Bimetallic Rivets Industry Knowledge

Bimetallic rivets are a new type of rivet joining two dissimilar metals through cold welding. Their core structure consists of a shank and a tail. The shank is made of a high-strength titanium alloy (such as TC4), ensuring excellent shear strength for the rivet. The tail is made of a titanium-niobium alloy (such as Ti-45Nb), leveraging its high plasticity to allow for plastic deformation during riveting. This structural design allows Bimetal Contact Rivets to maintain high strength while providing flexibility to adapt to diverse working conditions.

The performance of Bimetal Electronic Contacts stems from their unique material combination and structural design, offering the following key advantages:

1. Non-deformation of the shank: During the riveting process, the shank remains rigid and does not expand outward like traditional Silver Electrical Contacts. This prevents damage to the inner wall and surface of the hole in composite laminates, eliminating the problems of delamination and cracking of the holes that can occur with traditional rivets when joining composite materials.

2. Galvanic Corrosion Protection: The titanium alloy shank's positive potential matches the carbon fiber composite material, effectively preventing galvanic corrosion between the fastener and the base material, extending the service life of the joint. It is particularly suitable for corrosive environments such as marine and humid environments.

3. Excellent Comprehensive Mechanical Properties: The shank is made of TC4 titanium alloy. After solution aging treatment, it achieves a shear strength exceeding 655 MPa and a tensile strength exceeding 1100 MPa. The shank is made of Ti-45Nb alloy, which has high plasticity and excellent cold working properties. During riveting, only a small impact force is required to achieve plastic deformation of the shank, ensuring a secure riveted connection.

4. Lightweight and Simple Processing: Titanium alloy has a low density (approximately 4.5 g/cm³), significantly reducing weight compared to traditional steel rivets, helping to improve the structural efficiency of products such as aircraft and spacecraft. The installation process is simple and can be performed by press riveting or hammer riveting, making it suitable for installation in small spaces within aircraft fuselages.

Due to their performance advantages, Sliding Electrical Contacts are primarily used in the aerospace industry to connect composite structures. Specific applications include:

• Aircraft skin riveting: Connecting composite skins and frames on new-generation aircraft (such as the J-20 and Boeing 787) by replacing traditional titanium high-lock bolts or Fixed Silver Contact, reducing structural weight by approximately 15%-20%.

• Engine component joining: Riveting titanium alloy and composite casings on aircraft engines (such as the F-15 and F-22 engines) to meet strength requirements in high-temperature and high-vibration environments.

• Helicopter structural joining: Connecting composite components of helicopter rotors and fuselage frames to withstand high-frequency vibration and impact loads.

The installation process for Bimetal Contacts Ag/Cu requires strict control to ensure joint quality. The key steps are as follows:
1. Material Preparation: Select the appropriate Switch Silver Contact model (e.g., standard or large interference type) based on the application scenario. Clean (remove surface oil and oxides) and perform surface treatment (e.g., passivation) to improve adhesion between the rivet and the substrate.

2. Hole Preparation: Use a dedicated drill bit to drill a hole in the substrate (e.g., composite material, titanium alloy). The hole diameter should be slightly larger than the rivet diameter (usually d + 0.1mm to d + 0.2mm). Avoid drilling too large a hole, which may loosen the rivet, or drilling too small a hole, which may crack the substrate.

3. Positioning and Fixing: Use a fixture to accurately align the Cold Headed Bimetal Contacts with the substrate, ensuring that the rivet axis is perpendicular to the substrate surface to prevent skew during riveting.

4. Riveting: Using an inertia friction welding machine or a hydraulic riveting machine, pressure is applied to the nail tail, causing it to plastically deform (upsetting the head), thereby firmly connecting the shank to the base material. The pressure and deformation during riveting must be controlled to avoid deformation of the shank or damage to the base material.

5. Quality Inspection: After riveting, a visual inspection (surface free of cracks and defects), dimensional measurement (upsetting head diameter ≥ 1.3d, height ≥ 0.34d, where d is the rivet diameter), and performance testing (tensile and shear strength tests) are performed to ensure that the joint meets design requirements.