Experimental investigation of miniature flexible joint thrust vector characteristics

Two miniature flexible joints which have the same structure but different elastomer materials (natural rubber and silicone rubber, respectively) were designed.Axial deflection variation due to vessel pressure was tested.Spring torque at various temperatures (-50～70℃) and vessel pressures were also studied.In addition, the reinforcement hoop compressive stress at the inner radius was measured to examine the applicability of existing empirical formulas for miniature flexible joints.Results show that the axial compressive stiffness increases slightly nonlinearly with the vessel pressure, while the spring rate keeps almost constant over the vector angle range from 0°to 6°.Spring rates of different flexible joints experience different variations as the vessel pressure increases.The temperature shows a pronounced effect on the spring rate.For the natural rubber elastomer flexible joint, the spring rate increases significantly at low temperatures.However in the silicone rubber elastomer case, the spring rate remains stable throughout the temperature range from -50℃ to 70℃.The stress empirical formula which would cause give much higher stress due to pressure is not applicable to the miniature flexible joint.