Effects of Implemented Residual Stresses on Mechanical Responses and Behavior of the Full-Layered Murine Aortic Medial Ring: A Parametric Finite Element Study.

Purpose: It is known that elastic laminae (ELs) in the aortic wall, especially the inner layers, are structurally buckled due to residual stresses under unpressurized conditions. Herein, we aimed to develop a realistic computational model, replicating the mechanical behavior of an aortic ring from no-load to physiological conditions by considering inherent residual stresses, which has not been widely included in conventional modeling studies.

Methods: We determined specific conditions to reproduce EL buckling with a "preferable" residual stress distribution under no-load conditions by combining the design of experiments and multiobjective optimization.

Stiffness estimation of transversely anisotropic materials using a novel indentation tester with a rectangular hole.

Since embryos change their morphology drastically in the gastrulation stage, mechanical characterization of young embryos is important as they also change their tissue stiffness with the stage of development. Herein, virtual compression tests were conducted assuming that the gastrula has a spherical shape with transverse anisotropy. Based on the design of experiments, we found that the Young's moduli and material anisotropy can be efficiently determined by measuring the reaction force and surface displacement when indenting the tester into an embryo.

Theoretical elastic tensile behavior of muscle fiber bundles in traumatic loading events.

Background: The mechanical characterization of skeletal muscle under high-rate loading regimes is important for predicting traumatic injuries due to traffic accidents and contact sports. However, it is difficult to perform dynamic mechanical tests at rates relevant to such rapid loading events.

Methods: In the present study, a series of stress relaxation tests were conducted on rabbit hind-limb muscle fiber bundles using a custom tensile tester.

Variation in nerve fiber strain in brain tissue subjected to uniaxial stretch.

Diffuse axonal injury (DAI) is the most frequent type of closed head in jury involved in vehicular accidents, and is characterized by structural and functional damage of nerve fibers in the white matter that may be caused by their overstretch. Because nerve fibers in the white matter have a undulated network-like structure embedded in the neuroglia and extracellular matrix, and are expected to be much stiffer than other components, the strain in the nerve fiber is not necessarily equal to that in the white matter. In this study, the authors have measured strain of the nerve fibers running in various directions in porcine brain tissue subjected to uniaxial stretch and compared them with global strain (tissue strain).

Mechanical characterization of porcine abdominal organs.

Typical automotive related abdominal injuries occur due to contact with the rim of the steering wheel, seatbelt and armrest, however, the rate is less than in other body regions. When solid abdominal organs, such as the liver, kidneys and spleen are involved, the injury severity tends to be higher. Although sled and pendulum impact tests have been conducted using cadavers and animals, the mechanical properties and the tissue level injury tolerance of abdominal solid organs are not well characterized.