Core Advantages and Working Principles of Hollow Shafts  

A hollow shaft is a shaft component with a hollow structure used in mechanical design. It realizes power transmission through a central through-hole combined with internal and external keyways, and its outer surface is often processed into a stepped cylinder to adapt to different installation requirements. Compared with solid shafts, hollow shafts have significant weight advantages, while also exhibiting outstanding performance in torsional resistance and material utilization. According to the principles of material mechanics, when the shaft body bears torque, the outer edge bears the main torque, and the utilization rate of the internal area is low. Therefore, the hollow design can significantly reduce weight without affecting the overall load-bearing capacity.  

 

Core Advantages of Hollow Shafts  

1. Lightweight and Energy Saving  

By removing redundant central materials, hollow shafts can reduce weight by 30%-50%, which can significantly improve energy efficiency and load efficiency in automotive transmission systems and aerospace fields.  

 

2. High Torque Bearing Capacity  

Under the same cross-sectional area, the section moment of inertia of hollow shafts is larger, and the torsional stiffness is 1.5-2 times higher than that of solid shafts, making them suitable for high-torque scenarios such as wind turbine transmission systems.  

 

3. Multifunctional Integrated Design  

The central through-hole can be used to arrange hydraulic pipelines, cables, or cooling channels, enabling compact structural design in industrial robot joints and machine tool spindles.  

 

4. Optimization of Material Economy  

Retaining materials in the high-stress outer region ensures mechanical performance while reducing steel consumption, with material utilization increased by more than 20% compared with solid structures.  

 

Analysis of Key Application Scenarios  

- New Energy Vehicle Transmission Systems: The use of hollow half-shaft design reduces unsprung mass, and the stepped cylindrical structure improves power transmission efficiency.  

- High-Speed Industrial Robots: Aluminum alloy hollow shafts achieve 0.05-second-level dynamic response by reducing moment of inertia, meeting high-precision motion control requirements.  

- Large Wind Turbines: Titanium alloy hollow drive shafts can withstand instantaneous impact torques of 50,000 N·m while reducing the weight of the tower top.  

- Precision Medical Devices: Miniature stainless steel hollow shafts integrate biocompatible coating technology to realize the miniaturized integration of drug delivery systems and imaging equipment.  

 

Engineering Design and Material Selection Points  

1. Parameter Optimization Design  

Wall thickness calculation needs to comprehensively consider bending strength, torsional deformation, and critical speed. Under normal working conditions, the ratio of wall thickness to outer diameter is recommended to be controlled in the range of 1:8 to 1:12. The use of Finite Element Analysis (FEA) can accurately predict stress concentration areas, and the recommended transition fillet radius is ≥0.2 times the shaft diameter.  

 

2. Material Selection Strategy  

- Alloy Steel (42CrMo/20MnTiB): Suitable for heavy-duty transmission systems, with a yield strength of up to 785MPa  

- 7075 Aviation Aluminum: Density 2.8g/cm³, specific strength better than ordinary steel, suitable for high-speed moving parts  

- Ti-6Al-4V Titanium Alloy: Specific strength up to 260MPa·cm³/g, can replace steel under extreme working conditions

 

3. Advanced Processing Technology  

For hollow shafts with a length-diameter ratio >8, deep hole drilling + cold rolling forming technology is recommended, with a surface roughness of up to Ra0.8. For short shaft workpieces, the composite process of precision casting + CNC turning is applicable, which improves processing efficiency by 40%.  

 

Performance Verification Standards  

The flexural stiffness coefficient is determined by the three-point bending test, and the torsion test must reach the elastic deformation threshold specified in GB/T3077. For high-speed rotating scenarios, a dynamic balance test at 1.2 times the working speed is required, with a residual unbalance ≤0.5g·mm/kg.