Crashworthiness Analysis And Optimization Of Circular Thin-walled Tubes With Double Tapered Angles And Structural Hierarchy

Thin-walled structures are widely deployed in automobiles as safety components to absorb impact energy during collisions.And there is a continuous need for weight efficient thin-walled structures to safeguard occupant safety and properties.In real life,vehicular collisions often present in the form of oblique loading to thin-walled tubes,challenging the stability of crashworthiness performance under uncertain load angles.In the meantime,bio-inspired design principles,especially structural hierarchy,has been acknowledged and adopted in industrial designs.In such contexts,this paper carried out crashworthiness study and optimization of circular thin-walled tubes.The scope of work can be concluded as follows:1)This paper first proposed a novel multi-cell bi-tubular tapered tube with different outer and inner tapered angles,and compared the crashworthiness of the novel structure with multi-cell tapered tube,multi-cell straight tube and bi-tubular tapered tube in the load angle range of 0°-30°.Explicit finite element analysis shows that the outer tapered angle promoted stability of the structure,making the structure inclined to progressive folding even under oblique loading.While the inner tapered tube,and the multi-cell configuration improve the crushing strengthen of the tube.Furthermore,parametric studies indicate that the longitudinal and lateral stiffness can be altered by changing outer,inner tapered angle and tube thickness.Next,the optimal solutions of multi-cell bi-tubular tapered tube for single load angles and multiple load angles were obtained using multi-objective optimization algorithms.Finally,promosing results were achieved in a full-vehicle oblique impact finite element study.2)To explore the merits of adopting structural hierarchy in the crashworthiness of thin-walled tubes,a new class of 1^st and 2^nd order four-cell hierarchical circular tubes were developed by iteratively replacing the joint of internal ribs of a four-cell tube with smaller cells,respectively one 1^st order cell in the centre and four 2^nd order cells on the sides.Finite element analysis shows that crashworthiness improves withhigher order of structural hierarchy.Notably,mean crushing force is greatly improved.And the improvement of specific energy absorption outpaces peak crushing force.As for the superior 2^nd order structure,it has been identified that increasing the size of both 1^stand 2^ndorder cell can improve the mean crushing force,as more areas in the impact plane are subjected to higher strain,promoting energy absorption.However,this approach can also increase the mass of the structure,causing the specific energy absoption to drop,and very high peak crushing forces.To balance these conflicting objectives,optimal Latin hypercube method is adopted to sample the design space of1 st,2^nd order cell size and tube thickness,the response surface is then constructed using Kriging method.The pareto front is obtained using Multi-Objective Particles Swarm Optimization Method.