Digital image correlation for grain scale strain measurement in interstitial free high strength steel

Abstract

Deformation measurement of materials and structures subjected to various loading conditions is an important task of experimental solid mechanics. Apart from the widely used point wise strain gauge technique, various full field non-contact optical methods are used for this purpose. In this work, an automated scheme to measure the grain level deformation in tensile deformed interstitial free high strength steel has been introduced. The method is based on digital image correlation technique. The proposed scheme utilised high resolution scanning electron images of the specimen surface that are sequentially captured during tensile loading. It is found that grain to grain there is large variation in deformation response at a given load. The present work also reveals point to point variation of strain within a grain interior.

Keywords:

• Image correlation
• Strain measurement
• Grain segmentation
• Micrograph processing
• IFHS steel

Acknowledgement

The authors deeply acknowledge the Ministry of Steel (GOI) and TATA Steel Ltd., Jamshedpur, India, for providing research grant (file no. 11(7)/SDF/2007-TW) to create the experimental facility and carry out the investigation.