Structural analysis and testing of a miniature flexible joint under pressure and vector loading

The structural characteristics of a miniature tactical motor flexible joint subjected to pressure and vector loading were investigated using finite element analysis and bench test. Three-dimensional non-linear finite element analysis was conducted using ANSYS Code Version 11.0. The axial deflection, vectoring torque, and stress distributions in elastomeric and reinforcement rings were presented. The predicted values were consistent with the test data. Results indicate that the axial compressive stiffness increased gradually and nonlinearly with pressure, while the angular stiffness remained nearly constant in the vectoring angle range from 0° to 6°. Under pressure loading, the elastomeric shear stress was negative, high at both sides, and low at the center of the cross-section, while the reinforcement hoop stress was compressive at the inner radius and tensile at the outer radius. The compressive stress was also high. The flexible joint exhibited higher stress level with altered stress distribution when subjected to additional vector loading. Existing empirical formulas for reinforcement hoop compressive stress were determined to be not applicable to the miniature flexible joint, which significantly overestimated the stress caused by pressure and underestimated the stress caused by vectoring.