Bending Response of Lattice Structure Filled Tubes under Transverse Loading

Thin-walled tubes are widely used as passive energy-absorbing structures in a variety of industries. These structures are typically filled with lightweight materials to improve their energy absorption capabilities. At this point, additive manufacturing technology offers a great chance researchers for the production of novel filler structures to increase the crashworthiness performance of thin-walled tubes. In the current work, additive manufacturable body-centered cubic (BCC) lattice structures are suggested as filling materials for thin-walled tubes, and the bending response of these structures is investigated under transverse loads via a finite element modeling approach. The aspect ratio and strut diameter are considered as design parameters, and three-point bending simulations are conducted to understand the transverse load bearing behaviors of the structures. Different loading offsets are also taken into account for three-point bending simulations. The numerical results revealed that the BCC lattice structures used as filler materials significantly increase the energy absorption performance of thin-walled tubes due to synergetic interactions. In particular, the simulation results revealed that the hybrid tubes can absorb up to 84% more energy than the empty tubes, while the crush force efficiency of these structures is up to 42% higher compared to the empty tubes. The present study also showed that the transverse crushing characteristics of tubes can be considerably improved by suitable selection of the design parameters. These primary outcomes reveal that the proposed lattice structures can be considered as a potential alternative to traditional filler materials for enhancing the bending response of thin-walled tubes under transverse loading

Failure Analysis of Graphene Sheets with Multiple Stone-Thrower-Wales Defects Using Molecular-Mechanics Based Nonlinear Finite Element Models

Experimental studies show that Stone-Thrower-Wales STW defects generally exist in graphene sheets GSs and these defects considerably affect the fracture strength of GSs. Thus, prediction of failure modes of GSs with STW defects is useful for design of graphene based nanomaterials. In this paper, effects of multiple STW defects on fracture behavior of GSs are investigated by employing molecular mechanics based nonlinear finite element models. The modified Morse potential is used to define the non-linear characteristic of covalent bonds between carbon atoms and geometric nonlinearity effects are considered in models. Different tilting angles of STW defects are considered in simulations. The analysis results showed that the fracture strength of GSs strongly depends on tilting angle of multiple STW defects and the STW defects cause significant strength loss in GSs. The crack initiation and propagation are also studied and brittle failure characteristics are observed for all samples. The results obtained from this study provide some insights into design of GS based-structures with multiple STW defects

The Influence of the Attachment Type and Implant Number Supporting Mandibular Overdentures on Stress Distribution: An In Vitro Study, Part I

Objectives: The main goal of this study was to compare the stress distribution of mandibular overdentures (OVD) with different numbers of supporting implants and single versus splinted attachment types