| As a typical energy absorption structure with characteristics of good mechanical properties,thin-walled metal tubes filled with aluminum foam have been widely used in the collision energy dissipative systems of many engineering fields,such as automobile,railway transportation and aerospace,to realize safe guarding for equipment or personnel.For that reason,the mechanical properties of this structure subjected to quasi-static axial compression and dynamic impact load has been a hot point in academia and engineering applications.In recent years,with the increasingly serious problem of environmental pollution and resource consumption,the lightweight requirement for equipment structure has become more and more urgent in premise of fulfilling the established function.And it has been an important direction to exploit a thin-walled structure filled with aluminum foam,which has the characteristics of lightweight and flexible customization.On the basis of analyzing and summarizing the characteristics of axial energy absorption and adaptability of Al-Foam filled aluminum tube(AFAT)and Al-Foam filled steel tube(AFST),this paper proposes a novel buffer energy absorbing structure,Al-Foam filled clad tube(AFCT).Considering the rapid development of preparation technology of laminated composite pipe in recent years,this structure is made of aluminum foam and steel / aluminum clad tube in which the aluminum foam is filler material and the clad tube is lateral cladding.The structure not only has the advantages of AFCT,such as utility,cushioning property,light weight,but also has the advantages of AFST,the maximum compression displacement is smaller and the impact energy is higher.By changing the thickness ratio of AFCT and the porosity of foam aluminum,the flexible customization of static characteristics and impact resistance can be realized.In order to find out the axial energy absorption characteristics of AFCT,this paper combined the numerical simulation technology with the experimental study to provide theoretical guidance for engineering application.Firstly,with material constitutive model of crushable-foam and the tube-shell,the quasi-static compression and high-speed impact finite element models of AFCT are established on the ABAQUS platform.Through parameterized studying,the influence law of the material and structural parameters of AFCT,such as porosity,height-radius ratio,radius-thickness ratio,binding states(metallurgical bonding and physical contact)and the layer thickness ratio,on the energy absorption and deformation modes of the AFCT were simulated and analyzed.And the quasi-static compression and dynamic impact performance tests of AFCT were carried out respectively to verify the reliability of the numerical simulation results on WDW-3100 material testing machine,Split Hopkinson Pressure Bar(SHPB)and Instron CAEST-9350 drop hamper impact testing machine.The results indicate that the specific energy absorption characteristic of AFCT,which has a very good light effect,is obviously better than that of AFAT.And the deformation and energy absorption is best when the porosity is lower than 90%,the radius-thickness ratio is greater than 13 and the composite structure is fully bonded.The analysis of deformation mechanism shows that the deformation of each metallic composition is interdependence and inter-constraint,and the energy absorption capacity is enhanced by contribution of both buckling mode of steel / aluminum composite structures and the internal support of aluminum foam.In order to further reveal the collapse deformation mechanism of cell structures of aluminum foam and the coupling mechanism between aluminum foam and clad tube in the quasi-static compression and high speed impact,2D and 3D geometric model of AFCT with topology of foam structure were built respectively based on Voronoi.Combined with the explicit dynamic algorithm of ABAQUS,the influence of aluminum foam structure parameters,such as the cell diameter and cell wall thickness,on the deformation and energy absorption of AFCT under impact loading were simulated and analyzed.In terms of modeling method and simulation information extraction,it is complementary to the solid element modeling method based on the constitutive model of the porous foam.In the process of modern automobile industry,lightweight is a development direction.The improvement of safety performance is the most important thing in automobile design.The practice shows that,in the process of collision,the automobile crash box and bumper play a vital role in the easing the impact with absorbing a large number of external impact energy and effectively reducing the impact force.The new energy absorbing structure of AFCT provided a new idea for the design of vehicle crash box.In order to meet the requirements of crash box in practical application,the energy absorption characteristics of AFCT with circular,square,hexagonal and octagonal cross section were compared and analyzed,and the AFCT with square cross-section was finally selected as the structure of the energy absorbing box.Taking a domestic car as research object,the AFCT crash box was applied in the vehicle anti-collision beam structure.Using ANSYS Ls-dyna software,the application testing of AFCT crash box was respectively carried out with the simplified model of the vehicle collision beam and the whole vehicle model for the frontal collision and 40% frontal impact.The collision speed was set to be 18 km/h and 54 km/h.The collision results showed that the AFCT crash box has the similar energy absorption effect in low velocity impact to the existing crash box,but has higher energy absorption characteristic in high speed collision.It indicates that the AFCT meets the design goals of the crash box design.In conclusion,AFCT structure proposed in this paper has advantages in lightweight structure,static load and parametric design of impact energy absorbing characteristics.It has a good application prospect in the structure with special energy absorption requirements such as automotive crash box,anti-collision beam etc. |
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