There are no international standards or norms for the use of optical techniques for full-field strain measurement. In the paper the rationale and design of a reference material and a set of standarized materials for the calibration and evaluation of optical systems for full-field measurements of strain are outlined. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.
A suite of modelling tools is being created for the European Integrated Project "Emerging Nano-Patterning Methods". The idea of an optimal processing window for nano-imprints is presented, together with its limiting factors. Stemming from these factors, the need for a fully integrated multi-scale modelling is identified, where the overlap is on three levels: at the wafer scale for pressure and residual layer thickness distribution, at the cavity scale for fluid dynamics, and at the sub-nanometre scale for fluid-stamp interactions. The residual layer thickness is a critical parameter for embossing large areas, and accurate modelling at various scales is needed, in order to predict simultaneously cavity filling and thickness homogeneity at the wafer level. To do so, a finite element model is first introduced, where ANSYS is used to solve for the fluid flow in channels of infinite length. To check that the model accurately captures all the salient features of imprinting, two studies are carried-out. Firstly, it is shown that the model reproduces well the profile of the fluid front in a cavity for a range of viscosities. Secondly, the model is successfully compared to the experimental results of load-instrumented single cavity nano-imprint. Finally, a larger model is built by assembling the elementary channel feature defined above, and the velocity profiles in adjacent channels are analysed.
Optical techniques for full-field displacement/strain measurement are a powerful set of tools for use in defining the performance, design optimization, reliability and safety of various types of components, products and machines. The quality of the measurement data generated by optical techniques is strongly dependent on the instrumentation and procedures. Thus, there is a significant need to develop standardized tests that are applicable across the spectrum of optical techniques of strain measurement. This requires the description of a common standard measurement chain including:
(1) definition of standard physical and virtual materials;
(2) gathering experimental or simulated primary data (fringe/image map); (3) deconvolution phase maps from these data (numerical procedures); (4) calculation of required physical quantities from phase maps (numerical procedures including data scaling).
This scheme supports a calibration process for both instrumentation and procedures. Validation of this general methodology was performed using an example of displacement data gathered by grating interferometry followed by data processing scheme.