Material Selection for Drive Shaft Intermediate Supports: Performance and Application Considerations

Rubber-Based Elastic Elements for Vibration Isolation

Rubber is the most widely used material for intermediate support elastic components due to its ability to absorb vibrations and reduce noise. Nitrile rubber (NBR), known for its excellent oil resistance and thermal stability up to 95°C, is commonly applied in environments exposed to lubricants or high temperatures. Its high damping coefficient effectively minimizes transmission of radial forces caused by imbalances or misalignments in the drive shaft.

Chloroprene rubber (CR) offers superior weather resistance and ozone resistance, making it suitable for outdoor or harsh-environment applications. While its operating temperature range (up to 90°C) is slightly lower than NBR, CR maintains flexibility at temperatures as low as -10°C with additives, ensuring consistent performance in fluctuating climates.

Butyl rubber (IIR) excels in vibration isolation due to its high internal damping and low permeability, which also makes it ideal for sealing applications. However, its poor adhesion to metals requires specialized bonding processes during manufacturing. To optimize performance, manufacturers often select rubber grades based on specific environmental conditions, such as NBR for oil-exposed supports or CR for long-term outdoor use.

Metallic Components for Structural Integrity

The structural framework of intermediate supports relies on metallic materials to withstand mechanical stresses. Carbon steel (e.g., 45# steel) is frequently used for support brackets and bearings due to its balance of strength, ductility, and cost-effectiveness. After quenching and tempering, 45# steel achieves a tensile strength of 800–1,000 MPa, sufficient for most automotive applications.

For heavy-duty or high-speed scenarios, alloy steels like 40Cr or 35CrMo are preferred. These materials contain chromium (Cr ≥ 0.30%) and molybdenum (Mo ≥ 0.20%), which enhance hardenability and fatigue resistance. For example, a 40Cr bearing subjected to surface quenching can reach a surface hardness of 55–60 HRC while maintaining a tough core, critical for resisting cyclic loads in commercial vehicles.

Cast iron is another viable option for complex-shaped supports, offering excellent casting properties and vibration damping. Ductile iron (e.g., QT400-18) provides higher tensile strength (400 MPa) and elongation (18%) compared to gray iron, making it suitable for supports requiring both rigidity and impact resistance.

Bearing Materials for Load-Bearing Efficiency

Bearings in intermediate supports must endure high radial and axial loads while minimizing friction. Double-row tapered roller bearings are widely adopted for their ability to handle combined loads. These bearings typically use GCr15 bearing steel, a high-carbon chromium steel with a carbon content of 0.95–1.05% and chromium content of 1.40–1.65%. After heat treatment, GCr15 achieves a hardness of 61–65 HRC, ensuring wear resistance and long service life.

In applications with extreme temperatures or corrosive environments, stainless steel bearings (e.g., 316 grade) may be used. These bearings contain 18% chromium and 8% nickel, forming a passive oxide layer that prevents oxidation. For high-temperature settings, chromium-molybdenum alloy bearings (e.g., 35CrMo) retain strength at temperatures up to 500°C, making them suitable for exhaust-adjacent supports.

Advanced Composite Materials for Lightweight Design

To reduce vehicle weight and improve fuel efficiency, carbon fiber-reinforced polymers (CFRP) are emerging as alternatives to traditional metallic supports. CFRP offers a high strength-to-weight ratio, with tensile strengths exceeding 1,500 MPa at a density of just 1.6 g/cm³, compared to steel’s 7.8 g/cm³. Additionally, CFRP’s inherent damping properties reduce vibration transmission by up to 30% compared to metal supports.

However, CFRP’s higher cost and manufacturing complexity limit its current use to high-performance or electric vehicles where weight reduction is critical. Hybrid designs, combining CFRP with metallic inserts for load-bearing components, are being explored to balance performance and cost.

By carefully selecting materials based on load requirements, environmental conditions, and cost constraints, manufacturers can optimize intermediate supports for durability, efficiency, and vibration control across diverse automotive applications.