A novel efficient energy absorber: circular metal foam-filled tube under external inversion over a die

To enhance the energy-absorbing capacity of the energy absorber, the circular metal foam-filled tube (CMFFT) under external inversion over a circular die is designed. According to the rule of energy conservation, a theoretical model for the inversion of the CMFFT over a circular die is proposed, considering the radial bending of the CMFFT and the circumferential expansion of the CMFFT in the contact region and disengaging region, and the foam compression. Then, the die inversion deformation of the CMFFT under axial compression is investigated by the commercial software ABAQUS/Explicit. It is seen that the analytical model captures the numerical results reasonably. Next, the influences of the strength of the metal filled foam, the circular corner radius of the die, the average radius of the metal circular tube and the wall thickness of the metal circular tube are discussed. It is found that the force increases with the strength of the metal filled foam and the average radius of the metal circular tube. In addition, the force firstly decreases and then increases with the increase of the radius of the circular die and the wall thickness of the metal circular tube. The absorbed energy increases with the wall thickness of the metal circular tube, the circular corner radius of the die, the average radius of the metal circular tube, and the strength of the metal filled foam. The optimum radius of the circular die is proposed based on the theoretical model. The special energy absorption (SEA) efficiency of the CMFFT under external inversion over a circular die is significantly better than the metal empty tube. The SEA ratio of the CMFFT is 130.21%, when the compressive strength of metal filled foam \(\overline{\sigma }_{F} = 0.0{694}\). It is demonstrated that the CMFFT under external inversion over a die is a good energy absorber.