Effect of plastic deformation and boundary conditions combined with elastic wave propagation on the collapse site of a crash box

Abstract

Several papers have been published recently on the crashworthiness studies. The main task was to predict the energy absorption W p and average collapse forceF in time of sheet steel structures. The main objective of this contribution is to design a component that allows absorbing and dissipating a high energy W p allowing improvements of the survivability of passengers in vehicles. However, the range of applications is larger since it includes all civil and military applications related to safety of components, or more generally of construction elements being loaded by impacts or explosions. In the present 3D case, the aim of this numerical study on dynamic loading in adiabatic conditions of deformation is to analyze the effect of elastic wave propagation combined with plastic behavior on the collapse site of a rectangular tubular structure made of steel sheet. To demonstrate the strong coupling between the effects of strain rate sensitivity, accounted for in the constitutive relation that is used in numerical simulations, with the process of elastic wave reflection on the boundary conditions, a series of numerical simulation was performed. It is shown in this numerical study that the strain rate sensitivity influences the position of the first collapse site. Moreover, the first collapse initiation of a structure defines the level of power absorption. Since the process of folding may be combined with bending of the structure (in particular when a local buckling appears close to the opposite side of impact), in this non axial case the energy absorption W p decreases and the effectiveness of the structure to the energy absorption is insufficient.

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

“…This allows the determination of the volume frac tion of martensite in the post mortem specimens using XRD and therefore enables validation concerning the transfor mation kinetics . The range of loading rates covered during the experiments agrees with that expected in engineering applications such as crashworthiness (Rusinek et al, 2008), in which TRIP steels are frequently used.…”

Dynamic necking in materials with strain induced martensitic transformation

“…Thus, the knowledge of the energy absorption behavior is of importance for shape design and material selection in structures subjected to accidental impact and collision. Many studies have been published on the behavior of energyabsorbers through the inelastic response of the material (Hetherington, 1996;Jones, 1997;Jones et al, 2001;Lu and Yu, 2003;Dean et al, 2006;Rusinek et al, 2008;Rodríguez-Martínez et al, 2012). Analysis and design methods for energyabsorbers are different from standard structural design techniques, since they have to sustain strong impact loads and their deformation involves large geometric changes.…”

On the Taylor–Quinney coefficient in dynamically phase transforming materials. Application to 304 stainless steel

“…Many advanced processes in engineering such as high-speed metal forming (Rojek et al, 2001), cutting (Miguélez et al, 2009;Molinari et al, 2010;Ma et al, 2012), crash in energy absorbing structures (Reyes et al, 2002;Rusinek et al, 2008) or impact on metallic plates (Rosenberg and Dekel, 2004;Rodríguez-Martínez et al (2010a,b)) involve large strains at high strain rates. In these conditions, the thermodynamic process deviates from the isothermal state and approaches adiabaticity, leading to large and sometimes very rapid variations in the temperature field.…”