Optical control of fastener clamp load in bolted joints.

摘要

A new bolt tightening control method was presented in this thesis for the real-time monitoring and controlling of the clamping force in bolted assemblies. The method uses the full-field, non-contact Digital Speckle Pattern Interferometry (DSPI) technique to measure the joint surface deformation and to establish a reliable correlation with the clamp load provided by the fastener tightening. Because the effect of the frictional variables of the fastener on the relationship between the clamp load and joint deformation is insignificant, direct monitoring of the deformation in the clamped joint would provide a more reliable measure of the clamp load level, as compared to the conventional torque control method.;In the first part of this research, the relationship between the surface out-of-plane deformation and clamping force for a single-bolt joint is established by using FEA simulation. The effect of bearing friction and the hole clearance on the surface deformation in the bolted joint is also investigated. Verification Experiments are conducted by using a commercial available DSPI system to measure the joint surface out-of-plane deformation under different levels of clamp load for various levels of the bearing friction and hole clearance.;In the second part of this study, some relative techniques are discussed with regard to the in-plane deformation measurement, and joints with curved surface. The correlation between the clamp load and in-plane deformation is established on the joint of a chain link. The effect of the rigid body rotation on the in-plane deformation measurement is eliminated. The deformation measuring method for a curved surface has been discussed.;In the third part, a real-time Digital Speckle Pattern Interferometry (DSPI) system is developed for measuring the out-of-plane surface deformation in real-time. Spatial phase shifting technique is employed to quantitatively determine the distribution of phase. A Matlab software is developed for image acquisition and phase data calculations. The experimental verification is conducted on a centrally loaded diaphragm, a normal size bolted joint and a miniature bolted joint.