Hybrid Experimental-numerical Method For Strain Analysis On Bulging Of Sheet Metal

As a fundamental mechanical parameter, strain has profound reference valuein the study of sheet metal forming. According to the theory of elastic mechanics,strain is the derivative of displacement, in terms of such idiosyncracy ofcalculation which means that it’s highly susceptible to the discrete datas andexperimental scatter. In order to surmount the plight stated above, a novelapproach known as hybrid experimental-numerical method taking blendedadvantages of experimental measurement and numerical computation methodutilized in the analysis upon deformation of material is put forward in this paperto procure authentic full-field representation of in-plane strain objectively.The intrinsic ideas and features of general data processing algorithms arediscussed on the basis of a paradigm for the comparison with one another. Least-squares approximation is selected because of its greater application fordifferentiating discrete displacement datas and a smoothing functional isintroduced for the sake of preventing the calculation of strain from the impact ofundesirable fluctuations caused by errors at the most extent. After themeasurement region being divided into several elements, smoothing nodaldisplacement values could be determined by solving the constructed functionalwith FEM. In such a case, the strain field could be expeditiously acquired bytaking the isoparametric elements into consideration.The feasibility and validity are demonstrated by applying this proposedmethod to pertinent numerical-test which is contrived virtually. The numerical-test is carried out with the attachment of artificial errors generated by VisualFortran to specific theoretical result simulated by ANSYS LS-DYNA. Within thenumerical-test, the performance of smoothing functional on full-field fitting hasbeen studied in deepth, the influence of smoothing parameter on therepresentation of strain distribution has been quantificationally investigatedthroughly and the relationship between the amount of sampling sites andconfiguration of elements has been explicated pithily. The outgrowths indicatethat hybrid method has favorable side in diminution of error and enhancement ofprecision in spite of losing some details during smoothing process.Finally, a serial of bulging experiments are conducted and the straindistributions within specimens are analyzed by hybrid method. The outcomesthrough comparison with ASAME explicitly manifest that the hybrid method advanced in this work is practical and operable which can meet extensivelyfactual demand. Due to the efficacious data processing, hybrid method not onlycould guarantee the trustworthy strain distribution, but also could ameliorate thestrain distortion along the brink of the specimens.