Parametric Modeling And Optimal Design Of Crashworthiness For Thin-wall Structures With Variable Thickness Under Rolling Constraints

With the rapid development of electric vehicles,the cruising range of electric vehicles and the safety of battery packs have gradually become the focus.It is the key to improve crashworthiness and the lightweight level of electric vehicles.As an important energy-absorbing and force-transmitting component of a car,the front longitudinal beam plays a vital role in the field of car crash safety,which is a hot spot for CAE engineers.Therefore,They are widely used in crashworthiness and lightweighting of the front longitudinal beam due to the significant advantages of Variable-thickness Rolled Blank(VRB).At present,the research of front longitudinal beams with VRB is mainly based on VRB with linear thickness distribution.However,the optimization space is limited by the single transition form of VRB with linear thickness distribution.This paper proposes a double-power function type with VRB structure and a series of studies has been carried out.(1)Based on the principle of equal stress of unidirectional tensile test,a sample of equal cross-sectional area,which is suitable for the mechanical property test of VRB,has been designed,combined with DIC technology to accurately obtain the stress-strain curve of VRB at different thicknesses;the lagrangian interpolation function constructed the effective stress-effective strain field of the VRB at any thickness.Finally,the hardness experiment of VRB has been carried out to study the effect of the thickness variation of VRB on the hardness of the plate.(2)A double power function type with VRB has been proposed,and a mathematical model of the transition zone of the double power function type with VRB was established;Rolling constraint model of the double power function type with VRB was established based on the geometric constraints of rolling.The influencing factors of power exponent limit value and its changing law have been analyzed;the static stiffness characteristic law of power exponent and double power function type with VRB under rolling constraints has been studied.The equal thickness plate under the condition of equal mass,linear thickness distribution and polynomial thickness distribution in the form of static stiffness characteristics of variable-thickness blank has been compared The double power function type with VRB have better static stiffness performance.Finally,a mathematical model of rolling speed of the mill was established the relationship between shape of the double power function and the speed of rolling mill has been analyzed.(3)The principle of dividing the functional area of the front longitudinal beam with VRB has been proposed.A explicit parameterized model of the uniform thickness distribution of double power function type Variable-thickness Rolled Blank Double Hat Thin-walled(VRB-DH)structure was established based on the functional domain of the front longitudinal beam with VRB;Two different methods were used to establish the finite element model of VRB-DH structure,combined with the drop-weight impact test to verify the accuracy of the collision simulation of VRB-DH structure;the different thickness distribution parameters and their parameters based on the high-precision parameterized model were studied.Based on the high-precision parametric model,the influence law of different thickness distribution parameters and their combination on the deformation mode,collision load curve and energy absorption index of VRB-DH structure was studied.The sensitivity of each parameter is analyzed,among which the thickness parameter and the position of transition zone have great influence.(4)A high-precision PRS model of the VRB-DH structure has been constructed based on the ToPDE algorithm.The VRB-DH structure was taken as the research object.The total energy absorption and peak force were used as the optimization goals to establish the multi-objective optimization equation of the VRB-DH structure.The NSGA-? algorithm obtains the optimal thickness distribution form of the VRB-DH structure.The double power function type with VRB-DH structure is compared with the equal-thickness thin-walled structure and different types with VRB-DH structures.The double power function type with VRB-DH structure was verified in the crashworthiness design in terms of superiority.