
Hydro-viscous clutches are key components for transmitting high torque under demanding operating conditions, such as the breakout and restart of tunnel boring machine (TBM) cutterheads. During high-slip operation, however, gas entrainment and pressure variations within the oil film can compromise torque transmission and clutch performance. This study introduces a novel C-type composite groove designed to improve lubricant distribution and maintain a more favorable pressure environment within the friction interface. The optimized groove geometry promotes continuous oil coverage, suppresses gas accumulation, and enhances torque transmission compared with conventional groove designs. The cover illustrates the internal structure of a hydro-viscous clutch, the flow of lubricant through its engineered grooves, and its connection to the challenging operating conditions of TBM cutterhead breakout. It highlights how innovative groove design can control the complex gas-liquid behavior within the oil film, providing a promising route toward more reliable and efficient high-torque transmission.
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