On the kinematics of the head using linear acceleration measurements.
Abstract The paper deals with an application of the nine accelerometer scheme proposed by Padgaonkar et al. (1975) to the analysis of the head kinematics including the head angular acceleration and velocity using linear acceleration measurements. The computed results have been compared with the film analysis and with the actual measured quantities in the case of the dummy experiments. The study reveals an excellent agreement among these results and indicates the feasibility of the application of the method to biomechanical studies.
Recent advances in biomechanics of brain injury research: a review.
Biomechanics of cerebral trauma attempts to delineate the dynamic response of the cranial vault contents to a direct or indirect impact to the head. Consequently, brain injury mechanisms and associated tolerance to impact can be deduced by establishing a relationship between neurological deficit and mechanical dosage. The resulting information is invaluable to brain injury prevention and diagnosis. This paper presents an overview of our recent research on head injury focusing on establishing brain injury biomechanics by developing a comprehensive and validated mathematical model. To achieve our goal, we developed a comprehensive three-dimensional finite element human head model, finite element porcine head models, and sensors to monitor head kinematics and brain strains by neutral density accelerometers. The information obtained from this research thus far provided a predictive and somewhat validated mathematical model of the head, which clearly shows a correspondence between brain mechanical response and experimentally observed injuries.
Some new observations on yield surfaces
SummaryThis paper presents the results of experiments in which two thinwalled tubes of commercially pure aluminium in the annealed condition were loaded in combined tension and torsion in the plastic region at elevated temperatures. In the first test prestressing was in torsion but of a cyclic nature. In the other test prestressing included a path reversal in tension. It is shown that the hardening law introduced previously [3] is such that prestressing towards the origin of the stress space produces an increase in the width of the yield curve in the prestressing direction. It is also shown that a locus of zero deformation of yield surfaces can be postulated.In the present paper we also show the existence of negative plastic strains and we show that offset yield surfaces are closely related to envelopes of proportional limit yield surfaces.ZusammenfassungIn dieser Arbeit werden Resultate von Experimenten, in denen zwei dünnwandige Rohre aus handelsreinem, normal-geglühtem Aluminium durch Zug und Torsion bei erhöhten Temperaturen, im plastischen Bereich belastet wurden, angegeben. Im ersten Versuch wurde durch Torsion zyklisch vorverformt und im zweiten durch Zug bei Umkehr des Belastungsweges. Es wird gezeigt, daß das in [3] angegebene Verfestigungsgesetz bei Vorverformung gegen den Ursprung des Spanungsraumes eine Aufweitung der Fließkurve in der Vorverformungsrichtung bedingt. Es wird ferner gezeigt, daß die Existenz von Vorverformungen, die keine Veränderung der Fließflächen bewirken, postuliert werden kann.In dieser Arbeit wird außerdem die Existenz negativer plastischer Verzerrungen gezeigt, und, daß der Beginn der Fließflächen eng verknüpft ist mit den Einhüllenden der Proportionalitätsgrenzen-Flächen.