Pseudoelastic NiTi-based devices are often required to recover their shape repeatedly and their working performance can be judged from the amount of residual deformation after use. The quality problem in this respect can even be removed from fatigue life or safety issues and impact on the functional and aesthetic value of the product. While linear deformation can be appreciated quantitatively in a straightforward manner, the bending strains are more difficult to assess directly. We devised a very simple digital image-based method to measure the residual bending deformation by comparison of the pristine shape of the device with the one resulting from bending and free recovery. The program was written in LabView and is capable of reporting about the deflection and location of strain concentration along slender pseudoelastic elements in a semi-quantitative way appropriate for quality sample checks. The method is semi-automatic and provides a user-friendly interface for the operator. Apart from simple shapes like straight wires and ribbons, the method was tested on devices as complex as spectacles frames. This application is particularly interesting, where shape recovery and functional and aesthetic value are tightly linked, and deformation by severe handling is a typical effect of use.
Digital image-based method for quality control of residual bending deformation in slender pseudoelastic NiTi devices
Pittaccio S;Besseghini S
2013
Abstract
Pseudoelastic NiTi-based devices are often required to recover their shape repeatedly and their working performance can be judged from the amount of residual deformation after use. The quality problem in this respect can even be removed from fatigue life or safety issues and impact on the functional and aesthetic value of the product. While linear deformation can be appreciated quantitatively in a straightforward manner, the bending strains are more difficult to assess directly. We devised a very simple digital image-based method to measure the residual bending deformation by comparison of the pristine shape of the device with the one resulting from bending and free recovery. The program was written in LabView and is capable of reporting about the deflection and location of strain concentration along slender pseudoelastic elements in a semi-quantitative way appropriate for quality sample checks. The method is semi-automatic and provides a user-friendly interface for the operator. Apart from simple shapes like straight wires and ribbons, the method was tested on devices as complex as spectacles frames. This application is particularly interesting, where shape recovery and functional and aesthetic value are tightly linked, and deformation by severe handling is a typical effect of use.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.