Structural elements instrumented for load and integrity monitoring utilizing finite length displacement sensors

Due to their remote location, some applications of structures in space environments require that the structures themselves monitor their own loading history and structural integrity. Thus, an integrated sensor and structural element is sought that exhibits a high sensitivity to loading while preserving the stiffness and strength of the structural loadbearing member.;The use of finite length displacement sensors permits the development of transducers whose sensitivity scales with the geometry of the instrument rather than with the maximum strain in the transducer thus allowing the instrument to act as a load-bearing member. For example, the design of a six-resultant-load component transducer is described that, within the confines of linear elastostatics, produces zero cross-talk between load components while retaining the geometric scaling property. The above measurement of the torsion component is examined in detail to demonstrate practical considerations in the manufacturing of such an instrument.;In order to validate the analytical description of the behavior of the finite length displacement sensor presented, a torsion transducer was manufactured and evaluated. Its performance is compared to an error analysis based upon certain known manufacturing errors and demonstrates sensing behavior as predicted by the analytical model. Minimizing the sensitivity to the considered manufacturing errors is also discussed.;In addition, a technique is presented to monitor the in-situ structural integrity of prismatic structures. Since finite gauge length sensors integrate deformations over a relatively long path length this technique requires only a few sensors to monitor an entire structural volume and probable locations of damage do not have to be known a-priori. The technique acts as a "balance" device, indicating the presence of a flaw by deviation from a "null" signal, requiring little data processing. The monitoring of a solid circular cylinder with a spherical cavity is presented in detail to demonstrate the behavior of this technique.;The extension of this technique to anisotropic, nonhomogeneous materials is also presented. Finally, speculation is made as to further applications of finite length displacement sensors.