The effect of specimen thickness on the experimental and finite element characterization of CTOD in extra deep drawn steel sheets

• Published in: Sadhana (Bangalore) 2004-08, Vol.29 (4), p.365-380
• Main Authors: Kulkarni, D M, Prakash, Ravi, Talan, Pravin, Kumar, A N
• Format: Article
• Language: English
• ISSN: 0256-2499; 0973-7677
• DOI: 10.1007/BF02703688

Recent experimental results by us have indicated that the load-drop technique can serve as a valid fracture criterion for predicting elastic-plastic fracture in extra deep drawn (EDD) steel sheets or in predominantly plane stress conditions. The purpose of this investigation is to examine the validity of a J-integral as a fracture parameter and the J-CTOD relation for the determination of critical CTOD in predominantly plane stress fracture (CTOD-crack tip opening displacement). Fracture tests were performed and experimental results were generated on fracture behaviour of EDD (0.06%C) steel sheets with CT specimens and using 'load-drop' as a fracture criterion. Critical CTOD was determined by using the JCTOD relation in addition to several existing techniques. A full 3-D finite element model was formulated to verify the critical load, critical CTOD and plastic-zone size. The critical CTOD was shown to increase with increasing specimen thickness and appeared to be approaching a higher limiting value. The characteristic features of predominantly plane stress fracture or general yielding fracture mechanics are summarized in conclusion.