The formability of adhesive bonded steel sheets is experimentally evaluated and predicted with the influence of carbon black (CB) nano powder filled adhesive. The epoxy adhesive properties are modified by filling CB nano powder at different wt. %. The tensile and in-plane plane-strain (IPPS) formability tests are carried out to evaluate the formability of adhesive bonded blanks. The true stress–strain behaviour of adhesive bonded blanks is evaluated from the experimental tests and predicted using a finite element (FE) model. The forming limit strains are evaluated during predictions by necking criteria, namely thickness gradient based necking criterion (TGNC) and effective strain-rate based necking criterion (ESRC), and validated with the experimental limit strains. The results show that the adhesive bonded blanks show improved elongation and limit strains of base materials constituting adhesive bonded blanks with increase in CB up to 2 wt. %. There is a reasonable difference in adhesive bonded sheets limit strains between predictions and experiments due to the absence of interface bonding between adhesive and base materials. In the tensile test, about 9.1 %–21.7 % variation in true major strain and about 10.3 %–13.4 % in true minor strain during TGNC predictions are noticed, while ESRC shows more variation than TGNC. In the IPPS forming test, about 8.3 %–12.4 % difference in true major strain and about 2.2 %–13.4 % difference in true minor strain are noticed during prediction by TGNC. The ESRC predictions are equally efficient as compared to TGNC predictions in this case. The TGNC shows better prediction of about 13.5 % in true major strain, and about 7.5 % in true minor strain as compared to ESRC at different adhesive properties in the tensile test. Similarly, a better prediction of about 1 % in true major strain and about 0.3 % in true minor strain in IPPS formability test is observed.
G. R Narayanan and Dr. Satheeshkumar V, “Experimental Evaluation and Prediction of Formability of Adhesive Bonded Steel Sheets at Different Adhesive Properties”, Journal of Testing and Evaluation, vol. 44, 2016.