Strain Measurement in Local Volume by Non-Contact Videoextensometric Technique on Ultra High Strength Steels

The paper presents the results of strain measurement using two methods: videoextensometry (ME46) and digital image correlation (DIC)-ARAMIS. ME46 allows measuring and monitoring the major and minor strain on a planar surface of a loaded object. Experimental equipment uses a CCD camera for monitoring the process. The software calculates the displacements of contrast dots and subsequently the strain components are obtained. Another method for non-contact measurements is DIC technique; the measurements are done using three-dimensional image correlation system. The system uses two digital high-speed cameras providing a synchronized stereo view of the specimen where speckles are arranged on the surface. The results show the complete strain field during the tests, including details of the strain field when necking develops prior to the failure. Experimental results obtained on ultra high strength automotive steels DP 1000 and 1400M grades during static tensile test are presented in the paper. The outputs of both are deformation maps. Advantages and disadvantages of both methods are compared.