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1、Chapter 3 Material model and material characterization of automotive aluminium alloy 5052H343.1 preface The basic property of material decides the use function of the structure.in the research of car crashes and large deformation of key components,the key point of solving the problem is to build cor
2、responding physics-math model in order to acquire the specific material parameters.As for the automotive aluminium alloy in our research ,we need to consider the response characteristic of the material machanism on condition of real impact (such as dynamic loading,high-stress condition,including pri
3、mary defects or damage,etc) .By this way, numerous performance test and full-size componnet crash test need to be conducted ,which would exhaust great labor power and physical resources,but the result is still dubious.With the limited discret data obtain by the experiment,it can hardly cover the spa
4、ce of all solution of the model.For some extreme condition such as shearing stress condtion, high strain rate(12102),it hard to predict its machanism response. Therefore,this model we built has its comparatively large limitations.But combine with numerical simulations,it can expand the space of the
5、model effectively,while obtain complete material parameters. The result shows that the precision of numerical simulation is largely depend on the precision of material parameter to input. In the analysis of large deformation,mater-ial machanism must describe the material change from elastic deformat
6、ion,elastoplastic deformation,damage progession,evolvement,fracture,which is multi-step machanism procedure. Besides,various strain rate,anisotropic caused by processing history,etc need to be take into account to consider its affection with constitutive relations. Previously,this is a extremely com
7、plex project,where many problems is still unsolved. J.G.Blauel and D.Z.Su,etc simply used tensile bar experiment combined with finite element to simulate the characterization of AW6016 automotive aluminium alloy and crash test of the typical components in automobiles.It predicts the static and dynam
8、ic response of the aluminium alloy and key components in macro perspective,and expand G-T-N model in micro perspective,which explain the ductile fracture of the aluminium and its initiation and evlovement by machanism of growth of voids,that could be applied in engneering calculations.Franck Lauro a
9、nd Bruno Bennani built dynamical loading machanism model on finite-element calculation terrace.This model take elastic flow and anisotropic of micro holes damage evolvement into account.Thereby this could be used to predict situation of damage and fracture of materials with obvious texture deformati
10、on such as extruded aluminium alloys in circumstances of dynamic loading with large deformation. The other one contribution of Franks research is to develop iterative algorithm which is a experiment combine with numerical simulation to achieve solving and correct the key parameter in material model.
11、This method uses notch tensile data as the basic input,which can derive parameter of G-T-N damage model, and revise these parameters in consider of anisotropic factors.Eventually,the result of numerical simulation hit off with experiments.In compare with other material characterization method ,this
12、could avoid a great amount of experiment expenses,and improving the efficency of modeling rate. On the other hand,this method does not consider the changes of damage machanism of the materials under lower stress condition.The result proved that when three dimension stress degree is below 1,with the
13、reducing of stress degree,shear slip failure would take the dominent position, and damage of void type will be supressed. So,to adopte single damge model would limit its applicability. This chapter is trying to conduct material characterization,acquire fracture parameter of the material under simple
14、 tension,notch and shear stress,to carry out tensile test in condition of static,quasi-static and dynamic loading,and numerical simulation,furthermore,gain machanical property under different strain rate.Two kinds of damage model were built in this basis,compare the precision of model and sphere of
15、application of these two,to describe the damage and fracture behaviour in large deformation from macro phenomenon an micro machanism.3.2 Research of machanical property test of material under static and dynamic loading.3.2.1 Basic introduction of the experiment1.overall thinking of the experiments.
16、As for the automotive alminium alloy 5052H3.4,it is mainly used in weld production in bearing weight component of car-body,in actual collision design,these structure would mostly have large elastic deformation before failure.Therefore ,its not enough for material characterization only considering to satisfy strength demand,the rheological future of material in large elastic deformation,such as work hardening,anisotropic and facture features of primary
