The use of Digital Image Correlation to correct the thermoelastic curves in static tests

Abstract

Many studies have been carried out with the aid of thermal scanners for the analysis of the thermoelastic effect on materials. In particular, for tensile stresses, the gradient is negative and the thermal variations are proportional to the stress applied in the purely elastic phase. Thermoelastic analysis of materials from the static tests have shown that it is possible to detect information on the dynamic (fatigue) behavior.One of the main problems that occur in following the local thermal behavior in a static test is that of dimensional correction and tracking of the measuring point (spot). These do not allow to follow the same investigated area, that progressively undergoes a displacement as load increases.The purpose of this work, based on previous experiences, is to implement an algorithm and to define a procedure that allows the tracking of the area thermally investigated that, as the load increasing, inevitably undergoes a displacement. The radiometric spots on the specimen, selected at the beginning of test, are progressively updated by following thermographic frames. The displacement information derived from the Digital Image Correlation (D.I.C.), simultaneously was applied on the same specimens. This procedure can better define the trend of temperature changes during the static tensile test and can be used to measure the stress concentration factors in notched specimens.