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An engineering approach was developed to extract the failure plastic strain, thinning failure strain, and major in plane failure strain for finite element simulation applications. This approach takes into account the failure strain dependency on the element size when element deletion scheme is invoked in the simulation of material fracture. Both localized necking fracture and tensile shear fracture can be predicted when appropriate elements and material models are used in LS-DYNA simulations. This leads to a more accurate prediction of fracture and tearing in the finite element simulation of vehicle structure and crash loading conditions.

Inertia force during dynamic testing exists in any testing system. A generic system is analyzed using the principle of rigid body dynamics. It is shown that the load recorded by a load cell includes both the load experienced by the test specimen and the inertia force from the mass between the specimen and the load cell, when the load cell is placed on the fixed side of the test specimen. An impact fixture designed for spot weld strength test was then studied as an example. Test data were collected and analyzed to show the effect of inertia on the impact strength of the spot weld.

A previously developed finite element human head/cervical spine model was further enhanced to include the major muscles in the neck. The head/cervical spine model consists of the skull, C1-C7, disks, facets, and all the ligaments in this region. The vertebral bodies are simulated by deformable bodies and the soft tissues in the cervical spine are modeled by nonlinear anisotropic viscoelastic material. The motion segments in the cervical spine model were validated against three-dimensional cadaver test data reported in the literature. To simulate the passive and active muscle properties, the classical Hill muscle model was implemented in the LS-DYNA code and model parameters were based on measurements of cadaver neck musculature. The head/neck model was used to simulate a human volunteer flexion whiplash test reported in the literature. Simulation results showed that the neck muscle contraction and relaxation activities had a significant effect on the head/neck motion.

A finite element human thorax model was developed for predicting thoracic injury and studying the injury mechanisms under impact. Digital surface images of a human skeleton and internal organs were used to construct the three-dimensional finite element representation of the rib cage, the heart, the lungs, and the major blood vessels. The mechanical properties of the biological tissues in this model were based on test data found in the literature. The constitutive equations proposed in the literature for describing the mechanical behavior of the heart and the lungs were implemented in the code for modeling these organs. The model was validated against cadaver responses for both frontal and lateral impact. Good correlation between the model and the cadaver responses were achieved for the force and deflection time-histories.

Using finite element technique to model the human cervical spine can be found in a number of publications in the literature. These efforts have illustrated viable techniques and approaches for simulating the three-dimensional motion of the human cervical spine. However, these earlier studies also revealed difficulties due to insufficient geometric description for such a complex structure and the lack of experimental data for characterizing the mechanical behavior of the biological tissues in this anatomical region. Recent advancement of the computer technology has resulted in a large quantity of digital images of the human anatomical structure with high precision. In addition, new experimental techniques have also produced new test data on human biological tissue properties. In this study, we developed a finite element representation of the human cervical spine using detailed 3D anatomical data.