Application of NITINOL to High Stiffness Structural Joints.

摘要

The feasibility of utilizing the unique shape-recovery characteristics of NITINOL to achieve high preloads in structural joints was demonstrated. High performance missile systems require the shell stiffness in the longitudinal bending mode to be above a critical value to prevent dynamic coupling between the structure and high frequency control systems. In cases where the natural frequency is a limiting design requirement, joint preload greatly affects the design structural weight. NITINOL alloy can be used effectively to preload threaded joints to higher levels than obtainable by applying torque. Several joint concepts utilizing NITINOL were conceived. A NITINOL preloaded threaded joint was designed, analyzed, built, assembled and tested. A NITINOL alloy having a cryogenic transition temperature was used; its compressive recovery characteristics were measured. A method of modeling the recovery characteristics of NITINOL in a general finite-element analysis of the joint was developed. Preload level and joint stiffness were measured for the NITINOL preloaded joint and a conventional, torque preloaded joint of the same design. Results agreed closely with analytical predictions. NITINOL preloading produced significant performance improvements over conventional torque preloaded joints. (Author)