Experimental and numerical investigations of the mechanical behavior of half sandwich laminate in the context of blanking

In this study,the complex mechanical behavior of an aluminum/low-density polyethylene(LDPE)half sandwich structure was investigated during the blanking process.Mechanical tests were conducted for the polymer and metal layer and the delamination behavior of the adhesive between the two layers.A new testing device was designed for detecting the delamination under tensile mode.Corresponding finite element models were established for the mechanical tests of the metal layer and the delamination of both layers for inverse parameter identifcation.Material parameters for Lemaitre-type damage,Drucker-Prager,and cohesive zone modeIs were identified for the metal,polymer,and adhesive,respectively.A finiteelement(FE)model was established for the blanking process of the sandwich structures.The experimental forcedisplacement curves,obtained in the blanking process of the half sandwich sheet,were compared with the predicted results of the FE model.The results showed that the predicted force-displacement curves and the experimental results were in good agreement.Additionally,the correlation between cutting clearance and changes in the forcedisplacement curves was obtained.Three feature values quantitatively described the imperfection of the experimental cutting edge.The effect of punch clearance on these values was studied numerically and experimentally.The results indicated that a smaller clearance generated a better cutting-edge quality.The stress state of the half sandwich structure during blanking was analyzed using the established FE model.

Parameter identification and blanking simulations of DP1000 and Al6082-T6 using Lemaitre damage model

This work provides numerical and experimental investigations of blanking process,where the shear-enhanced Lemaitre’s damage model is fully characterized and successfully applied in blanking process to predict the cutting force and cutting edge geometry under different blanking process parameters.Advanced high strength steel DP1000 and an aluminum alloy Al6082-T6 are selected for series of experiments.To obtain the damage parameters in Lemaitre’s damage model the flat rectangular notched specimens tensile test was conducted and the inverse parameter identification procedure was performed.For characterizing the crack closure parameter h in the shear enhanced Lemaitre’s damage model,an in-plane torsion test with novel specimen design was conducted.The finite element model(FEM)of this test was established with the minimum mesh size of 0.01 mm which was consistent with the minimum mesh size in the shear zone of the FEM for blanking process simulation.The longitudinal strain distributions of four kinds of initial notch radius or central-hole specimen were measured and compared with simulation results to validate the FEMs for these four tests.Deformation analysis of blanking of a circular work piece also was performed under three clearances.The effects of blanking conditions on sheared part morphology were detected.Stress triaxiality distribution of the blank sheet was revealed taking advantage of the successfully established FEM.The availability of the testing method and the determination method of the parameters was investigated.