Papers by Keyword: Optical Techniques

Abstract: This paper reports the design assessment carried out on a subassembly of an advanced rocket using experimental techniques. The design was very complex and critical, since a cylindrical shell had a square cutout on the axial-hoop plane interacting with a notch in the axial-radial plane. Herein, two optical techniques have been employed for assessing the interaction between the notch and the cutout, and their individual contributions to the strain-field. Initially, a photoelastic model was studied to estimate the stresses at the notch tip. Subsequently, DIC was employed for measuring strains at the notch during the ground based testing of the actual component. The outcomes of these two experiments showed that the effect of the cutout to the strain concentration was negligible due to the extra stiffness provided by other assemblies.

Abstract: The paper describes the work towards a set of standardised tests for the evaluation of the performance of optical systems for measuring strain. In particular, the standardised tests are designed to allow the components of a system to be evaluated both in terms of hardware and software. The intention is to allow designers of optical systems to assess the efficacy of their innovations in instrumentation and algorithms, to assist manufacturers of systems in the quality assurance process, to permit end-users to evaluate system capabilities prior to purchase, and to support both manufacturers and end-users in setting up and fault diagnosis. Two standardised tests are proposed and described of which one is physical, a disc in contact with a half-space, and the other is virtual, a pair of shrinkage-fit thick rings or cylinders.

Abstract: Strain is a dimensionless quantity derived from displacement. To measure strain, devices such as resistive strain gauges and extensometers but also imaging methods are applied in engineering and experimental mechanics. The lack of standards and reference materials related to optical methods of strain measurement is tackled by the SPOTS project. It is intended to make full use of the modularity of different methods in order to develop a unified approach to standardisation. In this contribution we focus on the problem of traceability of optical strain measurement values and underline the role of strain measurement standards. We clarify the terminology and outline routes for traceability in analogy to widespread procedures for single value strain measurements.