Load Transfer Index for Composite Materials

Abstract

Load transfer analysis is a new paradigm for lightweight vehicle design. U* index has been proved to be an effective indicator for the load path. The U* theory indicates that the external loading mainly transfers through the parts with higher U* values in the structure. However, the fundamental equations of the theory are based on isotropic, homogenous, and linear elastic assumptions for the materials. Consequently, U* index is inadequate for composite materials which are increasingly used in automotive structures. In this study, a new load transfer index for composite structures, U*O, is proposed for the first time inspired by the basic U* theory. The U*O index considers the composite material as orthotropic instead of isotropic and eliminates the limitation of the basic U*. The effectiveness of the new U*O index on load path prediction is demonstrated by a case study for a general Graphite-epoxy lamina. The U*O index is capable to evaluate the accurate load path for the composite specimen. By contrast, the basic U* analysis shows the incorrect results.

Estimating the in vivo location of the talus from external surface landmarks

“…The nature of the system means that motion of one rigid body affects motion of connected (i.e., linked) bodies, and that forces on one side of a joint (e.g., distal femur) are transferred the other side of the joint (e.g., proximal tibia) (Karandikar & Vargas, 2011). The ground reaction force is transferred to the leg through the bones and joints of the foot using the stiffest path (Wang, Pejhan, Wu, & Telichev, 2016). Kinetic and kinematics analyses can provide the location of the foot's center of pressure, external marker locations (Figure 1), as well as the ground reaction force.…”

“…Kinetic and kinematics analyses can provide the location of the foot's center of pressure, external marker locations (Figure 1), as well as the ground reaction force. The ground reaction force is transferred to the leg through the bones and joints of the foot using the stiffest path (Wang, Pejhan, Wu, & Telichev, 2016). As the talus is the only bony (i.e., stiffest) connection between the foot and the leg, ground reaction forces generated while walking will travel to the talus through two pathways: through the talonavicular joint, when the ground reaction forces are applied to the forefoot (i.e., during late stance) or through the subtalar joint, when the ground reaction forces are transferred from the hindfoot (i.e., from heel strike to foot flat).…”

Demonstration of the effectiveness of U*-based design criteria on vehicle structural design

“…3 However, the stress concentration caused by the geometrical irregularities of the structure (like a notch or a hole) may render this method misleading. [4][5][6] An alternative approach to study the load transfer is the use of the load transfer index (U * ) which was firstly introduced by Takahashi. 7 The U * index theory introduces a mathematical index that characterizes the internal stiffness between an arbitrary point and the loading point of the structure.…”