Analysis of Thin Wall Structures for Energy Absorption Applications by ABAQUS

Crash-dynamics research has always concentrated significantly in the safety, survivability of passengers in a car crash. To identify the capability of energy absorption of a crash box, a thin-walled structure will be modeled and simulated by ABAQUS software. Investigate the influence of material, cross-sectional, thickness factors on the energy absorption capacity of the tube, using MCDM – Multi-Criteria Decision-Making to get the best option and testing the improvement while filling the tube with Foam material. In this study, beside the cross-sectional, aluminum alloys and steel materials and thickness are factors that influence the energy absorption evaluation criteria, the foam material with difference density are surveyed to compare effectiveness between the foam-filled and hollow crashboxes. The results show that the folds of the foam-filled tube after deformation along the compressive direction will be more continuous and stable. More, the higher foam density, the greater the energy absorption. This prevents the crashbox from deviating from the direction of the force, help directing the collapse of the tube, thereby improving energy absorption without significantly increasing the weight of the structure.

Anisotropic Composition and Mechanical Behavior of a Natural Thin-Walled Composite: Eagle Feather Shaft

Flight feather shafts are outstanding bioinspiration templates due to their unique light weight and their stiff and strong characteristics. As a thin wall of a natural composite beam, the keratinous cortex has evolved anisotropic features to support flight. Here, the anisotropic keratin composition, tensile response, dynamic properties of the cortex, and fracture behaviors of the shafts are clarified. The analysis of Fourier transform infrared (FTIR) spectra indicates that the protein composition of calamus cortex is almost homogeneous. In the middle and distal shafts (rachis), the content of the hydrogen bonds (HBs) and side-chain is the highest within the dorsal cortex and is consistently lower within the lateral wall. The tensile responses, including the properties and dominant damage pattern, are correlated with keratin composition and fiber orientation in the cortex. As for dynamic properties, the storage modulus and damping of the cortex are also anisotropic, corresponding to variation in protein composition and fibrous structure. The fracture behaviors of bent shafts include matrix breakage, fiber dissociation and fiber rupture on compressive dorsal cortex. To clarify, ‘real-time’ damage behaviors, and an integrated analysis between AE signals and fracture morphologies, are performed, indicating that calamus failure results from a straight buckling crack and final fiber rupture. Moreover, in the dorsal and lateral walls of rachis, the matrix breakage initially occurs, and then the propagation of the crack is restrained by ‘ligament-like’ fiber bundles and cross fiber, respectively. Subsequently, the further matrix breakage, interface dissociation and induced fiber rupture in the dorsal cortex result in the final failure.

Heat Exchange of the Cylindrical Liquid Body of a Limited Height with the Environment

The experimental investigations of the intensity of the heat exchange between the internal surface of the thin-wall metal cylinder and the studied liquid medium were carried out in conditions of its cooling (heating), i.e. under nonstationary heat exchange conditions. The existence of the regular thermal mode in the liquid medium surrounded by the thin-wall metal cylinder has been established. Local in time heat loss coefficients were derived using appropriate dimensionless equations for the stationary mode conditions of heat-exchange in a large volume. Heat loss coefficients were determined using regular thermal mode methods and computational-&-experimental heat loss coefficients. The changes in the relative values of the heat loss coefficients were analyzed using the method of regular thermal mode and computational-&-experimental heat loss coefficients. The deviations in the values of given coefficients in time are mainly within ± 10 %. Relative values of the heat loss coefficients deviate within ± 40 % using appropriate dimensionless equations for the conditions of the stationary mode of heat exchange in a large volume. This conclusion is natural because the cooling (heating) process is nonstationary.