs to be turned over or replaced. Wipe it until there is no black grease on the surface. Dry it for 10 minutes and then proceed to the next step. After cleaning, the surface must not be polluted again.
3.3 bonding surface activation
When wiping the clean bonding surface with a small amount of activator, wipe it in one direction only once, and then wipe off the excess activator with a clean wiping paper or cloth. After volatilization of 10 min, the next operation can be carried out. No further operation is required within 2 h after wiping. It needs to be cleaned and activated again.
3.4 brush primer
The adhesive surface is cleaned and activated as required, and the bottom coat is brushed. Primers need to be opened before they are opened.