Modeling of Stiffness Anisotropy in Simulation of Self-Piercing Riveted Components

The so-called substitute models based on shell elements can be used to design the self-piercing riveted components economically and with sufficient accuracy. In this study, the SPR3 (Self-Piercing Rivet) model with anisotropic stiffness parameters implemented in commercial simulation software LS-DYNA is used to describe the stiffness of self-piercing riveted joints subjected to different loading conditions. The model provides the basis for the subsequent fatigue life estimation of self-piercing riveted joints under cyclic loading. By accurate prediction of the stiffness of self-piercing riveted joints subjected to cyclic loading, the accuracy of the fatigue life estimation can be improved. To identify the stiffness parameters, the self-piercing riveted joints are subjected to loading conditions: axial tension, shear tension, and bending. To validate the model, the specimens are simulated under different loading conditions and the results are compared to the experiments. It is shown that the model with anisotropic stiffness parameters predicts the stiffness of specimens more accurately compared to the model with isotropic stiffness parameter.

Magnetic Micromanipulation for In Vivo Measurement of Stiffness Heterogeneity and Anisotropy in the Mouse Mandibular Arch

The mechanical properties of tissues are pivotal for morphogenesis and disease progression. Recent approaches have enabled measurements of the spatial distributions of viscoelastic properties among embryonic and pathological model systems and facilitated the generation of important hypotheses such as durotaxis and tissue-scale phase transition. There likely are many unexpected aspects of embryo biomechanics we have yet to discover which will change our views of mechanisms that govern development and disease. One area in the blind spot of even the most recent approaches to measuring tissue stiffness is the potentially anisotropic nature of that parameter. Here, we report a magnetic micromanipulation device that generates a uniform magnetic field gradient within a large workspace and permits measurement of the variation of tissue stiffness along three orthogonal axes. By applying the device to the organ-stage mouse embryo, we identify spatially heterogenous and directionally anisotropic stiffness within the mandibular arch. Those properties correspond to the domain of expression and the angular distribution of fibronectin and have potential implications for mechanisms that orient collective cell movements and shape tissues during development. Assessment of anisotropic properties extends the repertoire of current methods and will enable the generation and testing of hypotheses.

Finite Element Analysis of Mechanical Properties of 2.5D Woven Composites

It is calculated the effective anisotropic stiffness tensor of the representative volume element in 2.5D woven composites by energy method. The Multi-point constraints are applied to periodic boundary conditions. Compared with the static tensile tests, the validity of present method is verified.